createSession method

DragSession createSession(DragSessionType type)

Creates a drag session for managing drag operation lifecycle.

The session automatically handles canvas locking/unlocking. Elements just need to call lifecycle methods: start, end, cancel.

Only one session can be active at a time. Creating a new session while one is active will cancel the existing session first.

Example:

DragSession? _session;

void _handleDragStart(details) {
  _originalPosition = node.position.value; // Capture state
  _session = controller.createSession(DragSessionType.nodeDrag);
  _session!.start(); // Locks canvas
}

void _handleDragEnd(details) {
  _session?.end(); // Unlocks canvas
  _session = null;
}

void _handleDragCancel() {
  _session?.cancel(); // Unlocks canvas
  _session = null;
  node.position.value = _originalPosition!; // Restore state
}

Implementation

DragSession createSession(DragSessionType type) {
  // Cancel any existing active session
  _activeSession?.cancel();

  // Create new session
  _activeSession = _DragSessionImpl(type, interaction, _onSessionEnded);
  return _activeSession!;
}