BOOL FillRgn( CRgn* pRgn, CBrush* pBrush );
pRgn
Identifies the region to be filled. The coordinates for the given region are specified in device units.
pBrush
Identifies the brush to be used to fill the region.
Fills the region specified by pRgn with the brush specified by pBrush.
TRUE if the function is successful or FALSE if an error occurs.
CRgn, CDC::PaintRgn, CBrush, ::FillRgn