static void invalidatePaintOfScrollbarIfNeeded(Scrollbar* scrollbar, GraphicsLayer* graphicsLayer, bool& previouslyWasOverlay, LayoutRect& previousPaintInvalidationRect, bool needsPaintInvalidationArg, LayoutBox& box, const PaintInvalidationState& paintInvalidationState, const LayoutBoxModelObject& paintInvalidationContainer)
{
bool isOverlay = scrollbar && scrollbar->isOverlayScrollbar();
// Calculate paint invalidation rect of the scrollbar, except overlay composited scrollbars because we invalidate the graphics layer only.
LayoutRect newPaintInvalidationRect;
if (scrollbar && !(graphicsLayer && isOverlay))
newPaintInvalidationRect = scrollControlPaintInvalidationRect(scrollbar->frameRect(), box, paintInvalidationState, paintInvalidationContainer);
bool needsPaintInvalidation = needsPaintInvalidationArg;
if (graphicsLayer) {
// If the scrollbar needs paint invalidation but didn't change location/size or the scrollbar is an
// overlay scrollbar (paint invalidation rect is empty), invalidating the graphics layer is enough
// (which has been done in ScrollableArea::setScrollbarNeedsPaintInvalidation()).
// Otherwise invalidatePaintOfScrollControlIfNeeded() below will invalidate the old and new location
// of the scrollbar on the box's paint invalidation container to ensure newly expanded/shrunk areas
// of the box to be invalidated.
needsPaintInvalidation = false;
}
// Invalidate the box's display item client if the box's padding box size is affected by change of the
// non-overlay scrollbar width. We detect change of paint invalidation rect size instead of change of
// scrollbar width change, which may have some false-positives (e.g. the scrollbar changed length but
// not width) but won't invalidate more than expected because in the false-positive case the box must
// have changed size and have been invalidated.
LayoutSize newScrollbarUsedSpaceInBox;
if (!isOverlay)
newScrollbarUsedSpaceInBox = newPaintInvalidationRect.size();
LayoutSize previousScrollbarUsedSpaceInBox;
if (!previouslyWasOverlay)
previousScrollbarUsedSpaceInBox= previousPaintInvalidationRect.size();
if (newScrollbarUsedSpaceInBox != previousScrollbarUsedSpaceInBox)
paintInvalidationContainer.invalidateDisplayItemClientOnBacking(box, PaintInvalidationScroll);
bool invalidated = invalidatePaintOfScrollControlIfNeeded(newPaintInvalidationRect, previousPaintInvalidationRect, needsPaintInvalidation, box, paintInvalidationContainer);
previousPaintInvalidationRect = newPaintInvalidationRect;
previouslyWasOverlay = isOverlay;
if (!invalidated || !scrollbar || graphicsLayer)
return;
paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*scrollbar, PaintInvalidationScroll);
if (scrollbar->isCustomScrollbar())
toLayoutScrollbar(scrollbar)->invalidateDisplayItemClientsOfScrollbarParts(paintInvalidationContainer);
}
