Item containers
NodifyEditor wraps every item in an ItemContainer. The container gives arbitrary content a graph location, selection state, drag behavior, size, and focus visuals.
Why containers exist
The object in ItemsSource is graph data; its data template can render any Avalonia control. The surrounding ItemContainer supplies the behavior that all editor items share. Configure it with NodifyEditor.ItemContainerTheme:
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<nodify:NodifyEditor.ItemContainerTheme>
<ControlTheme TargetType="nodify:ItemContainer"
BasedOn="{StaticResource {x:Type nodify:ItemContainer}}">
<Setter Property="Location" Value="{Binding Location}" />
<Setter Property="IsSelectable" Value="{Binding CanSelect}" />
<Setter Property="IsDraggable" Value="{Binding CanMove}" />
</ControlTheme>
</nodify:NodifyEditor.ItemContainerTheme>
Location and size
Location stores the top-left point in graph coordinates and binds two-way by default. ActualSize reports the rendered size. PreviewLocation and DesiredSizeForSelection expose temporary values used during interaction.
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<Setter Property="Location" Value="{Binding Location}" />
<Setter Property="ActualSize" Value="{Binding Size, Mode=OneWayToSource}" />
LocationChanged fires after the effective location changes. Use the view-model binding for persistence and the event for view-only reactions.
Selection
IsSelectable controls whether the editor may select a container. IsSelected reflects its current state and can be styled:
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<Style Selector="^[IsSelected=True]">
<Setter Property="ZIndex" Value="10" />
</Style>
Bind the editor’s SelectedItems collection for MVVM selection. IsPreviewingSelection indicates how a real-time or pending area selection would affect the container.
Moving and dragging
IsDraggable controls pointer and keyboard movement. The default optimized drag updates PreviewLocation while the item moves and commits Location when the drag ends. If the static NodifyEditor.EnableDraggingContainersOptimizations property is false, Location changes during the drag instead. The container exposes the same operation programmatically:
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container.BeginDragging();
container.UpdateDragging(new Vector(20, 10));
container.EndDragging();
CancelDragging() restores the original location when NodifyEditor.AllowDraggingCancellation is enabled. Dragging near an editor edge can trigger auto-panning.
Locking selection
NodifyEditor.LockSelection() sets IsDraggable to false on selected containers; UnlockSelection() sets it to true. These methods do not remember each container’s previous value. The matching EditorCommands.LockSelection and EditorCommands.UnlockSelection commands support menus and toolbars.
If your view model owns a persistent lock flag, bind IsDraggable in the container theme and change the flag through a view-model command instead of using the editor’s locking methods.
Container events
Each container raises routed events for:
DragStartedDragDeltaDragCompletedLocationChangedIsSelectedChanged
PreviewLocationChanged reports preview updates before the final position is committed. At editor level, ItemsDragStartedCommand, ItemsDragCompletedCommand, and ItemsMoved are usually more convenient for undo and redo systems that operate on multiple selected items.