TextBlob: Start caching a text blob per InlineTextBox.

Source/core/rendering/InlineTextBox.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.
  *
@@ skipping 54 matching lines @@
     unsigned variables[1];
     unsigned short variables2[2];
     void* pointers[2];
 };
 
 COMPILE_ASSERT(sizeof(InlineTextBox) == sizeof(SameSizeAsInlineTextBox), InlineTextBox_should_stay_small);
 
 typedef WTF::HashMap<const InlineTextBox*, LayoutRect> InlineTextBoxOverflowMap;
 static InlineTextBoxOverflowMap* gTextBoxesWithOverflow;
 
+typedef WTF::HashMap<const InlineTextBox*, TextBlobPtr> InlineTextBoxBlobCacheMap;
+static InlineTextBoxBlobCacheMap* gTextBlobCache;
+
 static const int misspellingLineThickness = 3;
 
 void InlineTextBox::destroy()
 {
     AbstractInlineTextBox::willDestroy(this);
 
     if (!knownToHaveNoOverflow() && gTextBoxesWithOverflow)
         gTextBoxesWithOverflow->remove(this);
+    if (gTextBlobCache)
+        gTextBlobCache->remove(this);
     InlineBox::destroy();
 }
 
 void InlineTextBox::markDirty()
 {
+    // FIXME: Is it actually possible to try and paint a dirty InlineTextBox?
+    if (gTextBlobCache)
+        gTextBlobCache->remove(this);
+
     m_len = 0;
     m_start = 0;
     InlineBox::markDirty();
 }
 
 LayoutRect InlineTextBox::logicalOverflowRect() const
 {
     if (knownToHaveNoOverflow() || !gTextBoxesWithOverflow)
         return enclosingIntRect(logicalFrameRect());
     return gTextBoxesWithOverflow->get(this);
@@ skipping 484 matching lines @@
         textPainter.setCombinedText(combinedText);
 
     if (!paintSelectedTextOnly) {
         // FIXME: Truncate right-to-left text correctly.
         int startOffset = 0;
         int endOffset = length;
         if (paintSelectedTextSeparately && selectionStart < selectionEnd) {
             startOffset = selectionEnd;
             endOffset = selectionStart;
         }
-        textPainter.paint(startOffset, endOffset, length, textStyle);
+
+        // FIXME: This cache should probably ultimately be held somewhere else.
+        // A hashmap is convenient to avoid a memory hit when the
+        // RuntimeEnabledFeature is off.
+        bool textBlobIsCacheable = RuntimeEnabledFeatures::textBlobEnabled() && startOffset == 0 && endOffset == length;
+        TextBlobPtr* cachedTextBlob = 0;
+        if (textBlobIsCacheable) {
+            if (!gTextBlobCache)
+                gTextBlobCache = new InlineTextBoxBlobCacheMap;
+            cachedTextBlob = &gTextBlobCache->add(this, nullptr).storedValue->value;
+        }
+        textPainter.paint(startOffset, endOffset, length, textStyle, cachedTextBlob);
     }
 
     if ((paintSelectedTextOnly || paintSelectedTextSeparately) && selectionStart < selectionEnd) {
         // paint only the text that is selected
         textPainter.paint(selectionStart, selectionEnd, length, selectionStyle);
     }
 
     // Paint decorations
     TextDecoration textDecorations = styleToUse->textDecorationsInEffect();
     if (textDecorations != TextDecorationNone && !paintSelectedTextOnly) {
@@ skipping 767 matching lines @@
     printedCharacters = fprintf(stderr, "\t%s %p", obj.renderName(), &obj);
     const int rendererCharacterOffset = 24;
     for (; printedCharacters < rendererCharacterOffset; printedCharacters++)
         fputc(' ', stderr);
     fprintf(stderr, "(%d,%d) \"%s\"\n", start(), start() + len(), value.utf8().data());
 }
 
 #endif
 
 } // namespace blink