rebuild_visible_regions
rebuild_visible_regions(invalid, localVisible,
rebuild_visible_regions(invalid, invalid, BottomChild());
rebuild_visible_regions(invalid, localVisible, startFrom);
lay->rebuild_visible_regions(invalid, common, lay->BottomChild());
void rebuild_visible_regions(const BRegion &invalid,
topLayer->rebuild_visible_regions(BRegion(Bounds()), BRegion(Bounds()), NULL);