More fixes and extended lib

AGENTS.md

@@ -60,7 +60,7 @@ Responsibilities:
 - `views/`: handwritten widget/window/graphics behavior.
 - `views/models/`: Qt item models used by views.
 - `services/`: non-visual functionality such as files, clipboard, logging, and settings.
-- `models.py`: GUI metadata persisted inside the core document, currently including icons and shapes.
+- `models.py`: GUI metadata persisted inside the core document, including icon, graph, and simulation databases.
 - `bedit_core`: domain model and serialization. It must never import from `bedit_gui`.
 
 Preferred direction:
@@ -136,10 +136,12 @@ Clipboard support is intentionally extensible:
 - `services/component_clipboard.py`: component payload serialization and ID remapping.
 - `controllers/clipboard_controller.py`: focus-based action router and handlers.
 
-`ClipboardHandler` is the base implementation for future editors. Add a graph-editor handler later by subclassing it and registering that handler in `application.py`.
+`ClipboardHandler` is the base implementation for editor-specific routing. The document tree and graph editor have component handlers registered in `application.py`.
 
 Text widgets use their native `copy()`, `cut()`, and `paste()` methods. Component clipboard data uses the custom BEdit MIME type and JSON; never use pickle or live object references.
 
+The graph handler copies/cuts/deletes selected component items and deletes selected connection items. Paste targets the displayed graph and places new components at the mouse position, or at the viewport center when the mouse is outside the canvas.
+
 ## Icon editor conventions
 
 - Icons are GUI metadata stored in `document.metadata["icon_database"]`.
@@ -153,6 +155,23 @@ Text widgets use their native `copy()`, `cut()`, and `paste()` methods. Componen
 - Keep reusable widgets such as the RGBA color button independent of the icon editor.
 - Static icon previews belong in rendering utilities, not in the interactive editor scene.
 
+## Graph editor conventions
+
+- Graph GUI metadata is stored in `document.metadata["graph_database"]`. `GraphDatabase`, `Graph`, `GraphConnection`, and `GraphComponentLabel` live in `bedit_gui.models` and serialize through `to_data()`/`from_data()`.
+- Core graph topology and connections remain in `bedit_core.models`; positions, routed points, labels, and other presentation metadata belong in the GUI graph database.
+- Component positions are absolute scene positions. Connection metadata stores the full point list, including endpoints; only interior points are draggable corner items.
+- Component labels are visible by default, italic, and centered below the rendered icon. Their persisted position is relative to the icon’s bottom-center. Label visibility and completed label moves are undoable.
+- The graph editor has normal and connection modes. The toolbar actions are exclusive and Space toggles modes while focus is inside the editor.
+- Normal mode supports component and label dragging. Connection mode shows icon ports, prevents component/label movement, and uses two component clicks to choose a compatible port pair.
+- Signal connections require output-to-input. Signal outputs may fan out; signal inputs accept only one connection. A bond port accepts another connection only when its `multiplicity` is true. Bond domains must be compatible.
+- While choosing a connection, the first component is highlighted and a temporary dashed line follows the mouse. When several port pairs are possible, output-to-input choices are listed first.
+- Signal connections render with full arrows. Bond connections render with half arrows and a perpendicular causality tick. Connection endpoints are clipped to rendered icon bounds plus `CONNECTION_BOUNDING_BOX_SPACING`.
+- Components, connections, and connection points are separate graphics items. Connections are selectable/deletable; connection points are draggable and have their own delete context action.
+- Persistent canvas edits go through `Document` methods and graph-specific `QUndoCommand` classes. Incremental document signals must also update the editor’s cached `Graph`; otherwise rebuilding items during a mode switch can restore stale metadata.
+- `render_icon(..., render_ports=True)` is the single port-rendering path. Do not duplicate icon or port geometry in the graph editor.
+- Graph sizing and rendering constants, including `COMPONENT_LABEL_FONT_SIZE`, live near the top of `views/graph_editor_widget.py`.
+- Double-clicking a canvas component selects its document-tree row and opens its graph or equation editor. Canvas component context menus share the document-tree editing actions and add graph-only presentation actions such as Show Label.
+
 ## Actions and shortcut routing
 
 - Put visible actions in Designer menus/toolbars.
@@ -161,6 +180,12 @@ Text widgets use their native `copy()`, `cut()`, and `paste()` methods. Componen
 - Scope destructive shortcuts to the relevant widget where appropriate.
 - Always guard the operation itself even when an action is disabled for presentation.
 
+## Application settings
+
+- `ApplicationSettings` is the typed `QSettings` facade for BEdit preferences. The current settings include log level, graph snap-to-grid size, and ordered library paths under `libraries/paths`.
+- The Settings dialog edits library paths locally until OK is accepted. It supports BEdit `.bedit.json`/`.json` and `.beb` files, directories, duplicate suppression, extended selection, and list-focused Delete-key removal.
+- Add settings behavior in the handwritten dialog/controller/service modules, never in generated UI Python.
+
 ## Simulator application
 
 - `bedit_gui/simulation_application.py` is the composition root for the separate `bedit-sim` Qt application.
@@ -173,6 +198,14 @@ Text widgets use their native `copy()`, `cut()`, and `paste()` methods. Componen
 - BEdit launches the simulator as a separate process. Compile/Open Simulation integration may transfer a `.bes` file to that process.
 - Keep simulator file workflows in their own services/controllers rather than adding them to `MainWindow` or the editor document controller.
 - Keep compiled-executable launching, time-window progression, result loading, and cancellation inside `bedit_simulation`. GUI controllers may schedule backend calls and present state, but must not execute or manage simulation binaries themselves.
+- The BEdit Compile action performs bond-graph causality inference before Modelica compilation. Inference runs on a deep copy first, then inferred `causality`/`undesired` state is applied to the open document with an undoable command.
+- OpenModelica compilation runs `checkModel(...)` before `buildModel(...)`; the equation/variable summary flows through `ModelBuildResult.output` and is shown in the application log.
+
+### Causality inference caveats
+
+- `_CausalityEngine.inference()` clears every flattened bond’s causality to `NONE` before inference; it does not continue from saved causalities. It currently does not clear old `undesired` flags.
+- Preferred causalities are assigned before all junction constraints are resolved, and the engine has no backtracking to relax a preferred assignment. Some soft-preference conflicts therefore raise a junction error instead of marking a bond undesired.
+- `propagate_to_neighbor()` currently selects `connection.target` in both branches. When propagation starts at a target component, it should traverse to the source; account for this known bug when diagnosing inference behavior.
 
 ## Verification
 

icons/signal_base.json

@@ -0,0 +1,25 @@
+{
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+      "line_thickness": 5.0,
+      "corner_radius": 8.0,
+      "line_color": "#00007fff",
+      "fill_color": "#ebebebff"
+    }
+  },
+  "port_positions": {
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+      -8
+    ]
+  }
+}

icons/signal_cosine_source.json

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+{
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+}

icons/signal_sine_source.json

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+{
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+}

icons/signal_source_base.json

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+{
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+}

lib/icons/0.icon.json

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-{
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lib/icons/1.icon.json

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-{
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lib/icons/C.icon.json

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-{
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lib/icons/I.icon.json

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-{
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lib/icons/R.icon.json

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-{
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-      "italic": false,
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-      "text": "R"
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lib/icons/Se.icon.json

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-{
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-      "bold": true,
-      "italic": false,
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-      "text": "Se"
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-  "port_positions": {
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lib/icons/Sf.icon.json

@@ -1,25 +0,0 @@
-{
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-    "f1a38ee1-8a53-454d-a398-12c14032ba79": {
-      "layer": 0,
-      "type": "text",
-      "pos": [
-        -48,
-        -32
-      ],
-      "width": 96.0,
-      "height": 64.0,
-      "color": "#000000ff",
-      "bold": true,
-      "italic": false,
-      "size": 64.0,
-      "text": "Sf"
-    }
-  },
-  "port_positions": {
-    "856b4152-e18f-46d7-889d-626cb98474aa": [
-      -8,
-      -8
-    ]
-  }
-}

src/bedit_core/bondgraph/causality.py

@@ -83,6 +83,7 @@ class _CausalityEngine():
     def clear_causalities(self) -> None:
         for bond in self._network.bonds:
             bond.connection.causality = BondCausality.NONE
+            bond.connection.undesired = False
 
     def propagate_from_port(self, port: NetworkPort, causality: BondCausality) -> None:
         attached_connections = self._network.bonds_for(port)
@@ -106,7 +107,7 @@ class _CausalityEngine():
     def propagate_to_neighbor(self, component: Component, connection: NetworkBond) -> None:
         # Get neighor
         is_source = (component == connection.source.component)
-        neighbor = connection.target if is_source else connection.target
+        neighbor = connection.target if is_source else connection.source
         # Direct the evaluation based on what type of port it is
         if neighbor.port.causality_preference in [PortCausality.SINGLE_EFFORT_IN, PortCausality.SINGLE_FLOW_IN]:
             self.evaluate_junction_constraints(neighbor)

src/bedit_gui/application.py

@@ -5,9 +5,10 @@ import argparse
 
 from PySide6.QtWidgets import QApplication, QMessageBox
 
-from bedit_gui.controllers.clipboard_controller import ClipboardController, DocumentTreeClipboardHandler, TextClipboardHandler
+from bedit_gui.controllers.clipboard_controller import ClipboardController, DocumentTreeClipboardHandler, GraphEditorClipboardHandler, TextClipboardHandler
 from bedit_gui.controllers.document_controller import DocumentController
 from bedit_gui.controllers.log_controller import LogController
+from bedit_gui.controllers.library_controller import LibraryController
 from bedit_gui.controllers.settings_controller import SettingsController
 from bedit_gui.controllers.simulation_settings_controller import SimulationSettingsController
 from bedit_gui.controllers.simulation_controller import SimulationController
@@ -46,20 +47,22 @@ def main() -> int:
 
     settings = ApplicationSettings()
     document = Document(app)
-    window = MainWindow()
+    window = MainWindow(settings.snap_to_grid_size)
     window.ui.actionAbout.triggered.connect(lambda: QMessageBox.about(window, "About BEdit", f"BEdit {BEDIT_VERSION}"))
     window.ui.actionAbout_QT.triggered.connect(app.aboutQt)
 
     LogController(window, settings.log_level)
     DocumentController(document, window)
-    SettingsController(window, settings)
+    settings_controller = SettingsController(window, settings)
     SimulationSettingsController(document, window)
     SimulationController(document, window)
     UndoController(document, window)
     ViewMenuController(window)
     document_tree_controller = DocumentTreeController(document, window)
+    library_controller = LibraryController(window, settings)
+    settings_controller.library_paths_changed.connect(library_controller.reload)
     clipboard = ClipboardService(app)
-    ClipboardController(window, clipboard, [TextClipboardHandler(clipboard), DocumentTreeClipboardHandler(document, window.ui.documentTree, document_tree_controller.model, clipboard)])
+    ClipboardController(window, clipboard, [TextClipboardHandler(clipboard), DocumentTreeClipboardHandler(document, window.ui.documentTree, document_tree_controller.model, clipboard), GraphEditorClipboardHandler(document, window.graph_editor, clipboard)])
 
     window_state_controller = WindowStateController(app, window)
     window_state_controller.restore()

src/bedit_gui/commands/causality_command.py

@@ -0,0 +1,44 @@
+from PySide6.QtGui import QUndoCommand
+
+from bedit_core.models import BondCausality, BondConnection, Component, ConnectionID, GraphImplementation
+
+CausalityState = dict[ConnectionID, tuple[BondCausality, bool]]
+
+
+def causality_state(component: Component) -> CausalityState:
+    state = {}
+    if not isinstance(component.implementation, GraphImplementation):
+        return state
+    for connection_id, connection in component.implementation.graph.connections.items():
+        if isinstance(connection, BondConnection):
+            state[connection_id] = (connection.causality, connection.undesired)
+    for child in component.implementation.graph.components.values():
+        state.update(causality_state(child))
+    return state
+
+
+class ChangeCausalityCommand(QUndoCommand):
+    def __init__(self, document: object, component: Component, inferred_component: Component) -> None:
+        super().__init__("Infer causality")
+        self.document = document
+        self.component = component
+        self.old_state = causality_state(component)
+        self.new_state = causality_state(inferred_component)
+
+    def redo(self) -> None:
+        self._apply(self.component, self.new_state)
+        self.document.model_changed.emit(self.document.model)
+
+    def undo(self) -> None:
+        self._apply(self.component, self.old_state)
+        self.document.model_changed.emit(self.document.model)
+
+    @classmethod
+    def _apply(cls, component: Component, state: CausalityState) -> None:
+        if not isinstance(component.implementation, GraphImplementation):
+            return
+        for connection_id, connection in component.implementation.graph.connections.items():
+            if isinstance(connection, BondConnection) and connection_id in state:
+                connection.causality, connection.undesired = state[connection_id]
+        for child in component.implementation.graph.components.values():
+            cls._apply(child, state)

src/bedit_gui/commands/component_command.py

@@ -1,44 +1,52 @@
+from copy import deepcopy
+
 from PySide6.QtGui import QUndoCommand
 
-from bedit_core.models import Component, ComponentID, Connection, ConnectionID, EquationImplementation, Graph, GraphImplementation, Interface
-from bedit_gui.models import Icon
+from bedit_core.models import Component, ComponentID, Connection, ConnectionID, EquationImplementation, Graph, GraphImplementation, Interface, PortID
+from bedit_gui.models import Icon, PortMetadata
 
 
 class AddEmptyGraphComponent(QUndoCommand):
-    def __init__(self, document: object, parent: Component) -> None:
+    def __init__(self, document: object, parent: Component | dict[ComponentID, Component]) -> None:
         super().__init__("Add graph component")
-        if not isinstance(parent.implementation, GraphImplementation):
-            raise TypeError("parent component must have a graph implementation")
         self.document = document
-        self.graph = parent.implementation.graph
+        if isinstance(parent, Component):
+            if not isinstance(parent.implementation, GraphImplementation):
+                raise TypeError("parent component must have a graph implementation")
+            self.components = parent.implementation.graph.components
+        else:
+            self.components = parent
         self.component_id = ComponentID()
-        self.component = Component(name="New Graph Component", interface=Interface(), parameters={}, implementation=GraphImplementation(Graph()))
+        self.component = Component(name="new_graph_component", interface=Interface(), parameters={}, implementation=GraphImplementation(Graph()))
 
     def redo(self) -> None:
-        self.graph.components[self.component_id] = self.component
+        self.components[self.component_id] = self.component
         self.document.model_changed.emit(self.document.model)
 
     def undo(self) -> None:
-        del self.graph.components[self.component_id]
+        del self.components[self.component_id]
         self.document.model_changed.emit(self.document.model)
 
 
 class AddEmptyEquationComponent(QUndoCommand):
-    def __init__(self, document: object, parent: Component) -> None:
+    def __init__(self, document: object, parent: Component | dict[ComponentID, Component]) -> None:
         super().__init__("Add equation component")
-        if not isinstance(parent.implementation, GraphImplementation):
-            raise TypeError("parent component must have a graph implementation")
         self.document = document
-        self.graph = parent.implementation.graph
+        if isinstance(parent, Component):
+            if not isinstance(parent.implementation, GraphImplementation):
+                raise TypeError("parent component must have a graph implementation")
+            self.components = parent.implementation.graph.components
+        else:
+            self.components = parent
         self.component_id = ComponentID()
         self.component = Component(name="New Equation Component", interface=Interface(), parameters={}, implementation=EquationImplementation())
 
     def redo(self) -> None:
-        self.graph.components[self.component_id] = self.component
+        self.components[self.component_id] = self.component
         self.document.model_changed.emit(self.document.model)
 
     def undo(self) -> None:
-        del self.graph.components[self.component_id]
+        del self.components[self.component_id]
         self.document.model_changed.emit(self.document.model)
 
 
@@ -56,10 +64,16 @@ class DeleteComponent(QUndoCommand):
                 if connection.source in port_ids or connection.target in port_ids:
                     self.connections.append((index, connection_id, connection))
         self.icons = {}
+        self.port_metadata = {}
         for component_id in self._component_ids(self.component_id, component):
             icon = document.stored_component_icon(component_id)
             if icon is not None:
                 self.icons[component_id] = icon
+        database = document._port_metadata_database(False)
+        if database is not None:
+            for port_id in self._port_ids(component):
+                if port_id in database.ports:
+                    self.port_metadata[port_id] = deepcopy(database.ports[port_id])
 
     def redo(self) -> None:
         if self.parent_graph is not None:
@@ -69,6 +83,11 @@ class DeleteComponent(QUndoCommand):
         self.document.model_changed.emit(self.document.model)
         for component_id in self.icons:
             self.document._set_component_icon(component_id, None)
+        if self.port_metadata:
+            database = self.document.port_metadata_database()
+            for port_id in self.port_metadata:
+                database.ports.pop(port_id, None)
+            self.document._set_port_metadata_database(database)
 
     def undo(self) -> None:
         self._restore_item(self.components, self.component_id, self.component, self.component_index)
@@ -78,6 +97,10 @@ class DeleteComponent(QUndoCommand):
         self.document.model_changed.emit(self.document.model)
         for component_id, icon in self.icons.items():
             self.document._set_component_icon(component_id, icon)
+        if self.port_metadata:
+            database = self.document.port_metadata_database()
+            database.ports.update(deepcopy(self.port_metadata))
+            self.document._set_port_metadata_database(database)
 
     @classmethod
     def _find_component(cls, components: dict[ComponentID, Component], target: Component, parent_graph: Graph | None = None) -> tuple[dict[ComponentID, Component], ComponentID, Graph | None]:
@@ -99,6 +122,14 @@ class DeleteComponent(QUndoCommand):
                 component_ids.extend(cls._component_ids(child_id, child))
         return component_ids
 
+    @classmethod
+    def _port_ids(cls, component: Component) -> list[PortID]:
+        port_ids = list(component.interface.ports)
+        if isinstance(component.implementation, GraphImplementation):
+            for child in component.implementation.graph.components.values():
+                port_ids.extend(cls._port_ids(child))
+        return port_ids
+
     @staticmethod
     def _restore_item(items: dict, item_id: object, item: object, index: int) -> None:
         values = list(items.items())
@@ -108,22 +139,40 @@ class DeleteComponent(QUndoCommand):
 
 
 class PasteComponents(QUndoCommand):
-    def __init__(self, document: object, target: dict[ComponentID, Component], components: dict[ComponentID, Component], icons: dict[ComponentID, Icon]) -> None:
+    def __init__(self, document: object, target: dict[ComponentID, Component], components: dict[ComponentID, Component], icons: dict[ComponentID, Icon], graph_id: ComponentID | None = None, positions: dict[ComponentID, tuple[int, int]] | None = None, port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
         super().__init__("Paste components")
         self.document = document
         self.target = target
         self.components = components
         self.icons = icons
+        self.graph_id = graph_id
+        self.positions = positions or {}
+        self.port_metadata = deepcopy(port_metadata or {})
 
     def redo(self) -> None:
         self.target.update(self.components)
+        if self.graph_id is not None:
+            for component_id, position in self.positions.items():
+                self.document._set_graph_component_position(self.graph_id, component_id, position)
         self.document.model_changed.emit(self.document.model)
         for component_id, icon in self.icons.items():
             self.document._set_component_icon(component_id, icon)
+        if self.port_metadata:
+            database = self.document.port_metadata_database()
+            database.ports.update(deepcopy(self.port_metadata))
+            self.document._set_port_metadata_database(database)
 
     def undo(self) -> None:
         for component_id in self.components:
             self.target.pop(component_id, None)
+        if self.graph_id is not None:
+            for component_id in self.positions:
+                self.document._set_graph_component_position(self.graph_id, component_id, None)
         self.document.model_changed.emit(self.document.model)
         for component_id in self.icons:
             self.document._set_component_icon(component_id, None)
+        if self.port_metadata:
+            database = self.document.port_metadata_database()
+            for port_id in self.port_metadata:
+                database.ports.pop(port_id, None)
+            self.document._set_port_metadata_database(database)

src/bedit_gui/commands/graph_connection_command.py

@@ -0,0 +1,54 @@
+from copy import deepcopy
+
+from PySide6.QtGui import QUndoCommand
+
+from bedit_core.models import Component, Connection, ConnectionID, GraphImplementation
+
+
+class AddGraphConnectionCommand(QUndoCommand):
+    def __init__(self, document: object, graph_component: Component, connection: Connection) -> None:
+        super().__init__("Add connection")
+        if not isinstance(graph_component.implementation, GraphImplementation):
+            raise TypeError("component must have a graph implementation")
+        self.document = document
+        self.graph = graph_component.implementation.graph
+        self.connection_id = ConnectionID()
+        self.connection = connection
+
+    def redo(self) -> None:
+        self.graph.connections[self.connection_id] = self.connection
+        self.document.model_changed.emit(self.document.model)
+
+    def undo(self) -> None:
+        self.graph.connections.pop(self.connection_id, None)
+        self.document.model_changed.emit(self.document.model)
+
+
+class DeleteGraphConnectionCommand(QUndoCommand):
+    def __init__(self, document: object, graph_component: Component, connection_id: ConnectionID) -> None:
+        super().__init__("Delete connection")
+        if not isinstance(graph_component.implementation, GraphImplementation):
+            raise TypeError("component must have a graph implementation")
+        self.document = document
+        self.graph_id = document.component_id(graph_component)
+        self.connections = graph_component.implementation.graph.connections
+        self.connection_id = connection_id
+        self.connection = self.connections[connection_id]
+        self.index = list(self.connections).index(connection_id)
+        database = document._graph_database(False)
+        graph = database.graphs.get(self.graph_id) if database is not None else None
+        self.visual_connection = deepcopy(graph.connections.get(connection_id)) if graph is not None else None
+
+    def redo(self) -> None:
+        self.connections.pop(self.connection_id, None)
+        self.document._set_graph_connection_points(self.graph_id, self.connection_id, None)
+        self.document.model_changed.emit(self.document.model)
+
+    def undo(self) -> None:
+        items = list(self.connections.items())
+        items.insert(self.index, (self.connection_id, self.connection))
+        self.connections.clear()
+        self.connections.update(items)
+        if self.visual_connection is not None:
+            self.document._set_graph_connection_points(self.graph_id, self.connection_id, self.visual_connection.points)
+        self.document.model_changed.emit(self.document.model)

src/bedit_gui/commands/graph_connection_points_command.py

@@ -0,0 +1,24 @@
+from copy import deepcopy
+
+from PySide6.QtGui import QUndoCommand
+
+from bedit_core.models import ComponentID, ConnectionID
+
+
+class ChangeGraphConnectionPointsCommand(QUndoCommand):
+    def __init__(self, document: object, graph_id: ComponentID, connection_id: ConnectionID, points: list[tuple[int, int]], text: str) -> None:
+        super().__init__(text)
+        self.document = document
+        self.graph_id = graph_id
+        self.connection_id = connection_id
+        database = document._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        connection = graph.connections.get(connection_id) if graph is not None else None
+        self.old_points = deepcopy(connection.points) if connection is not None else None
+        self.new_points = deepcopy(points)
+
+    def redo(self) -> None:
+        self.document._set_graph_connection_points(self.graph_id, self.connection_id, self.new_points)
+
+    def undo(self) -> None:
+        self.document._set_graph_connection_points(self.graph_id, self.connection_id, self.old_points)

src/bedit_gui/commands/graph_label_command.py

@@ -0,0 +1,24 @@
+from copy import deepcopy
+
+from PySide6.QtGui import QUndoCommand
+
+from bedit_core.models import ComponentID
+from bedit_gui.models import GraphComponentLabel
+
+
+class ChangeGraphComponentLabelCommand(QUndoCommand):
+    def __init__(self, document: object, graph_id: ComponentID, component_id: ComponentID, label: GraphComponentLabel, text: str) -> None:
+        super().__init__(text)
+        self.document = document
+        self.graph_id = graph_id
+        self.component_id = component_id
+        database = document._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        self.old_label = deepcopy(graph.component_labels.get(component_id)) if graph is not None and component_id in graph.component_labels else None
+        self.new_label = deepcopy(label)
+
+    def redo(self) -> None:
+        self.document._set_graph_component_label(self.graph_id, self.component_id, self.new_label)
+
+    def undo(self) -> None:
+        self.document._set_graph_component_label(self.graph_id, self.component_id, self.old_label)

src/bedit_gui/commands/graph_position_command.py

@@ -0,0 +1,21 @@
+from PySide6.QtGui import QUndoCommand
+
+from bedit_core.models import ComponentID
+
+
+class MoveGraphComponentCommand(QUndoCommand):
+    def __init__(self, document: object, graph_id: ComponentID, component_id: ComponentID, position: tuple[int, int]) -> None:
+        super().__init__("Move graph component")
+        self.document = document
+        self.graph_id = graph_id
+        self.component_id = component_id
+        database = document._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        self.old_position = graph.component_positions.get(component_id) if graph is not None else None
+        self.new_position = position
+
+    def redo(self) -> None:
+        self.document._set_graph_component_position(self.graph_id, self.component_id, self.new_position)
+
+    def undo(self) -> None:
+        self.document._set_graph_component_position(self.graph_id, self.component_id, self.old_position)

src/bedit_gui/commands/port_metadata_command.py

@@ -0,0 +1,19 @@
+from copy import deepcopy
+
+from PySide6.QtGui import QUndoCommand
+
+from bedit_gui.models import PortMetadataDatabase
+
+
+class ChangePortMetadataDatabaseCommand(QUndoCommand):
+    def __init__(self, document: object, database: PortMetadataDatabase) -> None:
+        super().__init__("Change port metadata")
+        self.document = document
+        self.old_database = document.stored_port_metadata_database()
+        self.new_database = deepcopy(database)
+
+    def redo(self) -> None:
+        self.document._set_port_metadata_database(self.new_database)
+
+    def undo(self) -> None:
+        self.document._set_port_metadata_database(self.old_database)

src/bedit_gui/controllers/clipboard_controller.py

@@ -8,6 +8,7 @@ from bedit_core.models import Document as CoreDocument
 from bedit_gui.documents import Document
 from bedit_gui.services.clipboard import ClipboardService
 from bedit_gui.services.component_clipboard import export_components, import_components
+from bedit_gui.views.graph_editor_widget import GraphEditorWidget
 from bedit_gui.views.models.document_tree_model import DocumentTreeModel
 
 
@@ -28,6 +29,9 @@ class ClipboardHandler(QObject):
     def can_paste(self) -> bool:
         return False
 
+    def can_delete(self) -> bool:
+        return False
+
     def copy(self) -> None:
         pass
 
@@ -37,6 +41,9 @@ class ClipboardHandler(QObject):
     def paste(self) -> None:
         pass
 
+    def delete(self) -> None:
+        pass
+
 
 class TextClipboardHandler(ClipboardHandler):
     def __init__(self, clipboard: ClipboardService, parent: QObject | None = None) -> None:
@@ -106,6 +113,9 @@ class DocumentTreeClipboardHandler(ClipboardHandler):
     def can_paste(self) -> bool:
         return self._target() is not None and self.clipboard.has_format(ClipboardService.COMPONENTS_MIME)
 
+    def can_delete(self) -> bool:
+        return bool(self._selected_components())
+
     def copy(self) -> None:
         components = self._selected_components()
         if components:
@@ -123,11 +133,14 @@ class DocumentTreeClipboardHandler(ClipboardHandler):
         if target is None or payload is None:
             return
         try:
-            components, icons = import_components(payload)
+            components, icons, port_metadata = import_components(payload)
         except (TypeError, ValueError) as exc:
             QMessageBox.critical(self.tree, "Could not paste components", str(exc))
             return
-        self.document.paste_components(target, components, icons)
+        self.document.paste_components(target, components, icons, port_metadata)
+
+    def delete(self) -> None:
+        self.document.delete_components(self._selected_components())
 
     def _write_components(self, components: list[Component]) -> None:
         payload = export_components(self.document, components)
@@ -162,6 +175,87 @@ class DocumentTreeClipboardHandler(ClipboardHandler):
         return None
 
 
+class GraphEditorClipboardHandler(ClipboardHandler):
+    def __init__(self, document: Document, editor: GraphEditorWidget, clipboard: ClipboardService, parent: QObject | None = None) -> None:
+        super().__init__(parent)
+        self.document = document
+        self.editor = editor
+        self.clipboard = clipboard
+        editor.scene.selectionChanged.connect(self.availability_changed)
+        editor.component_drop_requested.connect(self.drop_components)
+
+    def owns_focus(self, widget: QWidget) -> bool:
+        return widget is self.editor or self.editor.isAncestorOf(widget)
+
+    def can_copy(self) -> bool:
+        return bool(self._selected_components())
+
+    def can_cut(self) -> bool:
+        return self.can_copy()
+
+    def can_paste(self) -> bool:
+        return self._target() is not None and self.clipboard.has_format(ClipboardService.COMPONENTS_MIME)
+
+    def can_delete(self) -> bool:
+        return bool(self._selected_components() or self.editor.selected_connection_ids())
+
+    def copy(self) -> None:
+        components = self._selected_components()
+        if components:
+            self._write_components(components)
+
+    def cut(self) -> None:
+        components = self._selected_components()
+        if components:
+            self._write_components(components)
+            self.document.delete_components(components)
+
+    def paste(self) -> None:
+        graph_component = self.editor.component()
+        payload = self.clipboard.get_json(ClipboardService.COMPONENTS_MIME)
+        if graph_component is None or not isinstance(graph_component.implementation, GraphImplementation) or payload is None:
+            return
+        x, y = self.editor.paste_position()
+        self._paste_payload(graph_component, payload, (x, y))
+
+    def drop_components(self, graph_component: Component, payload: dict, position: tuple[int, int]) -> None:
+        self._paste_payload(graph_component, payload, position)
+
+    def _paste_payload(self, graph_component: Component, payload: dict, position: tuple[int, int]) -> None:
+        try:
+            components, icons, port_metadata = import_components(payload)
+        except (TypeError, ValueError) as exc:
+            QMessageBox.critical(self.editor, "Could not paste components", str(exc))
+            return
+        x, y = position
+        spacing = self.editor.snap_to_grid_size * 4
+        positions = {component_id: (x + index * spacing, y + index * spacing) for index, component_id in enumerate(components)}
+        self.document.paste_graph_components(graph_component, components, icons, positions, port_metadata)
+
+    def delete(self) -> None:
+        components = self._selected_components()
+        connection_ids = self.editor.selected_connection_ids()
+        if components:
+            self.document.delete_components(components)
+        graph_component = self.editor.component()
+        if graph_component is not None and connection_ids:
+            self.document.delete_graph_connections(graph_component, connection_ids)
+
+    def _write_components(self, components: list[Component]) -> None:
+        payload = export_components(self.document, components)
+        self.clipboard.set_json(ClipboardService.COMPONENTS_MIME, payload, "\n".join(component.name for component in components))
+
+    def _selected_components(self) -> list[Component]:
+        target = self._target()
+        if target is None:
+            return []
+        return [target[component_id] for component_id in self.editor.selected_component_ids() if component_id in target]
+
+    def _target(self) -> dict | None:
+        component = self.editor.component()
+        return component.implementation.graph.components if component is not None and isinstance(component.implementation, GraphImplementation) else None
+
+
 class ClipboardController(QObject):
     def __init__(self, window: QMainWindow, clipboard: ClipboardService, handlers: list[ClipboardHandler]) -> None:
         super().__init__(window)
@@ -171,6 +265,7 @@ class ClipboardController(QObject):
         window.ui.actionCopy.triggered.connect(self.copy)
         window.ui.actionCut.triggered.connect(self.cut)
         window.ui.actionPaste.triggered.connect(self.paste)
+        window.ui.actionDelete.triggered.connect(self.delete)
         application = QApplication.instance()
         application.focusChanged.connect(self.update_actions)
         application.installEventFilter(self)
@@ -209,8 +304,15 @@ class ClipboardController(QObject):
             handler.paste()
         self.update_actions()
 
+    def delete(self) -> None:
+        handler = self.active_handler()
+        if handler is not None and handler.can_delete():
+            handler.delete()
+        self.update_actions()
+
     def update_actions(self, *_args: object) -> None:
         handler = self.active_handler()
         self.window.ui.actionCopy.setEnabled(handler is not None and handler.can_copy())
         self.window.ui.actionCut.setEnabled(handler is not None and handler.can_cut())
         self.window.ui.actionPaste.setEnabled(handler is not None and handler.can_paste())
+        self.window.ui.actionDelete.setEnabled(handler is not None and handler.can_delete())

src/bedit_gui/controllers/document_tree_controller.py

@@ -2,26 +2,27 @@ from collections.abc import Callable
 from functools import partial
 from typing import Protocol
 
-from PySide6.QtCore import QEvent, QObject, QPoint, QSize, Qt
+from PySide6.QtCore import QEvent, QItemSelectionModel, QObject, QPoint, QSize, Qt
 from PySide6.QtGui import QMouseEvent
 from PySide6.QtWidgets import QAbstractItemView, QDialog, QHeaderView, QMenu
 
-from bedit_core.models import Component, ComponentID, EquationImplementation, GraphImplementation, Port, PortID, Parameter, ParameterID
+from bedit_core.models import Component, ComponentID, ConnectionID, EquationImplementation, GraphImplementation, Port, PortID, Parameter, ParameterID
 from bedit_core.models import Document as CoreDocument
 from bedit_gui.documents import Document
-from bedit_gui.models import Icon
+from bedit_gui.models import Graph, GraphComponentLabel, Icon, PortMetadata
 from bedit_gui.views.dialogs.interface_editor_dialog import InterfaceEditorDialog
 from bedit_gui.views.dialogs.param_editor_dialog import ParamEditorDialog
 from bedit_gui.views.icon_editor_window import IconEditorWindow
 from bedit_gui.views.main_window import MainWindow
 from bedit_gui.views.models.document_tree_model import DocumentTreeModel
-from bedit_gui.utils.icon import render_icon
+from bedit_gui.utils.icon import render_fitted_icon
 
-ICON_SIZE = QSize(32, 32)
+ICON_SIZE = QSize(16, 16)
 
 class InterfaceEditorLike(Protocol):
     def exec(self) -> int: ...
     def ports(self) -> dict[PortID, Port]: ...
+    def port_metadata(self) -> dict[PortID, PortMetadata]: ...
 
 class ParamEditorLike(Protocol):
     def exec(self) -> int: ...
@@ -29,7 +30,7 @@ class ParamEditorLike(Protocol):
 
 
 InterfaceEditorFactory = Callable[
-    [dict[PortID, Port], MainWindow],
+    [dict[PortID, Port], dict[PortID, PortMetadata], MainWindow],
     InterfaceEditorLike,
 ]
 
@@ -60,12 +61,23 @@ class DocumentTreeController(QObject):
         window.ui.documentTree.setModel(self.model)
         window.ui.documentTree.selectionModel().selectionChanged.connect(self._selection_changed)
         window.equation_editor.equation_text_change_requested.connect(self.document.update_component_equation_text)
+        window.equation_editor.port_metadata_change_requested.connect(self._change_equation_port_metadata)
         document.model_changed.connect(self._on_document_changed)
         document.icon_changed.connect(self._on_icon_changed)
+        document.port_metadata_database_changed.connect(self._on_port_metadata_database_changed)
+        document.graph_component_position_changed.connect(self._on_graph_component_position_changed)
+        document.graph_component_label_changed.connect(self._on_graph_component_label_changed)
+        document.graph_connection_points_changed.connect(self._on_graph_connection_points_changed)
         document.equation_text_changed.connect(self._on_equation_text_changed)
         self.model.rename_document_requested.connect(self.document.rename)
         self.model.rename_component_requested.connect(self.document.rename_component)
-        window.ui.actionDelete.triggered.connect(self.delete_selected_component)
+        window.graph_editor.component_moves_requested.connect(self.document.move_graph_components)
+        window.graph_editor.component_label_move_requested.connect(self.document.move_graph_component_label)
+        window.graph_editor.component_context_menu_requested.connect(self._show_graph_component_context_menu)
+        window.graph_editor.component_open_requested.connect(self._open_graph_component)
+        window.graph_editor.connection_points_change_requested.connect(self.document.change_graph_connection_points)
+        window.graph_editor.connection_add_requested.connect(self.document.add_graph_connection)
+        window.graph_editor.connections_delete_requested.connect(self.document.delete_graph_connections)
 
         # Add deselection with esc to this widget
         window.ui.actionEscape.setShortcutContext(Qt.ShortcutContext.WidgetWithChildrenShortcut)
@@ -75,11 +87,11 @@ class DocumentTreeController(QObject):
         window.ui.documentTree.setHeaderHidden(True)
         window.ui.documentTree.setSelectionMode(QAbstractItemView.SelectionMode.ExtendedSelection)
         window.ui.documentTree.setSelectionBehavior(QAbstractItemView.SelectionBehavior.SelectRows)
-        window.ui.documentTree.setIconSize(QSize(48, 48))
+        window.ui.documentTree.setIconSize(QSize(24, 24))
         window.ui.documentTree.header().setStretchLastSection(False)
         window.ui.documentTree.header().setSectionResizeMode(0, QHeaderView.ResizeMode.Stretch)
         window.ui.documentTree.header().setSectionResizeMode(1, QHeaderView.ResizeMode.Fixed)
-        window.ui.documentTree.setColumnWidth(1, 56)
+        window.ui.documentTree.setColumnWidth(1, 28)
         self._tree_viewport = window.ui.documentTree.viewport()
         self._tree_viewport.installEventFilter(self)
 
@@ -96,13 +108,14 @@ class DocumentTreeController(QObject):
 
     def _on_document_changed(self, model: CoreDocument) -> None:
         """Rebuild the tree whenever New/Open replaces the core document."""
-        self._show_component(None)
+        displayed_component = self.window.graph_editor.component() or self.window.equation_editor.component()
         self.model.set_document(model)
         self._components = {}
         self._collect_components(model.root)
         for component_id, component in self._components.items():
             icon = self.document.component_icon(component_id)
-            self.model.set_component_icon(component_id, render_icon(icon, component.interface.ports, ICON_SIZE))
+            self.model.set_component_icon(component_id, render_fitted_icon(icon, component.interface.ports, ICON_SIZE))
+        self._show_component(displayed_component if any(component is displayed_component for component in self._components.values()) else None)
 
         # Optional presentation behavior. Later, you could instead remember
         # expanded component IDs and restore only those nodes.
@@ -115,13 +128,17 @@ class DocumentTreeController(QObject):
 
     def _show_component(self, component: Component | None) -> None:
         if component is not None and isinstance(component.implementation, EquationImplementation):
-            self.window.equation_editor.set_component(component)
+            port_metadata = {port_id: self.document.port_metadata(port_id) for port_id in component.interface.ports}
+            self.window.equation_editor.set_component(component, port_metadata)
             self.window.equation_editor.show()
         else:
             self.window.equation_editor.set_component(None)
             self.window.equation_editor.hide()
         if component is not None and isinstance(component.implementation, GraphImplementation):
-            self.window.graph_editor.set_component(component)
+            graph = self.document.graph_database().graphs.get(self.document.component_id(component), Graph())
+            icons = {component_id: self.document.component_icon(component_id) for component_id in component.implementation.graph.components}
+            port_metadata = {port_id: self.document.port_metadata(port_id) for child in component.implementation.graph.components.values() for port_id in child.interface.ports}
+            self.window.graph_editor.set_component(component, graph, icons, port_metadata)
             self.window.graph_editor.show()
         else:
             self.window.graph_editor.set_component(None)
@@ -135,7 +152,36 @@ class DocumentTreeController(QObject):
         component = self._components.get(component_id)
         if component is None:
             return
-        self.model.set_component_icon(component_id, render_icon(icon if isinstance(icon, Icon) else Icon(), component.interface.ports, ICON_SIZE))
+        self.model.set_component_icon(component_id, render_fitted_icon(icon if isinstance(icon, Icon) else Icon(), component.interface.ports, ICON_SIZE))
+        graph_component = self.window.graph_editor.component()
+        if graph_component is not None and isinstance(graph_component.implementation, GraphImplementation) and component_id in graph_component.implementation.graph.components:
+            self._show_component(graph_component)
+
+    def _on_port_metadata_database_changed(self, _database: object) -> None:
+        graph_component = self.window.graph_editor.component()
+        if graph_component is not None:
+            self._show_component(graph_component)
+        equation_component = self.window.equation_editor.component()
+        if equation_component is not None:
+            self.window.equation_editor.refresh_port_metadata({port_id: self.document.port_metadata(port_id) for port_id in equation_component.interface.ports})
+
+    def _change_equation_port_metadata(self, component: Component, port_metadata: dict[PortID, PortMetadata]) -> None:
+        self.document.update_component_ports(component, component.interface.ports, port_metadata)
+
+    def _on_graph_component_position_changed(self, graph_id: ComponentID, component_id: ComponentID, position: tuple[int, int] | None) -> None:
+        graph_component = self.window.graph_editor.component()
+        if graph_component is not None and self.document.component_id(graph_component) == graph_id:
+            self.window.graph_editor.set_component_position(component_id, position)
+
+    def _on_graph_component_label_changed(self, graph_id: ComponentID, component_id: ComponentID, label: object) -> None:
+        graph_component = self.window.graph_editor.component()
+        if graph_component is not None and self.document.component_id(graph_component) == graph_id:
+            self.window.graph_editor.set_component_label(component_id, label if isinstance(label, GraphComponentLabel) else None)
+
+    def _on_graph_connection_points_changed(self, graph_id: ComponentID, connection_id: ConnectionID, points: list[tuple[int, int]] | None) -> None:
+        graph_component = self.window.graph_editor.component()
+        if graph_component is not None and self.document.component_id(graph_component) == graph_id:
+            self.window.graph_editor.set_connection_points(connection_id, points)
 
     def _collect_components(self, components: dict[ComponentID, Component]) -> None:
         for component_id, component in components.items():
@@ -145,31 +191,66 @@ class DocumentTreeController(QObject):
 
     def _show_context_menu(self, position: QPoint) -> None:
         index = self.window.ui.documentTree.indexAt(position)
-        component = self.model.value(index)
-        if not isinstance(component, Component):
-            return
+        value = self.model.value(index)
+        global_position = self.window.ui.documentTree.viewport().mapToGlobal(position)
+        if isinstance(value, CoreDocument):
+            self._show_root_context_menu(global_position)
+        elif isinstance(value, Component):
+            self._show_component_context_menu(value, global_position)
 
+    def _show_root_context_menu(self, global_position: QPoint) -> None:
+        menu = QMenu(self.window.ui.documentTree)
+        add_graph_component = menu.addAction("Add Graph Component")
+        add_equation_component = menu.addAction("Add Equation Component")
+        selected = menu.exec(global_position)
+        if selected is add_graph_component:
+            self.document.add_empty_root_graph_component()
+        elif selected is add_equation_component:
+            self.document.add_empty_root_equation_component()
+
+    def _show_graph_component_context_menu(self, component_id: ComponentID, global_position: QPoint) -> None:
+        component = self._components.get(component_id)
+        if component is not None:
+            self._show_component_context_menu(component, global_position, component_id)
+
+    def _open_graph_component(self, component_id: ComponentID) -> None:
+        index = self.model.component_index(component_id)
+        if index.isValid():
+            self.window.ui.documentTree.selectionModel().setCurrentIndex(index, QItemSelectionModel.SelectionFlag.ClearAndSelect | QItemSelectionModel.SelectionFlag.Rows)
+            self.window.ui.documentTree.scrollTo(index)
+
+    def _show_component_context_menu(self, component: Component, global_position: QPoint, graph_component_id: ComponentID | None = None) -> None:
         menu = QMenu(self.window.ui.documentTree)
         edit_interface = menu.addAction("Edit Interface")
         edit_params = menu.addAction("Edit Parameters")
         edit_icon = menu.addAction("Edit Icon")
+        show_label = None
+        if graph_component_id is not None:
+            show_label = menu.addAction("Show Label")
+            show_label.setCheckable(True)
+            show_label.setChecked(self.window.graph_editor.component_label_visible(graph_component_id))
         menu.addSeparator()
-        add_graph_component = menu.addAction("Add Graph Component")
-        add_equation_component = menu.addAction("Add Equation Component")
-        menu.addSeparator()
+        add_graph_component = None
+        add_equation_component = None
+        if isinstance(component.implementation, GraphImplementation):
+            add_graph_component = menu.addAction("Add Graph Component")
+            add_equation_component = menu.addAction("Add Equation Component")
+            menu.addSeparator()
         delete_component = menu.addAction("Delete Component")
-        selected = menu.exec(
-            self.window.ui.documentTree.viewport().mapToGlobal(position)
-        )
+        selected = menu.exec(global_position)
         if selected is edit_interface:
             self._edit_interface(component)
         elif selected is edit_params:
             self._edit_params(component)
         elif selected is edit_icon:
             self._edit_icon(component)
-        elif selected is add_graph_component:
+        elif show_label is not None and selected is show_label:
+            graph_component = self.window.graph_editor.component()
+            if graph_component is not None:
+                self.document.set_graph_component_label_visible(graph_component, graph_component_id, show_label.isChecked())
+        elif add_graph_component is not None and selected is add_graph_component:
             self._add_graph_component(component)
-        elif selected is add_equation_component:
+        elif add_equation_component is not None and selected is add_equation_component:
             self._add_equation_component(component)
         elif selected is delete_component:
             self._delete_component(component)
@@ -177,10 +258,11 @@ class DocumentTreeController(QObject):
     def _edit_interface(self, component: Component) -> None:
         dialog = self.interface_editor_factory(
             component.interface.ports,
+            {port_id: self.document.port_metadata(port_id) for port_id in component.interface.ports},
             self.window,
         )
         if dialog.exec() == QDialog.DialogCode.Accepted:
-            self.document.update_component_ports(component, dialog.ports())
+            self.document.update_component_ports(component, dialog.ports(), dialog.port_metadata())
 
     def _edit_params(self, component: Component) -> None:
         dialog = self.param_editor_factory(

src/bedit_gui/controllers/library_controller.py

@@ -0,0 +1,81 @@
+from PySide6.QtCore import QObject, QSize, Qt
+from PySide6.QtWidgets import QAbstractItemView, QHeaderView
+
+from bedit_core.models import Component, ComponentID, GraphImplementation, PortID
+from bedit_gui.models import Icon, IconDatabase, PortMetadata, PortMetadataDatabase
+from bedit_gui.services.application_settings import ApplicationSettings
+from bedit_gui.services.component_clipboard import export_component_data
+from bedit_gui.services.libraries import load_library_documents
+from bedit_gui.utils.icon import render_fitted_icon
+from bedit_gui.views.main_window import MainWindow
+from bedit_gui.views.models.library_tree_model import LibraryTreeModel
+
+ICON_SIZE = QSize(32, 32)
+
+
+class LibraryController(QObject):
+    def __init__(self, window: MainWindow, settings: ApplicationSettings) -> None:
+        super().__init__(window)
+        self.window = window
+        self.settings = settings
+        self._component_sources: dict[int, tuple[ComponentID, dict[ComponentID, Icon], dict[PortID, PortMetadata]]] = {}
+        self.model = LibraryTreeModel(self._component_payload)
+
+        tree = window.ui.libraryTree
+        tree.setModel(self.model)
+        tree.setHeaderHidden(True)
+        tree.setSelectionMode(QAbstractItemView.SelectionMode.ExtendedSelection)
+        tree.setSelectionBehavior(QAbstractItemView.SelectionBehavior.SelectRows)
+        tree.setDragEnabled(True)
+        tree.setDragDropMode(QAbstractItemView.DragDropMode.DragOnly)
+        tree.setDefaultDropAction(Qt.DropAction.CopyAction)
+        tree.setIconSize(QSize(48, 48))
+        tree.header().setStretchLastSection(False)
+        tree.header().setSectionResizeMode(0, QHeaderView.ResizeMode.Stretch)
+        tree.header().setSectionResizeMode(1, QHeaderView.ResizeMode.Fixed)
+        tree.setColumnWidth(1, 56)
+
+        window.ui.actionReload_Libraries.triggered.connect(self.reload)
+        self.reload()
+
+    def reload(self) -> None:
+        libraries = load_library_documents(self.settings.library_paths)
+        self._component_sources = {}
+        for library in libraries:
+            database = library.document.metadata.get("icon_database") if library.document.metadata is not None else None
+            icons = database.icons if isinstance(database, IconDatabase) else {}
+            metadata_database = library.document.metadata.get("port_metadata_database") if library.document.metadata is not None else None
+            port_metadata = metadata_database.ports if isinstance(metadata_database, PortMetadataDatabase) else {}
+            self._collect_component_sources(library.document.root, icons, port_metadata)
+        self.model.set_documents([library.document for library in libraries])
+        for library in libraries:
+            database = library.document.metadata.get("icon_database") if library.document.metadata is not None else None
+            icons = database.icons if isinstance(database, IconDatabase) else {}
+            self._set_component_icons(library.document.root, icons)
+        self.window.ui.libraryTree.expandAll()
+
+    def _component_payload(self, components: list[Component]) -> dict:
+        roots = {}
+        icons = {}
+        port_metadata = {}
+        for component in components:
+            source = self._component_sources.get(id(component))
+            if source is None:
+                continue
+            component_id, source_icons, source_port_metadata = source
+            roots[component_id] = component
+            icons.update(source_icons)
+            port_metadata.update(source_port_metadata)
+        return export_component_data(roots, icons, port_metadata)
+
+    def _collect_component_sources(self, components: dict[ComponentID, Component], icons: dict[ComponentID, Icon], port_metadata: dict[PortID, PortMetadata]) -> None:
+        for component_id, component in components.items():
+            self._component_sources[id(component)] = (component_id, icons, port_metadata)
+            if isinstance(component.implementation, GraphImplementation):
+                self._collect_component_sources(component.implementation.graph.components, icons, port_metadata)
+
+    def _set_component_icons(self, components: dict[ComponentID, Component], icons: dict[ComponentID, Icon]) -> None:
+        for component_id, component in components.items():
+            self.model.set_component_icon(component_id, render_fitted_icon(icons.get(component_id, Icon()), component.interface.ports, ICON_SIZE))
+            if isinstance(component.implementation, GraphImplementation):
+                self._set_component_icons(component.implementation.graph.components, icons)

src/bedit_gui/controllers/log_controller.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import logging
 
 from PySide6.QtCore import QObject, Signal
+from PySide6.QtWidgets import QAbstractItemView
 
 from bedit_gui.services.application_logging import configure_logging
 from bedit_gui.views.main_window import MainWindow
@@ -49,4 +50,6 @@ class LogController(QObject):
         self.emitter.message.connect(self.model.append)
         self.model.rowsInserted.connect(window.ui.listView.scrollToBottom)
         window.ui.listView.setModel(self.model)
+        window.ui.listView.setWordWrap(True)
+        window.ui.listView.setVerticalScrollMode(QAbstractItemView.ScrollMode.ScrollPerPixel)
         configure_logging(self.handler, level)

src/bedit_gui/controllers/settings_controller.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 from collections.abc import Callable
 from typing import Protocol
 
-from PySide6.QtCore import QObject
+from PySide6.QtCore import QObject, Signal
 from PySide6.QtWidgets import QDialog
 
 from bedit_gui.services.application_logging import get_logger, set_log_level
@@ -18,15 +18,23 @@ class SettingsDialogLike(Protocol):
     @property
     def log_level(self) -> int: ...
 
+    @property
+    def snap_to_grid_size(self) -> int: ...
+
+    @property
+    def library_paths(self) -> list[str]: ...
+
     def exec(self) -> int: ...
 
 
-SettingsDialogFactory = Callable[[int, MainWindow], SettingsDialogLike]
+SettingsDialogFactory = Callable[[int, int, list[str], MainWindow], SettingsDialogLike]
 
 
 class SettingsController(QObject):
     """Opens the settings dialog and applies accepted preferences."""
 
+    library_paths_changed = Signal()
+
     def __init__(
         self,
         window: MainWindow,
@@ -41,10 +49,16 @@ class SettingsController(QObject):
         window.ui.actionSettings.triggered.connect(self.open_settings)
 
     def open_settings(self) -> None:
-        dialog = self.dialog_factory(self.settings.log_level, self.window)
+        dialog = self.dialog_factory(self.settings.log_level, self.settings.snap_to_grid_size, self.settings.library_paths, self.window)
         if dialog.exec() != QDialog.DialogCode.Accepted:
             return
 
+        old_library_paths = self.settings.library_paths
         self.settings.log_level = dialog.log_level
+        self.settings.snap_to_grid_size = dialog.snap_to_grid_size
+        self.settings.library_paths = dialog.library_paths
+        self.window.graph_editor.set_snap_to_grid_size(dialog.snap_to_grid_size)
         set_log_level(dialog.log_level)
+        if self.settings.library_paths != old_library_paths:
+            self.library_paths_changed.emit()
         logger.info("Application settings updated")

src/bedit_gui/controllers/simulation_controller.py

@@ -62,9 +62,10 @@ class SimulationController(QObject):
         self.window.statusBar().showMessage(f"Compiling {component_path}…")
         logger.info("Compiling model: %s", component_path)
         try:
+            self.document.infer_causality(component)
             build = self.compiler(component, build_directory)
         except (OSError, RuntimeError, ValueError) as exc:
-            logger.exception("Could not compile model %s", component_path)
+            logger.error("Could not compile model %s:\n%s", component_path, exc)
             QMessageBox.critical(self.window, "Could not compile", str(exc))
             self.window.statusBar().showMessage("Compilation failed")
             return None

src/bedit_gui/documents/document.py

@@ -6,17 +6,24 @@ from pathlib import Path
 from PySide6.QtCore import QObject, Signal
 from PySide6.QtGui import QUndoStack
 
-from bedit_core.models import ID, Component, ComponentID, GraphImplementation, Port, PortID, Parameter, ParameterID
+from bedit_core.models import ID, Component, ComponentID, Connection, ConnectionID, GraphImplementation, Port, PortID, Parameter, ParameterID
 from bedit_core.models import Document as CoreDocument
+from bedit_core.bondgraph import causality_inference
+from bedit_gui.commands.causality_command import ChangeCausalityCommand, causality_state
 from bedit_gui.commands.change_icon_command import ChangeIconCommand
 from bedit_gui.commands.equation_text_command import ChangeEquationTextCommand
+from bedit_gui.commands.graph_position_command import MoveGraphComponentCommand
+from bedit_gui.commands.graph_connection_points_command import ChangeGraphConnectionPointsCommand
+from bedit_gui.commands.graph_connection_command import AddGraphConnectionCommand, DeleteGraphConnectionCommand
+from bedit_gui.commands.graph_label_command import ChangeGraphComponentLabelCommand
 from bedit_gui.commands.port_commands import AddPortCommand, ChangePortCommand, RemovePortCommand
+from bedit_gui.commands.port_metadata_command import ChangePortMetadataDatabaseCommand
 from bedit_gui.commands.param_commands import AddParamCommand, ChangeParamCommand, RemoveParamCommand
 from bedit_gui.commands.rename_component_command import RenameComponentCommand
 from bedit_gui.commands.rename_document_command import RenameDocumentCommand
 from bedit_gui.commands.simulation_database_command import ChangeSimulationDatabaseCommand
 from bedit_gui.commands.component_command import AddEmptyEquationComponent, AddEmptyGraphComponent, DeleteComponent, PasteComponents
-from bedit_gui.models import Icon, IconDatabase, Simulation, SimulationDatabase
+from bedit_gui.models import Graph, GraphComponentLabel, GraphConnection, GraphDatabase, Icon, IconDatabase, PortMetadata, PortMetadataDatabase, Simulation, SimulationDatabase
 from bedit_gui.services import document_files
 
 
@@ -29,6 +36,10 @@ class Document(QObject):
     icon_changed = Signal(object, object)
     equation_text_changed = Signal(object, str)
     simulation_database_changed = Signal(object)
+    port_metadata_database_changed = Signal(object)
+    graph_component_position_changed = Signal(object, object, object)
+    graph_component_label_changed = Signal(object, object, object)
+    graph_connection_points_changed = Signal(object, object, object)
 
     def __init__(self, parent: QObject | None = None) -> None:
         super().__init__(parent)
@@ -98,6 +109,12 @@ class Document(QObject):
     def rename_component(self, component: Component, name: str) -> None:
         self.undo_stack.push(RenameComponentCommand(self, component, name))
 
+    def infer_causality(self, component: Component) -> None:
+        inferred_component = deepcopy(component)
+        causality_inference(inferred_component)
+        if causality_state(component) != causality_state(inferred_component):
+            self.undo_stack.push(ChangeCausalityCommand(self, component, inferred_component))
+
     def component_id(self, component: Component) -> ComponentID:
         def find(components: dict[ComponentID, Component]) -> ComponentID | None:
             for component_id, candidate in components.items():
@@ -121,6 +138,152 @@ class Document(QObject):
     def component_icon(self, component_id: ComponentID) -> Icon:
         return self.stored_component_icon(component_id) or Icon()
 
+    def graph_database(self) -> GraphDatabase:
+        database = self._graph_database(False)
+        return deepcopy(database) if database is not None else GraphDatabase()
+
+    def stored_port_metadata_database(self) -> PortMetadataDatabase | None:
+        database = self._port_metadata_database(False)
+        return deepcopy(database) if database is not None else None
+
+    def port_metadata_database(self) -> PortMetadataDatabase:
+        return self.stored_port_metadata_database() or PortMetadataDatabase()
+
+    def port_metadata(self, port_id: PortID) -> PortMetadata:
+        return deepcopy(self.port_metadata_database().ports.get(port_id, PortMetadata()))
+
+    def _set_port_metadata_database(self, database: PortMetadataDatabase | None) -> None:
+        if database is None or not database.ports:
+            if self.model.metadata is not None:
+                self.model.metadata.pop("port_metadata_database", None)
+        else:
+            if self.model.metadata is None:
+                self.model.metadata = {}
+            self.model.metadata["port_metadata_database"] = deepcopy(database)
+        self.port_metadata_database_changed.emit(self.stored_port_metadata_database())
+
+    def _port_metadata_database(self, create: bool) -> PortMetadataDatabase | None:
+        metadata = self.model.metadata
+        value = metadata.get("port_metadata_database") if metadata is not None else None
+        if isinstance(value, PortMetadataDatabase):
+            return value
+        if not create:
+            return None
+        if metadata is None:
+            metadata = {}
+            self.model.metadata = metadata
+        database = PortMetadataDatabase()
+        metadata["port_metadata_database"] = database
+        return database
+
+    def move_graph_component(self, graph_component: Component, component_id: ComponentID, position: tuple[int, int]) -> None:
+        graph_id = self.component_id(graph_component)
+        database = self._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        if graph is None or graph.component_positions.get(component_id) != position:
+            self.undo_stack.push(MoveGraphComponentCommand(self, graph_id, component_id, position))
+
+    def move_graph_components(self, graph_component: Component, positions: dict[ComponentID, tuple[int, int]]) -> None:
+        graph_id = self.component_id(graph_component)
+        database = self._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        changed = {component_id: position for component_id, position in positions.items() if graph is None or graph.component_positions.get(component_id) != position}
+        if not changed:
+            return
+        self.undo_stack.beginMacro("Move graph components" if len(changed) > 1 else "Move graph component")
+        for component_id, position in changed.items():
+            self.undo_stack.push(MoveGraphComponentCommand(self, graph_id, component_id, position))
+        self.undo_stack.endMacro()
+
+    def _set_graph_component_position(self, graph_id: ComponentID, component_id: ComponentID, position: tuple[int, int] | None) -> None:
+        if position is None:
+            database = self._graph_database(False)
+            graph = database.graphs.get(graph_id) if database is not None else None
+            if graph is not None:
+                graph.component_positions.pop(component_id, None)
+        else:
+            database = self._graph_database(True)
+            graph = database.graphs.setdefault(graph_id, Graph())
+            graph.component_positions[component_id] = position
+        self.graph_component_position_changed.emit(graph_id, component_id, position)
+
+    def move_graph_component_label(self, graph_component: Component, component_id: ComponentID, relative_position: tuple[int, int]) -> None:
+        graph_id = self.component_id(graph_component)
+        database = self._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        current = deepcopy(graph.component_labels.get(component_id)) if graph is not None and component_id in graph.component_labels else GraphComponentLabel()
+        if current.relative_position != relative_position:
+            current.relative_position = relative_position
+            self.undo_stack.push(ChangeGraphComponentLabelCommand(self, graph_id, component_id, current, "Move component label"))
+
+    def set_graph_component_label_visible(self, graph_component: Component, component_id: ComponentID, visible: bool) -> None:
+        graph_id = self.component_id(graph_component)
+        database = self._graph_database(False)
+        graph = database.graphs.get(graph_id) if database is not None else None
+        current = deepcopy(graph.component_labels.get(component_id)) if graph is not None and component_id in graph.component_labels else GraphComponentLabel()
+        if current.visible != visible:
+            current.visible = visible
+            self.undo_stack.push(ChangeGraphComponentLabelCommand(self, graph_id, component_id, current, "Show component label" if visible else "Hide component label"))
+
+    def _set_graph_component_label(self, graph_id: ComponentID, component_id: ComponentID, label: GraphComponentLabel | None) -> None:
+        if label is None:
+            database = self._graph_database(False)
+            graph = database.graphs.get(graph_id) if database is not None else None
+            if graph is not None:
+                graph.component_labels.pop(component_id, None)
+        else:
+            database = self._graph_database(True)
+            graph = database.graphs.setdefault(graph_id, Graph())
+            graph.component_labels[component_id] = deepcopy(label)
+        self.graph_component_label_changed.emit(graph_id, component_id, deepcopy(label))
+
+    def _graph_database(self, create: bool) -> GraphDatabase | None:
+        metadata = self.model.metadata
+        value = metadata.get("graph_database") if metadata is not None else None
+        if isinstance(value, dict):
+            value = GraphDatabase.from_data(value)
+            metadata["graph_database"] = value
+        if isinstance(value, GraphDatabase):
+            return value
+        if not create:
+            return None
+        if metadata is None:
+            metadata = {}
+            self.model.metadata = metadata
+        database = GraphDatabase()
+        metadata["graph_database"] = database
+        return database
+
+    def change_graph_connection_points(self, graph_component: Component, connection_id: ConnectionID, points: list[tuple[int, int]], text: str) -> None:
+        graph_id = self.component_id(graph_component)
+        self.undo_stack.push(ChangeGraphConnectionPointsCommand(self, graph_id, connection_id, points, text))
+
+    def add_graph_connection(self, graph_component: Component, connection: Connection) -> None:
+        self.undo_stack.push(AddGraphConnectionCommand(self, graph_component, connection))
+
+    def delete_graph_connections(self, graph_component: Component, connection_ids: list[ConnectionID]) -> None:
+        if not isinstance(graph_component.implementation, GraphImplementation):
+            return
+        connection_ids = [connection_id for connection_id in connection_ids if connection_id in graph_component.implementation.graph.connections]
+        if not connection_ids:
+            return
+        self.undo_stack.beginMacro("Delete connections")
+        for connection_id in connection_ids:
+            self.undo_stack.push(DeleteGraphConnectionCommand(self, graph_component, connection_id))
+        self.undo_stack.endMacro()
+
+    def _set_graph_connection_points(self, graph_id: ComponentID, connection_id: ConnectionID, points: list[tuple[int, int]] | None) -> None:
+        if points is None:
+            database = self._graph_database(False)
+            graph = database.graphs.get(graph_id) if database is not None else None
+            if graph is not None:
+                graph.connections.pop(connection_id, None)
+        else:
+            database = self._graph_database(True)
+            graph = database.graphs.setdefault(graph_id, Graph())
+            graph.connections[connection_id] = GraphConnection(points=list(points))
+        self.graph_connection_points_changed.emit(graph_id, connection_id, points)
+
     def change_icon(self, component_id: ComponentID, icon: Icon) -> None:
         self.undo_stack.push(ChangeIconCommand(self, component_id, icon))
 
@@ -194,7 +357,7 @@ class Document(QObject):
         metadata["icon_database"] = database
         return database
 
-    def update_component_ports(self, component: Component, ports: dict[PortID, Port]) -> None:
+    def update_component_ports(self, component: Component, ports: dict[PortID, Port], port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
         current = component.interface.ports
         removed = [
             RemovePortCommand(self, component, port_id)
@@ -210,12 +373,23 @@ class Document(QObject):
             if current[port_id] != ports[port_id]
         ]
         commands = [*removed, *added, *changed]
-        if not commands:
+        database = self.port_metadata_database()
+        component_port_ids = set(current) | set(ports)
+        for port_id in component_port_ids:
+            metadata = port_metadata.get(port_id, PortMetadata()) if port_metadata is not None and port_id in ports else PortMetadata()
+            if metadata == PortMetadata():
+                database.ports.pop(port_id, None)
+            else:
+                database.ports[port_id] = deepcopy(metadata)
+        metadata_changed = database != self.port_metadata_database()
+        if not commands and not metadata_changed:
             return
 
         self.undo_stack.beginMacro("Edit interface")
         for command in commands:
             self.undo_stack.push(command)
+        if metadata_changed:
+            self.undo_stack.push(ChangePortMetadataDatabaseCommand(self, database))
         self.undo_stack.endMacro()
 
 
@@ -254,12 +428,22 @@ class Document(QObject):
             command.component.name = self._unique_component_name(component.implementation.graph.components, command.component.name)
             self.undo_stack.push(command)
 
+    def add_empty_root_graph_component(self) -> None:
+        command = AddEmptyGraphComponent(self, self.model.root)
+        command.component.name = self._unique_component_name(self.model.root, command.component.name)
+        self.undo_stack.push(command)
+
     def add_empty_equation_component(self, component: Component) -> None:
         if isinstance(component.implementation, GraphImplementation):
             command = AddEmptyEquationComponent(self, component)
             command.component.name = self._unique_component_name(component.implementation.graph.components, command.component.name)
             self.undo_stack.push(command)
 
+    def add_empty_root_equation_component(self) -> None:
+        command = AddEmptyEquationComponent(self, self.model.root)
+        command.component.name = self._unique_component_name(self.model.root, command.component.name)
+        self.undo_stack.push(command)
+
     def delete_component(self, component: Component) -> None:
         self.undo_stack.push(DeleteComponent(self, component))
 
@@ -271,14 +455,24 @@ class Document(QObject):
             self.undo_stack.push(DeleteComponent(self, component))
         self.undo_stack.endMacro()
 
-    def paste_components(self, target: dict[ComponentID, Component], components: dict[ComponentID, Component], icons: dict[ComponentID, Icon]) -> None:
+    def paste_components(self, target: dict[ComponentID, Component], components: dict[ComponentID, Component], icons: dict[ComponentID, Icon], port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
         if not components:
             return
         names = {component.name for component in target.values()}
         for component in components.values():
             component.name = self._unique_name(names, component.name)
             names.add(component.name)
-        self.undo_stack.push(PasteComponents(self, target, components, icons))
+        self.undo_stack.push(PasteComponents(self, target, components, icons, port_metadata=port_metadata))
+
+    def paste_graph_components(self, graph_component: Component, components: dict[ComponentID, Component], icons: dict[ComponentID, Icon], positions: dict[ComponentID, tuple[int, int]], port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
+        if not isinstance(graph_component.implementation, GraphImplementation) or not components:
+            return
+        target = graph_component.implementation.graph.components
+        names = {component.name for component in target.values()}
+        for component in components.values():
+            component.name = self._unique_name(names, component.name)
+            names.add(component.name)
+        self.undo_stack.push(PasteComponents(self, target, components, icons, self.component_id(graph_component), positions, port_metadata))
 
     @staticmethod
     def _unique_component_name(components: dict[ComponentID, Component], name: str) -> str:

src/bedit_gui/models.py

@@ -5,7 +5,7 @@ from dataclasses import dataclass, field
 from enum import Enum
 from typing import Any
 
-from bedit_core.models import ComponentID, ID, PortID
+from bedit_core.models import ComponentID, ConnectionID, ID, PortID
 
 
 class ShapeID(ID):
@@ -24,6 +24,8 @@ class Shape:
     def from_data(cls, data: Mapping[str, Any]) -> Shape:
         if cls is Shape and data.get("type") == "rectangle":
             return Rectangle.from_data(data)
+        if cls is Shape and data.get("type") == "ellipse":
+            return Ellipse.from_data(data)
         if cls is Shape and data.get("type") == "text":
             return Text.from_data(data)
         if cls is Shape and data.get("type") == "line":
@@ -77,6 +79,24 @@ class Rectangle(Shape):
     def to_data(self) -> dict[str, Any]:
         return {**super().to_data(), "width": self.width, "height": self.height, "line_type": self.line_type.value, "line_thickness": self.line_thickness, "corner_radius": self.corner_radius, "line_color": self.line_color, "fill_color": self.fill_color}
 
+@dataclass
+class Ellipse(Shape):
+    type: str = field(init=False, default="ellipse")
+    width: float = 32.0
+    height: float = 32.0
+    line_type: LineType = LineType.SOLID
+    line_thickness: float = 1.0
+    line_color: str = "#000000ff"
+    fill_color: str = "#ffffff00"
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> Ellipse:
+        pos = data.get("pos", [0, 0])
+        return cls(layer=int(data.get("layer", 0)), pos=(int(pos[0]), int(pos[1])), width=float(data.get("width", 100.0)), height=float(data.get("height", 100.0)), line_type=LineType(data.get("line_type", "solid")), line_thickness=float(data.get("line_thickness", 1.0)), line_color=str(data.get("line_color", "#000000ff")), fill_color=str(data.get("fill_color", "#ffffff00")))
+
+    def to_data(self) -> dict[str, Any]:
+        return {**super().to_data(), "width": self.width, "height": self.height, "line_type": self.line_type.value, "line_thickness": self.line_thickness, "line_color": self.line_color, "fill_color": self.fill_color}
+
 @dataclass
 class Text(Shape):
     type: str = field(init=False, default="text")
@@ -123,6 +143,91 @@ class IconDatabase:
     def to_data(self) -> dict[str, Any]:
         return {"format_version": self.format_version, "icons": {str(key): icon.to_data() for key, icon in self.icons.items()}}
 
+@dataclass
+class PortMetadata:
+    connection_annotation: str | None = None
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> PortMetadata:
+        annotation = data.get("connection_annotation")
+        return cls(connection_annotation=str(annotation) if annotation else None)
+
+    def to_data(self) -> dict[str, Any]:
+        return {"connection_annotation": self.connection_annotation}
+
+@dataclass
+class PortMetadataDatabase:
+    format_version: int = 1
+    ports: dict[PortID, PortMetadata] = field(default_factory=dict)
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> PortMetadataDatabase:
+        ports = {PortID(key): PortMetadata.from_data(value) for key, value in data.get("ports", {}).items()}
+        return cls(format_version=int(data.get("format_version", 1)), ports=ports)
+
+    def to_data(self) -> dict[str, Any]:
+        return {"format_version": self.format_version, "ports": {str(key): metadata.to_data() for key, metadata in self.ports.items()}}
+
+@dataclass
+class GraphConnection:
+    points: list[tuple[int, int]] = field(default_factory=list)
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> GraphConnection:
+        return cls(points=[(int(point[0]), int(point[1])) for point in data.get("points", [])])
+
+    def to_data(self) -> dict[str, Any]:
+        return {"points": [list(point) for point in self.points]}
+
+@dataclass
+class GraphComponentLabel:
+    relative_position: tuple[int, int] = (0, 8)
+    visible: bool = True
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> GraphComponentLabel:
+        position = data.get("relative_position", [0, 8])
+        return cls(relative_position=(int(position[0]), int(position[1])), visible=bool(data.get("visible", True)))
+
+    def to_data(self) -> dict[str, Any]:
+        return {"relative_position": list(self.relative_position), "visible": self.visible}
+
+@dataclass
+class Graph:
+    shapes: dict[ShapeID, Shape] = field(default_factory=dict)
+    component_positions: dict[ComponentID, tuple[int, int]] = field(default_factory=dict)
+    connections: dict[ConnectionID, GraphConnection] = field(default_factory=dict)
+    component_labels: dict[ComponentID, GraphComponentLabel] = field(default_factory=dict)
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> Graph:
+        shapes = {ShapeID(key): Shape.from_data(value) for key, value in data.get("shapes", {}).items()}
+        component_positions = {ComponentID(key): (int(value[0]), int(value[1])) for key, value in data.get("component_positions", {}).items()}
+        component_labels = {ComponentID(key): GraphComponentLabel.from_data(value) for key, value in data.get("component_labels", {}).items()}
+        connections = {ConnectionID(key): GraphConnection.from_data(value) for key, value in data.get("connections", {}).items()}
+        return cls(shapes=shapes, component_positions=component_positions, component_labels=component_labels, connections=connections)
+
+    def to_data(self) -> dict[str, Any]:
+        return {
+            "shapes": {str(key): shape.to_data() for key, shape in self.shapes.items()},
+            "component_positions": {str(key): list(position) for key, position in self.component_positions.items()},
+            "component_labels": {str(key): label.to_data() for key, label in self.component_labels.items()},
+            "connections": {str(key): connection.to_data() for key, connection in self.connections.items()},
+        }
+
+@dataclass
+class GraphDatabase:
+    format_version: int = 1
+    graphs: dict[ComponentID, Graph] = field(default_factory=dict)
+
+    @classmethod
+    def from_data(cls, data: Mapping[str, Any]) -> GraphDatabase:
+        graphs = {ComponentID(key): Graph.from_data(value) for key, value in data.get("graphs", {}).items()}
+        return cls(format_version=int(data.get("format_version", 1)), graphs=graphs)
+
+    def to_data(self) -> dict[str, Any]:
+        return {"format_version": self.format_version, "graphs": {str(key): graph.to_data() for key, graph in self.graphs.items()}}
+
 class SimulationMethod(Enum):
     DASSL = "dassl"
 

src/bedit_gui/services/application_settings.py

@@ -10,6 +10,9 @@ class ApplicationSettings:
 
     LOG_LEVEL_KEY = "logging/level"
     DEFAULT_LOG_LEVEL = logging.INFO
+    SNAP_TO_GRID_SIZE_KEY = "graph/snap_to_grid_size"
+    DEFAULT_SNAP_TO_GRID_SIZE = 4
+    LIBRARY_PATHS_KEY = "libraries/paths"
 
     def __init__(self, settings: QSettings | None = None) -> None:
         self._settings = settings if settings is not None else QSettings()
@@ -26,6 +29,27 @@ class ApplicationSettings:
     def log_level(self, level: int) -> None:
         self._settings.setValue(self.LOG_LEVEL_KEY, level)
 
+    @property
+    def snap_to_grid_size(self) -> int:
+        return max(1, self._settings.value(self.SNAP_TO_GRID_SIZE_KEY, self.DEFAULT_SNAP_TO_GRID_SIZE, type=int))
+
+    @snap_to_grid_size.setter
+    def snap_to_grid_size(self, size: int) -> None:
+        if size < 1:
+            raise ValueError("snap-to-grid size must be positive")
+        self._settings.setValue(self.SNAP_TO_GRID_SIZE_KEY, size)
+
+    @property
+    def library_paths(self) -> list[str]:
+        value = self._settings.value(self.LIBRARY_PATHS_KEY, [])
+        if isinstance(value, str):
+            return [value]
+        return [str(path) for path in value] if isinstance(value, (list, tuple)) else []
+
+    @library_paths.setter
+    def library_paths(self, paths: list[str]) -> None:
+        self._settings.setValue(self.LIBRARY_PATHS_KEY, list(dict.fromkeys(paths)))
+
 class SimulationApplicationSettings:
     """Typed access to persistent BEsim application settings."""
 

src/bedit_gui/services/clipboard.py

@@ -6,9 +6,11 @@ from typing import Any
 from PySide6.QtCore import QMimeData, QObject, Signal
 from PySide6.QtGui import QClipboard, QGuiApplication
 
+from bedit_gui.services.component_clipboard import COMPONENTS_MIME
+
 
 class ClipboardService(QObject):
-    COMPONENTS_MIME = "application/x-bedit-components+json"
+    COMPONENTS_MIME = COMPONENTS_MIME
     changed = Signal()
 
     def __init__(self, parent: QObject | None = None) -> None:

src/bedit_gui/services/component_clipboard.py

@@ -6,24 +6,37 @@ from typing import Any
 from bedit_core.models import Component, ComponentID, ConnectionID, Document, GraphImplementation, ID, ParameterID, PortID
 from bedit_core.serialization.schema import document_from_data, document_to_data
 from bedit_gui.documents import Document as GuiDocument
-from bedit_gui.models import Icon, ShapeID
+from bedit_gui.models import Icon, PortMetadata, ShapeID
 
 FORMAT_VERSION = 1
+COMPONENTS_MIME = "application/x-bedit-components+json"
 
 
 def export_components(document: GuiDocument, components: list[Component]) -> dict[str, Any]:
     roots = {document.component_id(component): component for component in components}
-    serialized = document_to_data(Document(format_version=1, id=ID(), name="Clipboard", root=roots))
     component_ids = _all_component_ids(roots)
     icons = {}
+    port_metadata = {}
     for component_id in component_ids:
         icon = document.stored_component_icon(component_id)
         if icon is not None:
-            icons[str(component_id)] = icon.to_data()
-    return {"format_version": FORMAT_VERSION, "type": "components", "components": serialized["root"], "icons": icons}
+            icons[component_id] = icon
+    database = document.port_metadata_database()
+    for port_id in _all_port_ids(roots):
+        if port_id in database.ports:
+            port_metadata[port_id] = database.ports[port_id]
+    return export_component_data(roots, icons, port_metadata)
 
 
-def import_components(payload: dict[str, Any]) -> tuple[dict[ComponentID, Component], dict[ComponentID, Icon]]:
+def export_component_data(components: dict[ComponentID, Component], icons: dict[ComponentID, Icon], port_metadata: dict[PortID, PortMetadata] | None = None) -> dict[str, Any]:
+    serialized = document_to_data(Document(format_version=1, id=ID(), name="Clipboard", root=components))
+    component_ids = set(_all_component_ids(components))
+    icon_data = {str(component_id): icon.to_data() for component_id, icon in icons.items() if component_id in component_ids}
+    metadata_data = {str(port_id): metadata.to_data() for port_id, metadata in (port_metadata or {}).items() if port_id in set(_all_port_ids(components))}
+    return {"format_version": FORMAT_VERSION, "type": "components", "components": serialized["root"], "icons": icon_data, "port_metadata": metadata_data}
+
+
+def import_components(payload: dict[str, Any]) -> tuple[dict[ComponentID, Component], dict[ComponentID, Icon], dict[PortID, PortMetadata]]:
     if payload.get("format_version") != FORMAT_VERSION or payload.get("type") != "components":
         raise ValueError("unsupported component clipboard format")
     components = payload.get("components")
@@ -45,7 +58,11 @@ def import_components(payload: dict[str, Any]) -> tuple[dict[ComponentID, Compon
         icon.shapes = {ShapeID(): shape for shape in icon.shapes.values()}
         icon.port_positions = {port_map[port_id]: position for port_id, position in icon.port_positions.items() if port_id in port_map}
         icons[new_component_id] = icon
-    return remapped, icons
+    metadata_data = payload.get("port_metadata", {})
+    if not isinstance(metadata_data, dict):
+        raise TypeError("component clipboard port metadata must be an object")
+    port_metadata = {port_map[PortID(old_id)]: PortMetadata.from_data(data) for old_id, data in metadata_data.items() if PortID(old_id) in port_map and isinstance(data, dict)}
+    return remapped, icons, port_metadata
 
 
 def _remap_components(components: dict[ComponentID, Component], component_map: dict[ComponentID, ComponentID], port_map: dict[PortID, PortID]) -> dict[ComponentID, Component]:
@@ -80,3 +97,12 @@ def _all_component_ids(components: dict[ComponentID, Component]) -> list[Compone
         if isinstance(component.implementation, GraphImplementation):
             component_ids.extend(_all_component_ids(component.implementation.graph.components))
     return component_ids
+
+
+def _all_port_ids(components: dict[ComponentID, Component]) -> list[PortID]:
+    port_ids: list[PortID] = []
+    for component in components.values():
+        port_ids.extend(component.interface.ports)
+        if isinstance(component.implementation, GraphImplementation):
+            port_ids.extend(_all_port_ids(component.implementation.graph.components))
+    return port_ids

src/bedit_gui/services/document_files.py

@@ -6,7 +6,7 @@ from pathlib import Path
 from bedit_core.models import Document
 from bedit_core.serialization import load as load_document
 from bedit_core.serialization import save as save_document
-from bedit_gui.models import IconDatabase, SimulationDatabase
+from bedit_gui.models import GraphDatabase, IconDatabase, PortMetadataDatabase, SimulationDatabase
 
 
 def load(path: str | Path) -> Document:
@@ -14,8 +14,12 @@ def load(path: str | Path) -> Document:
     document = load_document(path)
     if document.metadata is not None and isinstance(document.metadata.get("icon_database"), dict):
         document.metadata["icon_database"] = IconDatabase.from_data(document.metadata["icon_database"])
+    if document.metadata is not None and isinstance(document.metadata.get("graph_database"), dict):
+        document.metadata["graph_database"] = GraphDatabase.from_data(document.metadata["graph_database"])
     if document.metadata is not None and isinstance(document.metadata.get("simulation_database"), dict):
         document.metadata["simulation_database"] = SimulationDatabase.from_data(document.metadata["simulation_database"])
+    if document.metadata is not None and isinstance(document.metadata.get("port_metadata_database"), dict):
+        document.metadata["port_metadata_database"] = PortMetadataDatabase.from_data(document.metadata["port_metadata_database"])
     return document
 
 
@@ -24,6 +28,10 @@ def save(document: Document, path: str | Path) -> None:
     saved_document = deepcopy(document)
     if saved_document.metadata is not None and isinstance(saved_document.metadata.get("icon_database"), IconDatabase):
         saved_document.metadata["icon_database"] = saved_document.metadata["icon_database"].to_data()
+    if saved_document.metadata is not None and isinstance(saved_document.metadata.get("graph_database"), GraphDatabase):
+        saved_document.metadata["graph_database"] = saved_document.metadata["graph_database"].to_data()
     if saved_document.metadata is not None and isinstance(saved_document.metadata.get("simulation_database"), SimulationDatabase):
         saved_document.metadata["simulation_database"] = saved_document.metadata["simulation_database"].to_data()
+    if saved_document.metadata is not None and isinstance(saved_document.metadata.get("port_metadata_database"), PortMetadataDatabase):
+        saved_document.metadata["port_metadata_database"] = saved_document.metadata["port_metadata_database"].to_data()
     save_document(saved_document, path)

src/bedit_gui/services/libraries.py

@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+
+from bedit_core.models import Document
+from bedit_gui.services import document_files
+from bedit_gui.services.application_logging import get_logger
+
+logger = get_logger(__name__)
+
+
+@dataclass(frozen=True)
+class LoadedLibrary:
+    path: Path
+    document: Document
+
+
+def list_library_files(library_paths: list[str]) -> list[Path]:
+    files = []
+    seen = set()
+    for configured_path in library_paths:
+        path = Path(configured_path).expanduser()
+        candidates = [path] if path.is_file() else sorted(path.rglob("*"), key=lambda candidate: str(candidate).casefold()) if path.is_dir() else []
+        for candidate in candidates:
+            if not candidate.is_file() or candidate.suffix.lower() not in (".beb", ".json"):
+                continue
+            resolved = candidate.resolve()
+            if resolved not in seen:
+                seen.add(resolved)
+                files.append(resolved)
+    return files
+
+
+def load_library_documents(library_paths: list[str]) -> list[LoadedLibrary]:
+    libraries = []
+    for path in list_library_files(library_paths):
+        try:
+            libraries.append(LoadedLibrary(path, document_files.load(path)))
+        except (KeyError, OSError, TypeError, ValueError) as exc:
+            logger.warning("Could not load library %s: %s", path, exc)
+    return libraries

src/bedit_gui/ui/forms/graph_editor_widget.ui

@@ -40,10 +40,9 @@
      <property name="floatable">
       <bool>false</bool>
      </property>
-     <addaction name="actionSelect"/>
-     <addaction name="actionAddComponent"/>
-     <addaction name="actionAddConnection"/>
-     <addaction name="actionDelete"/>
+     <addaction name="actionZoomToFit"/>
+     <addaction name="actionMouseMode"/>
+     <addaction name="actionConnectionMode"/>
     </widget>
    </item>
    <item>
@@ -51,48 +50,60 @@
      <property name="frameShape">
       <enum>QFrame::Shape::NoFrame</enum>
      </property>
-     <property name="dragMode">
-      <enum>QGraphicsView::DragMode::RubberBandDrag</enum>
-     </property>
      <property name="renderHints">
       <set>QPainter::RenderHint::Antialiasing</set>
      </property>
+     <property name="dragMode">
+      <enum>QGraphicsView::DragMode::RubberBandDrag</enum>
+     </property>
     </widget>
    </item>
   </layout>
-  <action name="actionSelect">
+  <action name="actionZoomToFit">
+   <property name="icon">
+    <iconset resource="../../resources/resources.qrc">
+     <normaloff>:/icons/icons/zoom-original.png</normaloff>:/icons/icons/zoom-original.png</iconset>
+   </property>
    <property name="text">
-    <string>Select</string>
+    <string>Zoom to Fit</string>
    </property>
    <property name="toolTip">
-    <string>Select graph items</string>
+    <string>Zoom canvas to fit</string>
    </property>
   </action>
-  <action name="actionAddComponent">
+  <action name="actionMouseMode">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="../../resources/resources.qrc">
+     <normaloff>:/icons/icons/edit-select.png</normaloff>:/icons/icons/edit-select.png</iconset>
+   </property>
    <property name="text">
-    <string>Add Component</string>
+    <string>Mouse Mode</string>
    </property>
    <property name="toolTip">
-    <string>Add a component</string>
+    <string>Mouse Mode</string>
    </property>
   </action>
-  <action name="actionAddConnection">
+  <action name="actionConnectionMode">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="../../resources/resources.qrc">
+     <normaloff>:/icons/icons/network-connect.png</normaloff>:/icons/icons/network-connect.png</iconset>
+   </property>
    <property name="text">
-    <string>Add Connection</string>
+    <string>Connection Mode</string>
    </property>
    <property name="toolTip">
-    <string>Add a connection</string>
-   </property>
-  </action>
-  <action name="actionDelete">
-   <property name="text">
-    <string>Delete</string>
-   </property>
-   <property name="toolTip">
-    <string>Delete selected graph items</string>
+    <string>Connection Mode</string>
    </property>
   </action>
  </widget>
- <resources/>
+ <resources>
+  <include location="../../resources/resources.qrc"/>
+ </resources>
  <connections/>
 </ui>

src/bedit_gui/ui/forms/graph_editor_widget_ui.py

@@ -0,0 +1,90 @@
+# -*- coding: utf-8 -*-
+
+################################################################################
+## Form generated from reading UI file 'graph_editor_widget.ui'
+##
+## Created by: Qt User Interface Compiler version 6.11.1
+##
+## WARNING! All changes made in this file will be lost when recompiling UI file!
+################################################################################
+
+from PySide6.QtCore import (QCoreApplication, QDate, QDateTime, QLocale,
+    QMetaObject, QObject, QPoint, QRect,
+    QSize, QTime, QUrl, Qt)
+from PySide6.QtGui import (QAction, QBrush, QColor, QConicalGradient,
+    QCursor, QFont, QFontDatabase, QGradient,
+    QIcon, QImage, QKeySequence, QLinearGradient,
+    QPainter, QPalette, QPixmap, QRadialGradient,
+    QTransform)
+from PySide6.QtWidgets import (QApplication, QFrame, QGraphicsView, QSizePolicy,
+    QToolBar, QVBoxLayout, QWidget)
+import resources_rc
+
+class Ui_graphEditorWidget(object):
+    def setupUi(self, graphEditorWidget):
+        if not graphEditorWidget.objectName():
+            graphEditorWidget.setObjectName(u"graphEditorWidget")
+        graphEditorWidget.resize(1079, 730)
+        self.actionZoomToFit = QAction(graphEditorWidget)
+        self.actionZoomToFit.setObjectName(u"actionZoomToFit")
+        icon = QIcon()
+        icon.addFile(u":/icons/icons/zoom-original.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionZoomToFit.setIcon(icon)
+        self.actionMouseMode = QAction(graphEditorWidget)
+        self.actionMouseMode.setObjectName(u"actionMouseMode")
+        self.actionMouseMode.setCheckable(True)
+        icon1 = QIcon()
+        icon1.addFile(u":/icons/icons/edit-select.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionMouseMode.setIcon(icon1)
+        self.actionConnectionMode = QAction(graphEditorWidget)
+        self.actionConnectionMode.setObjectName(u"actionConnectionMode")
+        self.actionConnectionMode.setCheckable(True)
+        icon2 = QIcon()
+        icon2.addFile(u":/icons/icons/network-connect.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionConnectionMode.setIcon(icon2)
+        self.verticalLayout = QVBoxLayout(graphEditorWidget)
+        self.verticalLayout.setSpacing(0)
+        self.verticalLayout.setObjectName(u"verticalLayout")
+        self.verticalLayout.setContentsMargins(0, 0, 0, 0)
+        self.graphToolBar = QToolBar(graphEditorWidget)
+        self.graphToolBar.setObjectName(u"graphToolBar")
+        self.graphToolBar.setMovable(False)
+        self.graphToolBar.setFloatable(False)
+
+        self.verticalLayout.addWidget(self.graphToolBar)
+
+        self.graphicsView = QGraphicsView(graphEditorWidget)
+        self.graphicsView.setObjectName(u"graphicsView")
+        self.graphicsView.setFrameShape(QFrame.Shape.NoFrame)
+        self.graphicsView.setRenderHints(QPainter.RenderHint.Antialiasing)
+        self.graphicsView.setDragMode(QGraphicsView.DragMode.RubberBandDrag)
+
+        self.verticalLayout.addWidget(self.graphicsView)
+
+
+        self.graphToolBar.addAction(self.actionZoomToFit)
+        self.graphToolBar.addAction(self.actionMouseMode)
+        self.graphToolBar.addAction(self.actionConnectionMode)
+
+        self.retranslateUi(graphEditorWidget)
+
+        QMetaObject.connectSlotsByName(graphEditorWidget)
+    # setupUi
+
+    def retranslateUi(self, graphEditorWidget):
+        graphEditorWidget.setWindowTitle(QCoreApplication.translate("graphEditorWidget", u"Graph Editor", None))
+        self.actionZoomToFit.setText(QCoreApplication.translate("graphEditorWidget", u"Zoom to Fit", None))
+#if QT_CONFIG(tooltip)
+        self.actionZoomToFit.setToolTip(QCoreApplication.translate("graphEditorWidget", u"Zoom canvas to fit", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionMouseMode.setText(QCoreApplication.translate("graphEditorWidget", u"Mouse Mode", None))
+#if QT_CONFIG(tooltip)
+        self.actionMouseMode.setToolTip(QCoreApplication.translate("graphEditorWidget", u"Mouse Mode", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionConnectionMode.setText(QCoreApplication.translate("graphEditorWidget", u"Connection Mode", None))
+#if QT_CONFIG(tooltip)
+        self.actionConnectionMode.setToolTip(QCoreApplication.translate("graphEditorWidget", u"Connection Mode", None))
+#endif // QT_CONFIG(tooltip)
+        self.graphToolBar.setWindowTitle(QCoreApplication.translate("graphEditorWidget", u"Graph tools", None))
+    # retranslateUi
+

src/bedit_gui/ui/forms/icon_editor_window.ui

@@ -30,7 +30,7 @@
      <x>0</x>
      <y>0</y>
      <width>800</width>
-     <height>22</height>
+     <height>19</height>
     </rect>
    </property>
    <widget class="QMenu" name="menuEdit">
@@ -80,6 +80,7 @@
     <bool>false</bool>
    </attribute>
    <addaction name="actionAdd_Rectangle"/>
+   <addaction name="actionAdd_Circle"/>
    <addaction name="actionAdd_Text"/>
    <addaction name="actionAdd_Line"/>
   </widget>
@@ -236,6 +237,21 @@
     <enum>QAction::MenuRole::NoRole</enum>
    </property>
   </action>
+  <action name="actionAdd_Circle">
+   <property name="icon">
+    <iconset resource="../../resources/resources.qrc">
+     <normaloff>:/icons/icons/draw-circle.png</normaloff>:/icons/icons/draw-circle.png</iconset>
+   </property>
+   <property name="text">
+    <string>Add Ellipse</string>
+   </property>
+   <property name="toolTip">
+    <string>Add a circle</string>
+   </property>
+   <property name="menuRole">
+    <enum>QAction::MenuRole::NoRole</enum>
+   </property>
+  </action>
  </widget>
  <resources>
   <include location="../../resources/resources.qrc"/>

src/bedit_gui/ui/forms/icon_editor_window_ui.py

@@ -0,0 +1,206 @@
+# -*- coding: utf-8 -*-
+
+################################################################################
+## Form generated from reading UI file 'icon_editor_window.ui'
+##
+## Created by: Qt User Interface Compiler version 6.11.1
+##
+## WARNING! All changes made in this file will be lost when recompiling UI file!
+################################################################################
+
+from PySide6.QtCore import (QCoreApplication, QDate, QDateTime, QLocale,
+    QMetaObject, QObject, QPoint, QRect,
+    QSize, QTime, QUrl, Qt)
+from PySide6.QtGui import (QAction, QBrush, QColor, QConicalGradient,
+    QCursor, QFont, QFontDatabase, QGradient,
+    QIcon, QImage, QKeySequence, QLinearGradient,
+    QPainter, QPalette, QPixmap, QRadialGradient,
+    QTransform)
+from PySide6.QtWidgets import (QApplication, QGraphicsView, QMainWindow, QMenu,
+    QMenuBar, QSizePolicy, QStatusBar, QToolBar,
+    QVBoxLayout, QWidget)
+import resources_rc
+
+class Ui_iconEditor(object):
+    def setupUi(self, iconEditor):
+        if not iconEditor.objectName():
+            iconEditor.setObjectName(u"iconEditor")
+        iconEditor.resize(800, 600)
+        icon = QIcon()
+        icon.addFile(u":/icons/icons/draw-path.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        iconEditor.setWindowIcon(icon)
+        self.actionUndo = QAction(iconEditor)
+        self.actionUndo.setObjectName(u"actionUndo")
+        icon1 = QIcon()
+        icon1.addFile(u":/icons/icons/edit-undo.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionUndo.setIcon(icon1)
+        self.actionUndo.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionRedo = QAction(iconEditor)
+        self.actionRedo.setObjectName(u"actionRedo")
+        icon2 = QIcon()
+        icon2.addFile(u":/icons/icons/edit-redo.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionRedo.setIcon(icon2)
+        self.actionRedo.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionSave = QAction(iconEditor)
+        self.actionSave.setObjectName(u"actionSave")
+        icon3 = QIcon()
+        icon3.addFile(u":/icons/icons/document-save.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionSave.setIcon(icon3)
+        self.actionSave.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionCancel = QAction(iconEditor)
+        self.actionCancel.setObjectName(u"actionCancel")
+        icon4 = QIcon()
+        icon4.addFile(u":/icons/icons/dialog-close.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionCancel.setIcon(icon4)
+        self.actionCancel.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionAdd_Rectangle = QAction(iconEditor)
+        self.actionAdd_Rectangle.setObjectName(u"actionAdd_Rectangle")
+        icon5 = QIcon()
+        icon5.addFile(u":/icons/icons/draw-rectangle.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionAdd_Rectangle.setIcon(icon5)
+        self.actionAdd_Rectangle.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionAdd_Text = QAction(iconEditor)
+        self.actionAdd_Text.setObjectName(u"actionAdd_Text")
+        icon6 = QIcon()
+        icon6.addFile(u":/icons/icons/draw-text.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionAdd_Text.setIcon(icon6)
+        self.actionAdd_Text.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionSave_to_File = QAction(iconEditor)
+        self.actionSave_to_File.setObjectName(u"actionSave_to_File")
+        icon7 = QIcon()
+        icon7.addFile(u":/icons/icons/document-save-as.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionSave_to_File.setIcon(icon7)
+        self.actionSave_to_File.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionOpen_from_File = QAction(iconEditor)
+        self.actionOpen_from_File.setObjectName(u"actionOpen_from_File")
+        icon8 = QIcon()
+        icon8.addFile(u":/icons/icons/document-open.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionOpen_from_File.setIcon(icon8)
+        self.actionOpen_from_File.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionAdd_Line = QAction(iconEditor)
+        self.actionAdd_Line.setObjectName(u"actionAdd_Line")
+        self.actionAdd_Line.setIcon(icon)
+        self.actionAdd_Line.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionAdd_Circle = QAction(iconEditor)
+        self.actionAdd_Circle.setObjectName(u"actionAdd_Circle")
+        icon9 = QIcon()
+        icon9.addFile(u":/icons/icons/draw-circle.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionAdd_Circle.setIcon(icon9)
+        self.actionAdd_Circle.setMenuRole(QAction.MenuRole.NoRole)
+        self.centralwidget = QWidget(iconEditor)
+        self.centralwidget.setObjectName(u"centralwidget")
+        self.verticalLayout = QVBoxLayout(self.centralwidget)
+        self.verticalLayout.setObjectName(u"verticalLayout")
+        self.graphicsView = QGraphicsView(self.centralwidget)
+        self.graphicsView.setObjectName(u"graphicsView")
+
+        self.verticalLayout.addWidget(self.graphicsView)
+
+        iconEditor.setCentralWidget(self.centralwidget)
+        self.menubar = QMenuBar(iconEditor)
+        self.menubar.setObjectName(u"menubar")
+        self.menubar.setGeometry(QRect(0, 0, 800, 19))
+        self.menuEdit = QMenu(self.menubar)
+        self.menuEdit.setObjectName(u"menuEdit")
+        self.menuFile = QMenu(self.menubar)
+        self.menuFile.setObjectName(u"menuFile")
+        iconEditor.setMenuBar(self.menubar)
+        self.statusbar = QStatusBar(iconEditor)
+        self.statusbar.setObjectName(u"statusbar")
+        iconEditor.setStatusBar(self.statusbar)
+        self.actionToolbar = QToolBar(iconEditor)
+        self.actionToolbar.setObjectName(u"actionToolbar")
+        iconEditor.addToolBar(Qt.ToolBarArea.TopToolBarArea, self.actionToolbar)
+        self.iconToolbar = QToolBar(iconEditor)
+        self.iconToolbar.setObjectName(u"iconToolbar")
+        iconEditor.addToolBar(Qt.ToolBarArea.TopToolBarArea, self.iconToolbar)
+
+        self.menubar.addAction(self.menuFile.menuAction())
+        self.menubar.addAction(self.menuEdit.menuAction())
+        self.menuEdit.addAction(self.actionUndo)
+        self.menuEdit.addAction(self.actionRedo)
+        self.menuFile.addAction(self.actionOpen_from_File)
+        self.menuFile.addAction(self.actionSave_to_File)
+        self.menuFile.addSeparator()
+        self.menuFile.addAction(self.actionSave)
+        self.menuFile.addAction(self.actionCancel)
+        self.actionToolbar.addAction(self.actionUndo)
+        self.actionToolbar.addAction(self.actionRedo)
+        self.actionToolbar.addAction(self.actionSave)
+        self.actionToolbar.addAction(self.actionCancel)
+        self.iconToolbar.addAction(self.actionAdd_Rectangle)
+        self.iconToolbar.addAction(self.actionAdd_Circle)
+        self.iconToolbar.addAction(self.actionAdd_Text)
+        self.iconToolbar.addAction(self.actionAdd_Line)
+
+        self.retranslateUi(iconEditor)
+
+        QMetaObject.connectSlotsByName(iconEditor)
+    # setupUi
+
+    def retranslateUi(self, iconEditor):
+        iconEditor.setWindowTitle(QCoreApplication.translate("iconEditor", u"MainWindow", None))
+        self.actionUndo.setText(QCoreApplication.translate("iconEditor", u"Undo", None))
+#if QT_CONFIG(tooltip)
+        self.actionUndo.setToolTip(QCoreApplication.translate("iconEditor", u"Undo", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionUndo.setShortcut(QCoreApplication.translate("iconEditor", u"Ctrl+Z", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionRedo.setText(QCoreApplication.translate("iconEditor", u"Redo", None))
+#if QT_CONFIG(tooltip)
+        self.actionRedo.setToolTip(QCoreApplication.translate("iconEditor", u"Redo", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionRedo.setShortcut(QCoreApplication.translate("iconEditor", u"Ctrl+Y", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionSave.setText(QCoreApplication.translate("iconEditor", u"Save", None))
+#if QT_CONFIG(tooltip)
+        self.actionSave.setToolTip(QCoreApplication.translate("iconEditor", u"Save icon", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionSave.setShortcut(QCoreApplication.translate("iconEditor", u"Return", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionCancel.setText(QCoreApplication.translate("iconEditor", u"Cancel", None))
+#if QT_CONFIG(tooltip)
+        self.actionCancel.setToolTip(QCoreApplication.translate("iconEditor", u"Cancel icon editing", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionCancel.setShortcut(QCoreApplication.translate("iconEditor", u"Shift+Esc", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionAdd_Rectangle.setText(QCoreApplication.translate("iconEditor", u"Add Rectangle", None))
+#if QT_CONFIG(tooltip)
+        self.actionAdd_Rectangle.setToolTip(QCoreApplication.translate("iconEditor", u"Add a rectangle", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionAdd_Text.setText(QCoreApplication.translate("iconEditor", u"Add Text", None))
+#if QT_CONFIG(tooltip)
+        self.actionAdd_Text.setToolTip(QCoreApplication.translate("iconEditor", u"Add a text field", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionSave_to_File.setText(QCoreApplication.translate("iconEditor", u"Save to File", None))
+#if QT_CONFIG(tooltip)
+        self.actionSave_to_File.setToolTip(QCoreApplication.translate("iconEditor", u"Save icon to a file", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionSave_to_File.setShortcut(QCoreApplication.translate("iconEditor", u"Ctrl+Shift+S", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionOpen_from_File.setText(QCoreApplication.translate("iconEditor", u"Open from File", None))
+#if QT_CONFIG(tooltip)
+        self.actionOpen_from_File.setToolTip(QCoreApplication.translate("iconEditor", u"Open icon from File", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionOpen_from_File.setShortcut(QCoreApplication.translate("iconEditor", u"Ctrl+Shift+O", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionAdd_Line.setText(QCoreApplication.translate("iconEditor", u"Add Line", None))
+#if QT_CONFIG(tooltip)
+        self.actionAdd_Line.setToolTip(QCoreApplication.translate("iconEditor", u"Add a line", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionAdd_Circle.setText(QCoreApplication.translate("iconEditor", u"Add Ellipse", None))
+#if QT_CONFIG(tooltip)
+        self.actionAdd_Circle.setToolTip(QCoreApplication.translate("iconEditor", u"Add a circle", None))
+#endif // QT_CONFIG(tooltip)
+        self.menuEdit.setTitle(QCoreApplication.translate("iconEditor", u"Edit", None))
+        self.menuFile.setTitle(QCoreApplication.translate("iconEditor", u"File", None))
+        self.actionToolbar.setWindowTitle(QCoreApplication.translate("iconEditor", u"toolBar", None))
+        self.iconToolbar.setWindowTitle(QCoreApplication.translate("iconEditor", u"toolBar", None))
+    # retranslateUi
+

src/bedit_gui/ui/forms/main_window.ui

@@ -30,7 +30,7 @@
      <x>0</x>
      <y>0</y>
      <width>940</width>
-     <height>22</height>
+     <height>19</height>
     </rect>
    </property>
    <widget class="QMenu" name="menuFile">
@@ -59,6 +59,7 @@
     <addaction name="actionDelete"/>
     <addaction name="separator"/>
     <addaction name="actionSettings"/>
+    <addaction name="actionReload_Libraries"/>
    </widget>
    <widget class="QMenu" name="menuView">
     <property name="title">
@@ -127,7 +128,7 @@
    <property name="minimumSize">
     <size>
      <width>150</width>
-     <height>533</height>
+     <height>200</height>
     </size>
    </property>
    <property name="windowTitle">
@@ -180,6 +181,27 @@
    <addaction name="actionCompile_Model"/>
    <addaction name="actionOpen_Simulation_Window"/>
   </widget>
+  <widget class="QDockWidget" name="libraryWidget">
+   <property name="minimumSize">
+    <size>
+     <width>150</width>
+     <height>200</height>
+    </size>
+   </property>
+   <property name="windowTitle">
+    <string>Libraries</string>
+   </property>
+   <attribute name="dockWidgetArea">
+    <number>1</number>
+   </attribute>
+   <widget class="QWidget" name="dockWidgetContents_4">
+    <layout class="QVBoxLayout" name="verticalLayout_4">
+     <item>
+      <widget class="QTreeView" name="libraryTree"/>
+     </item>
+    </layout>
+   </widget>
+  </widget>
   <action name="actionOpen_File">
    <property name="icon">
     <iconset resource="../../resources/resources.qrc">
@@ -330,6 +352,17 @@
     <string>Settings</string>
    </property>
   </action>
+  <action name="actionReload_Libraries">
+   <property name="text">
+    <string>Reload Libraries</string>
+   </property>
+   <property name="toolTip">
+    <string>Reload configured libraries</string>
+   </property>
+   <property name="menuRole">
+    <enum>QAction::MenuRole::NoRole</enum>
+   </property>
+  </action>
   <action name="actionDelete">
    <property name="icon">
     <iconset resource="../../resources/resources.qrc">

src/bedit_gui/ui/forms/main_window_ui.py

@@ -0,0 +1,370 @@
+# -*- coding: utf-8 -*-
+
+################################################################################
+## Form generated from reading UI file 'main_window.ui'
+##
+## Created by: Qt User Interface Compiler version 6.11.1
+##
+## WARNING! All changes made in this file will be lost when recompiling UI file!
+################################################################################
+
+from PySide6.QtCore import (QCoreApplication, QDate, QDateTime, QLocale,
+    QMetaObject, QObject, QPoint, QRect,
+    QSize, QTime, QUrl, Qt)
+from PySide6.QtGui import (QAction, QBrush, QColor, QConicalGradient,
+    QCursor, QFont, QFontDatabase, QGradient,
+    QIcon, QImage, QKeySequence, QLinearGradient,
+    QPainter, QPalette, QPixmap, QRadialGradient,
+    QTransform)
+from PySide6.QtWidgets import (QApplication, QDockWidget, QHeaderView, QListView,
+    QMainWindow, QMenu, QMenuBar, QSizePolicy,
+    QStatusBar, QTabWidget, QToolBar, QTreeView,
+    QVBoxLayout, QWidget)
+import resources_rc
+
+class Ui_MainWindow(object):
+    def setupUi(self, MainWindow):
+        if not MainWindow.objectName():
+            MainWindow.setObjectName(u"MainWindow")
+        MainWindow.resize(940, 729)
+        icon = QIcon()
+        icon.addFile(u":/icons/icons/office-chart-line.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        MainWindow.setWindowIcon(icon)
+        MainWindow.setDocumentMode(False)
+        MainWindow.setTabShape(QTabWidget.TabShape.Triangular)
+        self.actionOpen_File = QAction(MainWindow)
+        self.actionOpen_File.setObjectName(u"actionOpen_File")
+        icon1 = QIcon()
+        icon1.addFile(u":/icons/icons/document-open.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionOpen_File.setIcon(icon1)
+        self.actionOpen_File.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionNew_File = QAction(MainWindow)
+        self.actionNew_File.setObjectName(u"actionNew_File")
+        icon2 = QIcon()
+        icon2.addFile(u":/icons/icons/document-new.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionNew_File.setIcon(icon2)
+        self.actionNew_File.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionSave_File = QAction(MainWindow)
+        self.actionSave_File.setObjectName(u"actionSave_File")
+        icon3 = QIcon()
+        icon3.addFile(u":/icons/icons/document-save.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionSave_File.setIcon(icon3)
+        self.actionSave_File.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionSave_File_As = QAction(MainWindow)
+        self.actionSave_File_As.setObjectName(u"actionSave_File_As")
+        icon4 = QIcon()
+        icon4.addFile(u":/icons/icons/document-save-as.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionSave_File_As.setIcon(icon4)
+        self.actionSave_File_As.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionClose = QAction(MainWindow)
+        self.actionClose.setObjectName(u"actionClose")
+        self.actionClose.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionAbout_QT = QAction(MainWindow)
+        self.actionAbout_QT.setObjectName(u"actionAbout_QT")
+        self.actionAbout_QT.setMenuRole(QAction.MenuRole.AboutQtRole)
+        self.actionUndo = QAction(MainWindow)
+        self.actionUndo.setObjectName(u"actionUndo")
+        icon5 = QIcon()
+        icon5.addFile(u":/icons/icons/edit-undo.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionUndo.setIcon(icon5)
+        self.actionUndo.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionRedo = QAction(MainWindow)
+        self.actionRedo.setObjectName(u"actionRedo")
+        icon6 = QIcon()
+        icon6.addFile(u":/icons/icons/edit-redo.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionRedo.setIcon(icon6)
+        self.actionRedo.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionReset_Layout = QAction(MainWindow)
+        self.actionReset_Layout.setObjectName(u"actionReset_Layout")
+        self.actionReset_Layout.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionPanels = QAction(MainWindow)
+        self.actionPanels.setObjectName(u"actionPanels")
+        self.actionToolbars = QAction(MainWindow)
+        self.actionToolbars.setObjectName(u"actionToolbars")
+        self.actionSettings = QAction(MainWindow)
+        self.actionSettings.setObjectName(u"actionSettings")
+        self.actionReload_Libraries = QAction(MainWindow)
+        self.actionReload_Libraries.setObjectName(u"actionReload_Libraries")
+        self.actionReload_Libraries.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionDelete = QAction(MainWindow)
+        self.actionDelete.setObjectName(u"actionDelete")
+        icon7 = QIcon()
+        icon7.addFile(u":/icons/icons/edit-delete.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionDelete.setIcon(icon7)
+        self.actionDelete.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionEscape = QAction(MainWindow)
+        self.actionEscape.setObjectName(u"actionEscape")
+        self.actionEscape.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionCopy = QAction(MainWindow)
+        self.actionCopy.setObjectName(u"actionCopy")
+        icon8 = QIcon()
+        icon8.addFile(u":/icons/icons/edit-copy.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionCopy.setIcon(icon8)
+        self.actionCopy.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionPaste = QAction(MainWindow)
+        self.actionPaste.setObjectName(u"actionPaste")
+        icon9 = QIcon()
+        icon9.addFile(u":/icons/icons/edit-paste.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionPaste.setIcon(icon9)
+        self.actionPaste.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionCut = QAction(MainWindow)
+        self.actionCut.setObjectName(u"actionCut")
+        icon10 = QIcon()
+        icon10.addFile(u":/icons/icons/edit-cut.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionCut.setIcon(icon10)
+        self.actionCut.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionSimulation_Settings = QAction(MainWindow)
+        self.actionSimulation_Settings.setObjectName(u"actionSimulation_Settings")
+        icon11 = QIcon()
+        icon11.addFile(u":/icons/icons/configure.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionSimulation_Settings.setIcon(icon11)
+        self.actionSimulation_Settings.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionEdit_Parameters = QAction(MainWindow)
+        self.actionEdit_Parameters.setObjectName(u"actionEdit_Parameters")
+        icon12 = QIcon()
+        icon12.addFile(u":/icons/icons/view-form-table.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionEdit_Parameters.setIcon(icon12)
+        self.actionEdit_Parameters.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionCompile_Model = QAction(MainWindow)
+        self.actionCompile_Model.setObjectName(u"actionCompile_Model")
+        icon13 = QIcon()
+        icon13.addFile(u":/icons/icons/run-build.png", QSize(), QIcon.Mode.Normal, QIcon.State.Off)
+        self.actionCompile_Model.setIcon(icon13)
+        self.actionCompile_Model.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionOpen_Simulation_Window = QAction(MainWindow)
+        self.actionOpen_Simulation_Window.setObjectName(u"actionOpen_Simulation_Window")
+        self.actionOpen_Simulation_Window.setIcon(icon)
+        self.actionOpen_Simulation_Window.setMenuRole(QAction.MenuRole.NoRole)
+        self.actionAbout = QAction(MainWindow)
+        self.actionAbout.setObjectName(u"actionAbout")
+        self.centralwidget = QWidget(MainWindow)
+        self.centralwidget.setObjectName(u"centralwidget")
+        MainWindow.setCentralWidget(self.centralwidget)
+        self.menubar = QMenuBar(MainWindow)
+        self.menubar.setObjectName(u"menubar")
+        self.menubar.setGeometry(QRect(0, 0, 940, 19))
+        self.menuFile = QMenu(self.menubar)
+        self.menuFile.setObjectName(u"menuFile")
+        self.menuEdit = QMenu(self.menubar)
+        self.menuEdit.setObjectName(u"menuEdit")
+        self.menuView = QMenu(self.menubar)
+        self.menuView.setObjectName(u"menuView")
+        self.menuHelp = QMenu(self.menubar)
+        self.menuHelp.setObjectName(u"menuHelp")
+        self.menuSimulation = QMenu(self.menubar)
+        self.menuSimulation.setObjectName(u"menuSimulation")
+        MainWindow.setMenuBar(self.menubar)
+        self.statusbar = QStatusBar(MainWindow)
+        self.statusbar.setObjectName(u"statusbar")
+        MainWindow.setStatusBar(self.statusbar)
+        self.fileToolBar = QToolBar(MainWindow)
+        self.fileToolBar.setObjectName(u"fileToolBar")
+        MainWindow.addToolBar(Qt.ToolBarArea.TopToolBarArea, self.fileToolBar)
+        self.undoToolBar = QToolBar(MainWindow)
+        self.undoToolBar.setObjectName(u"undoToolBar")
+        MainWindow.addToolBar(Qt.ToolBarArea.TopToolBarArea, self.undoToolBar)
+        self.documentTreeWidget = QDockWidget(MainWindow)
+        self.documentTreeWidget.setObjectName(u"documentTreeWidget")
+        self.documentTreeWidget.setMinimumSize(QSize(150, 200))
+        self.dockWidgetContents = QWidget()
+        self.dockWidgetContents.setObjectName(u"dockWidgetContents")
+        self.verticalLayout = QVBoxLayout(self.dockWidgetContents)
+        self.verticalLayout.setObjectName(u"verticalLayout")
+        self.documentTree = QTreeView(self.dockWidgetContents)
+        self.documentTree.setObjectName(u"documentTree")
+
+        self.verticalLayout.addWidget(self.documentTree)
+
+        self.documentTreeWidget.setWidget(self.dockWidgetContents)
+        MainWindow.addDockWidget(Qt.DockWidgetArea.LeftDockWidgetArea, self.documentTreeWidget)
+        self.logWidget = QDockWidget(MainWindow)
+        self.logWidget.setObjectName(u"logWidget")
+        self.logWidget.setMinimumSize(QSize(150, 107))
+        self.dockWidgetContents_5 = QWidget()
+        self.dockWidgetContents_5.setObjectName(u"dockWidgetContents_5")
+        self.verticalLayout_2 = QVBoxLayout(self.dockWidgetContents_5)
+        self.verticalLayout_2.setObjectName(u"verticalLayout_2")
+        self.listView = QListView(self.dockWidgetContents_5)
+        self.listView.setObjectName(u"listView")
+
+        self.verticalLayout_2.addWidget(self.listView)
+
+        self.logWidget.setWidget(self.dockWidgetContents_5)
+        MainWindow.addDockWidget(Qt.DockWidgetArea.BottomDockWidgetArea, self.logWidget)
+        self.simToolBar = QToolBar(MainWindow)
+        self.simToolBar.setObjectName(u"simToolBar")
+        MainWindow.addToolBar(Qt.ToolBarArea.TopToolBarArea, self.simToolBar)
+        self.libraryWidget = QDockWidget(MainWindow)
+        self.libraryWidget.setObjectName(u"libraryWidget")
+        self.libraryWidget.setMinimumSize(QSize(150, 200))
+        self.dockWidgetContents_4 = QWidget()
+        self.dockWidgetContents_4.setObjectName(u"dockWidgetContents_4")
+        self.verticalLayout_4 = QVBoxLayout(self.dockWidgetContents_4)
+        self.verticalLayout_4.setObjectName(u"verticalLayout_4")
+        self.libraryTree = QTreeView(self.dockWidgetContents_4)
+        self.libraryTree.setObjectName(u"libraryTree")
+
+        self.verticalLayout_4.addWidget(self.libraryTree)
+
+        self.libraryWidget.setWidget(self.dockWidgetContents_4)
+        MainWindow.addDockWidget(Qt.DockWidgetArea.LeftDockWidgetArea, self.libraryWidget)
+
+        self.menubar.addAction(self.menuFile.menuAction())
+        self.menubar.addAction(self.menuEdit.menuAction())
+        self.menubar.addAction(self.menuView.menuAction())
+        self.menubar.addAction(self.menuSimulation.menuAction())
+        self.menubar.addAction(self.menuHelp.menuAction())
+        self.menuFile.addAction(self.actionNew_File)
+        self.menuFile.addAction(self.actionOpen_File)
+        self.menuFile.addSeparator()
+        self.menuFile.addAction(self.actionSave_File)
+        self.menuFile.addAction(self.actionSave_File_As)
+        self.menuFile.addSeparator()
+        self.menuFile.addAction(self.actionClose)
+        self.menuEdit.addAction(self.actionUndo)
+        self.menuEdit.addAction(self.actionRedo)
+        self.menuEdit.addSeparator()
+        self.menuEdit.addAction(self.actionCopy)
+        self.menuEdit.addAction(self.actionCut)
+        self.menuEdit.addAction(self.actionPaste)
+        self.menuEdit.addSeparator()
+        self.menuEdit.addAction(self.actionDelete)
+        self.menuEdit.addSeparator()
+        self.menuEdit.addAction(self.actionSettings)
+        self.menuEdit.addAction(self.actionReload_Libraries)
+        self.menuView.addAction(self.actionReset_Layout)
+        self.menuView.addAction(self.actionPanels)
+        self.menuView.addAction(self.actionToolbars)
+        self.menuHelp.addAction(self.actionAbout)
+        self.menuHelp.addAction(self.actionAbout_QT)
+        self.menuSimulation.addAction(self.actionSimulation_Settings)
+        self.menuSimulation.addAction(self.actionEdit_Parameters)
+        self.menuSimulation.addSeparator()
+        self.menuSimulation.addAction(self.actionCompile_Model)
+        self.menuSimulation.addAction(self.actionOpen_Simulation_Window)
+        self.fileToolBar.addAction(self.actionNew_File)
+        self.fileToolBar.addAction(self.actionOpen_File)
+        self.fileToolBar.addAction(self.actionSave_File)
+        self.fileToolBar.addAction(self.actionSave_File_As)
+        self.undoToolBar.addAction(self.actionUndo)
+        self.undoToolBar.addAction(self.actionRedo)
+        self.undoToolBar.addAction(self.actionCopy)
+        self.undoToolBar.addAction(self.actionCut)
+        self.undoToolBar.addAction(self.actionPaste)
+        self.simToolBar.addAction(self.actionSimulation_Settings)
+        self.simToolBar.addAction(self.actionEdit_Parameters)
+        self.simToolBar.addAction(self.actionCompile_Model)
+        self.simToolBar.addAction(self.actionOpen_Simulation_Window)
+
+        self.retranslateUi(MainWindow)
+
+        QMetaObject.connectSlotsByName(MainWindow)
+    # setupUi
+
+    def retranslateUi(self, MainWindow):
+        MainWindow.setWindowTitle(QCoreApplication.translate("MainWindow", u"MainWindow", None))
+        self.actionOpen_File.setText(QCoreApplication.translate("MainWindow", u"Open File", None))
+#if QT_CONFIG(tooltip)
+        self.actionOpen_File.setToolTip(QCoreApplication.translate("MainWindow", u"Open a file", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionOpen_File.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+O", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionNew_File.setText(QCoreApplication.translate("MainWindow", u"New File", None))
+#if QT_CONFIG(tooltip)
+        self.actionNew_File.setToolTip(QCoreApplication.translate("MainWindow", u"Create a new file", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionNew_File.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+N", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionSave_File.setText(QCoreApplication.translate("MainWindow", u"Save File", None))
+#if QT_CONFIG(tooltip)
+        self.actionSave_File.setToolTip(QCoreApplication.translate("MainWindow", u"Save a file to disk", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionSave_File.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+S", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionSave_File_As.setText(QCoreApplication.translate("MainWindow", u"Save File As...", None))
+#if QT_CONFIG(tooltip)
+        self.actionSave_File_As.setToolTip(QCoreApplication.translate("MainWindow", u"Save file to disk as another file", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionSave_File_As.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+Shift+S", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionClose.setText(QCoreApplication.translate("MainWindow", u"Close", None))
+#if QT_CONFIG(tooltip)
+        self.actionClose.setToolTip(QCoreApplication.translate("MainWindow", u"Close application", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionClose.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+Q", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionAbout_QT.setText(QCoreApplication.translate("MainWindow", u"About QT", None))
+        self.actionUndo.setText(QCoreApplication.translate("MainWindow", u"Undo", None))
+#if QT_CONFIG(shortcut)
+        self.actionUndo.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+Z", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionRedo.setText(QCoreApplication.translate("MainWindow", u"Redo", None))
+#if QT_CONFIG(shortcut)
+        self.actionRedo.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+Y", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionReset_Layout.setText(QCoreApplication.translate("MainWindow", u"Reset Layout", None))
+#if QT_CONFIG(tooltip)
+        self.actionReset_Layout.setToolTip(QCoreApplication.translate("MainWindow", u"Reset window layout to default", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionPanels.setText(QCoreApplication.translate("MainWindow", u"Panels", None))
+        self.actionToolbars.setText(QCoreApplication.translate("MainWindow", u"Toolbars", None))
+        self.actionSettings.setText(QCoreApplication.translate("MainWindow", u"Settings", None))
+        self.actionReload_Libraries.setText(QCoreApplication.translate("MainWindow", u"Reload Libraries", None))
+#if QT_CONFIG(tooltip)
+        self.actionReload_Libraries.setToolTip(QCoreApplication.translate("MainWindow", u"Reload configured libraries", None))
+#endif // QT_CONFIG(tooltip)
+        self.actionDelete.setText(QCoreApplication.translate("MainWindow", u"Delete", None))
+#if QT_CONFIG(tooltip)
+        self.actionDelete.setToolTip(QCoreApplication.translate("MainWindow", u"Delete selected", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionDelete.setShortcut(QCoreApplication.translate("MainWindow", u"Del", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionEscape.setText(QCoreApplication.translate("MainWindow", u"Escape", None))
+#if QT_CONFIG(shortcut)
+        self.actionEscape.setShortcut(QCoreApplication.translate("MainWindow", u"Esc", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionCopy.setText(QCoreApplication.translate("MainWindow", u"Copy", None))
+#if QT_CONFIG(tooltip)
+        self.actionCopy.setToolTip(QCoreApplication.translate("MainWindow", u"Copy selected", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionCopy.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+C", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionPaste.setText(QCoreApplication.translate("MainWindow", u"Paste", None))
+#if QT_CONFIG(tooltip)
+        self.actionPaste.setToolTip(QCoreApplication.translate("MainWindow", u"Paste selected", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionPaste.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+V", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionCut.setText(QCoreApplication.translate("MainWindow", u"Cut", None))
+#if QT_CONFIG(tooltip)
+        self.actionCut.setToolTip(QCoreApplication.translate("MainWindow", u"Cut selected", None))
+#endif // QT_CONFIG(tooltip)
+#if QT_CONFIG(shortcut)
+        self.actionCut.setShortcut(QCoreApplication.translate("MainWindow", u"Ctrl+X", None))
+#endif // QT_CONFIG(shortcut)
+        self.actionSimulation_Settings.setText(QCoreApplication.translate("MainWindow", u"Simulation Settings", None))
+        self.actionEdit_Parameters.setText(QCoreApplication.translate("MainWindow", u"Edit Parameters", None))
+        self.actionCompile_Model.setText(QCoreApplication.translate("MainWindow", u"Compile Model", None))
+        self.actionOpen_Simulation_Window.setText(QCoreApplication.translate("MainWindow", u"Open Simulation Window", None))
+        self.actionAbout.setText(QCoreApplication.translate("MainWindow", u"About", None))
+        self.menuFile.setTitle(QCoreApplication.translate("MainWindow", u"File", None))
+        self.menuEdit.setTitle(QCoreApplication.translate("MainWindow", u"Edit", None))
+        self.menuView.setTitle(QCoreApplication.translate("MainWindow", u"View", None))
+        self.menuHelp.setTitle(QCoreApplication.translate("MainWindow", u"Help", None))
+        self.menuSimulation.setTitle(QCoreApplication.translate("MainWindow", u"Simulation", None))
+        self.fileToolBar.setWindowTitle(QCoreApplication.translate("MainWindow", u"toolBar", None))
+        self.undoToolBar.setWindowTitle(QCoreApplication.translate("MainWindow", u"toolBar", None))
+        self.documentTreeWidget.setWindowTitle(QCoreApplication.translate("MainWindow", u"Document Tree", None))
+        self.logWidget.setWindowTitle(QCoreApplication.translate("MainWindow", u"Log", None))
+        self.simToolBar.setWindowTitle(QCoreApplication.translate("MainWindow", u"toolBar", None))
+        self.libraryWidget.setWindowTitle(QCoreApplication.translate("MainWindow", u"Libraries", None))
+    # retranslateUi
+

src/bedit_gui/ui/forms/port_editor_widget.ui

@@ -148,6 +148,20 @@
          </property>
         </widget>
        </item>
+       <item row="5" column="0">
+        <widget class="QLabel" name="connectionAnnotationLabel">
+         <property name="text">
+          <string>Connection annotation:</string>
+         </property>
+        </widget>
+       </item>
+       <item row="5" column="1">
+        <widget class="QLineEdit" name="connectionAnnotationEdit">
+         <property name="placeholderText">
+          <string>For example, + or -</string>
+         </property>
+        </widget>
+       </item>
       </layout>
      </item>
      <item>

src/bedit_gui/ui/forms/port_editor_widget_ui.py

@@ -0,0 +1,268 @@
+# -*- coding: utf-8 -*-
+
+################################################################################
+## Form generated from reading UI file 'port_editor_widget.ui'
+##
+## Created by: Qt User Interface Compiler version 6.11.1
+##
+## WARNING! All changes made in this file will be lost when recompiling UI file!
+################################################################################
+
+from PySide6.QtCore import (QCoreApplication, QDate, QDateTime, QLocale,
+    QMetaObject, QObject, QPoint, QRect,
+    QSize, QTime, QUrl, Qt)
+from PySide6.QtGui import (QBrush, QColor, QConicalGradient, QCursor,
+    QFont, QFontDatabase, QGradient, QIcon,
+    QImage, QKeySequence, QLinearGradient, QPainter,
+    QPalette, QPixmap, QRadialGradient, QTransform)
+from PySide6.QtWidgets import (QApplication, QCheckBox, QComboBox, QFormLayout,
+    QFrame, QHBoxLayout, QLabel, QLineEdit,
+    QListView, QPlainTextEdit, QPushButton, QRadioButton,
+    QSizePolicy, QSpacerItem, QSpinBox, QVBoxLayout,
+    QWidget)
+
+class Ui_PortEditor(object):
+    def setupUi(self, PortEditor):
+        if not PortEditor.objectName():
+            PortEditor.setObjectName(u"PortEditor")
+        PortEditor.resize(541, 420)
+        self.horizontalLayout_2 = QHBoxLayout(PortEditor)
+        self.horizontalLayout_2.setObjectName(u"horizontalLayout_2")
+        self.leftColumn = QVBoxLayout()
+        self.leftColumn.setObjectName(u"leftColumn")
+        self.portList = QListView(PortEditor)
+        self.portList.setObjectName(u"portList")
+
+        self.leftColumn.addWidget(self.portList)
+
+        self.buttonRow = QHBoxLayout()
+        self.buttonRow.setObjectName(u"buttonRow")
+        self.addPort = QPushButton(PortEditor)
+        self.addPort.setObjectName(u"addPort")
+
+        self.buttonRow.addWidget(self.addPort)
+
+        self.removePort = QPushButton(PortEditor)
+        self.removePort.setObjectName(u"removePort")
+
+        self.buttonRow.addWidget(self.removePort)
+
+
+        self.leftColumn.addLayout(self.buttonRow)
+
+
+        self.horizontalLayout_2.addLayout(self.leftColumn)
+
+        self.rightColumn = QVBoxLayout()
+        self.rightColumn.setObjectName(u"rightColumn")
+        self.basicForm = QFormLayout()
+        self.basicForm.setObjectName(u"basicForm")
+        self.nameLabel = QLabel(PortEditor)
+        self.nameLabel.setObjectName(u"nameLabel")
+
+        self.basicForm.setWidget(0, QFormLayout.ItemRole.LabelRole, self.nameLabel)
+
+        self.nameEdit = QLineEdit(PortEditor)
+        self.nameEdit.setObjectName(u"nameEdit")
+
+        self.basicForm.setWidget(0, QFormLayout.ItemRole.FieldRole, self.nameEdit)
+
+        self.typeLabel = QLabel(PortEditor)
+        self.typeLabel.setObjectName(u"typeLabel")
+
+        self.basicForm.setWidget(1, QFormLayout.ItemRole.LabelRole, self.typeLabel)
+
+        self.typeRow = QHBoxLayout()
+        self.typeRow.setObjectName(u"typeRow")
+        self.typeSignal = QRadioButton(PortEditor)
+        self.typeSignal.setObjectName(u"typeSignal")
+
+        self.typeRow.addWidget(self.typeSignal)
+
+        self.typeBond = QRadioButton(PortEditor)
+        self.typeBond.setObjectName(u"typeBond")
+
+        self.typeRow.addWidget(self.typeBond)
+
+
+        self.basicForm.setLayout(1, QFormLayout.ItemRole.FieldRole, self.typeRow)
+
+        self.orientationLabel = QLabel(PortEditor)
+        self.orientationLabel.setObjectName(u"orientationLabel")
+
+        self.basicForm.setWidget(2, QFormLayout.ItemRole.LabelRole, self.orientationLabel)
+
+        self.orientationRow = QHBoxLayout()
+        self.orientationRow.setObjectName(u"orientationRow")
+        self.inputOrientation = QRadioButton(PortEditor)
+        self.inputOrientation.setObjectName(u"inputOrientation")
+
+        self.orientationRow.addWidget(self.inputOrientation)
+
+        self.outputOrientation = QRadioButton(PortEditor)
+        self.outputOrientation.setObjectName(u"outputOrientation")
+
+        self.orientationRow.addWidget(self.outputOrientation)
+
+
+        self.basicForm.setLayout(2, QFormLayout.ItemRole.FieldRole, self.orientationRow)
+
+        self.sizeLabel = QLabel(PortEditor)
+        self.sizeLabel.setObjectName(u"sizeLabel")
+
+        self.basicForm.setWidget(3, QFormLayout.ItemRole.LabelRole, self.sizeLabel)
+
+        self.sizeRow = QHBoxLayout()
+        self.sizeRow.setObjectName(u"sizeRow")
+        self.widthSize = QSpinBox(PortEditor)
+        self.widthSize.setObjectName(u"widthSize")
+        self.widthSize.setMinimum(1)
+
+        self.sizeRow.addWidget(self.widthSize)
+
+        self.heightSize = QSpinBox(PortEditor)
+        self.heightSize.setObjectName(u"heightSize")
+        self.heightSize.setMinimum(1)
+
+        self.sizeRow.addWidget(self.heightSize)
+
+
+        self.basicForm.setLayout(3, QFormLayout.ItemRole.FieldRole, self.sizeRow)
+
+        self.domainLabel = QLabel(PortEditor)
+        self.domainLabel.setObjectName(u"domainLabel")
+
+        self.basicForm.setWidget(4, QFormLayout.ItemRole.LabelRole, self.domainLabel)
+
+        self.multiplicityCheckBox = QCheckBox(PortEditor)
+        self.multiplicityCheckBox.setObjectName(u"multiplicityCheckBox")
+
+        self.basicForm.setWidget(4, QFormLayout.ItemRole.FieldRole, self.multiplicityCheckBox)
+
+        self.connectionAnnotationLabel = QLabel(PortEditor)
+        self.connectionAnnotationLabel.setObjectName(u"connectionAnnotationLabel")
+
+        self.basicForm.setWidget(5, QFormLayout.ItemRole.LabelRole, self.connectionAnnotationLabel)
+
+        self.connectionAnnotationEdit = QLineEdit(PortEditor)
+        self.connectionAnnotationEdit.setObjectName(u"connectionAnnotationEdit")
+
+        self.basicForm.setWidget(5, QFormLayout.ItemRole.FieldRole, self.connectionAnnotationEdit)
+
+
+        self.rightColumn.addLayout(self.basicForm)
+
+        self.line = QFrame(PortEditor)
+        self.line.setObjectName(u"line")
+        self.line.setFrameShape(QFrame.Shape.HLine)
+        self.line.setFrameShadow(QFrame.Shadow.Sunken)
+
+        self.rightColumn.addWidget(self.line)
+
+        self.signalOptions = QFormLayout()
+        self.signalOptions.setObjectName(u"signalOptions")
+        self.signalTypeLabel = QLabel(PortEditor)
+        self.signalTypeLabel.setObjectName(u"signalTypeLabel")
+
+        self.signalOptions.setWidget(0, QFormLayout.ItemRole.LabelRole, self.signalTypeLabel)
+
+        self.signalTypeComboBox = QComboBox(PortEditor)
+        self.signalTypeComboBox.setObjectName(u"signalTypeComboBox")
+
+        self.signalOptions.setWidget(0, QFormLayout.ItemRole.FieldRole, self.signalTypeComboBox)
+
+
+        self.rightColumn.addLayout(self.signalOptions)
+
+        self.bondOptions = QFormLayout()
+        self.bondOptions.setObjectName(u"bondOptions")
+        self.domainLabel_2 = QLabel(PortEditor)
+        self.domainLabel_2.setObjectName(u"domainLabel_2")
+
+        self.bondOptions.setWidget(0, QFormLayout.ItemRole.LabelRole, self.domainLabel_2)
+
+        self.domainComboBox = QComboBox(PortEditor)
+        self.domainComboBox.setObjectName(u"domainComboBox")
+
+        self.bondOptions.setWidget(0, QFormLayout.ItemRole.FieldRole, self.domainComboBox)
+
+        self.causalityLabel = QLabel(PortEditor)
+        self.causalityLabel.setObjectName(u"causalityLabel")
+
+        self.bondOptions.setWidget(1, QFormLayout.ItemRole.LabelRole, self.causalityLabel)
+
+        self.causalityComboBox = QComboBox(PortEditor)
+        self.causalityComboBox.setObjectName(u"causalityComboBox")
+
+        self.bondOptions.setWidget(1, QFormLayout.ItemRole.FieldRole, self.causalityComboBox)
+
+
+        self.rightColumn.addLayout(self.bondOptions)
+
+        self.verticalSpacer = QSpacerItem(20, 40, QSizePolicy.Policy.Minimum, QSizePolicy.Policy.Expanding)
+
+        self.rightColumn.addItem(self.verticalSpacer)
+
+        self.line_2 = QFrame(PortEditor)
+        self.line_2.setObjectName(u"line_2")
+        self.line_2.setFrameShape(QFrame.Shape.HLine)
+        self.line_2.setFrameShadow(QFrame.Shadow.Sunken)
+
+        self.rightColumn.addWidget(self.line_2)
+
+        self.descriptionForm = QFormLayout()
+        self.descriptionForm.setObjectName(u"descriptionForm")
+        self.descriptionForm.setFieldGrowthPolicy(QFormLayout.FieldGrowthPolicy.AllNonFixedFieldsGrow)
+        self.descriptionLabel = QLabel(PortEditor)
+        self.descriptionLabel.setObjectName(u"descriptionLabel")
+
+        self.descriptionForm.setWidget(0, QFormLayout.ItemRole.LabelRole, self.descriptionLabel)
+
+        self.descriptionEdit = QPlainTextEdit(PortEditor)
+        self.descriptionEdit.setObjectName(u"descriptionEdit")
+        sizePolicy = QSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.MinimumExpanding)
+        sizePolicy.setHorizontalStretch(0)
+        sizePolicy.setVerticalStretch(0)
+        sizePolicy.setHeightForWidth(self.descriptionEdit.sizePolicy().hasHeightForWidth())
+        self.descriptionEdit.setSizePolicy(sizePolicy)
+        self.descriptionEdit.setMinimumSize(QSize(0, 20))
+        self.descriptionEdit.setMaximumSize(QSize(16777215, 60))
+
+        self.descriptionForm.setWidget(0, QFormLayout.ItemRole.FieldRole, self.descriptionEdit)
+
+
+        self.rightColumn.addLayout(self.descriptionForm)
+
+
+        self.horizontalLayout_2.addLayout(self.rightColumn)
+
+
+        self.retranslateUi(PortEditor)
+
+        QMetaObject.connectSlotsByName(PortEditor)
+    # setupUi
+
+    def retranslateUi(self, PortEditor):
+        PortEditor.setWindowTitle(QCoreApplication.translate("PortEditor", u"Form", None))
+        self.addPort.setText(QCoreApplication.translate("PortEditor", u"Add Port", None))
+        self.removePort.setText(QCoreApplication.translate("PortEditor", u"Remove Port", None))
+        self.nameLabel.setText(QCoreApplication.translate("PortEditor", u"Name:", None))
+        self.typeLabel.setText(QCoreApplication.translate("PortEditor", u"Type:", None))
+        self.typeSignal.setText(QCoreApplication.translate("PortEditor", u"Signal", None))
+        self.typeBond.setText(QCoreApplication.translate("PortEditor", u"Power Bond", None))
+        self.orientationLabel.setText(QCoreApplication.translate("PortEditor", u"Orientation:", None))
+        self.inputOrientation.setText(QCoreApplication.translate("PortEditor", u"Input", None))
+        self.outputOrientation.setText(QCoreApplication.translate("PortEditor", u"Output", None))
+        self.sizeLabel.setText(QCoreApplication.translate("PortEditor", u"Size", None))
+        self.widthSize.setSuffix(QCoreApplication.translate("PortEditor", u" rows", None))
+        self.heightSize.setSuffix(QCoreApplication.translate("PortEditor", u" columns", None))
+        self.domainLabel.setText("")
+        self.multiplicityCheckBox.setText(QCoreApplication.translate("PortEditor", u"Allow multiple connections", None))
+        self.connectionAnnotationLabel.setText(QCoreApplication.translate("PortEditor", u"Connection annotation:", None))
+        self.connectionAnnotationEdit.setPlaceholderText(QCoreApplication.translate("PortEditor", u"For example, + or -", None))
+        self.signalTypeLabel.setText(QCoreApplication.translate("PortEditor", u"Signal Type:", None))
+        self.domainLabel_2.setText(QCoreApplication.translate("PortEditor", u"Domain:", None))
+        self.causalityLabel.setText(QCoreApplication.translate("PortEditor", u"Causality:", None))
+        self.descriptionLabel.setText(QCoreApplication.translate("PortEditor", u"Description:", None))
+    # retranslateUi
+

src/bedit_gui/ui/forms/settings_dialog.ui

@@ -17,7 +17,7 @@
    <item>
     <widget class="QTabWidget" name="tabWidget">
      <property name="currentIndex">
-      <number>0</number>
+      <number>1</number>
      </property>
      <widget class="QWidget" name="General">
       <attribute name="title">
@@ -55,7 +55,27 @@
          </property>
         </widget>
        </item>
+       <item row="1" column="0">
+        <widget class="QLabel" name="labelSnapToGridSize">
+         <property name="text">
+          <string>Snap-to-grid size:</string>
+         </property>
+        </widget>
+       </item>
        <item row="1" column="1">
+        <widget class="QSpinBox" name="snapToGridSize">
+         <property name="minimum">
+          <number>1</number>
+         </property>
+         <property name="maximum">
+          <number>256</number>
+         </property>
+         <property name="value">
+          <number>4</number>
+         </property>
+        </widget>
+       </item>
+       <item row="2" column="1">
         <spacer name="verticalSpacer">
          <property name="orientation">
           <enum>Qt::Orientation::Vertical</enum>
@@ -70,6 +90,34 @@
        </item>
       </layout>
      </widget>
+     <widget class="QWidget" name="Libraries">
+      <attribute name="title">
+       <string>Libraries</string>
+      </attribute>
+      <layout class="QVBoxLayout" name="verticalLayout_2">
+       <item>
+        <widget class="QListView" name="listView"/>
+       </item>
+       <item>
+        <layout class="QHBoxLayout" name="horizontalLayout">
+         <item>
+          <widget class="QPushButton" name="addLibButton">
+           <property name="text">
+            <string>Add library</string>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QPushButton" name="addDirButton">
+           <property name="text">
+            <string>Add directory</string>
+           </property>
+          </widget>
+         </item>
+        </layout>
+       </item>
+      </layout>
+     </widget>
     </widget>
    </item>
    <item>

src/bedit_gui/ui/forms/settings_dialog_ui.py

@@ -0,0 +1,128 @@
+# -*- coding: utf-8 -*-
+
+################################################################################
+## Form generated from reading UI file 'settings_dialog.ui'
+##
+## Created by: Qt User Interface Compiler version 6.11.1
+##
+## WARNING! All changes made in this file will be lost when recompiling UI file!
+################################################################################
+
+from PySide6.QtCore import (QCoreApplication, QDate, QDateTime, QLocale,
+    QMetaObject, QObject, QPoint, QRect,
+    QSize, QTime, QUrl, Qt)
+from PySide6.QtGui import (QBrush, QColor, QConicalGradient, QCursor,
+    QFont, QFontDatabase, QGradient, QIcon,
+    QImage, QKeySequence, QLinearGradient, QPainter,
+    QPalette, QPixmap, QRadialGradient, QTransform)
+from PySide6.QtWidgets import (QAbstractButton, QApplication, QComboBox, QDialog,
+    QDialogButtonBox, QFormLayout, QHBoxLayout, QLabel,
+    QListView, QPushButton, QSizePolicy, QSpacerItem,
+    QSpinBox, QTabWidget, QVBoxLayout, QWidget)
+
+class Ui_Settings(object):
+    def setupUi(self, Settings):
+        if not Settings.objectName():
+            Settings.setObjectName(u"Settings")
+        Settings.resize(400, 230)
+        self.verticalLayout = QVBoxLayout(Settings)
+        self.verticalLayout.setObjectName(u"verticalLayout")
+        self.tabWidget = QTabWidget(Settings)
+        self.tabWidget.setObjectName(u"tabWidget")
+        self.General = QWidget()
+        self.General.setObjectName(u"General")
+        self.formLayout = QFormLayout(self.General)
+        self.formLayout.setObjectName(u"formLayout")
+        self.logLevel = QComboBox(self.General)
+        self.logLevel.addItem("")
+        self.logLevel.addItem("")
+        self.logLevel.addItem("")
+        self.logLevel.addItem("")
+        self.logLevel.setObjectName(u"logLevel")
+
+        self.formLayout.setWidget(0, QFormLayout.ItemRole.FieldRole, self.logLevel)
+
+        self.lableLogLevel = QLabel(self.General)
+        self.lableLogLevel.setObjectName(u"lableLogLevel")
+
+        self.formLayout.setWidget(0, QFormLayout.ItemRole.LabelRole, self.lableLogLevel)
+
+        self.labelSnapToGridSize = QLabel(self.General)
+        self.labelSnapToGridSize.setObjectName(u"labelSnapToGridSize")
+
+        self.formLayout.setWidget(1, QFormLayout.ItemRole.LabelRole, self.labelSnapToGridSize)
+
+        self.snapToGridSize = QSpinBox(self.General)
+        self.snapToGridSize.setObjectName(u"snapToGridSize")
+        self.snapToGridSize.setMinimum(1)
+        self.snapToGridSize.setMaximum(256)
+        self.snapToGridSize.setValue(4)
+
+        self.formLayout.setWidget(1, QFormLayout.ItemRole.FieldRole, self.snapToGridSize)
+
+        self.verticalSpacer = QSpacerItem(20, 40, QSizePolicy.Policy.Minimum, QSizePolicy.Policy.Expanding)
+
+        self.formLayout.setItem(2, QFormLayout.ItemRole.FieldRole, self.verticalSpacer)
+
+        self.tabWidget.addTab(self.General, "")
+        self.Libraries = QWidget()
+        self.Libraries.setObjectName(u"Libraries")
+        self.verticalLayout_2 = QVBoxLayout(self.Libraries)
+        self.verticalLayout_2.setObjectName(u"verticalLayout_2")
+        self.listView = QListView(self.Libraries)
+        self.listView.setObjectName(u"listView")
+
+        self.verticalLayout_2.addWidget(self.listView)
+
+        self.horizontalLayout = QHBoxLayout()
+        self.horizontalLayout.setObjectName(u"horizontalLayout")
+        self.addLibButton = QPushButton(self.Libraries)
+        self.addLibButton.setObjectName(u"addLibButton")
+
+        self.horizontalLayout.addWidget(self.addLibButton)
+
+        self.addDirButton = QPushButton(self.Libraries)
+        self.addDirButton.setObjectName(u"addDirButton")
+
+        self.horizontalLayout.addWidget(self.addDirButton)
+
+
+        self.verticalLayout_2.addLayout(self.horizontalLayout)
+
+        self.tabWidget.addTab(self.Libraries, "")
+
+        self.verticalLayout.addWidget(self.tabWidget)
+
+        self.buttonBox = QDialogButtonBox(Settings)
+        self.buttonBox.setObjectName(u"buttonBox")
+        self.buttonBox.setOrientation(Qt.Orientation.Horizontal)
+        self.buttonBox.setStandardButtons(QDialogButtonBox.StandardButton.Cancel|QDialogButtonBox.StandardButton.Ok)
+
+        self.verticalLayout.addWidget(self.buttonBox)
+
+
+        self.retranslateUi(Settings)
+        self.buttonBox.accepted.connect(Settings.accept)
+        self.buttonBox.rejected.connect(Settings.reject)
+
+        self.tabWidget.setCurrentIndex(1)
+
+
+        QMetaObject.connectSlotsByName(Settings)
+    # setupUi
+
+    def retranslateUi(self, Settings):
+        Settings.setWindowTitle(QCoreApplication.translate("Settings", u"Settings", None))
+        self.logLevel.setItemText(0, QCoreApplication.translate("Settings", u"Debug", None))
+        self.logLevel.setItemText(1, QCoreApplication.translate("Settings", u"Info", None))
+        self.logLevel.setItemText(2, QCoreApplication.translate("Settings", u"Warning", None))
+        self.logLevel.setItemText(3, QCoreApplication.translate("Settings", u"Error", None))
+
+        self.lableLogLevel.setText(QCoreApplication.translate("Settings", u"Log level:", None))
+        self.labelSnapToGridSize.setText(QCoreApplication.translate("Settings", u"Snap-to-grid size:", None))
+        self.tabWidget.setTabText(self.tabWidget.indexOf(self.General), QCoreApplication.translate("Settings", u"General", None))
+        self.addLibButton.setText(QCoreApplication.translate("Settings", u"Add library", None))
+        self.addDirButton.setText(QCoreApplication.translate("Settings", u"Add directory", None))
+        self.tabWidget.setTabText(self.tabWidget.indexOf(self.Libraries), QCoreApplication.translate("Settings", u"Libraries", None))
+    # retranslateUi
+

src/bedit_gui/utils/icon.py

@@ -1,13 +1,18 @@
 from __future__ import annotations
 
+from math import ceil
+
 from PySide6.QtCore import QRectF, QSize, Qt
-from PySide6.QtGui import QBrush, QColor, QFont, QIcon, QPainter, QPen, QPixmap
+from PySide6.QtGui import QBrush, QColor, QFont, QIcon, QPainter, QPen, QPixmap, QRegion
 
 from bedit_core.models import Port, PortID, SignalDirection
-from bedit_gui.models import Icon, Line, LineType, Rectangle, Text
+from bedit_gui.models import Ellipse, Icon, Line, LineType, Rectangle, Text
 
 PORT_SIZE = 16
 DEFAULT_ICON_SIZE = QSize(48, 48)
+EMPTY_NATURAL_ICON_SIZE = QSize(32, 32)
+ICON_MARGIN = 4
+ICON_PREVIEW_OVERSAMPLE = 4
 
 
 def get_bounding_box(icon: Icon) -> QRectF:
@@ -16,7 +21,7 @@ def get_bounding_box(icon: Icon) -> QRectF:
     for shape in icon.shapes.values():
         x, y = shape.pos
         points.append((x, y))
-        if isinstance(shape, (Rectangle, Text)):
+        if isinstance(shape, (Rectangle, Ellipse, Text)):
             points.append((x + shape.width, y + shape.height))
         elif isinstance(shape, Line):
             points.append(shape.end)
@@ -35,6 +40,19 @@ def get_bounding_box(icon: Icon) -> QRectF:
     return QRectF(left, top, right - left, bottom - top)
 
 
+def get_pixmap_bounding_box(pixmap: QPixmap) -> QRectF:
+    """Return the bounds of the pixels actually painted in a transparent pixmap."""
+    bounds = QRegion(pixmap.mask()).boundingRect()
+    return QRectF(bounds) if not bounds.isEmpty() else QRectF(0, 0, pixmap.width(), pixmap.height())
+
+
+def get_natural_icon_size(icon: Icon) -> QSize:
+    bounds = get_bounding_box(icon)
+    if bounds.isEmpty():
+        return QSize(EMPTY_NATURAL_ICON_SIZE)
+    return QSize(max(1, ceil(bounds.width()) + ICON_MARGIN), max(1, ceil(bounds.height()) + ICON_MARGIN))
+
+
 def render_icon(icon: Icon, ports: dict[PortID, Port], size: QSize = DEFAULT_ICON_SIZE, render_ports: bool = False) -> QIcon:
     pixmap = QPixmap(size)
     pixmap.fill(Qt.GlobalColor.transparent)
@@ -42,9 +60,7 @@ def render_icon(icon: Icon, ports: dict[PortID, Port], size: QSize = DEFAULT_ICO
     if not icon.shapes and not icon.port_positions:
         return QIcon(pixmap)
 
-    available_width = max(1, size.width() - 4)
-    available_height = max(1, size.height() - 4)
-    scale = min(available_width / max(1, bounds.width()), available_height / max(1, bounds.height()))
+    scale = _render_scale(bounds, size)
     painter = QPainter(pixmap)
     painter.setRenderHint(QPainter.RenderHint.Antialiasing)
     painter.translate(size.width() / 2, size.height() / 2)
@@ -56,6 +72,10 @@ def render_icon(icon: Icon, ports: dict[PortID, Port], size: QSize = DEFAULT_ICO
             painter.setPen(_line_pen(shape.line_type, shape.line_thickness, shape.line_color))
             painter.setBrush(QBrush(_color(shape.fill_color)))
             painter.drawRoundedRect(QRectF(shape.pos[0], shape.pos[1], shape.width, shape.height), shape.corner_radius, shape.corner_radius)
+        elif isinstance(shape, Ellipse):
+            painter.setPen(_line_pen(shape.line_type, shape.line_thickness, shape.line_color))
+            painter.setBrush(QBrush(_color(shape.fill_color)))
+            painter.drawEllipse(QRectF(shape.pos[0], shape.pos[1], shape.width, shape.height))
         elif isinstance(shape, Text):
             font = QFont()
             font.setPixelSize(max(1, round(shape.size)))
@@ -82,6 +102,28 @@ def render_icon(icon: Icon, ports: dict[PortID, Port], size: QSize = DEFAULT_ICO
     return QIcon(pixmap)
 
 
+def render_fitted_icon(icon: Icon, ports: dict[PortID, Port], size: QSize = DEFAULT_ICON_SIZE) -> QIcon:
+    """Render an icon preview with its painted content fitted to a uniform size."""
+    render_size = QSize(size.width() * ICON_PREVIEW_OVERSAMPLE, size.height() * ICON_PREVIEW_OVERSAMPLE)
+    rendered = render_icon(icon, ports, render_size).pixmap(render_size)
+    bounds = get_pixmap_bounding_box(rendered).toAlignedRect()
+    content = rendered.copy(bounds)
+    available = QSize(max(1, size.width() - ICON_MARGIN), max(1, size.height() - ICON_MARGIN))
+    fitted = content.scaled(available, Qt.AspectRatioMode.KeepAspectRatio, Qt.TransformationMode.SmoothTransformation)
+    pixmap = QPixmap(size)
+    pixmap.fill(Qt.GlobalColor.transparent)
+    painter = QPainter(pixmap)
+    painter.drawPixmap((size.width() - fitted.width()) // 2, (size.height() - fitted.height()) // 2, fitted)
+    painter.end()
+    return QIcon(pixmap)
+
+
+def _render_scale(bounds: QRectF, size: QSize) -> float:
+    available_width = max(1, size.width() - ICON_MARGIN)
+    available_height = max(1, size.height() - ICON_MARGIN)
+    return min(available_width / max(1, bounds.width()), available_height / max(1, bounds.height()))
+
+
 def _line_pen(line_type: LineType, thickness: float, color: str) -> QPen:
     styles = {LineType.SOLID: Qt.PenStyle.SolidLine, LineType.DASHED: Qt.PenStyle.DashLine, LineType.DOTTED: Qt.PenStyle.DotLine, LineType.DASH_DOT: Qt.PenStyle.DashDotLine}
     if line_type is LineType.NONE:

src/bedit_gui/views/dialogs/interface_editor_dialog.py

@@ -8,6 +8,7 @@ from PySide6.QtWidgets import (
 )
 
 from bedit_core.models import Port, PortID
+from bedit_gui.models import PortMetadata
 from bedit_gui.views.port_editor_widget import PortEditorWidget
 
 
@@ -17,6 +18,7 @@ class InterfaceEditorDialog(QDialog):
     def __init__(
         self,
         ports: dict[PortID, Port],
+        port_metadata: dict[PortID, PortMetadata] | None = None,
         parent: QWidget | None = None,
     ) -> None:
         super().__init__(parent)
@@ -25,7 +27,7 @@ class InterfaceEditorDialog(QDialog):
 
         layout = QVBoxLayout(self)
         self.editor = PortEditorWidget(self)
-        self.editor.set_ports(ports)
+        self.editor.set_ports(ports, port_metadata)
         layout.addWidget(self.editor)
 
         buttons = QDialogButtonBox(
@@ -38,3 +40,6 @@ class InterfaceEditorDialog(QDialog):
 
     def ports(self) -> dict[PortID, Port]:
         return self.editor.ports()
+
+    def port_metadata(self) -> dict[PortID, PortMetadata]:
+        return self.editor.port_metadata()

src/bedit_gui/views/dialogs/settings_dialog.py

@@ -1,8 +1,11 @@
 from __future__ import annotations
 
 import logging
+from pathlib import Path
 
-from PySide6.QtWidgets import QDialog, QWidget
+from PySide6.QtCore import QStringListModel, Qt
+from PySide6.QtGui import QKeySequence, QShortcut
+from PySide6.QtWidgets import QAbstractItemView, QDialog, QFileDialog, QWidget
 
 from bedit_gui.ui.generated.ui_settings_dialog import Ui_Settings
 
@@ -20,6 +23,8 @@ class SettingsDialog(QDialog):
     def __init__(
         self,
         log_level: int,
+        snap_to_grid_size: int,
+        library_paths: list[str],
         parent: QWidget | None = None,
     ) -> None:
         super().__init__(parent)
@@ -35,7 +40,46 @@ class SettingsDialog(QDialog):
         self.ui.logLevel.setCurrentIndex(
             selected if selected >= 0 else self.LOG_LEVELS.index(logging.INFO)
         )
+        self.ui.snapToGridSize.setValue(snap_to_grid_size)
+        self._library_paths = QStringListModel(list(library_paths), self)
+        self.ui.listView.setModel(self._library_paths)
+        self.ui.listView.setSelectionMode(QAbstractItemView.SelectionMode.ExtendedSelection)
+        self.ui.addLibButton.clicked.connect(self._add_library_file)
+        self.ui.addDirButton.clicked.connect(self._add_library_directory)
+        self._delete_shortcut = QShortcut(QKeySequence.StandardKey.Delete, self.ui.listView)
+        self._delete_shortcut.setContext(Qt.ShortcutContext.WidgetShortcut)
+        self._delete_shortcut.activated.connect(self._delete_selected_paths)
 
     @property
     def log_level(self) -> int:
         return int(self.ui.logLevel.currentData())
+
+    @property
+    def snap_to_grid_size(self) -> int:
+        return self.ui.snapToGridSize.value()
+
+    @property
+    def library_paths(self) -> list[str]:
+        return self._library_paths.stringList()
+
+    def _add_library_file(self) -> None:
+        path, _selected_filter = QFileDialog.getOpenFileName(self, "Add BEdit Library", "", "BEdit documents (*.bedit.json *.beb *.json)")
+        if path:
+            self._add_library_path(path)
+
+    def _add_library_directory(self) -> None:
+        path = QFileDialog.getExistingDirectory(self, "Add Library Directory")
+        if path:
+            self._add_library_path(path)
+
+    def _add_library_path(self, path: str) -> None:
+        normalized = str(Path(path).resolve())
+        paths = self._library_paths.stringList()
+        if normalized not in paths:
+            paths.append(normalized)
+            self._library_paths.setStringList(paths)
+
+    def _delete_selected_paths(self) -> None:
+        rows = sorted((index.row() for index in self.ui.listView.selectionModel().selectedRows()), reverse=True)
+        for row in rows:
+            self._library_paths.removeRow(row)

src/bedit_gui/views/equation_editor_widget.py

@@ -3,7 +3,8 @@ from __future__ import annotations
 from PySide6.QtCore import QEvent, QObject, QTimer, Qt, Signal
 from PySide6.QtWidgets import QWidget
 
-from bedit_core.models import Component, EquationImplementation
+from bedit_core.models import Component, EquationImplementation, PortID
+from bedit_gui.models import PortMetadata
 from bedit_gui.ui.generated.ui_equation_editor_widget import Ui_equationEditorWidget
 from bedit_gui.views.param_editor_widget import ParamEditorWidget
 from bedit_gui.views.port_editor_widget import PortEditorWidget
@@ -14,6 +15,7 @@ class EquationEditorWidget(QWidget):
 
     component_changed = Signal(object)
     equation_text_change_requested = Signal(object, str, object, int)
+    port_metadata_change_requested = Signal(object, object)
     sidebar_visible_changed = Signal(bool)
 
     def __init__(self, parent: QWidget | None = None) -> None:
@@ -22,6 +24,7 @@ class EquationEditorWidget(QWidget):
         self.ui = Ui_equationEditorWidget()
         self.ui.setupUi(self)
         self._component: Component | None = None
+        self._port_metadata: dict[PortID, PortMetadata] = {}
         self._loading = False
         self._edit_id = 0
         self._edit_timer = QTimer(self)
@@ -45,11 +48,12 @@ class EquationEditorWidget(QWidget):
 
         self._set_editors_enabled(False)
 
-    def set_component(self, component: Component | None) -> None:
+    def set_component(self, component: Component | None, port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
         if component is not None and not isinstance(component.implementation, EquationImplementation):
             raise TypeError("EquationEditorWidget only supports components with an equation implementation")
 
         self._component = component
+        self._port_metadata = port_metadata or {}
         self.refresh()
 
     def component(self) -> Component | None:
@@ -88,7 +92,7 @@ class EquationEditorWidget(QWidget):
             self.ui.initialEquationsTextEdit.setPlainText("\n".join(implementation.initial_equations))
             self.ui.equationsTextEdit.setPlainText("\n".join(implementation.equations))
             self.param_editor.set_params(component.parameters)
-            self.port_editor.set_ports(component.interface.ports)
+            self.port_editor.set_ports(component.interface.ports, self._port_metadata)
         self._loading = False
         self._set_editors_enabled(component is not None)
 
@@ -145,8 +149,21 @@ class EquationEditorWidget(QWidget):
     def _ports_changed(self) -> None:
         if self._loading or self._component is None:
             return
-        self._component.interface.ports = self.port_editor.ports()
-        self.component_changed.emit(self._component)
+        ports = self.port_editor.ports()
+        metadata = self.port_editor.port_metadata()
+        if ports != self._component.interface.ports:
+            self._component.interface.ports = ports
+            self.component_changed.emit(self._component)
+        if metadata != self._port_metadata:
+            self._port_metadata = metadata
+            self.port_metadata_change_requested.emit(self._component, metadata)
+
+    def refresh_port_metadata(self, port_metadata: dict[PortID, PortMetadata]) -> None:
+        if port_metadata == self._port_metadata:
+            return
+        self._port_metadata = port_metadata
+        if self._component is not None:
+            self.port_editor.set_ports(self._component.interface.ports, port_metadata)
 
     def _replace_placeholder(self, placeholder: QWidget, editor: QWidget) -> None:
         self.ui.verticalLayout_2.replaceWidget(placeholder, editor)

src/bedit_gui/views/graph_editor_widget.py

@@ -1,17 +1,47 @@
 from __future__ import annotations
 
-from PySide6.QtCore import QEvent, QObject, QRectF, Qt
-from PySide6.QtGui import QColor, QPainter, QPen, QWheelEvent
-from PySide6.QtWidgets import QGraphicsScene, QGraphicsView, QWidget
+import json
+from enum import Enum
+from itertools import pairwise
+from math import hypot
 
-from bedit_core.models import Component, GraphImplementation
+from PySide6.QtCore import QEvent, QObject, QPointF, QRectF, QTimer, Qt, Signal
+from PySide6.QtGui import QActionGroup, QBrush, QColor, QCursor, QDragEnterEvent, QDragMoveEvent, QDropEvent, QKeySequence, QMouseEvent, QPainter, QPainterPath, QPen, QShortcut, QWheelEvent
+from PySide6.QtWidgets import QGraphicsEllipseItem, QGraphicsItem, QGraphicsPathItem, QGraphicsPixmapItem, QGraphicsScene, QGraphicsSceneMouseEvent, QGraphicsTextItem, QGraphicsView, QMenu, QWidget
+
+from bedit_core.models import BondCausality, BondConnection, BondPort, Component, ComponentID, Connection, ConnectionID, GraphImplementation, Port, PortID, SignalConnection, SignalDirection, SignalPort
+from bedit_gui.models import Graph, GraphComponentLabel, GraphConnection, Icon, PortMetadata
+from bedit_gui.services.component_clipboard import COMPONENTS_MIME
 from bedit_gui.ui.generated.ui_graph_editor_widget import Ui_graphEditorWidget
+from bedit_gui.utils.icon import get_natural_icon_size, get_pixmap_bounding_box, render_icon
 
-GRID_SPACING = 32
+GRID_SPACING = 64
 SCENE_SIZE = 10000
 MIN_ZOOM = 0.2
 MAX_ZOOM = 4.0
 ZOOM_STEP = 1.15
+ZOOM_TO_FIT_PADDING = 32.0
+COMPONENT_LABEL_FONT_SIZE = 24.0
+FALLBACK_COMPONENT_SPACING = 128
+CONNECTION_WIDTH = 4.0
+BOND_CONNECTION_COLOR = "#000000"
+SIGNAL_CONNECTION_COLOR = "#00007f"
+BOND_CONNECTION_BOUNDING_BOX_SPACING = 16.0
+SIGNAL_CONNECTION_BOUNDING_BOX_SPACING = 0.0
+CONNECTION_STRAIGHTEN_TOLERANCE = 8.0
+ARROW_LENGTH = 32.0
+ARROW_HALF_WIDTH = 16.0
+SIGNAL_ARROW_LENGTH = ARROW_LENGTH / 2
+SIGNAL_ARROW_HALF_WIDTH = ARROW_HALF_WIDTH / 2
+CAUSALITY_TICK_HALF_LENGTH = 16.0
+CONNECTION_ANNOTATION_FONT_SIZE = 18.0
+CONNECTION_ANNOTATION_BACK_OFFSET = 24.0
+CONNECTION_ANNOTATION_SIDE_OFFSET = 14.0
+
+
+class GraphEditorMode(Enum):
+    NORMAL = "normal"
+    CONNECTION = "connection"
 
 
 class GraphGraphicsScene(QGraphicsScene):
@@ -22,41 +52,781 @@ class GraphGraphicsScene(QGraphicsScene):
         pen = QPen(QColor(205, 205, 205), 0, Qt.PenStyle.DotLine)
         painter.setPen(pen)
 
+        scene_rect = self.sceneRect()
         left = int(rect.left()) - int(rect.left()) % GRID_SPACING
         top = int(rect.top()) - int(rect.top()) % GRID_SPACING
         x = left
         while x <= rect.right():
-            painter.drawLine(x, rect.top(), x, rect.bottom())
+            painter.drawLine(x, scene_rect.top(), x, scene_rect.bottom())
             x += GRID_SPACING
         y = top
         while y <= rect.bottom():
-            painter.drawLine(rect.left(), y, rect.right(), y)
+            painter.drawLine(scene_rect.left(), y, scene_rect.right(), y)
             y += GRID_SPACING
 
 
+class GraphConnectionItem(QGraphicsPathItem):
+    """A routed connection with a full signal arrow or half bond arrow."""
+
+    def __init__(self, points: list[tuple[float, float]], *, half_arrow: bool, tick_at_source: bool | None = None, connection_id: ConnectionID | None = None, editor: GraphEditorWidget | None = None) -> None:
+        super().__init__()
+        self.connection_id = connection_id
+        self.editor = editor
+        self.setPath(self._connection_path(points, half_arrow, tick_at_source))
+        color = QColor(BOND_CONNECTION_COLOR if half_arrow else SIGNAL_CONNECTION_COLOR)
+        pen = QPen(color, CONNECTION_WIDTH)
+        self.setPen(pen)
+        self.setBrush(QBrush(color))
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsSelectable)
+        self.setZValue(-1)
+
+    def contextMenuEvent(self, event) -> None:
+        if self.editor is None or self.connection_id is None:
+            return
+        if not self.isSelected():
+            self.scene().clearSelection()
+            self.setSelected(True)
+        menu = QMenu(self.editor)
+        add_point = menu.addAction("Add Point")
+        delete_connection = menu.addAction("Delete Connection")
+        selected = menu.exec(event.screenPos())
+        if selected is add_point:
+            self.editor.add_connection_point(self.connection_id, event.scenePos())
+        elif selected is delete_connection:
+            self.editor.delete_selected_connections()
+        event.accept()
+
+    @staticmethod
+    def _connection_path(points: list[tuple[float, float]], half_arrow: bool, tick_at_source: bool | None = None) -> QPainterPath:
+        path = QPainterPath(QPointF(*points[0]))
+        for point in points[1:]:
+            path.lineTo(QPointF(*point))
+
+        target = QPointF(*points[-1])
+        previous = next((QPointF(*point) for point in reversed(points[:-1]) if QPointF(*point) != target), None)
+        if previous is None:
+            return path
+        dx = target.x() - previous.x()
+        dy = target.y() - previous.y()
+        length = hypot(dx, dy)
+        arrow_length = ARROW_LENGTH if half_arrow else SIGNAL_ARROW_LENGTH
+        arrow_half_width = ARROW_HALF_WIDTH if half_arrow else SIGNAL_ARROW_HALF_WIDTH
+        back_x = target.x() - arrow_length * dx / length
+        back_y = target.y() - arrow_length * dy / length
+        perpendicular_x = -arrow_half_width * dy / length
+        perpendicular_y = arrow_half_width * dx / length
+        path.moveTo(target)
+        path.lineTo(back_x + perpendicular_x, back_y + perpendicular_y)
+        if not half_arrow:
+            path.lineTo(back_x - perpendicular_x, back_y - perpendicular_y)
+            path.closeSubpath()
+        if tick_at_source is not None:
+            GraphConnectionItem._add_causality_tick(path, points, tick_at_source)
+        return path
+
+    @staticmethod
+    def _add_causality_tick(path: QPainterPath, points: list[tuple[float, float]], at_source: bool) -> None:
+        if at_source:
+            endpoint = QPointF(*points[0])
+            neighbor = next((QPointF(*point) for point in points[1:] if QPointF(*point) != endpoint), None)
+        else:
+            endpoint = QPointF(*points[-1])
+            neighbor = next((QPointF(*point) for point in reversed(points[:-1]) if QPointF(*point) != endpoint), None)
+        if neighbor is None:
+            return
+        dx = neighbor.x() - endpoint.x()
+        dy = neighbor.y() - endpoint.y()
+        length = hypot(dx, dy)
+        perpendicular_x = -CAUSALITY_TICK_HALF_LENGTH * dy / length
+        perpendicular_y = CAUSALITY_TICK_HALF_LENGTH * dx / length
+        path.moveTo(endpoint.x() - perpendicular_x, endpoint.y() - perpendicular_y)
+        path.lineTo(endpoint.x() + perpendicular_x, endpoint.y() + perpendicular_y)
+
+
+class GraphComponentItem(QGraphicsPixmapItem):
+    def __init__(self, component_id: ComponentID, pixmap, editor: GraphEditorWidget) -> None:
+        super().__init__(pixmap)
+        self.component_id = component_id
+        self.editor = editor
+        self._drag_start = QPointF()
+        self._dragging = False
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsSelectable)
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsMovable, editor.mode is GraphEditorMode.NORMAL)
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemSendsGeometryChanges)
+
+    def itemChange(self, change: QGraphicsItem.GraphicsItemChange, value: object) -> object:
+        if change == QGraphicsItem.GraphicsItemChange.ItemPositionChange and self.component_id in self.editor._component_drag_starts and isinstance(value, QPointF):
+            grid_size = self.editor.snap_to_grid_size
+            value = QPointF(round(value.x() / grid_size) * grid_size, round(value.y() / grid_size) * grid_size)
+        result = super().itemChange(change, value)
+        if change == QGraphicsItem.GraphicsItemChange.ItemPositionHasChanged:
+            self.editor.refresh_connections()
+        return result
+
+    def mousePressEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        if event.button() == Qt.MouseButton.LeftButton and self.editor.mode is GraphEditorMode.CONNECTION:
+            event.accept()
+            return
+        self._drag_start = QPointF(self.pos())
+        self._dragging = True
+        super().mousePressEvent(event)
+        self.editor.begin_component_move()
+
+    def mouseReleaseEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        if self.editor.mode is GraphEditorMode.CONNECTION:
+            if event.button() == Qt.MouseButton.LeftButton:
+                self.editor.choose_connection_component(self.component_id, event.screenPos())
+            event.accept()
+            return
+        super().mouseReleaseEvent(event)
+        self._dragging = False
+        self.editor.finish_component_moves()
+
+    def mouseDoubleClickEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        if event.button() == Qt.MouseButton.LeftButton:
+            self.editor.open_component(self.component_id)
+            event.accept()
+            return
+        super().mouseDoubleClickEvent(event)
+
+    def contextMenuEvent(self, event) -> None:
+        if not self.isSelected():
+            self.scene().clearSelection()
+            self.setSelected(True)
+        self.editor.component_context_menu_requested.emit(self.component_id, event.screenPos())
+        event.accept()
+
+
+class GraphComponentLabelItem(QGraphicsTextItem):
+    def __init__(self, component_id: ComponentID, text: str, label: GraphComponentLabel, component_item: GraphComponentItem, editor: GraphEditorWidget) -> None:
+        super().__init__(text, component_item)
+        self.component_id = component_id
+        self.editor = editor
+        self._dragging = False
+        self._drag_start = label.relative_position
+        font = self.font()
+        font.setItalic(True)
+        font.setPointSizeF(COMPONENT_LABEL_FONT_SIZE)
+        self.setFont(font)
+        self.setDefaultTextColor(QColor("#202020"))
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsSelectable)
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsMovable, editor.mode is GraphEditorMode.NORMAL)
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemSendsGeometryChanges)
+        self.set_relative_position(label.relative_position)
+
+    def relative_position(self) -> tuple[int, int]:
+        component_bounds = self.editor._component_bounds[self.component_id]
+        return round(self.pos().x() + self.boundingRect().width() / 2), round(self.pos().y() - component_bounds.bottom())
+
+    def set_relative_position(self, position: tuple[int, int]) -> None:
+        component_bounds = self.editor._component_bounds[self.component_id]
+        self.setPos(position[0] - self.boundingRect().width() / 2, component_bounds.bottom() + position[1])
+
+    def itemChange(self, change: QGraphicsItem.GraphicsItemChange, value: object) -> object:
+        if change == QGraphicsItem.GraphicsItemChange.ItemPositionChange and self._dragging and isinstance(value, QPointF):
+            component_bounds = self.editor._component_bounds[self.component_id]
+            size = self.editor.snap_to_grid_size
+            relative_x = value.x() + self.boundingRect().width() / 2
+            relative_y = value.y() - component_bounds.bottom()
+            value = QPointF(round(relative_x / size) * size - self.boundingRect().width() / 2, component_bounds.bottom() + round(relative_y / size) * size)
+        return super().itemChange(change, value)
+
+    def mousePressEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        self._drag_start = self.relative_position()
+        self._dragging = True
+        super().mousePressEvent(event)
+
+    def mouseReleaseEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        super().mouseReleaseEvent(event)
+        self._dragging = False
+        position = self.relative_position()
+        self.set_relative_position(position)
+        if position != self._drag_start:
+            self.editor.finish_component_label_move(self.component_id, position)
+
+    def contextMenuEvent(self, event) -> None:
+        self.editor.component_context_menu_requested.emit(self.component_id, event.screenPos())
+        event.accept()
+
+
+class GraphConnectionPointItem(QGraphicsEllipseItem):
+    def __init__(self, connection_id: ConnectionID, index: int, position: tuple[int, int], editor: GraphEditorWidget) -> None:
+        radius = CONNECTION_WIDTH
+        super().__init__(-radius, -radius, radius * 2, radius * 2)
+        self.connection_id = connection_id
+        self.index = index
+        self.editor = editor
+        self._drag_start = QPointF()
+        self._dragging = False
+        self.setPos(*position)
+        self.setPen(QPen(Qt.PenStyle.NoPen))
+        self.setBrush(QBrush(QColor("#202020")))
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsMovable)
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemIsSelectable)
+        self.setFlag(QGraphicsItem.GraphicsItemFlag.ItemSendsGeometryChanges)
+
+    def itemChange(self, change: QGraphicsItem.GraphicsItemChange, value: object) -> object:
+        if change == QGraphicsItem.GraphicsItemChange.ItemPositionChange and self._dragging and isinstance(value, QPointF):
+            size = self.editor.snap_to_grid_size
+            value = QPointF(round(value.x() / size) * size, round(value.y() / size) * size)
+        result = super().itemChange(change, value)
+        if change == QGraphicsItem.GraphicsItemChange.ItemPositionHasChanged:
+            self.editor.refresh_connections()
+        return result
+
+    def mousePressEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        self._drag_start = QPointF(self.pos())
+        self._dragging = True
+        super().mousePressEvent(event)
+
+    def mouseReleaseEvent(self, event: QGraphicsSceneMouseEvent) -> None:
+        super().mouseReleaseEvent(event)
+        self._dragging = False
+        position = (round(self.pos().x()), round(self.pos().y()))
+        self.setPos(*position)
+        if self.pos() != self._drag_start:
+            self.editor.finish_connection_point_move(self.connection_id)
+
+    def contextMenuEvent(self, event) -> None:
+        menu = QMenu(self.editor)
+        delete_point = menu.addAction("Delete Point")
+        if menu.exec(event.screenPos()) is delete_point:
+            self.editor.delete_connection_point(self.connection_id, self.index)
+        event.accept()
+
+
 class GraphEditorWidget(QWidget):
-    def __init__(self, parent: QWidget | None = None) -> None:
+    component_moves_requested = Signal(object, object)
+    component_context_menu_requested = Signal(object, object)
+    component_open_requested = Signal(object)
+    component_label_move_requested = Signal(object, object, object)
+    connection_points_change_requested = Signal(object, object, object, str)
+    connection_add_requested = Signal(object, object)
+    connections_delete_requested = Signal(object, object)
+    component_drop_requested = Signal(object, object, object)
+
+    def __init__(self, parent: QWidget | None = None, snap_to_grid_size: int = 4) -> None:
         super().__init__(parent)
 
         self.ui = Ui_graphEditorWidget()
         self.ui.setupUi(self)
         self._component: Component | None = None
+        self._graph = Graph()
+        self._icons: dict[ComponentID, Icon] = {}
+        self._port_metadata: dict[PortID, PortMetadata] = {}
+        self._mode = GraphEditorMode.NORMAL
+        self._connection_start: ComponentID | None = None
+        self._connection_preview: QGraphicsPathItem | None = None
+        self._component_items: dict[ComponentID, GraphComponentItem] = {}
+        self._component_drag_starts: dict[ComponentID, tuple[int, int]] = {}
+        self._component_bounds: dict[ComponentID, QRectF] = {}
+        self._component_label_items: dict[ComponentID, GraphComponentLabelItem] = {}
+        self._connection_items: dict[ConnectionID, GraphConnectionItem] = {}
+        self._connection_point_items: dict[ConnectionID, list[GraphConnectionPointItem]] = {}
+        self._connection_annotation_items: dict[ConnectionID, QGraphicsTextItem] = {}
+        self.set_snap_to_grid_size(snap_to_grid_size)
         self.scene = GraphGraphicsScene(self)
         self.scene.setSceneRect(-SCENE_SIZE / 2, -SCENE_SIZE / 2, SCENE_SIZE, SCENE_SIZE)
         self.ui.graphicsView.setScene(self.scene)
+        self.ui.graphicsView.setRenderHint(QPainter.RenderHint.Antialiasing)
         self.ui.graphicsView.setTransformationAnchor(QGraphicsView.ViewportAnchor.AnchorUnderMouse)
         self.ui.graphicsView.viewport().installEventFilter(self)
+        self.ui.graphicsView.viewport().setAcceptDrops(True)
+        self._mode_actions = QActionGroup(self)
+        self._mode_actions.setExclusive(True)
+        self._mode_actions.addAction(self.ui.actionMouseMode)
+        self._mode_actions.addAction(self.ui.actionConnectionMode)
+        self.ui.actionMouseMode.triggered.connect(lambda: self.set_mode(GraphEditorMode.NORMAL))
+        self.ui.actionConnectionMode.triggered.connect(lambda: self.set_mode(GraphEditorMode.CONNECTION))
+        self.ui.actionMouseMode.setChecked(True)
+        self._mode_shortcut = QShortcut(QKeySequence(Qt.Key.Key_Space), self)
+        self._mode_shortcut.setContext(Qt.ShortcutContext.WidgetWithChildrenShortcut)
+        self._mode_shortcut.activated.connect(self.toggle_mode)
+        self.ui.actionZoomToFit.triggered.connect(self.zoom_to_fit)
+        self.ui.graphicsView.viewport().setMouseTracking(True)
         self.ui.graphicsView.centerOn(0, 0)
 
-    def set_component(self, component: Component | None) -> None:
+    @property
+    def snap_to_grid_size(self) -> int:
+        return self._snap_to_grid_size
+
+    def set_snap_to_grid_size(self, size: int) -> None:
+        if size < 1:
+            raise ValueError("snap-to-grid size must be positive")
+        self._snap_to_grid_size = size
+
+    @property
+    def mode(self) -> GraphEditorMode:
+        return self._mode
+
+    def set_mode(self, mode: GraphEditorMode) -> None:
+        if mode is self._mode:
+            return
+        self._mode = mode
+        self.ui.actionMouseMode.setChecked(mode is GraphEditorMode.NORMAL)
+        self.ui.actionConnectionMode.setChecked(mode is GraphEditorMode.CONNECTION)
+        self._clear_connection_start()
+        component = self._component
+        if component is not None:
+            self.set_component(component, self._graph, self._icons, self._port_metadata)
+
+    def toggle_mode(self) -> None:
+        self.set_mode(GraphEditorMode.CONNECTION if self._mode is GraphEditorMode.NORMAL else GraphEditorMode.NORMAL)
+
+    def set_component(self, component: Component | None, graph: Graph | None = None, icons: dict[ComponentID, Icon] | None = None, port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
         if component is not None and not isinstance(component.implementation, GraphImplementation):
             raise TypeError("GraphEditorWidget only supports components with a graph implementation")
+        component_changed = component is not self._component
+        self._clear_connection_start()
         self._component = component
+        self._graph = graph or Graph()
+        self._icons = icons or {}
+        self._port_metadata = port_metadata or {}
+        self._component_drag_starts = {}
+        self._component_items = {}
+        self._component_bounds = {}
+        self._component_label_items = {}
+        self._connection_items = {}
+        self._connection_point_items = {}
+        self._connection_annotation_items = {}
+        self.scene.clear()
+        if component is None:
+            return
+
+        graph = self._graph
+        icons = self._icons
+        positions = {component_id: graph.component_positions.get(component_id, (index * FALLBACK_COMPONENT_SPACING, 0)) for index, component_id in enumerate(component.implementation.graph.components)}
+        for component_id, child in component.implementation.graph.components.items():
+            icon = icons.get(component_id, Icon())
+            icon_size = get_natural_icon_size(icon)
+            pixmap = render_icon(icon, child.interface.ports, icon_size, render_ports=self._mode is GraphEditorMode.CONNECTION).pixmap(icon_size)
+            item = GraphComponentItem(component_id, pixmap, self)
+            item.setOffset(-pixmap.width() / 2, -pixmap.height() / 2)
+            item.setPos(*positions[component_id])
+            item.setToolTip(child.name)
+            bounds = get_pixmap_bounding_box(pixmap)
+            self._component_items[component_id] = item
+            self._component_bounds[component_id] = bounds.translated(-pixmap.width() / 2, -pixmap.height() / 2)
+            self.scene.addItem(item)
+
+        for component_id, child in component.implementation.graph.components.items():
+            label = graph.component_labels.get(component_id, GraphComponentLabel())
+            if label.visible:
+                self._create_component_label_item(component_id, child.name, label)
+
+        for connection_id, connection in component.implementation.graph.connections.items():
+            if not isinstance(connection, (SignalConnection, BondConnection)):
+                continue
+            tick_at_source = None
+            if isinstance(connection, BondConnection):
+                if connection.causality is BondCausality.EFFORT_OUT:
+                    tick_at_source = False
+                elif connection.causality is BondCausality.FLOW_OUT:
+                    tick_at_source = True
+            connection_item = GraphConnectionItem([(0, 0), (1, 0)], half_arrow=isinstance(connection, BondConnection), tick_at_source=tick_at_source, connection_id=connection_id, editor=self)
+            connection_item.setData(0, str(connection_id))
+            self._connection_items[connection_id] = connection_item
+            self.scene.addItem(connection_item)
+            annotation = self._port_metadata.get(connection.target, PortMetadata()).connection_annotation if isinstance(connection, SignalConnection) else None
+            if annotation:
+                annotation_item = QGraphicsTextItem(annotation)
+                font = annotation_item.font()
+                font.setBold(True)
+                font.setPointSizeF(CONNECTION_ANNOTATION_FONT_SIZE)
+                annotation_item.setFont(font)
+                annotation_item.setDefaultTextColor(QColor(SIGNAL_CONNECTION_COLOR))
+                annotation_item.setZValue(1)
+                self._connection_annotation_items[connection_id] = annotation_item
+                self.scene.addItem(annotation_item)
+            visual_connection = graph.connections.get(connection_id)
+            self._create_connection_point_items(connection_id, visual_connection.points[1:-1] if visual_connection is not None and len(visual_connection.points) >= 2 else [])
+        self.refresh_connections()
+        if component_changed:
+            QTimer.singleShot(0, self.ui.actionZoomToFit.trigger)
+
+    def refresh_connections(self) -> None:
+        component = self._component
+        if component is None or not self._connection_items:
+            return
+        port_owners = {port_id: component_id for component_id, child in component.implementation.graph.components.items() for port_id in child.interface.ports}
+        for connection_id, item in self._connection_items.items():
+            connection = component.implementation.graph.connections.get(connection_id)
+            if connection is None:
+                continue
+            source_component = port_owners.get(connection.source)
+            target_component = port_owners.get(connection.target)
+            if source_component is None or target_component is None:
+                continue
+            source_position = self._item_position(source_component)
+            target_position = self._item_position(target_component)
+            point_items = self._connection_point_items.get(connection_id, [])
+            points = [source_position, *((point.pos().x(), point.pos().y()) for point in point_items), target_position]
+            points = self._straighten_direct_connection(points)
+            source_bounds = self._component_bounds[source_component].translated(*source_position)
+            target_bounds = self._component_bounds[target_component].translated(*target_position)
+            spacing = BOND_CONNECTION_BOUNDING_BOX_SPACING if isinstance(connection, BondConnection) else SIGNAL_CONNECTION_BOUNDING_BOX_SPACING
+            points = self._clip_connection(points, source_bounds, target_bounds, spacing)
+            tick_at_source = None
+            if isinstance(connection, BondConnection):
+                tick_at_source = False if connection.causality is BondCausality.EFFORT_OUT else True if connection.causality is BondCausality.FLOW_OUT else None
+            item.setPath(item._connection_path(points, isinstance(connection, BondConnection), tick_at_source))
+            annotation_item = self._connection_annotation_items.get(connection_id)
+            if annotation_item is not None:
+                self._position_connection_annotation(annotation_item, points)
+
+    @staticmethod
+    def _position_connection_annotation(item: QGraphicsTextItem, points: list[tuple[float, float]]) -> None:
+        target = QPointF(*points[-1])
+        previous = next((QPointF(*point) for point in reversed(points[:-1]) if QPointF(*point) != target), None)
+        if previous is None:
+            return
+        dx = target.x() - previous.x()
+        dy = target.y() - previous.y()
+        length = hypot(dx, dy)
+        x = target.x() - CONNECTION_ANNOTATION_BACK_OFFSET * dx / length - CONNECTION_ANNOTATION_SIDE_OFFSET * dy / length
+        y = target.y() - CONNECTION_ANNOTATION_BACK_OFFSET * dy / length + CONNECTION_ANNOTATION_SIDE_OFFSET * dx / length
+        bounds = item.boundingRect()
+        item.setPos(x - bounds.width() / 2, y - bounds.height() / 2)
+
+    def add_connection_point(self, connection_id: ConnectionID, scene_position: QPointF) -> None:
+        points = self._connection_metadata_points(connection_id)
+        position = self._snap_position(scene_position)
+        index = self._nearest_segment_index(points, position) + 1
+        points.insert(index, position)
+        self._request_connection_points_change(connection_id, points, "Add connection point")
+
+    def delete_connection_point(self, connection_id: ConnectionID, index: int) -> None:
+        points = self._connection_metadata_points(connection_id)
+        if 0 < index < len(points) - 1:
+            points.pop(index)
+            self._request_connection_points_change(connection_id, points, "Delete connection point")
+
+    def finish_connection_point_move(self, connection_id: ConnectionID) -> None:
+        self._request_connection_points_change(connection_id, self._connection_metadata_points(connection_id), "Move connection point")
+
+    def set_connection_points(self, connection_id: ConnectionID, points: list[tuple[int, int]] | None) -> None:
+        if points is None:
+            self._graph.connections.pop(connection_id, None)
+            for item in self._connection_point_items.pop(connection_id, []):
+                self.scene.removeItem(item)
+            connection_item = self._connection_items.pop(connection_id, None)
+            if connection_item is not None:
+                self.scene.removeItem(connection_item)
+            annotation_item = self._connection_annotation_items.pop(connection_id, None)
+            if annotation_item is not None:
+                self.scene.removeItem(annotation_item)
+            return
+        self._graph.connections[connection_id] = GraphConnection(points=list(points))
+        interior_points = points[1:-1]
+        items = self._connection_point_items.get(connection_id, [])
+        if len(items) == len(interior_points):
+            for item, position in zip(items, interior_points):
+                item.setPos(*position)
+        else:
+            for item in items:
+                self.scene.removeItem(item)
+            self._create_connection_point_items(connection_id, interior_points)
+        self.refresh_connections()
+
+    def _create_connection_point_items(self, connection_id: ConnectionID, positions: list[tuple[int, int]]) -> None:
+        items = [GraphConnectionPointItem(connection_id, index, position, self) for index, position in enumerate(positions, 1)]
+        self._connection_point_items[connection_id] = items
+        for item in items:
+            self.scene.addItem(item)
+
+    def _connection_metadata_points(self, connection_id: ConnectionID) -> list[tuple[int, int]]:
+        component = self._component
+        if component is None:
+            return []
+        connection = component.implementation.graph.connections[connection_id]
+        port_owners = {port_id: component_id for component_id, child in component.implementation.graph.components.items() for port_id in child.interface.ports}
+        source = self._item_position(port_owners[connection.source])
+        target = self._item_position(port_owners[connection.target])
+        interior = [(round(item.pos().x()), round(item.pos().y())) for item in self._connection_point_items.get(connection_id, [])]
+        return [(round(source[0]), round(source[1])), *interior, (round(target[0]), round(target[1]))]
+
+    def _request_connection_points_change(self, connection_id: ConnectionID, points: list[tuple[int, int]], text: str) -> None:
+        if self._component is not None:
+            self.connection_points_change_requested.emit(self._component, connection_id, points, text)
+
+    def _snap_position(self, position: QPointF) -> tuple[int, int]:
+        size = self.snap_to_grid_size
+        return round(position.x() / size) * size, round(position.y() / size) * size
+
+    @staticmethod
+    def _nearest_segment_index(points: list[tuple[int, int]], position: tuple[int, int]) -> int:
+        best_index = 0
+        best_distance = float("inf")
+        for index, (start, end) in enumerate(pairwise(points)):
+            dx = end[0] - start[0]
+            dy = end[1] - start[1]
+            length_squared = dx * dx + dy * dy
+            ratio = 0.0 if not length_squared else max(0.0, min(1.0, ((position[0] - start[0]) * dx + (position[1] - start[1]) * dy) / length_squared))
+            closest_x = start[0] + ratio * dx
+            closest_y = start[1] + ratio * dy
+            distance = (position[0] - closest_x) ** 2 + (position[1] - closest_y) ** 2
+            if distance < best_distance:
+                best_index = index
+                best_distance = distance
+        return best_index
+
+    def begin_component_move(self) -> None:
+        self._component_drag_starts = {item.component_id: (round(item.pos().x()), round(item.pos().y())) for item in self.scene.selectedItems() if isinstance(item, GraphComponentItem)}
+
+    def finish_component_moves(self) -> None:
+        starts = self._component_drag_starts
+        self._component_drag_starts = {}
+        if self._component is None:
+            return
+        positions = {}
+        for component_id, old_position in starts.items():
+            item = self._component_items[component_id]
+            position = (round(item.pos().x()), round(item.pos().y()))
+            item.setPos(*position)
+            if position != old_position:
+                positions[component_id] = position
+        if positions:
+            self.component_moves_requested.emit(self._component, positions)
+
+    def finish_component_label_move(self, component_id: ComponentID, relative_position: tuple[int, int]) -> None:
+        if self._component is not None:
+            self.component_label_move_requested.emit(self._component, component_id, relative_position)
+
+    def component_label_visible(self, component_id: ComponentID) -> bool:
+        return self._graph.component_labels.get(component_id, GraphComponentLabel()).visible
+
+    def set_component_label(self, component_id: ComponentID, label: GraphComponentLabel | None) -> None:
+        if label is None:
+            self._graph.component_labels.pop(component_id, None)
+            label = GraphComponentLabel()
+        else:
+            self._graph.component_labels[component_id] = label
+        item = self._component_label_items.pop(component_id, None)
+        if item is not None:
+            item.setParentItem(None)
+            self.scene.removeItem(item)
+        component = self._component
+        if component is not None and label.visible and component_id in component.implementation.graph.components:
+            self._create_component_label_item(component_id, component.implementation.graph.components[component_id].name, label)
+
+    def _create_component_label_item(self, component_id: ComponentID, text: str, label: GraphComponentLabel) -> None:
+        item = GraphComponentLabelItem(component_id, text, label, self._component_items[component_id], self)
+        self._component_label_items[component_id] = item
+
+    def set_component_position(self, component_id: ComponentID, position: tuple[int, int] | None) -> None:
+        item = self._component_items.get(component_id)
+        if item is None:
+            return
+        if position is None:
+            self._graph.component_positions.pop(component_id, None)
+            index = list(self._component_items).index(component_id)
+            position = (index * FALLBACK_COMPONENT_SPACING, 0)
+        else:
+            self._graph.component_positions[component_id] = position
+        item.setPos(*position)
+        self.refresh_connections()
+
+    def _item_position(self, component_id: ComponentID) -> tuple[float, float]:
+        position = self._component_items[component_id].pos()
+        return position.x(), position.y()
+
+    @staticmethod
+    def _straighten_direct_connection(points: list[tuple[float, float]]) -> list[tuple[float, float]]:
+        if len(points) != 2:
+            return points
+        source, target = points
+        dx = target[0] - source[0]
+        dy = target[1] - source[1]
+        if abs(dx) <= CONNECTION_STRAIGHTEN_TOLERANCE and abs(dx) < abs(dy):
+            x = (source[0] + target[0]) / 2
+            return [(x, source[1]), (x, target[1])]
+        if abs(dy) <= CONNECTION_STRAIGHTEN_TOLERANCE and abs(dy) < abs(dx):
+            y = (source[1] + target[1]) / 2
+            return [(source[0], y), (target[0], y)]
+        return points
+
+    @staticmethod
+    def _clip_connection(points: list[tuple[float, float]], source_bounds: QRectF, target_bounds: QRectF, spacing: float) -> list[tuple[float, float]]:
+        source = points[0]
+        target = points[-1]
+        source_direction = next((point for point in points[1:] if point != source), None)
+        target_direction = next((point for point in reversed(points[:-1]) if point != target), None)
+        if source_direction is None or target_direction is None:
+            return points
+        clipped = list(points)
+        clipped[0] = GraphEditorWidget._bounding_box_edge(source_bounds, source, source_direction, spacing)
+        clipped[-1] = GraphEditorWidget._bounding_box_edge(target_bounds, target, target_direction, spacing)
+        return clipped
+
+    @staticmethod
+    def _bounding_box_edge(bounds: QRectF, origin: tuple[float, float], toward: tuple[float, float], spacing: float) -> tuple[float, float]:
+        bounds = bounds.adjusted(-spacing, -spacing, spacing, spacing)
+        dx = toward[0] - origin[0]
+        dy = toward[1] - origin[1]
+        horizontal_scale = (bounds.right() - origin[0]) / dx if dx > 0 else (bounds.left() - origin[0]) / dx if dx < 0 else float("inf")
+        vertical_scale = (bounds.bottom() - origin[1]) / dy if dy > 0 else (bounds.top() - origin[1]) / dy if dy < 0 else float("inf")
+        scale = min(horizontal_scale, vertical_scale)
+        return origin[0] + dx * scale, origin[1] + dy * scale
 
     def component(self) -> Component | None:
         return self._component
 
+    def selected_component_ids(self) -> list[ComponentID]:
+        return [item.component_id for item in self.scene.selectedItems() if isinstance(item, GraphComponentItem)]
+
+    def selected_connection_ids(self) -> list[ConnectionID]:
+        return [item.connection_id for item in self.scene.selectedItems() if isinstance(item, GraphConnectionItem) and item.connection_id is not None]
+
+    def delete_selected_connections(self) -> None:
+        if self._component is not None:
+            self.connections_delete_requested.emit(self._component, self.selected_connection_ids())
+
+    def open_component(self, component_id: ComponentID) -> None:
+        self._clear_connection_start()
+        self.component_open_requested.emit(component_id)
+
+    def choose_connection_component(self, component_id: ComponentID, screen_position) -> None:
+        if self._component is None or self._mode is not GraphEditorMode.CONNECTION:
+            return
+        if self._connection_start is None:
+            self.scene.clearSelection()
+            self._component_items[component_id].setSelected(True)
+            self._connection_start = component_id
+            self._connection_preview = QGraphicsPathItem()
+            self._connection_preview.setPen(QPen(QColor("#606060"), CONNECTION_WIDTH, Qt.PenStyle.DashLine))
+            self._connection_preview.setZValue(-0.5)
+            self.scene.addItem(self._connection_preview)
+            return
+        start = self._connection_start
+        self._clear_connection_start()
+        self.scene.clearSelection()
+        if start == component_id:
+            return
+        options = self._connection_options(start, component_id)
+        if len(options) == 1:
+            self.connection_add_requested.emit(self._component, options[0][1])
+            return
+        if not options:
+            return
+        menu = QMenu(self)
+        actions = []
+        for label, connection, _preferred in options:
+            action = menu.addAction(label)
+            actions.append((action, connection))
+        menu.setActiveAction(actions[0][0])
+        selected = menu.exec(screen_position)
+        for action, connection in actions:
+            if selected is action:
+                self.connection_add_requested.emit(self._component, connection)
+                break
+
+    def _update_connection_preview(self, mouse_position: QPointF) -> None:
+        if self._connection_start is None or self._connection_preview is None:
+            return
+        source = self._item_position(self._connection_start)
+        if mouse_position == QPointF(*source):
+            self._connection_preview.setPath(QPainterPath(mouse_position))
+            return
+        bounds = self._component_bounds[self._connection_start].translated(*source)
+        spacing = max(BOND_CONNECTION_BOUNDING_BOX_SPACING, SIGNAL_CONNECTION_BOUNDING_BOX_SPACING)
+        start = self._bounding_box_edge(bounds, source, (mouse_position.x(), mouse_position.y()), spacing)
+        path = QPainterPath(QPointF(*start))
+        path.lineTo(mouse_position)
+        self._connection_preview.setPath(path)
+
+    def _clear_connection_start(self) -> None:
+        self._connection_start = None
+        if self._connection_preview is not None and self._connection_preview.scene() is self.scene:
+            self.scene.removeItem(self._connection_preview)
+        self._connection_preview = None
+
+    def _connection_options(self, first_id: ComponentID, second_id: ComponentID) -> list[tuple[str, Connection, bool]]:
+        if self._component is None:
+            return []
+        components = self._component.implementation.graph.components
+        first = components[first_id]
+        second = components[second_id]
+        used_ports = {port_id for connection in self._component.implementation.graph.connections.values() for port_id in (connection.source, connection.target)}
+        options = []
+        for first_port_id, first_port in first.interface.ports.items():
+            for second_port_id, second_port in second.interface.ports.items():
+                if not self._compatible_ports(first_port, second_port) or not self._port_available(first_port_id, first_port, used_ports) or not self._port_available(second_port_id, second_port, used_ports):
+                    continue
+                preferred = first_port.direction is SignalDirection.OUTPUT and second_port.direction is SignalDirection.INPUT
+                reverse_preferred = second_port.direction is SignalDirection.OUTPUT and first_port.direction is SignalDirection.INPUT
+                if reverse_preferred:
+                    source_id, source_port, source_name = second_port_id, second_port, second.name
+                    target_id, target_port, target_name = first_port_id, first_port, first.name
+                else:
+                    source_id, source_port, source_name = first_port_id, first_port, first.name
+                    target_id, target_port, target_name = second_port_id, second_port, second.name
+                connection_type = SignalConnection if isinstance(source_port, SignalPort) else BondConnection
+                label = f"{source_name}.{source_port.name} → {target_name}.{target_port.name}"
+                options.append((label, connection_type(source=source_id, target=target_id), preferred or reverse_preferred))
+        return sorted(options, key=lambda option: not option[2])
+
+    @staticmethod
+    def _compatible_ports(first: Port, second: Port) -> bool:
+        if isinstance(first, SignalPort) and isinstance(second, SignalPort):
+            return first.direction is not second.direction
+        if isinstance(first, BondPort) and isinstance(second, BondPort):
+            return not first.domain or not second.domain or first.domain == second.domain
+        return False
+
+    @staticmethod
+    def _port_available(port_id: PortID, port: Port, used_ports: set[PortID]) -> bool:
+        if isinstance(port, SignalPort):
+            return port.direction is SignalDirection.OUTPUT or port.multiplicity or port_id not in used_ports
+        if isinstance(port, BondPort):
+            return port.multiplicity or port_id not in used_ports
+        return False
+
+    def paste_position(self) -> tuple[int, int]:
+        viewport = self.ui.graphicsView.viewport()
+        viewport_position = viewport.mapFromGlobal(QCursor.pos())
+        if not viewport.rect().contains(viewport_position):
+            viewport_position = viewport.rect().center()
+        scene_position = self.ui.graphicsView.mapToScene(viewport_position)
+        size = self.snap_to_grid_size
+        return round(scene_position.x() / size) * size, round(scene_position.y() / size) * size
+
+    def zoom_to_fit(self) -> None:
+        bounds = self.scene.itemsBoundingRect()
+        if bounds.isEmpty():
+            self.ui.graphicsView.resetTransform()
+            self.ui.graphicsView.centerOn(0, 0)
+            return
+        bounds.adjust(-ZOOM_TO_FIT_PADDING, -ZOOM_TO_FIT_PADDING, ZOOM_TO_FIT_PADDING, ZOOM_TO_FIT_PADDING)
+        self.ui.graphicsView.fitInView(bounds, Qt.AspectRatioMode.KeepAspectRatio)
+        current_zoom = self.ui.graphicsView.transform().m11()
+        target_zoom = min(MAX_ZOOM, max(MIN_ZOOM, current_zoom))
+        if target_zoom != current_zoom:
+            self.ui.graphicsView.scale(target_zoom / current_zoom, target_zoom / current_zoom)
+        self.ui.graphicsView.centerOn(bounds.center())
+
     def eventFilter(self, watched: QObject, event: QEvent) -> bool:
+        if watched is self.ui.graphicsView.viewport() and event.type() in (QEvent.Type.DragEnter, QEvent.Type.DragMove):
+            assert isinstance(event, (QDragEnterEvent, QDragMoveEvent))
+            if self._component is not None and event.mimeData().hasFormat(COMPONENTS_MIME):
+                event.setDropAction(Qt.DropAction.CopyAction)
+                event.accept()
+                return True
+        if watched is self.ui.graphicsView.viewport() and event.type() == QEvent.Type.Drop:
+            assert isinstance(event, QDropEvent)
+            if self._component is not None and event.mimeData().hasFormat(COMPONENTS_MIME):
+                try:
+                    payload = json.loads(bytes(event.mimeData().data(COMPONENTS_MIME)).decode("utf-8"))
+                except (UnicodeDecodeError, json.JSONDecodeError):
+                    return True
+                if isinstance(payload, dict):
+                    position = self._snap_position(self.ui.graphicsView.mapToScene(event.position().toPoint()))
+                    self.component_drop_requested.emit(self._component, payload, position)
+                    event.setDropAction(Qt.DropAction.CopyAction)
+                    event.accept()
+                return True
+        if watched is self.ui.graphicsView.viewport() and event.type() == QEvent.Type.MouseMove:
+            assert isinstance(event, QMouseEvent)
+            self._update_connection_preview(self.ui.graphicsView.mapToScene(event.position().toPoint()))
         if watched is self.ui.graphicsView.viewport() and event.type() == QEvent.Type.Wheel:
             assert isinstance(event, QWheelEvent)
             if event.modifiers() & Qt.KeyboardModifier.ControlModifier:

src/bedit_gui/views/icon_editor_window.py

@@ -11,7 +11,7 @@ from bedit_gui.models import Icon, Shape, ShapeID
 from bedit_gui.services import icon_files
 from bedit_gui.services.application_logging import get_logger
 from bedit_gui.ui.generated.ui_icon_editor_window import Ui_iconEditor
-from bedit_gui.views.icon_graphics_scene import IconGraphicsScene, LineCreationTool, RectangleCreationTool, TextCreationTool
+from bedit_gui.views.icon_graphics_scene import EllipseCreationTool, IconGraphicsScene, LineCreationTool, RectangleCreationTool, TextCreationTool
 from bedit_gui.views.shape_options_dialog import ShapeOptionsDialog
 
 logger = get_logger(__name__)
@@ -123,6 +123,8 @@ class IconEditorWindow(QMainWindow):
         self.ui.graphicsView.viewport().installEventFilter(self)
         self.ui.actionAdd_Rectangle.setCheckable(True)
         self.ui.actionAdd_Rectangle.triggered.connect(self._start_rectangle_tool)
+        self.ui.actionAdd_Circle.setCheckable(True)
+        self.ui.actionAdd_Circle.triggered.connect(self._start_ellipse_tool)
         self.ui.actionAdd_Text.setCheckable(True)
         self.ui.actionAdd_Text.triggered.connect(self._start_text_tool)
         self.ui.actionAdd_Line.setCheckable(True)
@@ -306,14 +308,24 @@ class IconEditorWindow(QMainWindow):
 
     def _start_rectangle_tool(self) -> None:
         layer = max((shape.layer for shape in self._icon.shapes.values()), default=-1) + 1
+        self.ui.actionAdd_Circle.setChecked(False)
         self.ui.actionAdd_Text.setChecked(False)
         self.ui.actionAdd_Line.setChecked(False)
         self.scene.set_creation_tool(RectangleCreationTool(self.scene, layer))
         self.ui.actionAdd_Rectangle.setChecked(True)
 
+    def _start_ellipse_tool(self) -> None:
+        layer = max((shape.layer for shape in self._icon.shapes.values()), default=-1) + 1
+        self.ui.actionAdd_Rectangle.setChecked(False)
+        self.ui.actionAdd_Text.setChecked(False)
+        self.ui.actionAdd_Line.setChecked(False)
+        self.scene.set_creation_tool(EllipseCreationTool(self.scene, layer))
+        self.ui.actionAdd_Circle.setChecked(True)
+
     def _start_text_tool(self) -> None:
         layer = max((shape.layer for shape in self._icon.shapes.values()), default=-1) + 1
         self.ui.actionAdd_Rectangle.setChecked(False)
+        self.ui.actionAdd_Circle.setChecked(False)
         self.ui.actionAdd_Line.setChecked(False)
         self.scene.set_creation_tool(TextCreationTool(self.scene, layer))
         self.ui.actionAdd_Text.setChecked(True)
@@ -321,6 +333,7 @@ class IconEditorWindow(QMainWindow):
     def _start_line_tool(self) -> None:
         layer = max((shape.layer for shape in self._icon.shapes.values()), default=-1) + 1
         self.ui.actionAdd_Rectangle.setChecked(False)
+        self.ui.actionAdd_Circle.setChecked(False)
         self.ui.actionAdd_Text.setChecked(False)
         self.scene.set_creation_tool(LineCreationTool(self.scene, layer))
         self.ui.actionAdd_Line.setChecked(True)
@@ -328,6 +341,7 @@ class IconEditorWindow(QMainWindow):
     def _tool_active_changed(self, active: bool) -> None:
         if not active:
             self.ui.actionAdd_Rectangle.setChecked(False)
+            self.ui.actionAdd_Circle.setChecked(False)
             self.ui.actionAdd_Text.setChecked(False)
             self.ui.actionAdd_Line.setChecked(False)
         cursor = Qt.CursorShape.CrossCursor if active else Qt.CursorShape.ArrowCursor

src/bedit_gui/views/icon_graphics_scene.py

@@ -6,10 +6,12 @@ from typing import Protocol
 
 from PySide6.QtCore import QLineF, QObject, QPointF, QRectF, Qt, Signal
 from PySide6.QtGui import QBrush, QColor, QFont, QPainter, QPainterPath, QPen
-from PySide6.QtWidgets import QGraphicsItem, QGraphicsLineItem, QGraphicsPathItem, QGraphicsRectItem, QGraphicsScene, QGraphicsSceneContextMenuEvent, QGraphicsSceneMouseEvent, QMenu, QStyleOptionGraphicsItem, QWidget
+from PySide6.QtWidgets import QGraphicsEllipseItem, QGraphicsItem, QGraphicsLineItem, QGraphicsPathItem, QGraphicsRectItem, QGraphicsScene, QGraphicsSceneContextMenuEvent, QGraphicsSceneMouseEvent, QMenu, QStyleOptionGraphicsItem, QWidget
 
 from bedit_core.models import Port, PortID, SignalDirection
-from bedit_gui.models import Icon, Line, LineType, Rectangle, Shape, ShapeID, Text
+from bedit_gui.models import Ellipse, Icon, Line, LineType, Rectangle, Shape, ShapeID, Text
+
+ICON_SCENE_SIZE = 512
 
 
 class ShapeCreationTool(Protocol):
@@ -24,7 +26,7 @@ class RectangleCreationTool:
         self.scene = scene
         self.layer = layer
         self.start: QPointF | None = None
-        self.preview: QGraphicsRectItem | None = None
+        self.preview: QGraphicsRectItem | QGraphicsEllipseItem | None = None
 
     def begin(self, position: QPointF) -> None:
         position = self._bounded(position)
@@ -67,6 +69,16 @@ class TextCreationTool(RectangleCreationTool):
         return Text(layer=self.layer, pos=(round(rect.x()), round(rect.y())), width=rect.width(), height=rect.height(), text="Text")
 
 
+class EllipseCreationTool(RectangleCreationTool):
+    def begin(self, position: QPointF) -> None:
+        position = self._bounded(position)
+        self.start = position
+        self.preview = self.scene.addEllipse(QRectF(position, position), QPen(Qt.PenStyle.DashLine))
+
+    def create_shape(self, rect: QRectF) -> Shape:
+        return Ellipse(layer=self.layer, pos=(round(rect.x()), round(rect.y())), width=rect.width(), height=rect.height())
+
+
 class LineCreationTool:
     def __init__(self, scene: QGraphicsScene, layer: int) -> None:
         self.scene = scene
@@ -107,7 +119,8 @@ class LineCreationTool:
 
 
 class ShapeGraphicsItem(QGraphicsPathItem):
-    handle_size = 6.0
+    handle_size = 8.0
+    handle_hit_size = 16.0
 
     def __init__(self, shape_id: ShapeID, shape: Shape, scene: IconGraphicsScene) -> None:
         super().__init__()
@@ -126,13 +139,24 @@ class ShapeGraphicsItem(QGraphicsPathItem):
     def resize_handles(self) -> dict[str, QRectF]:
         return {"size": self.resize_handle_rect()}
 
+    def resize_handle_hit_rects(self) -> dict[str, QRectF]:
+        size = self.handle_hit_size
+        return {name: QRectF(rect.center().x() - size / 2, rect.center().y() - size / 2, size, size) for name, rect in self.resize_handles().items()}
+
     def boundingRect(self) -> QRectF:
-        margin = self.handle_size / 2
+        margin = self.handle_hit_size / 2
         return super().boundingRect().adjusted(-margin, -margin, margin, margin)
 
+    def shape(self) -> QPainterPath:
+        path = super().shape()
+        if self.isSelected():
+            for rect in self.resize_handle_hit_rects().values():
+                path.addRect(rect)
+        return path
+
     def mousePressEvent(self, event: QGraphicsSceneMouseEvent) -> None:
         self._original_shape = self.current_shape()
-        self._resize_handle = next((name for name, rect in self.resize_handles().items() if self.isSelected() and rect.contains(event.pos())), None)
+        self._resize_handle = next((name for name, rect in self.resize_handle_hit_rects().items() if self.isSelected() and rect.contains(event.pos())), None)
         if self._resize_handle is not None:
             event.accept()
             return
@@ -224,6 +248,37 @@ class RectangleGraphicsItem(ShapeGraphicsItem):
         self.setPath(path)
 
 
+class EllipseGraphicsItem(ShapeGraphicsItem):
+    def __init__(self, shape_id: ShapeID, shape: Ellipse, scene: IconGraphicsScene) -> None:
+        super().__init__(shape_id, shape, scene)
+        self.ellipse = deepcopy(shape)
+        self.setPos(shape.pos[0], shape.pos[1])
+        self._set_size(shape.width, shape.height)
+        self.setPen(scene._pen(shape))
+        self.setBrush(QBrush(scene._color(shape.fill_color)))
+        self.setZValue(shape.layer)
+
+    def current_shape(self) -> Ellipse:
+        shape = deepcopy(self.ellipse)
+        shape.pos = (round(self.pos().x()), round(self.pos().y()))
+        rect = self.path().boundingRect()
+        shape.width = rect.width()
+        shape.height = rect.height()
+        return shape
+
+    def resize_to(self, position: QPointF, _handle: str) -> None:
+        bounds = self.icon_scene.sceneRect()
+        width = max(1.0, min(bounds.right(), round(position.x())) - self.pos().x())
+        height = max(1.0, min(bounds.bottom(), round(position.y())) - self.pos().y())
+        self._set_size(width, height)
+
+    def _set_size(self, width: float, height: float) -> None:
+        self.prepareGeometryChange()
+        path = QPainterPath()
+        path.addEllipse(QRectF(0, 0, width, height))
+        self.setPath(path)
+
+
 class TextGraphicsItem(ShapeGraphicsItem):
     def __init__(self, shape_id: ShapeID, shape: Text, scene: IconGraphicsScene) -> None:
         super().__init__(shape_id, shape, scene)
@@ -356,7 +411,7 @@ class IconGraphicsScene(QGraphicsScene):
         super().__init__(parent)
         self._tool: ShapeCreationTool | None = None
         self._ports: dict[PortID, Port] = {}
-        self.setSceneRect(-64, -64, 128, 128)
+        self.setSceneRect(-ICON_SCENE_SIZE / 2, -ICON_SCENE_SIZE / 2, ICON_SCENE_SIZE, ICON_SCENE_SIZE)
 
     def set_ports(self, ports: dict[PortID, Port]) -> None:
         self._ports = deepcopy(ports)
@@ -438,13 +493,15 @@ class IconGraphicsScene(QGraphicsScene):
     def _add_shape_item(self, shape_id: ShapeID, shape: Shape) -> None:
         if isinstance(shape, Rectangle):
             self.addItem(RectangleGraphicsItem(shape_id, shape, self))
+        elif isinstance(shape, Ellipse):
+            self.addItem(EllipseGraphicsItem(shape_id, shape, self))
         elif isinstance(shape, Text):
             self.addItem(TextGraphicsItem(shape_id, shape, self))
         elif isinstance(shape, Line):
             self.addItem(LineGraphicsItem(shape_id, shape, self))
 
     @staticmethod
-    def _pen(shape: Rectangle) -> QPen:
+    def _pen(shape: Rectangle | Ellipse) -> QPen:
         return IconGraphicsScene._line_pen(shape.line_type, shape.line_thickness, shape.line_color)
 
     @staticmethod

src/bedit_gui/views/main_window.py

@@ -7,7 +7,7 @@ from bedit_gui.views.graph_editor_widget import GraphEditorWidget
 
 
 class MainWindow(QMainWindow):
-    def __init__(self) -> None:
+    def __init__(self, snap_to_grid_size: int = 4) -> None:
         super().__init__()
 
         self.ui = Ui_MainWindow()
@@ -18,7 +18,7 @@ class MainWindow(QMainWindow):
         self.equation_editor = EquationEditorWidget(self.ui.centralwidget)
         self.equation_editor.hide()
         central_layout.addWidget(self.equation_editor)
-        self.graph_editor = GraphEditorWidget(self.ui.centralwidget)
+        self.graph_editor = GraphEditorWidget(self.ui.centralwidget, snap_to_grid_size)
         self.graph_editor.hide()
         central_layout.addWidget(self.graph_editor)
 

src/bedit_gui/views/models/document_tree_model.py

@@ -22,19 +22,21 @@ class DocumentTreeModel(QAbstractItemModel):
     rename_document_requested = Signal(str)
     rename_component_requested = Signal(Component, str)
 
-    def __init__(self) -> None:
+    def __init__(self, editable: bool = True) -> None:
         super().__init__()
-        self._document: CoreDocument | None = None
+        self._editable = editable
         self._root = DocumentTreeNode("Document", None, None, None, [])
         self._component_icons: dict[ComponentID, QIcon] = {}
         self._component_nodes: dict[ComponentID, DocumentTreeNode] = {}
 
     def set_document(self, document: CoreDocument) -> None:
+        self.set_documents([document])
+
+    def set_documents(self, documents: list[CoreDocument]) -> None:
         self.beginResetModel()
-        self._document = document
         self._component_icons = {}
         self._component_nodes = {}
-        self._root = self._build_tree(document)
+        self._root = self._build_tree(documents)
         self.endResetModel()
 
     def set_component_icon(self, component_id: ComponentID, icon: QIcon) -> None:
@@ -131,6 +133,12 @@ class DocumentTreeModel(QAbstractItemModel):
         node = index.internalPointer()
         return node.value if isinstance(node, DocumentTreeNode) else None
 
+    def component_index(self, component_id: ComponentID) -> QModelIndex:
+        node = self._component_nodes.get(component_id)
+        if node is None or node.parent is None:
+            return QModelIndex()
+        return self.createIndex(node.parent.children.index(node), 0, node)
+
     def flags(self, index: QModelIndex) -> Qt.ItemFlag:
         flags = super().flags(index)
 
@@ -140,12 +148,12 @@ class DocumentTreeModel(QAbstractItemModel):
         node = index.internalPointer()
 
         # Make the document root node editable
-        if index.column() == 0 and isinstance(node, DocumentTreeNode) and isinstance(node.value, (CoreDocument, Component)):
+        if self._editable and index.column() == 0 and isinstance(node, DocumentTreeNode) and isinstance(node.value, (CoreDocument, Component)):
             flags |= Qt.ItemFlag.ItemIsEditable
 
         return flags
 
-    def _build_tree(self, document: CoreDocument) -> DocumentTreeNode:
+    def _build_tree(self, documents: list[CoreDocument]) -> DocumentTreeNode:
         # QT's invisible root
         root = DocumentTreeNode(
             name="",
@@ -154,19 +162,18 @@ class DocumentTreeModel(QAbstractItemModel):
             parent=None,
             children=[],
         )
-        # Add itself as a child so the document root is visible in the tree
-        document_root = DocumentTreeNode(name=document.name, value=document, component_id=None, parent=root, children=[])
-        root.children.append(document_root)
-
-        def _list_children(root: DocumentTreeNode, components: dict[ComponentID, Component]) -> None:
+        def _list_children(parent: DocumentTreeNode, components: dict[ComponentID, Component]) -> None:
             for component_id, component in sorted(components.items(), key=lambda item: (item[1].name.casefold(), item[1].name, str(item[0]))):
-                component_node = DocumentTreeNode(name=component.name, value=component, component_id=component_id, parent=root, children=[])
-                root.children.append(component_node)
+                component_node = DocumentTreeNode(name=component.name, value=component, component_id=component_id, parent=parent, children=[])
+                parent.children.append(component_node)
                 self._component_nodes[component_id] = component_node
 
                 if isinstance(component.implementation, GraphImplementation):
                     _list_children(component_node, component.implementation.graph.components)
 
-        _list_children(document_root, document.root)
+        for document in documents:
+            document_root = DocumentTreeNode(name=document.name, value=document, component_id=None, parent=root, children=[])
+            root.children.append(document_root)
+            _list_children(document_root, document.root)
 
         return root

src/bedit_gui/views/models/library_tree_model.py

@@ -0,0 +1,55 @@
+from __future__ import annotations
+
+import json
+from collections.abc import Callable
+
+from PySide6.QtCore import QMimeData, QModelIndex, Qt
+
+from bedit_core.models import Component
+from bedit_gui.services.component_clipboard import COMPONENTS_MIME
+from bedit_gui.views.models.document_tree_model import DocumentTreeModel
+
+PayloadFactory = Callable[[list[Component]], dict]
+
+
+class LibraryTreeModel(DocumentTreeModel):
+    def __init__(self, payload_factory: PayloadFactory) -> None:
+        super().__init__(editable=False)
+        self._payload_factory = payload_factory
+
+    def flags(self, index: QModelIndex) -> Qt.ItemFlag:
+        flags = super().flags(index)
+        if isinstance(self.value(index), Component):
+            flags |= Qt.ItemFlag.ItemIsDragEnabled
+        return flags
+
+    def mimeTypes(self) -> list[str]:
+        return [COMPONENTS_MIME]
+
+    def mimeData(self, indexes: list[QModelIndex]) -> QMimeData:
+        rows = [index for index in indexes if index.column() == 0 and isinstance(self.value(index), Component)]
+        selected = {id(self.value(index)) for index in rows}
+        components = []
+        added = set()
+        for index in rows:
+            parent = index.parent()
+            if any(id(self.value(parent_index)) in selected for parent_index in self._parents(parent)):
+                continue
+            component = self.value(index)
+            if isinstance(component, Component) and id(component) not in added:
+                components.append(component)
+                added.add(id(component))
+        mime = QMimeData()
+        if components:
+            mime.setData(COMPONENTS_MIME, json.dumps(self._payload_factory(components)).encode("utf-8"))
+            mime.setText("\n".join(component.name for component in components))
+        return mime
+
+    def supportedDragActions(self) -> Qt.DropAction:
+        return Qt.DropAction.CopyAction
+
+    @staticmethod
+    def _parents(index: QModelIndex):
+        while index.isValid():
+            yield index
+            index = index.parent()

src/bedit_gui/views/port_editor_widget.py

@@ -7,6 +7,7 @@ from PySide6.QtGui import QStandardItem, QStandardItemModel
 from PySide6.QtWidgets import QButtonGroup, QLayout, QWidget
 
 from bedit_core.models import BondPort, Port, PortCausality, PortID, SignalDirection, SignalPort, ValueType
+from bedit_gui.models import PortMetadata
 from bedit_gui.ui.generated.ui_port_editor_widget import Ui_PortEditor
 
 
@@ -21,6 +22,7 @@ class PortEditorWidget(QWidget):
         self.ui = Ui_PortEditor()
         self.ui.setupUi(self)
         self._ports: dict[PortID, Port] = {}
+        self._port_metadata: dict[PortID, PortMetadata] = {}
         self._port_ids: list[PortID] = []
         self._loading = False
 
@@ -54,6 +56,7 @@ class PortEditorWidget(QWidget):
         self.ui.widthSize.valueChanged.connect(self._form_changed)
         self.ui.heightSize.valueChanged.connect(self._form_changed)
         self.ui.multiplicityCheckBox.toggled.connect(self._form_changed)
+        self.ui.connectionAnnotationEdit.textChanged.connect(self._form_changed)
         self.ui.signalTypeComboBox.currentIndexChanged.connect(self._form_changed)
         self.ui.domainComboBox.currentTextChanged.connect(self._form_changed)
         self.ui.causalityComboBox.currentIndexChanged.connect(self._form_changed)
@@ -62,14 +65,18 @@ class PortEditorWidget(QWidget):
         self._set_editor_enabled(False)
         self._update_option_visibility()
 
-    def set_ports(self, ports: dict[PortID, Port]) -> None:
+    def set_ports(self, ports: dict[PortID, Port], port_metadata: dict[PortID, PortMetadata] | None = None) -> None:
         self._ports = deepcopy(ports)
+        self._port_metadata = deepcopy(port_metadata or {})
         self._port_ids = list(self._ports)
         self._rebuild_list()
 
     def ports(self) -> dict[PortID, Port]:
         return deepcopy(self._ports)
 
+    def port_metadata(self) -> dict[PortID, PortMetadata]:
+        return deepcopy(self._port_metadata)
+
     def _rebuild_list(self, selected_id: PortID | None = None) -> None:
         self._list_model.clear()
         for port_id in self._port_ids:
@@ -90,7 +97,7 @@ class PortEditorWidget(QWidget):
         self.ui.removePort.setEnabled(port_id is not None)
         self._set_editor_enabled(port_id is not None)
         if port_id is not None:
-            self._load_port(self._ports[port_id])
+            self._load_port(self._ports[port_id], self._port_metadata.get(port_id, PortMetadata()))
 
     def _selected_port_id(self) -> PortID | None:
         index = self.ui.portList.currentIndex()
@@ -98,7 +105,7 @@ class PortEditorWidget(QWidget):
             return None
         return self._port_ids[index.row()]
 
-    def _load_port(self, port: Port) -> None:
+    def _load_port(self, port: Port, metadata: PortMetadata) -> None:
         self._loading = True
         self.ui.nameEdit.setText(port.name)
         self.ui.inputOrientation.setChecked(port.direction is SignalDirection.INPUT)
@@ -106,6 +113,7 @@ class PortEditorWidget(QWidget):
         self.ui.widthSize.setValue(port.matrix_size[0])
         self.ui.heightSize.setValue(port.matrix_size[1])
         self.ui.multiplicityCheckBox.setChecked(port.multiplicity)
+        self.ui.connectionAnnotationEdit.setText(metadata.connection_annotation or "")
         self.ui.descriptionEdit.setPlainText(port.description or "")
 
         if isinstance(port, SignalPort):
@@ -135,6 +143,12 @@ class PortEditorWidget(QWidget):
 
         old_port = self._ports[port_id]
         self._ports[port_id] = self._port_from_form(old_port)
+        annotation = (self.ui.connectionAnnotationEdit.text().strip() or None) if self.ui.multiplicityCheckBox.isChecked() else None
+        metadata = PortMetadata(connection_annotation=annotation)
+        if metadata == PortMetadata():
+            self._port_metadata.pop(port_id, None)
+        else:
+            self._port_metadata[port_id] = metadata
         self._list_model.item(self._port_ids.index(port_id)).setText(
             self._ports[port_id].name
         )
@@ -188,6 +202,7 @@ class PortEditorWidget(QWidget):
             return
         row = self._port_ids.index(port_id)
         del self._ports[port_id]
+        self._port_metadata.pop(port_id, None)
         self._port_ids.remove(port_id)
         selected = (
             self._port_ids[min(row, len(self._port_ids) - 1)]
@@ -201,6 +216,9 @@ class PortEditorWidget(QWidget):
         signal = self.ui.typeSignal.isChecked()
         self._set_layout_visible(self.ui.signalOptions, signal)
         self._set_layout_visible(self.ui.bondOptions, not signal)
+        annotation_visible = self.ui.multiplicityCheckBox.isChecked()
+        self.ui.connectionAnnotationLabel.setVisible(annotation_visible)
+        self.ui.connectionAnnotationEdit.setVisible(annotation_visible)
 
     @staticmethod
     def _set_layout_visible(layout: QLayout, visible: bool) -> None:

src/bedit_gui/views/shape_options_dialog.py

@@ -5,7 +5,7 @@ from copy import deepcopy
 from PySide6.QtCore import QRectF
 from PySide6.QtWidgets import QCheckBox, QComboBox, QDialog, QDialogButtonBox, QDoubleSpinBox, QFormLayout, QLabel, QLineEdit, QSpinBox, QVBoxLayout, QWidget
 
-from bedit_gui.models import Line, LineType, Rectangle, Shape, Text
+from bedit_gui.models import Ellipse, Line, LineType, Rectangle, Shape, Text
 from bedit_gui.views.color_button import ColorButton
 
 
@@ -34,6 +34,8 @@ class ShapeOptionsDialog(QDialog):
 
         if isinstance(shape, Rectangle):
             self._add_rectangle_fields(shape)
+        elif isinstance(shape, Ellipse):
+            self._add_ellipse_fields(shape)
         elif isinstance(shape, Text):
             self._add_text_fields(shape)
         elif isinstance(shape, Line):
@@ -51,6 +53,10 @@ class ShapeOptionsDialog(QDialog):
             width = min(self.width.value(), self._scene_rect.right() - self.x.value())
             height = min(self.height.value(), self._scene_rect.bottom() - self.y.value())
             return Rectangle(layer=self.layer.value(), pos=(self.x.value(), self.y.value()), width=width, height=height, line_type=self.line_type.currentData(), line_thickness=self.line_thickness.value(), corner_radius=self.corner_radius.value(), line_color=self.line_color.color(), fill_color=self.fill_color.color())
+        if isinstance(self._shape, Ellipse):
+            width = min(self.width.value(), self._scene_rect.right() - self.x.value())
+            height = min(self.height.value(), self._scene_rect.bottom() - self.y.value())
+            return Ellipse(layer=self.layer.value(), pos=(self.x.value(), self.y.value()), width=width, height=height, line_type=self.line_type.currentData(), line_thickness=self.line_thickness.value(), line_color=self.line_color.color(), fill_color=self.fill_color.color())
         if isinstance(self._shape, Text):
             width = min(self.width.value(), self._scene_rect.right() - self.x.value())
             height = min(self.height.value(), self._scene_rect.bottom() - self.y.value())
@@ -89,6 +95,29 @@ class ShapeOptionsDialog(QDialog):
         self.form.addRow("Line color", self.line_color)
         self.form.addRow("Fill color", self.fill_color)
 
+    def _add_ellipse_fields(self, shape: Ellipse) -> None:
+        self.width = QSpinBox()
+        self.width.setRange(1, round(self._scene_rect.width()))
+        self.width.setValue(round(shape.width))
+        self.height = QSpinBox()
+        self.height.setRange(1, round(self._scene_rect.height()))
+        self.height.setValue(round(shape.height))
+        self.line_type = QComboBox()
+        for line_type in LineType:
+            self.line_type.addItem(line_type.value.replace("_", " ").title(), line_type)
+        self.line_type.setCurrentIndex(self.line_type.findData(shape.line_type))
+        self.line_thickness = QDoubleSpinBox()
+        self.line_thickness.setRange(0, 1000)
+        self.line_thickness.setValue(shape.line_thickness)
+        self.line_color = ColorButton(shape.line_color)
+        self.fill_color = ColorButton(shape.fill_color)
+        self.form.addRow("Width", self.width)
+        self.form.addRow("Height", self.height)
+        self.form.addRow("Line type", self.line_type)
+        self.form.addRow("Line thickness", self.line_thickness)
+        self.form.addRow("Line color", self.line_color)
+        self.form.addRow("Fill color", self.fill_color)
+
     def _add_text_fields(self, shape: Text) -> None:
         self.width = QSpinBox()
         self.width.setRange(1, round(self._scene_rect.width()))

src/bedit_simulation/openmodelica.py

@@ -24,6 +24,14 @@ class ProcessResult:
     stdout: str
     stderr: str
 
+    def diagnostics(self) -> str:
+        sections = []
+        if self.stdout.strip():
+            sections.append(f"OpenModelica output:\n{self.stdout.strip()}")
+        if self.stderr.strip():
+            sections.append(f"OpenModelica errors:\n{self.stderr.strip()}")
+        return "\n\n".join(sections)
+
 
 class OpenModelicaError(RuntimeError):
     """Raised when OMC cannot start or reports a failure."""
@@ -80,7 +88,7 @@ class OpenModelicaRunner:
                 f"OpenModelica timed out after {error.timeout} seconds"
             ) from error
         if result.return_code != 0:
-            details = result.stderr.strip() or result.stdout.strip()
+            details = result.diagnostics()
             suffix = f": {details}" if details else ""
             raise OpenModelicaError(
                 f"OpenModelica exited with status {result.return_code}{suffix}"
@@ -128,7 +136,7 @@ class OpenModelicaRunner:
                 continue
         result = ProcessResult(command=tuple(command), return_code=process.returncode, stdout=stdout, stderr=stderr)
         if result.return_code != 0:
-            details = result.stderr.strip() or result.stdout.strip()
+            details = result.diagnostics()
             suffix = f": {details}" if details else ""
             raise OpenModelicaError(f"simulation exited with status {result.return_code}{suffix}")
         return result

src/bedit_simulation/simulation.py

@@ -27,6 +27,7 @@ from .results import SimulationResult, load_openmodelica_csv
 _MODEL_FILE = "model.mo"
 _RUN_SCRIPT_FILE = "run.mos"
 _RUN_OUTPUT_FILE = "simulation-output.txt"
+_DEFAULT_LIBRARIES = ("Modelica",)
 
 
 @dataclass(frozen=True)
@@ -374,6 +375,7 @@ class Simulation:
         process = self._run_model_commands(
             modelica,
             [
+                f"checkModel({model_name})",
                 f'buildModel({model_name}, outputFormat="csv")',
                 "getErrorString()",
             ],
@@ -385,7 +387,7 @@ class Simulation:
             if windows_executable.is_file():
                 executable = windows_executable
             else:
-                details = process.stderr.strip() or process.stdout.strip()
+                details = process.diagnostics()
                 suffix = f": {details}" if details else ""
                 raise OpenModelicaError(
                     f"OpenModelica did not build {model_name!r}{suffix}"
@@ -691,10 +693,20 @@ def _load_model_script(
     working_directory: Path,
     commands: Sequence[str],
 ) -> str:
-    """Create a script that loads ``model.mo`` before custom commands."""
+    """Create a script that loads default libraries and ``model.mo`` before custom commands."""
+    load_libraries = []
+    for library in _DEFAULT_LIBRARIES:
+        load_libraries.extend([
+            f"loaded := loadModel({library});",
+            "if not loaded then",
+            "  print(getErrorString());",
+            "  exit(1);",
+            "end if;",
+        ])
     return "\n".join(
         [
             f"cd({json.dumps(str(working_directory.resolve()))});",
+            *load_libraries,
             f"loaded := loadFile({json.dumps(_MODEL_FILE)});",
             "if not loaded then",
             "  print(getErrorString());",