protected override void OnMouseUp(MouseEventArgs e)
        {
            base.OnMouseUp(e);

            if (e.Button == MouseButtons.Left && _selectedTooltip != null)
            {
                _selectedTooltip.StopMouseDrag();
                _selectedTooltip = null;
            }
        }
        protected override void OnMouseDown(MouseEventArgs e)
        {
            base.OnMouseDown(e);

            if (e.Button == MouseButtons.Left && gxOff != null)
            {
                for (int index = _markersOverlay.Markers.Count - 1; index >= 0; index--)
                {
                    var markerPos = FromLatLngToLocal(_markersOverlay.Markers[index].Position);

                    var tooltip = (GMapRoundedToolTip)_markersOverlay.Markers[index].ToolTip;

                    if (tooltip.IsMouseOver(gxOff, e.Location, markerPos))
                    {
                        _selectedTooltip = tooltip;
                        _selectedTooltip.StartMouseDrag(e);
                        return;
                    }
                }
            }
        }