[SPv2] Track paint offset change

third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.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/ObjectPaintInvalidator.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/api/LayoutPartItem.h"
@@ skipping 511 matching lines @@
 PaintInvalidationReason
 ObjectPaintInvalidatorWithContext::invalidatePaintIfNeededWithComputedReason(
     PaintInvalidationReason reason) {
   // We need to invalidate the selection before checking for whether we are
   // doing a full invalidation.  This is because we need to update the previous
   // selection rect regardless.
   invalidateSelectionIfNeeded(reason);
 
   switch (reason) {
     case PaintInvalidationNone:
-      // TODO(trchen): Currently we don't keep track of paint offset of layout
-      // objects.  There are corner cases that the display items need to be
-      // invalidated for paint offset mutation, but incurs no pixel difference
-      // (i.e. bounds stay the same) so no rect-based invalidation is issued.
-      // See crbug.com/508383 and crbug.com/515977.  This is a workaround to
-      // force display items to update paint offset. Exclude non-root SVG whose
-      // paint offset is always zero.
-      if ((!m_object.isSVG() || m_object.isSVGRoot()) &&
-          (m_context.forcedSubtreeInvalidationFlags &
-           PaintInvalidatorContext::ForcedSubtreeInvalidationChecking)) {
-        reason = PaintInvalidationLocationChange;
-        break;
+      // There are corner cases that the display items need to be invalidated
+      // for paint offset mutation, but incurs no pixel difference (i.e. bounds
+      // stay the same) so no rect-based invalidation is issued. See
+      // crbug.com/508383 and crbug.com/515977.
+      if (m_context.forcedSubtreeInvalidationFlags &
+          PaintInvalidatorContext::ForcedSubtreeInvalidationChecking) {
+        if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+          if (m_context.oldPaintOffset != m_context.newPaintOffset) {
+            reason = PaintInvalidationLocationChange;
+            break;
+          }
+        } else {
+          // For SPv1, we conservatively assume the object changed paint offset
+          // except for non-root SVG whose paint offset is always zero.

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

SPv2 fixes the issue of paint offset always being 0?

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

The paint offsets are always 0 intentionally. For SPv2, they always don't change
because they are always zero. The condition is just to make SPv1 and SPv2
behaves in the same for SVG objects to reduce layout test result differences.
The condition was added before this CL.

+          if (!m_object.isSVG() || m_object.isSVGRoot()) {
+            reason = PaintInvalidationLocationChange;
+            break;
+          }
+        }
       }
+
       if (m_object.isSVG() &&
           (m_context.forcedSubtreeInvalidationFlags &
            PaintInvalidatorContext::ForcedSubtreeSVGResourceChange)) {
         reason = PaintInvalidationSVGResourceChange;
         break;
       }
       return PaintInvalidationNone;
     case PaintInvalidationDelayedFull:
       return PaintInvalidationDelayedFull;
     default:
       DCHECK(isImmediateFullPaintInvalidationReason(reason));
       fullyInvalidatePaint(reason, m_context.oldVisualRect,
                            m_context.newVisualRect);
   }
 
   m_context.paintingLayer->setNeedsRepaint();
   m_object.invalidateDisplayItemClients(reason);
   return reason;
 }
 
 DisablePaintInvalidationStateAsserts::DisablePaintInvalidationStateAsserts()
     : m_disabler(&gDisablePaintInvalidationStateAsserts, true) {}
 
 }  // namespace blink