Use wxGrid::UpdateGridWindows() helper in wxGridSelection code

This function advantageously replaces the ugly casts that were used in
wxGridSelection code before.

include/wx/generic/grid.h

@@ -1068,6 +1068,7 @@ public:
     void DrawAllGridLines( wxDC& dc, const wxRegion & reg );
     void DrawCell( wxDC& dc, const wxGridCellCoords& );
     void DrawHighlight(wxDC& dc, const wxGridCellCoordsArray& cells);
+    void UpdateGridWindows() const;
 
     // this function is called when the current cell highlight must be redrawn
     // and may be overridden by the user

src/generic/grid.cpp

@@ -4629,6 +4629,10 @@ void wxGrid::EnableDragColMove( bool enable )
     // order, whereas now you can always call ResetColPos() manually if needed
 }
 
+void wxGrid::UpdateGridWindows() const
+{
+    m_gridWin->Update();
+}
 
 //
 // ------ interaction with data model

src/generic/gridsel.cpp

@@ -915,7 +915,7 @@ void wxGridSelection::ClearSelection()
                 ((wxWindow *)m_grid->m_gridWin)->Refresh( false, &r );
 
 #ifdef __WXMAC__
-                ((wxWindow *)m_grid->m_gridWin)->Update();
+                m_grid->UpdateGridWindows();
 #endif
             }
         }
@@ -935,7 +935,7 @@ void wxGridSelection::ClearSelection()
             ((wxWindow *)m_grid->m_gridWin)->Refresh( false, &r );
 
 #ifdef __WXMAC__
-            ((wxWindow *)m_grid->m_gridWin)->Update();
+            m_grid->UpdateGridWindows();
 #endif
         }
     }
@@ -955,7 +955,7 @@ void wxGridSelection::ClearSelection()
                 ((wxWindow *)m_grid->m_gridWin)->Refresh( false, &r );
 
 #ifdef __WXMAC__
-                ((wxWindow *)m_grid->m_gridWin)->Update();
+                m_grid->UpdateGridWindows();
 #endif
             }
         }
@@ -976,7 +976,7 @@ void wxGridSelection::ClearSelection()
                 ((wxWindow *)m_grid->m_gridWin)->Refresh( false, &r );
 
 #ifdef __WXMAC__
-                ((wxWindow *)m_grid->m_gridWin)->Update();
+                m_grid->UpdateGridWindows();
 #endif
             }
         }