(WIP) Paint invalidation for slimming paint v2

Source/core/layout/LayoutObject.cpp

Index: Source/core/layout/LayoutObject.cpp
diff --git a/Source/core/layout/LayoutObject.cpp b/Source/core/layout/LayoutObject.cpp
index 330908c1373a39287787cecc3288ad5f4e1e4e70..b77a062f89d9d694bd70ee39b113cef197595cf0 100644
--- a/Source/core/layout/LayoutObject.cpp
+++ b/Source/core/layout/LayoutObject.cpp
@@ -673,6 +673,9 @@ LayoutFlowThread* LayoutObject::locateFlowThreadContainingBlock() const
     return LayoutFlowThread::locateFlowThreadContainingBlockOf(*this);
 }
 
+// TODO: May remove this for slimming paint v2 because if the object paints
+// nothing, then repainting is fast and invalidation of it won't generate any
+// rastarization invalidation.
 bool LayoutObject::skipInvalidationWhenLaidOutChildren() const
 {
     if (!m_bitfields.neededLayoutBecauseOfChildren())
@@ -1044,6 +1047,11 @@ const LayoutBoxModelObject& LayoutObject::containerForPaintInvalidationOnRootedT
 
 const LayoutBoxModelObject* LayoutObject::enclosingCompositedContainer() const
 {
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+        // Get the LayoutView of the top level frame. This is temporary before we remove blink compositing.
+        return adjustCompositedContainerForSpecialAncestors(nullptr);
+    }
+
     LayoutBoxModelObject* container = nullptr;
     // FIXME: CompositingState is not necessarily up to date for many callers of this function.
     DisableCompositingQueryAsserts disabler;
@@ -1204,7 +1212,7 @@ void LayoutObject::invalidateDisplayItemClients(const LayoutBoxModelObject& pain
 void LayoutObject::setNeedsRepaint()
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
-    ASSERT(document().lifecycle().state() <= DocumentLifecycle::InPaintInvalidation);
+    ASSERT(document().lifecycle().state() <= DocumentLifecycle::InPaintForSlimmingPaintV2);
 
     if (!selfNeedsRepaint()) {
         m_bitfields.setSelfNeedsRepaint(true);
@@ -1215,7 +1223,7 @@ void LayoutObject::setNeedsRepaint()
 void LayoutObject::setChildNeedsRepaint()
 {
     ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
-    ASSERT(document().lifecycle().state() <= DocumentLifecycle::InPaintInvalidation);
+    ASSERT(document().lifecycle().state() <= DocumentLifecycle::InPaintForSlimmingPaintV2);
 
     if (!childNeedsRepaint()) {
         m_bitfields.setChildNeedsRepaint(true);
@@ -1443,6 +1451,37 @@ PaintInvalidationReason LayoutObject::invalidatePaintIfNeeded(PaintInvalidationS
     return invalidationReason;
 }
 
+PaintInvalidationReason LayoutObject::invalidatePaintIfNeededForSlimmingPaintV2(const LayoutPoint& newPaintOffset)
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+    if (!selfShouldCheckForPaintInvalidation())
+        return PaintInvalidationNone;
+
+    LayoutPoint oldPaintOffset = m_previousPaintOffset;
+    m_previousPaintOffset = newPaintOffset;
+
+    const LayoutBoxModelObject& paintInvalidationContainer = containerForPaintInvalidationOnRootedTree(); // This is fast for slimming paint v2.
+    PaintInvalidationReason invalidationReason = paintInvalidationReason(paintInvalidationContainer, LayoutRect(), oldPaintOffset, LayoutRect(), newPaintOffset);
+
+    bool boxDecorationBackgroundObscured = boxDecorationBackgroundIsKnownToBeObscured();
+    if (!isFullPaintInvalidationReason(invalidationReason) && boxDecorationBackgroundObscured != m_bitfields.lastBoxDecorationBackgroundObscured())
+        invalidationReason = PaintInvalidationBackgroundObscurationChange;
+    m_bitfields.setLastBoxDecorationBackgroundObscured(boxDecorationBackgroundObscured);
+
+    TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("blink.invalidation"), "LayoutObject::invalidatePaintIfNeededForSlimmingPaintV2()",
+        "object", this->debugName().ascii(),
+        // TODO: Update the function to reflect new meanings.
+        "", jsonObjectForOldAndNewRects(LayoutRect(), oldPaintOffset, LayoutRect(), newPaintOffset));
+
+    if (invalidationReason == PaintInvalidationNone)
+        return invalidationReason;
+
+    invalidateDisplayItemClients(paintInvalidationContainer);
+
+    clearSelfPaintInvalidationFlags();
+    return invalidationReason;
+}
+
 PaintInvalidationReason LayoutObject::paintInvalidationReason(const LayoutBoxModelObject& paintInvalidationContainer,
     const LayoutRect& oldBounds, const LayoutPoint& oldPositionFromPaintInvalidationBacking,
     const LayoutRect& newBounds, const LayoutPoint& newPositionFromPaintInvalidationBacking) const
@@ -3232,6 +3271,11 @@ inline void LayoutObject::markContainerChainForPaintInvalidation()
 
 void LayoutObject::setShouldInvalidateSelection()
 {
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+        setShouldDoFullPaintInvalidation(PaintInvalidationSelection);
+        return;
+    }
+
     if (!canUpdateSelectionOnRootLineBoxes())
         return;
 
@@ -3273,8 +3317,13 @@ void LayoutObject::clearPaintInvalidationState(const PaintInvalidationState& pai
     // paintInvalidationStateIsDirty should be kept in sync with the
     // booleans that are cleared below.
     ASSERT(paintInvalidationState.ancestorHadPaintInvalidationForLocationChange() || paintInvalidationStateIsDirty());
-    clearShouldDoFullPaintInvalidation();
     m_bitfields.setChildShouldCheckForPaintInvalidation(false);
+    clearSelfPaintInvalidationFlags();
+}
+
+void LayoutObject::clearSelfPaintInvalidationFlags()
+{
+    clearShouldDoFullPaintInvalidation();
     m_bitfields.setNeededLayoutBecauseOfChildren(false);
     m_bitfields.setShouldInvalidateOverflowForPaint(false);
     m_bitfields.setMayNeedPaintInvalidation(false);