This document explains how DockControl routes pointer input through the docking pipeline. Reading this guide together with the source code will help you understand how layout changes are performed.
While the high level guides focus on using the provided factories this section dives into the low level mechanics. Understanding these classes is useful when you need behaviour not covered by the default implementation.
DockControl is the main Avalonia control that hosts a layout. Its constructor registers pointer handlers and creates both a DockManager and a DockControlState:
_dockManager = new DockManager();
_dockControlState = new DockControlState();
AddHandler(PointerPressedEvent, PressedHandler);
AddHandler(PointerReleasedEvent, ReleasedHandler);
AddHandler(PointerMovedEvent, MovedHandler);
When the Layout property changes the control is reinitialised with the new root dock:
protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs e)
{
if (e.Property == LayoutProperty)
Initialize(e.NewValue as IDock);
base.OnPropertyChanged(e);
}
The private Initialize method wires up the factory and optionally calls InitLayout:
private void Initialize(IDock? layout)
{
if (layout is null)
return;
Layout = layout;
Layout.Factory?.InitLayout(layout);
}
Pointer events are forwarded to DockControlState.Process which performs hit testing and drag logic:
private void PressedHandler(object? sender, PointerPressedEventArgs e)
{
var position = e.GetPosition(this);
_dockControlState.Process(position, Vector.Zero, EventType.Pressed, ToDragAction(e), this, Layout?.Factory?.DockControls);
}
DockControlState keeps track of the current drag operation. It validates potential drop targets using DockManager and displays DockTarget adorners when appropriate. Once the user releases the pointer the state calls DockManager.ValidateDockable with execution enabled.
DockManager implements the algorithms that move, swap or split dockables. Methods such as MoveDockable, SwapDockable and SplitToolDockable call back into the factory to modify the view models.
// Example: move a document
_dockManager.MoveDockable(document, targetDock, index);
When the user drags a tab or tool the pointer handlers in DockControl delegate the event stream to DockControlState. The state object determines the target area and executes the appropriate operation through DockManager. The manager calls the factory which updates collections on the dock view models, completing the layout update.
If you wish to extend this pipeline—for example to implement custom drag
restrictions—you can subclass DockManager and override its methods before
assigning it to the DockControl instance.
For an overview of all guides see the documentation index.