/// <summary>
/// Event raised when the user starts to drag a node.
/// </summary>
private void NodeItem_DragStarted(object source, NodeDragStartedEventArgs e)
{
e.Handled = true;
IsDragging = true;
IsNotDragging = false;
IsDraggingNode = true;
IsNotDraggingNode = false;
var eventArgs = new NodeDragStartedEventArgs(NodeDragStartedEvent, this, SelectedNodes);
RaiseEvent(eventArgs);
e.Cancel = eventArgs.Cancel;
}
/// <summary>
/// Called when the mouse cursor is moved.
/// </summary>
protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);
if (_isDragging)
{
//
// Raise the event to notify that dragging is in progress.
//
var curMousePoint = e.GetPosition(ParentNetworkView);
object item = this;
if (DataContext != null)
{
item = DataContext;
}
var offset = curMousePoint - _lastMousePoint;
if (offset.Length <= Epsilon)
{
return;
}
_lastMousePoint = curMousePoint;
RaiseEvent(new NodeDraggingEventArgs(NodeDraggingEvent, this, new[] { item }, offset.X, offset.Y));
}
else if (_isLeftMouseDown && ParentNetworkView.EnableNodeDragging)
{
//
// The user is left-dragging the node,
// but don't initiate the drag operation until
// the mouse cursor has moved more than the threshold distance.
//
var curMousePoint = e.GetPosition(ParentNetworkView);
var dragDelta = curMousePoint - _lastMousePoint;
var dragDistance = Math.Abs(dragDelta.Length);
if (dragDistance > DragThreshold)
{
//
// When the mouse has been dragged more than the threshold value commence dragging the node.
//
//
// Raise an event to notify that that dragging has commenced.
//
var eventArgs = new NodeDragStartedEventArgs(NodeDragStartedEvent, this, new[] { this });
RaiseEvent(eventArgs);
if (eventArgs.Cancel)
{
//
// Handler of the event disallowed dragging of the node.
//
_isLeftMouseDown = false;
_isLeftMouseAndControlDown = false;
return;
}
_isDragging = true;
CaptureMouse();
e.Handled = true;
}
}
}
