activate grid button and widget size

src/Vtk/vtkViewport.h

@@ -61,6 +61,10 @@ public:
     vtkCornerAnnotation*        GetAnnotation()  { return m_Annotation; }
     vtkCameraOrientationWidget* GetCameraWidget(){ return m_CameraWidget; }
 
+    // Grid control
+    void SetGridVisible(bool visible);
+    bool GetGridVisible() const;
+
 protected:
     void SetupPipeline(vtkRenderWindowInteractor* iren);