private void OnCanvasMouseUp(object sender, MouseButtonEventArgs e)
 {
     if (_currentListener != null)
     {
         _currentListener.MouseUp(MapArea, GeometryHelper.Convert(e.GetPosition(MapArea)));
         _currentListener = null;
     }
 }
 private void OnCanvasMouseDown(object sender, MouseButtonEventArgs e)
 {
     _currentListener = GetNewActiveTool();
     if (_currentListener != null)
     {
         _currentListener.MouseDown(MapArea, GeometryHelper.Convert(e.GetPosition(MapArea)));
     }
 }