Implement Paint Containment

third_party/WebKit/Source/core/layout/LayoutInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 1119 matching lines @@
 
     if (container->hasOverflowClip())
         offset -= toLayoutBox(container)->scrolledContentOffset();
 
     if (offsetDependsOnPoint)
         *offsetDependsOnPoint = (container->isBox() && container->style()->isFlippedBlocksWritingMode()) || container->isLayoutFlowThread();
 
     return offset;
 }
 
+PaintLayerType LayoutInline::layerTypeRequired() const
+{
+    return isInFlowPositioned() || createsGroup() || hasClipPath() || style()->shouldCompositeForCurrentAnimations()
+        ||  style()->hasCompositorProxy() || style()->containsPaint() ? NormalPaintLayer : NoPaintLayer;

[ojan, 2015/12/10 02:21:40]

Is there a future world in which we don't need a PaintLayer for contained
elements? It's actually an encouraged use of this feature to put it on all the
block elements on a page, but we wouldn't want to create a PaintLayer for each
of them as that's too expensive.

I was going to ask for a TODO to make it not require a layer, but I wasn't sure
what work that would involve.

[chrishtr, 2015/12/10 16:10:52]

PaintLayer may go away in the future in favor of something else, but the things
that make it more heavyweight may or may not.
Well we shouldn't encourage it then...
This is a huge undertaking, right? Stacking contexts are implemented by
PaintLayer.

+}
+
 void LayoutInline::mapLocalToContainer(const LayoutBoxModelObject* paintInvalidationContainer, TransformState& transformState, MapCoordinatesFlags mode, bool* wasFixed, const PaintInvalidationState* paintInvalidationState) const
 {
     if (paintInvalidationContainer == this)
         return;
 
     if (paintInvalidationState && paintInvalidationState->canMapToContainer(paintInvalidationContainer)) {
         LayoutSize offset = paintInvalidationState->paintOffset();
         if (style()->hasInFlowPosition() && layer())
             offset += layer()->offsetForInFlowPosition();
         transformState.move(offset);
@@ skipping 268 matching lines @@
 {
     LayoutBoxModelObject::invalidateDisplayItemClients(paintInvalidationContainer, invalidationReason, paintInvalidationRect);
 
     // Use the paintInvalidationRect of LayoutInline for inline boxes, which saves the cost to calculate paint invalidation rect
     // for every inline box. This won't cause more rasterization invalidations because the whole LayoutInline is being invalidated.
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box, invalidationReason, paintInvalidationRect);
 }
 
 } // namespace blink