Fix InlineTextBox::characterWidths() not to measure every substring

third_party/WebKit/Source/core/layout/line/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 12 matching lines @@
 #include "core/layout/line/InlineTextBox.h"
 
 #include "core/layout/HitTestResult.h"
 #include "core/layout/api/LineLayoutBR.h"
 #include "core/layout/api/LineLayoutBox.h"
 #include "core/layout/api/LineLayoutRubyRun.h"
 #include "core/layout/api/LineLayoutRubyText.h"
 #include "core/layout/line/AbstractInlineTextBox.h"
 #include "core/layout/line/EllipsisBox.h"
 #include "core/paint/InlineTextBoxPainter.h"
+#include "platform/fonts/CharacterRange.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/fonts/shaping/SimpleShaper.h"
 #include "wtf/Vector.h"
 #include "wtf/text/StringBuilder.h"
 
 #include <algorithm>
 
 namespace blink {
 
 struct SameSizeAsInlineTextBox : public InlineBox {
@@ skipping 494 matching lines @@
 {
     if (!m_len)
         return;
 
     FontCachePurgePreventer fontCachePurgePreventer;
     ASSERT(getLineLayoutItem().text());
 
     const ComputedStyle& styleToUse = getLineLayoutItem().styleRef(isFirstLineStyle());
     const Font& font = styleToUse.font();
 
-    float lastWidth = 0;
-    widths.resize(m_len);
-    for (unsigned i = 0; i < m_len; i++) {
-        StringView substringView = getLineLayoutItem().text().createView();
-        substringView.narrow(start(), 1 + i);
-        TextRun textRun = constructTextRun(styleToUse, font, substringView, m_len);
-        widths[i] = font.width(textRun, nullptr, nullptr) - lastWidth;
-        lastWidth = font.width(textRun, nullptr, nullptr);
-    }
+    TextRun textRun = constructTextRun(styleToUse, font);
+    Vector<CharacterRange> ranges = font.individualCharacterRanges(textRun);
+    DCHECK_EQ(ranges.size(), m_len);
+
+    widths.resize(ranges.size());
+    for (unsigned i = 0; i < ranges.size(); i++)
+        widths[i] = ranges[i].width();
 }
 
 TextRun InlineTextBox::constructTextRun(const ComputedStyle& style, const Font& font, StringBuilder* charactersWithHyphen) const
 {
     ASSERT(getLineLayoutItem().text());
 
     StringView string = getLineLayoutItem().text().createView();
     unsigned startPos = start();
     unsigned length = len();
 
@@ skipping 60 matching lines @@
     printedCharacters = fprintf(stderr, "\t%s %p", obj.name(), obj.debugPointer());
     const int layoutObjectCharacterOffset = 75;
     for (; printedCharacters < layoutObjectCharacterOffset; printedCharacters++)
         fputc(' ', stderr);
     fprintf(stderr, "(%d,%d) \"%s\"\n", start(), start() + len(), value.utf8().data());
 }
 
 #endif
 
 } // namespace blink