Make CSSFontFace::willUseFontData() load fonts with unicode-range

Source/core/css/CSSFontFace.cpp

Index: Source/core/css/CSSFontFace.cpp
diff --git a/Source/core/css/CSSFontFace.cpp b/Source/core/css/CSSFontFace.cpp
index 891795c3fd7eb390600cb5e69917e963172db9a9..0cd6340e1b077fed332476600096bf05f92aa706 100644
--- a/Source/core/css/CSSFontFace.cpp
+++ b/Source/core/css/CSSFontFace.cpp
@@ -126,16 +126,16 @@ PassRefPtr<SimpleFontData> CSSFontFace::getFontData(const FontDescription& fontD
     return nullptr;
 }
 
-void CSSFontFace::willUseFontData(const FontDescription& fontDescription)
+bool CSSFontFace::willUseFontData(const FontDescription& fontDescription, const String& text)
 {
-    // Kicks off font load here only if the @font-face has no unicode-range.
-    // @font-faces with unicode-range will be loaded when a GlyphPage for the
-    // font is created.
-    // FIXME: Pass around the text to render from RenderText, and kick download
-    // if m_ranges intersects with the text. Make sure this does not cause
-    // performance regression.
-    if (m_ranges.isEntireRange())
+    // This is an optimization that kicks off font load early (before layout).
+    // In order to make it fast, we only check if the first character of |text|
+    // is included in the unicode-range.
+    if (!text.isEmpty() && m_ranges.contains(text.characterStartingAt(0))) {

[dglazkov, 2014/04/29 16:37:00]

text.isEmpty check is not necessary, right? The RenderText::styleDidChange
already checks for this with text().containsOnlyWhitespace().

Which makes me wonder if we could just pass the first character?

[Kunihiko Sakamoto, 2014/04/30 03:31:21]

Ah, you're right.
Changed to pass the first character.

         load(fontDescription);
+        return true;
+    }
+    return false;
 }
 
 void CSSFontFace::load(const FontDescription& fontDescription, CSSFontSelector* fontSelector)
@@ -217,6 +217,14 @@ CSSFontFace::UnicodeRangeSet::UnicodeRangeSet(const Vector<UnicodeRange>& ranges
     m_ranges.shrink(targetIndex);
 }
 
+bool CSSFontFace::UnicodeRangeSet::contains(UChar32 c) const
+{
+    if (isEntireRange())
+        return true;
+    Vector<UnicodeRange>::const_iterator it = std::lower_bound(m_ranges.begin(), m_ranges.end(), c);
+    return it != m_ranges.end() && it->contains(c);
+}
+
 bool CSSFontFace::UnicodeRangeSet::intersectsWith(const String& text) const
 {
     if (text.isEmpty())
@@ -230,8 +238,7 @@ bool CSSFontFace::UnicodeRangeSet::intersectsWith(const String& text) const
     while (index < text.length()) {
         UChar32 c = text.characterStartingAt(index);
         index += U16_LENGTH(c);
-        Vector<UnicodeRange>::const_iterator it = std::lower_bound(m_ranges.begin(), m_ranges.end(), c);
-        if (it != m_ranges.end() && it->contains(c))
+        if (contains(c))
             return true;
     }
     return false;