Separate repaint and layout requirements of StyleDifference (Step 4)

Source/core/rendering/style/RenderStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2011 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 358 matching lines @@
 StyleDifference RenderStyle::visualInvalidationDiff(const RenderStyle& other, unsigned& changedContextSensitiveProperties) const
 {
     // Note, we use .get() on each DataRef below because DataRef::operator== will do a deep
     // compare, which is duplicate work when we're going to compare each property inside
     // this function anyway.
 
     StyleDifference diff;
     if (m_svgStyle.get() != other.m_svgStyle.get())
         diff = m_svgStyle->diff(other.m_svgStyle.get());
 
+    if ((!diff.needsFullLayout() || !diff.needsRepaint()) && diffNeedsFullLayoutAndRepaint(other)) {
+        diff.setNeedsFullLayout();
+        diff.setNeedsRepaintObject();
+    }
+
     if (!diff.needsFullLayout() && diffNeedsFullLayout(other))
         diff.setNeedsFullLayout();
 
     if (!diff.needsFullLayout() && position() != StaticPosition && surround->offset != other.surround->offset) {
         // Optimize for the case where a positioned layer is moving but not changing size.
         if ((position() == AbsolutePosition || position() == FixedPosition)
             && positionedObjectMovedOnly(surround->offset, other.surround->offset, m_box->width())) {
             diff.setNeedsPositionedMovementLayout();
         } else {
             // FIXME: We would like to use SimplifiedLayout for relative positioning, but we can't quite do that yet.
@@ skipping 15 matching lines @@
 
     // Cursors are not checked, since they will be set appropriately in response to mouse events,
     // so they don't need to cause any repaint or layout.
 
     // Animations don't need to be checked either. We always set the new style on the RenderObject, so we will get a chance to fire off
     // the resulting transition properly.
 
     return diff;
 }
 
-bool RenderStyle::diffNeedsFullLayout(const RenderStyle& other) const
+bool RenderStyle::diffNeedsFullLayoutAndRepaint(const RenderStyle& other) const
 {
+    // FIXME: Not all cases in this method need both full layout and repaint.
+    // Should move cases into diffNeedsFullLayout() if
+    // - don't need repaint at all;
+    // - or the renderer knows how to repaint caused by layout change.

[Julien - ping for review, 2014/05/12 15:08:46]

I don't understand this sentence: when do we *not* know how to repaint after a
layout change?

[Xianzhu, 2014/05/12 21:31:51]

I mean the renderer knows how to repaint optimally other than the forced full
repaint. Updated the comments.

+
     if (m_box.get() != other.m_box.get()) {
         if (m_box->width() != other.m_box->width()
             || m_box->minWidth() != other.m_box->minWidth()
             || m_box->maxWidth() != other.m_box->maxWidth()
             || m_box->height() != other.m_box->height()
             || m_box->minHeight() != other.m_box->minHeight()
             || m_box->maxHeight() != other.m_box->maxHeight())
             return true;
 
         if (m_box->verticalAlign() != other.m_box->verticalAlign())
@@ skipping 170 matching lines @@
     if (!m_background->outline().visuallyEqual(other.m_background->outline())) {
         // FIXME: We only really need to recompute the overflow but we don't have an optimized layout for it.
         return true;
     }
 
     // Movement of non-static-positioned object is special cased in RenderStyle::visualInvalidationDiff().
 
     return false;
 }
 
+bool RenderStyle::diffNeedsFullLayout(const RenderStyle& other) const
+{
+    return false;
+}
+
 bool RenderStyle::diffNeedsRepaintLayer(const RenderStyle& other) const
 {
     if (position() != StaticPosition && (visual->clip != other.visual->clip || visual->hasClip != other.visual->hasClip))
         return true;
 
     if (rareNonInheritedData.get() != other.rareNonInheritedData.get()) {
         if (RuntimeEnabledFeatures::cssCompositingEnabled()
             && (rareNonInheritedData->m_effectiveBlendMode != other.rareNonInheritedData->m_effectiveBlendMode
                 || rareNonInheritedData->m_isolation != other.rareNonInheritedData->m_isolation))
             return true;
@@ skipping 1056 matching lines @@
     // right
     radiiSum = radii.topRight().height() + radii.bottomRight().height();
     if (radiiSum > rect.height())
         factor = std::min(rect.height() / radiiSum, factor);
 
     ASSERT(factor <= 1);
     return factor;
 }
 
 } // namespace WebCore