Disable FTA when max multiplier is 1.

Source/core/rendering/FastTextAutosizer.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 45 matching lines @@
             return parent;
     }
     return 0;
 }
 
 FastTextAutosizer::FastTextAutosizer(const Document* document)
     : m_document(document)
     , m_frameWidth(0)
     , m_layoutWidth(0)
     , m_baseMultiplier(0)
+    , m_maxMultiplier(0)
     , m_firstBlock(0)
 #ifndef NDEBUG
     , m_renderViewInfoPrepared(false)
     , m_blocksThatHaveBegunLayout()
 #endif
     , m_superclusters()
     , m_clusterStack()
     , m_fingerprintMapper()
 {
 }
 
 void FastTextAutosizer::record(const RenderBlock* block)
 {
     if (!enabled())

[pdr., 2014/02/28 22:13:33]

enabled() can end up depending on layout (for the render view info). I don't see
how this call (before layout) can be right. It seems that we will unnecessarily
call updateRenderViewInfo many times.

[skobes, 2014/03/01 01:45:38]

I think updateRenderViewInfo doesn't depend on layout.

         return;
 
     ASSERT(!m_blocksThatHaveBegunLayout.contains(block));
 
     if (!isFingerprintingCandidate(block))
         return;
 
     if (Fingerprint fingerprint = computeFingerprint(block))
         m_fingerprintMapper.addTentativeClusterRoot(block, fingerprint);
 }
@@ skipping 24 matching lines @@
 }
 
 void FastTextAutosizer::beginLayout(RenderBlock* block)
 {
     ASSERT(enabled());
 #ifndef NDEBUG
     m_blocksThatHaveBegunLayout.add(block);
 #endif
 
     if (!m_firstBlock)  {
-        prepareRenderViewInfo();
         prepareClusterStack(block->parent());
         m_firstBlock = block;

[pdr., 2014/02/28 22:13:33]

Can we move m_firstBlock = block above prepareClusterStack? I think this will
prevent us from accidentally depending on a wrong inLayout() in
prepareClusterStack.

[skobes, 2014/03/01 01:45:38]

Done, but prepareClusterStack doesn't call isInLayout.

     } else if (block == currentCluster()->m_root) {
         // Ignore beginLayout on the same block twice.
         // This can happen with paginated overflow.
         return;
     }
 
     if (Cluster* cluster = maybeCreateCluster(block)) {
         m_clusterStack.append(adoptPtr(cluster));
         if (block->isTable())
             inflateTable(toRenderTable(block));
     }
 
     if (block->childrenInline())
         inflate(block);
 }
 
+bool FastTextAutosizer::isInLayout() const
+{
+    return !!m_firstBlock;
+}
+
 void FastTextAutosizer::inflateListItem(RenderListItem* listItem, RenderListMarker* listItemMarker)
 {
     if (!enabled())
         return;
     ASSERT(listItem && listItemMarker);
 #ifndef NDEBUG
     m_blocksThatHaveBegunLayout.add(listItem);
 #endif
     // Force the LI to be inside the DBCAT when computing the multiplier.
     // This guarantees that the DBCAT has entered layout, so we can ask for its width.
@@ skipping 69 matching lines @@
             if (!multiplier)
                 multiplier = cluster->m_autosize ? clusterMultiplier(cluster) : 1.0f;
             applyMultiplier(descendant, multiplier);
             applyMultiplier(descendant->parent(), multiplier); // Parent handles line spacing.
         }
     }
 }
 
 bool FastTextAutosizer::enabled()
 {
-    if (!m_document->settings() || !m_document->page() || m_document->printing())
+    if (!m_document->settings()
+        || !m_document->page()
+        || m_document->printing()
+        || !m_document->settings()->textAutosizingEnabled())
         return false;
 
-    return m_document->settings()->textAutosizingEnabled();
+    if (!m_maxMultiplier)
+        updateRenderViewInfo();
+
+    if (m_maxMultiplier == 1.0f)
+        return false;
+
+    return true;
 }
 
-void FastTextAutosizer::prepareRenderViewInfo()
+void FastTextAutosizer::updateRenderViewInfo()
 {
+    if (!m_document->settings()
+        || !m_document->page()
+        || m_document->printing()
+        || !m_document->settings()->textAutosizingEnabled())
+        return;
+
     RenderView* renderView = toRenderView(m_document->renderer());
     bool horizontalWritingMode = isHorizontalWritingMode(renderView->style()->writingMode());
 
     LocalFrame* mainFrame = m_document->page()->mainFrame();
     IntSize frameSize = m_document->settings()->textAutosizingWindowSizeOverride();
     if (frameSize.isEmpty())
         frameSize = mainFrame->view()->unscaledVisibleContentSize(IncludeScrollbars);
     m_frameWidth = horizontalWritingMode ? frameSize.width() : frameSize.height();
 
     IntSize layoutSize = m_document->page()->mainFrame()->view()->layoutSize();
     m_layoutWidth = horizontalWritingMode ? layoutSize.width() : layoutSize.height();
 
     // Compute the base font scale multiplier based on device and accessibility settings.
     m_baseMultiplier = m_document->settings()->accessibilityFontScaleFactor();
     // If the page has a meta viewport or @viewport, don't apply the device scale adjustment.
     const ViewportDescription& viewportDescription = m_document->page()->mainFrame()->document()->viewportDescription();
     if (!viewportDescription.isSpecifiedByAuthor()) {
         float deviceScaleAdjustment = m_document->settings()->deviceScaleAdjustment();
         m_baseMultiplier *= deviceScaleAdjustment;
     }
+    m_maxMultiplier = m_frameWidth ? max(m_baseMultiplier *

[pdr., 2014/02/28 22:13:33]

m_maxMultiplier is never actually used as a float. Can we replace it with a bool
with a more descriptive name? m_autosizingEnabled?

[skobes, 2014/03/01 01:45:38]

Replaced with an enum.

+        (static_cast<float>(m_layoutWidth) / m_frameWidth), 1.0f) : 1.0f;
+
 #ifndef NDEBUG
     m_renderViewInfoPrepared = true;
 #endif
 }
 
 bool FastTextAutosizer::isFingerprintingCandidate(const RenderBlock* block)
 {
     // FIXME: move the logic out of TextAutosizer.cpp into this class.
     return block->isRenderView()
         || (TextAutosizer::isAutosizingContainer(block)
@@ skipping 241 matching lines @@
 
 float FastTextAutosizer::multiplierFromBlock(const RenderBlock* block)
 {
     // If block->needsLayout() is false, it does not need to be in m_blocksThatHaveBegunLayout.
     // This can happen during layout of a positioned object if the cluster's DBCAT is deeper
     // than the positioned object's containing block, and wasn't marked as needing layout.
     ASSERT(m_blocksThatHaveBegunLayout.contains(block) || !block->needsLayout());
 
     // Block width, in CSS pixels.
     float blockWidth = widthFromBlock(block);
-    float multiplier = min(blockWidth, static_cast<float>(m_layoutWidth)) / m_frameWidth;
+    float multiplier = m_frameWidth ? min(blockWidth, static_cast<float>(m_layoutWidth)) / m_frameWidth : 1.0f;
 
     return max(m_baseMultiplier * multiplier, 1.0f);
 }
 
 const RenderBlock* FastTextAutosizer::deepestBlockContainingAllText(Cluster* cluster)
 {
     if (!cluster->m_deepestBlockContainingAllText)
         cluster->m_deepestBlockContainingAllText = deepestBlockContainingAllText(cluster->m_root);
 
     return cluster->m_deepestBlockContainingAllText;
@@ skipping 164 matching lines @@
     return *m_blocksForFingerprint.get(fingerprint);
 }
 
 RenderObject* FastTextAutosizer::nextChildSkippingChildrenOfBlocks(const RenderObject* current, const RenderObject* stayWithin)
 {
     if (current == stayWithin || !current->isRenderBlock())
         return current->nextInPreOrder(stayWithin);
     return current->nextInPreOrderAfterChildren(stayWithin);
 }
 
+FastTextAutosizer::LayoutScope::LayoutScope(RenderBlock* block)
+    : m_textAutosizer(block->document().fastTextAutosizer())
+    , m_block(block)
+{
+    if (m_textAutosizer) {
+        if (!m_textAutosizer->isInLayout())
+            m_textAutosizer->updateRenderViewInfo();
+
+        if (m_textAutosizer->enabled())
+            m_textAutosizer->beginLayout(m_block);
+        else
+            m_textAutosizer = 0;
+    }
+}
+
+FastTextAutosizer::LayoutScope::~LayoutScope()
+{
+    if (m_textAutosizer)
+        m_textAutosizer->endLayout(m_block);
+}
+
 } // namespace WebCore