(WIP) Paint invalidation for slimming paint v2

Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 1382 matching lines @@
             if (area->hasHorizontalBarDamage())
                 invalidatePaintRectangleNotInvalidatingDisplayItemClients(LayoutRect(area->horizontalBarDamage()));
         }
     }
 
     // This is for the next invalidatePaintIfNeeded so must be at the end.
     savePreviousBoxSizesIfNeeded();
     return reason;
 }
 
+PaintInvalidationReason LayoutBox::invalidatePaintIfNeededForSlimmingPaintV2(const LayoutPoint& paintOffset)
+{
+    PaintInvalidationReason fullInvalidationReason = fullPaintInvalidationReason();
+    // If the current paint invalidation reason is PaintInvalidationDelayedFull, then this paint invalidation can delayed if the
+    // LayoutBox in question is not on-screen. The logic to decide whether this is appropriate exists at the site of the original
+    // paint invalidation that chose PaintInvalidationDelayedFull.
+    if (fullInvalidationReason == PaintInvalidationDelayedFull) {
+        if (!intersectsVisibleViewport())
+            return PaintInvalidationDelayedFull;
+
+        // Reset state back to regular full paint invalidation if the object is onscreen.
+        setShouldDoFullPaintInvalidation(PaintInvalidationFull);
+    }
+
+    PaintInvalidationReason reason = LayoutBoxModelObject::invalidatePaintIfNeededForSlimmingPaintV2(paintOffset);
+
+    // This is for the next invalidatePaintIfNeeded so must be at the end.
+    savePreviousBoxSizesIfNeeded();
+    return reason;
+}
+
 void LayoutBox::clearPaintInvalidationState(const PaintInvalidationState& paintInvalidationState)
 {
     LayoutBoxModelObject::clearPaintInvalidationState(paintInvalidationState);
 
     if (ScrollableArea* area = scrollableArea())
         area->resetScrollbarDamage();
 }
 
 #if ENABLE(ASSERT)
 bool LayoutBox::paintInvalidationStateIsDirty() const
@@ skipping 2570 matching lines @@
     }
 
     if (oldBorderBoxSize.width() != newBorderBoxSize.width() && mustInvalidateBackgroundOrBorderPaintOnWidthChange())
         return PaintInvalidationBorderBoxChange;
     if (oldBorderBoxSize.height() != newBorderBoxSize.height() && mustInvalidateBackgroundOrBorderPaintOnHeightChange())
         return PaintInvalidationBorderBoxChange;
 
     return PaintInvalidationIncremental;
 }
 
+// TODO: Remove incremental invalidation for slimming paint v2.
 void LayoutBox::incrementallyInvalidatePaint(const LayoutBoxModelObject& paintInvalidationContainer, const LayoutRect& oldBounds, const LayoutRect& newBounds, const LayoutPoint& positionFromPaintInvalidationBacking)
 {
     LayoutObject::incrementallyInvalidatePaint(paintInvalidationContainer, oldBounds, newBounds, positionFromPaintInvalidationBacking);
 
     bool hasBoxDecorations = style()->hasBoxDecorations();
     if (!style()->hasBackground() && !hasBoxDecorations)
         return;
 
     LayoutSize oldBorderBoxSize = computePreviousBorderBoxSize(oldBounds.size());
     LayoutSize newBorderBoxSize = size();
@@ skipping 573 matching lines @@
 
 bool LayoutBox::needToSavePreviousBoxSizes()
 {
     // If m_rareData is already created, always save.
     if (m_rareData)
         return true;
 
     LayoutSize paintInvalidationSize = previousPaintInvalidationRectSize();
     // Don't save old box sizes if the paint rect is empty because we'll
     // full invalidate once the paint rect becomes non-empty.
-    if (paintInvalidationSize.isEmpty())
+    if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && paintInvalidationSize.isEmpty())
         return false;
 
     // We need the old box sizes only when the box has background, decorations, or masks.
     // Main LayoutView paints base background, thus interested in box size.
     if (!isLayoutView() && !style()->hasBackground() && !style()->hasBoxDecorations() && !style()->hasMask())
         return false;
 
     // No need to save old border box size if we can use size of the old paint
     // rect as the old border box size in the next invalidation.
-    if (paintInvalidationSize != size())
+    if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && paintInvalidationSize != size())
         return true;
 
     // Background and mask layers can depend on other boxes than border box. See crbug.com/490533
     if (style()->backgroundLayers().thisOrNextLayersUseContentBox() || style()->backgroundLayers().thisOrNextLayersHaveLocalAttachment()
         || style()->maskLayers().thisOrNextLayersUseContentBox())
         return true;
 
     return false;
 }
 
@@ skipping 129 matching lines @@
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 ShapeOutsideInfo* LayoutBox::shapeOutsideInfo() const
 {
     return ShapeOutsideInfo::isEnabledFor(*this) ? ShapeOutsideInfo::info(*this) : nullptr;
 }
 
 } // namespace blink