Rectangle IDockDragSource.BeginDrag(Point ptMouse)
{
Point location = PointToScreen(new Point(0, 0));
Size size;
DockPane floatPane = ActiveContent.DockHandler.FloatPane;
if (DockState == DockState.Float || floatPane == null || floatPane.FloatWindow.NestedPanes.Count != 1)
size = DockPanel.DefaultFloatWindowSize;
else
size = floatPane.FloatWindow.Size;
if (ptMouse.X > location.X + size.Width)
location.X += ptMouse.X - (location.X + size.Width) + DockPanel.Theme.Measures.SplitterSize;
return new Rectangle(location, size);
}