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_pageNeedsAutosizing(PageNeedsAutosizing_Unknown)
     , m_firstBlock(0)
 #ifndef NDEBUG
     , m_renderViewInfoPrepared(false)
     , m_blocksThatHaveBegunLayout()
 #endif
     , m_superclusters()
     , m_clusterStack()
     , m_fingerprintMapper()
 {
 }
@@ skipping 38 matching lines @@
 }
 
 void FastTextAutosizer::beginLayout(RenderBlock* block)
 {
     ASSERT(enabled());
 #ifndef NDEBUG
     m_blocksThatHaveBegunLayout.add(block);
 #endif
 
     if (!m_firstBlock)  {
-        prepareRenderViewInfo();
+        m_firstBlock = block;
         prepareClusterStack(block->parent());
-        m_firstBlock = block;
     } 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 42 matching lines @@
 }
 
 void FastTextAutosizer::endLayout(RenderBlock* block)
 {
     ASSERT(enabled());
 
     if (currentCluster()->m_root == block)
         m_clusterStack.removeLast();
 
     if (block == m_firstBlock) {
         m_firstBlock = 0;

[pdr., 2014/03/01 05:16:43]

Should we reset m_pageNeedsAutosizing here?

         m_clusterStack.clear();
         m_superclusters.clear();
 #ifndef NDEBUG
         m_blocksThatHaveBegunLayout.clear();
 #endif
     }
 }
 
 void FastTextAutosizer::inflate(RenderBlock* block)
 {
     Cluster* cluster = currentCluster();
     float multiplier = 0;
     for (RenderObject* descendant = nextChildSkippingChildrenOfBlocks(block, block); descendant; descendant = nextChildSkippingChildrenOfBlocks(descendant, block)) {
         if (descendant->isText()) {
             // We only calculate this multiplier on-demand to ensure the parent block of this text
             // has entered layout.
             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_pageNeedsAutosizing == PageNeedsAutosizing_Unknown)
+        updateRenderViewInfo();
+
+    if (m_pageNeedsAutosizing == PageNeedsAutosizing_No)
+        return false;
+
+    return true;
 }
 
-void FastTextAutosizer::prepareRenderViewInfo()
+void FastTextAutosizer::updateRenderViewInfo()
 {
+    if (!m_document->settings()

[pdr., 2014/03/01 05:16:43]

Having these checks in two places doesn't seem right to me.

I think we will always get a fresh style recalc if any of these values change.
Can we just check these once on the first record() and cache them as m_enabled?

+        || !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;
     }
+
+    if (m_frameWidth) {
+        m_pageNeedsAutosizing = (m_baseMultiplier * (static_cast<float>(m_layoutWidth) / m_frameWidth) > 1.0f)
+            ? PageNeedsAutosizing_Yes : PageNeedsAutosizing_No;
+    } else {
+        m_pageNeedsAutosizing = PageNeedsAutosizing_Unknown;
+    }
+
 #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)
             && (TextAutosizer::isIndependentDescendant(block)
                 || mightBeWiderOrNarrowerDescendant(block)));
 }
 
 bool FastTextAutosizer::clusterWouldHaveEnoughTextToAutosize(const RenderBlock* root, const RenderBlock* widthProvider)
 {
     Cluster hypotheticalCluster(root, true, 0);
     return clusterHasEnoughTextToAutosize(&hypotheticalCluster, widthProvider);
 }
 
 bool FastTextAutosizer::clusterHasEnoughTextToAutosize(Cluster* cluster, const RenderBlock* widthProvider)
 {
-    if (cluster->m_hasEnoughTextToAutosize != Unknown)
-        return cluster->m_hasEnoughTextToAutosize == Yes;
+    if (cluster->m_hasEnoughTextToAutosize != HasEnoughTextToAutosize_Unknown)
+        return cluster->m_hasEnoughTextToAutosize == HasEnoughTextToAutosize_Yes;
 
     const RenderBlock* root = cluster->m_root;
     if (!widthProvider)
         widthProvider = clusterWidthProvider(root);
 
     // TextAreas and user-modifiable areas get a free pass to autosize regardless of text content.
     if (root->isTextArea() || (root->style() && root->style()->userModify() != READ_ONLY)) {
-        cluster->m_hasEnoughTextToAutosize = Yes;
+        cluster->m_hasEnoughTextToAutosize = HasEnoughTextToAutosize_Yes;
         return true;
     }
 
     if (!TextAutosizer::containerShouldBeAutosized(root)) {
-        cluster->m_hasEnoughTextToAutosize = No;
+        cluster->m_hasEnoughTextToAutosize = HasEnoughTextToAutosize_No;
         return false;
     }
 
     // 4 lines of text is considered enough to autosize.
     float minimumTextLengthToAutosize = widthFromBlock(widthProvider) * 4;
 
     float length = 0;
     RenderObject* descendant = root->nextInPreOrder(root);
     while (descendant) {
         if (descendant->isRenderBlock()) {
             RenderBlock* block = toRenderBlock(descendant);
             if (TextAutosizer::isAutosizingContainer(block)) {
                 // Note: Ideally we would check isWiderOrNarrowerDescendant here but we only know that
                 //       after the block has entered layout, which may not be the case.
                 bool isAutosizingClusterRoot = TextAutosizer::isIndependentDescendant(block);
                 if (isAutosizingClusterRoot || !TextAutosizer::containerShouldBeAutosized(block)) {
                     descendant = descendant->nextInPreOrderAfterChildren(root);
                     continue;
                 }
             }
         } else if (descendant->isText()) {
             // Note: Using text().stripWhiteSpace().length() instead of renderedTextLength() because
             // the lineboxes will not be built until layout. These values can be different.
             // Note: This is an approximation assuming each character is 1em wide.
             length += toRenderText(descendant)->text().stripWhiteSpace().length() * descendant->style()->specifiedFontSize();
 
             if (length >= minimumTextLengthToAutosize) {
-                cluster->m_hasEnoughTextToAutosize = Yes;
+                cluster->m_hasEnoughTextToAutosize = HasEnoughTextToAutosize_Yes;
                 return true;
             }
         }
         descendant = descendant->nextInPreOrder(root);
     }
 
-    cluster->m_hasEnoughTextToAutosize = No;
+    cluster->m_hasEnoughTextToAutosize = HasEnoughTextToAutosize_No;
     return false;
 }
 
 FastTextAutosizer::Fingerprint FastTextAutosizer::getFingerprint(const RenderObject* renderer)
 {
     Fingerprint result = m_fingerprintMapper.get(renderer);
     if (!result) {
         result = computeFingerprint(renderer);
         m_fingerprintMapper.add(renderer, result);
     }
@@ skipping 169 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();

[pdr., 2014/03/01 05:16:43]

Won't the enabled check below handle calling 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