ConstrainClipping
fPainter->ConstrainClipping(region);
void ConstrainClipping(const BRegion* region);
drawingEngine->ConstrainClipping(effectiveClipping);
fDrawingEngine->ConstrainClipping(&effectiveClipping);
fDrawingEngine->ConstrainClipping(&dirtyBorderRegion);
fDrawingEngine->ConstrainClipping(NULL);
void ConstrainClipping(BRegion* region);
void ConstrainClipping(const BRegion& region);