Incrementally build main thread scrolling reasons [spv2]

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1461 matching lines @@
 }
 
 void FrameView::addBackgroundAttachmentFixedObject(LayoutObject* object) {
   ASSERT(!m_backgroundAttachmentFixedObjects.contains(object));
 
   m_backgroundAttachmentFixedObjects.add(object);
   if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
     scrollingCoordinator->frameViewHasBackgroundAttachmentFixedObjectsDidChange(
         this);
 
-  // TODO(pdr): When slimming paint v2 is enabled, invalidate the scroll paint
-  // property subtree for this so main thread scroll reasons are recomputed.
+  // Ensure main thread scrolling reasons are recomputed.
+  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+    setNeedsPaintPropertyUpdate();
+    // The object's scroll properties are not affected by its own background.
+    object->setAllAncestorsNeedPaintPropertyUpdate();
+  }
 }
 
 void FrameView::removeBackgroundAttachmentFixedObject(LayoutObject* object) {
   ASSERT(m_backgroundAttachmentFixedObjects.contains(object));
 
   m_backgroundAttachmentFixedObjects.remove(object);
   if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
     scrollingCoordinator->frameViewHasBackgroundAttachmentFixedObjectsDidChange(
         this);
 
-  // TODO(pdr): When slimming paint v2 is enabled, invalidate the scroll paint
-  // property subtree for this so main thread scroll reasons are recomputed.
+  // Ensure main thread scrolling reasons are recomputed.
+  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+    setNeedsPaintPropertyUpdate();
+    // The object's scroll properties are not affected by its own background.
+    object->setAllAncestorsNeedPaintPropertyUpdate();
+  }
 }
 
 void FrameView::addViewportConstrainedObject(LayoutObject* object) {
   if (!m_viewportConstrainedObjects)
     m_viewportConstrainedObjects = wrapUnique(new ViewportConstrainedObjectSet);
 
   if (!m_viewportConstrainedObjects->contains(object)) {
     m_viewportConstrainedObjects->add(object);
 
     if (ScrollingCoordinator* scrollingCoordinator =
@@ skipping 85 matching lines @@
 void FrameView::scrollContentsIfNeededRecursive() {
   forAllNonThrottledFrameViews(
       [](FrameView& frameView) { frameView.scrollContentsIfNeeded(); });
 }
 
 void FrameView::invalidateBackgroundAttachmentFixedObjects() {
   for (const auto& layoutObject : m_backgroundAttachmentFixedObjects)
     layoutObject->setShouldDoFullPaintInvalidation();
 }
 
+bool FrameView::hasBackgroundAttachmentFixedDescendants(
+    const LayoutObject& object) const {
+  for (const auto* potentialDescendant : m_backgroundAttachmentFixedObjects) {
+    if (potentialDescendant == &object)
+      continue;
+    if (potentialDescendant->isDescendantOf(&object))
+      return true;
+  }
+  return false;
+}
+
 bool FrameView::invalidateViewportConstrainedObjects() {
   bool fastPathAllowed = true;
   for (const auto& viewportConstrainedObject : *m_viewportConstrainedObjects) {
     LayoutObject* layoutObject = viewportConstrainedObject;
     LayoutItem layoutItem = LayoutItem(layoutObject);
     ASSERT(layoutItem.style()->hasViewportConstrainedPosition());
     ASSERT(layoutItem.hasLayer());
     PaintLayer* layer = LayoutBoxModel(layoutItem).layer();
 
     if (layer->isPaintInvalidationContainer())
@@ skipping 2974 matching lines @@
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.width();
 }
 
 int FrameView::initialViewportHeight() const {
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.height();
 }
 
 }  // namespace blink