Disable FTA when max multiplier is 1.

Source/core/rendering/FastTextAutosizer.cpp

Index: Source/core/rendering/FastTextAutosizer.cpp
diff --git a/Source/core/rendering/FastTextAutosizer.cpp b/Source/core/rendering/FastTextAutosizer.cpp
index 7d9c5172dc9c58b62cd208684b087fa016f9e9ae..c8db110d20b0ed7514dfefe6a1618077b31d535a 100644
--- a/Source/core/rendering/FastTextAutosizer.cpp
+++ b/Source/core/rendering/FastTextAutosizer.cpp
@@ -63,6 +63,7 @@ FastTextAutosizer::FastTextAutosizer(const Document* document)
     , m_frameWidth(0)
     , m_layoutWidth(0)
     , m_baseMultiplier(0)
+    , m_maxMultiplier(0)
     , m_firstBlock(0)
 #ifndef NDEBUG
     , m_renderViewInfoPrepared(false)
@@ -121,7 +122,6 @@ void FastTextAutosizer::beginLayout(RenderBlock* 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) {
@@ -140,6 +140,11 @@ void FastTextAutosizer::beginLayout(RenderBlock* block)
         inflate(block);
 }
 
+bool FastTextAutosizer::isInLayout() const
+{
+    return !!m_firstBlock;
+}
+
 void FastTextAutosizer::inflateListItem(RenderListItem* listItem, RenderListMarker* listItemMarker)
 {
     if (!enabled())
@@ -229,14 +234,29 @@ void FastTextAutosizer::inflate(RenderBlock* block)
 
 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());
 
@@ -257,6 +277,9 @@ void FastTextAutosizer::prepareRenderViewInfo()
         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
@@ -518,7 +541,7 @@ float FastTextAutosizer::multiplierFromBlock(const RenderBlock* block)
 
     // 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);
 }
@@ -703,4 +726,25 @@ RenderObject* FastTextAutosizer::nextChildSkippingChildrenOfBlocks(const RenderO
     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