Reduce invalidation on children-needs-layout containers

Source/core/rendering/LayoutRepainter.cpp

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #include "config.h"
 #include "core/rendering/LayoutRepainter.h"
 
+#include "core/rendering/RenderBlock.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderObject.h"
 
 namespace WebCore {
 
 LayoutRepainter::LayoutRepainter(RenderObject& object, bool checkForRepaint)
     : m_object(object)
     , m_repaintContainer(0)
     , m_checkForRepaint(checkForRepaint)
 {
     if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
         return;
 
     if (m_checkForRepaint) {
         m_repaintContainer = m_object.containerForRepaint();
         {
             // Hits in compositing/video/video-controls-layer-creation.html
             DisableCompositingQueryAsserts disabler;
             m_oldBounds = m_object.clippedOverflowRectForRepaint(m_repaintContainer);
         }
         m_oldOutlineBox = m_object.outlineBoundsForRepaint(m_repaintContainer);
     }
 }
 
 bool LayoutRepainter::repaintAfterLayout()
 {
     if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
         return false;
 
+    if (!m_object.needsLayoutBecauseOfChildren()) {
+        // FIXME: We disable the optimization for SVG renderers for now.

[leviw_travelin_and_unemployed, 2014/03/20 21:12:13]

Looking at this and seeing a FIXME about an optimization doesn't immediately
tell me what the optimization is. Instead I have to parse through what's being
checked. How about a static inline method or something that gives this
optimization a name? :)

[Julien - ping for review, 2014/03/20 22:25:33]

Done, named it skipInvalidationWhenLayingOutChildren().

+        // RenderBlock with line boxes are responsible to repaint them so we can't ignore them.
+        bool rendererDisallowOptimization = m_object.isSVG() || (m_object.isRenderBlock() && toRenderBlock(&m_object)->firstLineBox());
+        bool hasEffectVisualOverflow = m_object.style()->hasVisualOverflowingEffect() || m_object.style()->hasOutline();
+        if (!rendererDisallowOptimization && !hasEffectVisualOverflow && !m_object.style()->hasBorder() && !m_object.style()->hasBackground())
+            return false;
+    }
+
     // Hits in compositing/video/video-controls-layer-creation.html
     DisableCompositingQueryAsserts disabler;
 
     return m_checkForRepaint ? m_object.repaintAfterLayoutIfNeeded(m_repaintContainer, m_object.selfNeedsLayout(), m_oldBounds, m_oldOutlineBox) : false;
 }
 
 } // namespace WebCore