private void DragTimer_Tick(object sender, EventArgs e)
        {
            if (_dockPanel.MouseButtonState != MouseButtons.Left)
            {
                StopDrag();
                return;
            }

            var difference = new Point(_initialContact.X - Cursor.Position.X, _initialContact.Y - Cursor.Position.Y);

            _activeSplitter.UpdateOverlay(difference);
        }
        private void DragTimer_Tick(object sender, EventArgs e)
        {
            if (_dockPanel.MouseButtonState != MouseButtons.Left)
            {
                StopDrag();
                return;
            }

            if (CursorInDockPanel())
            {
                _activeSplitter.UpdateOverlay(SplitterDifference());
            }
        }