Add infrastructure for partial layouts

Source/core/rendering/RenderView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple 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,
@@ skipping 102 matching lines @@
 {
     return child->isBox();
 }
 
 void RenderView::layoutContent(const LayoutState& state)
 {
     UNUSED_PARAM(state);
     ASSERT(needsLayout());
 
     RenderBlock::layout();
+
+    if (m_frameView->partialLayout().shouldStop())
+        return;
+
     if (hasRenderNamedFlowThreads())
         flowThreadController()->layoutRenderNamedFlowThreads();
+
 #ifndef NDEBUG
     checkLayoutState(state);
 #endif
 }
 
 #ifndef NDEBUG
 void RenderView::checkLayoutState(const LayoutState& state)
 {
     ASSERT(layoutDeltaMatches(LayoutSize()));
     ASSERT(!m_layoutStateDisableCount);
@@ skipping 72 matching lines @@
 // 1. The flows are laid out from the outer flow to the inner flow. This successfully computes the outer non-auto-height regions size so the
 // inner flows have the necessary information to correctly fragment the content.
 // 2. The flows are laid out from the inner flow to the outer flow. After an inner flow is laid out it goes into the constrained layout phase
 // and marks the auto-height regions they need layout. This means the outer flows will relayout if they depend on regions with auto-height regions
 // belonging to inner flows. This step will correctly set the computedAutoHeight for the auto-height regions. It's possible for non-auto-height
 // regions to relayout if they depend on auto-height regions. This will invalidate the inner flow threads and mark them as needing layout.
 // 3. The last step is to do one last layout if there are pathological dependencies between non-auto-height regions and auto-height regions
 // as detected in the previous step.
 void RenderView::layoutContentInAutoLogicalHeightRegions(const LayoutState& state)
 {
+    if (!m_frameView->partialLayout().shouldStop()) {
+        // Disable partial layout for any two-pass layout algorithm.
+        m_frameView->partialLayout().reset();
+    }
+
     // We need to invalidate all the flows with auto-height regions if one such flow needs layout.
     // If none is found we do a layout a check back again afterwards.
     if (!flowThreadController()->updateFlowThreadsNeedingLayout()) {
         // Do a first layout of the content. In some cases more layouts are not needed (e.g. only flows with non-auto-height regions have changed).
         layoutContent(state);
 
         // If we find no named flow needing a two step layout after the first layout, exit early.
         // Otherwise, initiate the two step layout algorithm and recompute all the flows.
         if (!flowThreadController()->updateFlowThreadsNeedingTwoStepLayout())
             return;
@@ skipping 49 matching lines @@
     bool isSeamlessAncestorInFlowThread = initializeLayoutState(state);
 
     m_pageLogicalHeightChanged = false;
     m_layoutState = &state;
 
     if (checkTwoPassLayoutForAutoHeightRegions())
         layoutContentInAutoLogicalHeightRegions(state);
     else
         layoutContent(state);
 
+    if (m_frameView->partialLayout().shouldStop()) {
+        m_layoutState = 0;
+        return;
+    }
+
 #ifndef NDEBUG
     checkLayoutState(state);
 #endif
     m_layoutState = 0;
     clearNeedsLayout();
 
     if (isSeamlessAncestorInFlowThread)
         flowThreadController()->setCurrentRenderFlowThread(0);
 }
 
@@ skipping 857 matching lines @@
 #endif
 
     if (layoutState)
         layoutState->m_isPaginated = m_fragmenting;
 
     if (m_flowThreadState != RenderObject::NotInsideFlowThread)
         m_root->setFlowThreadStateIncludingDescendants(m_flowThreadState);
 }
 
 } // namespace WebCore