| gridLayout | Grid that the brush is being used on. | 
| brushTarget | Target of the GridBrushBase.Tool operation. By default the currently selected GameObject. | 
| position | Current selected location of the brush. | 
| tool | Current GridBrushBase.Tool selected. | 
| executing | Whether brush is being used. | 
Callback for painting the GUI for the GridBrush in the Scene View.