[SPv2] Track paint offset change

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

 // Copyright 2016 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/PaintInvalidator.h"
 
 #include "core/editing/FrameSelection.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
@@ skipping 314 matching lines @@
   // TODO(crbug.com/648274): This is a workaround for multi-column contents.
   if (object.hasFilterInducingProperty() || object.isLayoutFlowThread())
     context.forcedSubtreeInvalidationFlags |=
         PaintInvalidatorContext::ForcedSubtreeSlowPathRect;
 
   ObjectPaintInvalidator objectPaintInvalidator(object);
   context.oldVisualRect = object.previousVisualRect();
   context.oldLocation = objectPaintInvalidator.previousLocationInBacking();
   context.newVisualRect = computeVisualRectInBacking(object, context);
   context.newLocation = computeLocationInBacking(object, context);
+  context.oldPaintOffset = object.previousPaintOffset();
+  context.newPaintOffset = context.treeBuilderContext.current.paintOffset;
 
   IntSize adjustment = object.scrollAdjustmentForPaintInvalidation(
       *context.paintInvalidationContainer);
   context.newLocation.move(adjustment);
   context.newVisualRect.move(adjustment);
 
   object.getMutableForPainting().setPreviousVisualRect(context.newVisualRect);
   objectPaintInvalidator.setPreviousLocationInBacking(context.newLocation);
+  object.getMutableForPainting().setPreviousPaintOffset(context.newPaintOffset);
 }
 
 void PaintInvalidator::invalidatePaintIfNeeded(
     FrameView& frameView,
     PaintInvalidatorContext& context) {
   LayoutView* layoutView = frameView.layoutView();
   CHECK(layoutView);
 
   context.paintInvalidationContainer =
       context.paintInvalidationContainerForStackedContents =
@@ skipping 70 matching lines @@
                ForcedSubtreeFullInvalidationForStackedContents);
       break;
     case PaintInvalidationSVGResourceChange:
       context.forcedSubtreeInvalidationFlags |=
           PaintInvalidatorContext::ForcedSubtreeSVGResourceChange;
       break;
     default:
       break;
   }
 
-  if (context.oldLocation != context.newLocation)
+  if (context.oldLocation != context.newLocation ||
+      (RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
+       context.oldPaintOffset != context.newPaintOffset)) {
     context.forcedSubtreeInvalidationFlags |=
         PaintInvalidatorContext::ForcedSubtreeInvalidationChecking;
+  }
 
   // TODO(crbug.com/533277): This is a workaround for the bug. Remove when we

[pdr., 2016/11/10 07:35:32]

WDYT about adding a little more info to this comment to make the spv1 and spv2
differences easier to understand?
// This is a workaround for detecting paint offset changes in fixed position
// subtrees and isn't necessary with SPv2 paint offset tracking. See:
crbug.com/533277

[Xianzhu, 2016/11/10 17:41:10]

Done.

   // detect paint offset change.
-  if (reason != PaintInvalidationNone &&
-      hasPercentageTransform(object.styleRef()))
+  if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&

[chrishtr, 2016/11/10 18:42:00]

How was this fixed for SPv2?

[Xianzhu, 2016/11/10 22:51:50]

Good question. To answer your question, at first I thought this were incorrect
because we do need to traverse the subtree to check for changed paint offsets.
Then I debugged with the test case
paint/invalidation/percentage-transform-paint-offset.html, and found that the
logic is actually redundant, even for SPv1. Created
https://codereview.chromium.org/2493673005/ to remove the logic. Waiting for try
results. Rebased this CL onto it.

+      reason != PaintInvalidationNone &&
+      hasPercentageTransform(object.styleRef())) {
     context.forcedSubtreeInvalidationFlags |=
         PaintInvalidatorContext::ForcedSubtreeInvalidationChecking;
+  }
 
   // TODO(crbug.com/490725): This is a workaround for the bug, to force
   // descendant to update visual rects on clipping change.
   if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
       context.oldVisualRect != context.newVisualRect
       // Note that isLayoutView() below becomes unnecessary after the launch of
       // root layer scrolling.
       && (object.hasOverflowClip() || object.isLayoutView()) &&
       !toLayoutBox(object).usesCompositedScrolling())
     context.forcedSubtreeInvalidationFlags |=
         PaintInvalidatorContext::ForcedSubtreeInvalidationRectUpdate;
 
   object.getMutableForPainting().clearPaintInvalidationFlags();
 }
 
 void PaintInvalidator::processPendingDelayedPaintInvalidations() {
   for (auto target : m_pendingDelayedPaintInvalidations)
     target->getMutableForPainting().setShouldDoFullPaintInvalidation(
         PaintInvalidationDelayedFull);
 }
 
 }  // namespace blink