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 | virtual | 
Called by the framework to fill the background of toolbar button.
The default implementation uses the standard color to fill the background. Override this member function in your CBCGPVisualManager - derived class to customize the background of a toolbar button. Do not call the default.
The state of a toolbar button can be one of the following BCGBUTTON_STATE enumerated values:
| pDC | A pointer to a device context of a toolbar button. | 
| pButton | A pointer to a toolbar button object to fill. | 
| rect | Specifies the bounding rectangle of a toolbar button. | 
| state | Specifies the state of a toolbar button. |