[SPInvalidation] Update paint properties when layer or paintsWithTransform status change

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
@@ skipping 201 matching lines @@
   bool usesPaintOffsetTranslation = false;
   if (RuntimeEnabledFeatures::rootLayerScrollingEnabled() &&
       object.isLayoutView()) {
     // Root layer scrolling always creates a translation node for LayoutView to
     // ensure fixed and absolute contexts use the correct transform space.
     usesPaintOffsetTranslation = true;
   } else if (object.isBoxModelObject() &&
              context.current.paintOffset != LayoutPoint()) {
     // TODO(trchen): Eliminate PaintLayer dependency.
     PaintLayer* layer = toLayoutBoxModelObject(object).layer();
-    if (layer && layer->paintsWithTransform(GlobalPaintNormalPhase))
+    if (layer &&
+        layer->paintsWithTransform(GlobalPaintFlattenCompositingLayers))

[Xianzhu, 2016/12/14 18:41:00]

This avoids paintsWithTransform from depending on compositing state, making it
possible to use the same condition in LayoutBoxModelObject::styleDidChange() for
setting needsPaintPropertyUpdate.

[pdr., 2016/12/14 21:52:53]

"compositingState() != PaintsIntoOwnBacking" should always be false in spv2, so
I think we should track this differently. It feels like a layering violation to
use values on the paint property tree for detecting changes. I think we should
be able to catch these changes just based on style. Would it be sufficient to
check for cases where a transform style or fixed style is added or removed?

[Xianzhu, 2016/12/14 22:02:31]

When you posted this comment, I just uploaded a patch-set adding TODO(chrishtr)
here and in LayoutBoxModelObject::styleDidChange() because Chris seems about to
make further change about this (https://codereview.chromium.org/2570423003), and
I'd like to leave the follow-up of the above code to Chris.

I changed the parameter of paintsWithTransform in this CL to ensure correctness
for SlimmingPaintInvalidation.

       usesPaintOffsetTranslation = true;
   }
 
   // We should use the same subpixel paint offset values for snapping
   // regardless of whether a transform is present. If there is a transform
   // we round the paint offset but keep around the residual fractional
   // component for the transformed content to paint with.  In spv1 this was
   // called "subpixel accumulation". For more information, see
   // PaintLayer::subpixelAccumulation() and
   // PaintLayerPainter::paintFragmentByApplyingTransform.
@@ skipping 672 matching lines @@
 #endif
 
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 }
 
 }  // namespace blink