Use unicode-range to prevent unnecessary @font-face donwnloads

Source/core/platform/graphics/SimpleFontData.h

Index: Source/core/platform/graphics/SimpleFontData.h
diff --git a/Source/core/platform/graphics/SimpleFontData.h b/Source/core/platform/graphics/SimpleFontData.h
index 8b15f55d8a657196138ebfae1463c081c32ec65a..d9047841ae7c78799ab95f52d78b118210a3ee02 100644
--- a/Source/core/platform/graphics/SimpleFontData.h
+++ b/Source/core/platform/graphics/SimpleFontData.h
@@ -47,6 +47,7 @@
 
 namespace WebCore {
 
+class CSSFontFaceSource;
 class FontDescription;
 class SharedBuffer;
 struct WidthIterator;
@@ -68,9 +69,9 @@ public:
     };
 
     // Used to create platform fonts.
-    static PassRefPtr<SimpleFontData> create(const FontPlatformData& platformData, bool isCustomFont = false, bool isLoading = false, bool isTextOrientationFallback = false)
+    static PassRefPtr<SimpleFontData> create(const FontPlatformData& platformData, bool isCustomFont = false, bool isLoadingFallback = false, bool isTextOrientationFallback = false)
     {
-        return adoptRef(new SimpleFontData(platformData, isCustomFont, isLoading, isTextOrientationFallback));
+        return adoptRef(new SimpleFontData(platformData, isCustomFont, isLoadingFallback, isTextOrientationFallback));
     }
 
     // Used to create SVG Fonts.
@@ -156,14 +157,17 @@ public:
 
     AdditionalFontData* fontData() const { return m_fontData.get(); }
     bool isSVGFont() const { return m_fontData; }
+    bool isLoadingFallback() const { return m_isLoadingFallback; }
 
     virtual bool isCustomFont() const { return m_isCustomFont; }
-    virtual bool isLoading() const { return m_isLoading; }
+    virtual bool isLoading() const { return m_isLoadingFallback && m_isUsed; }
     virtual bool isSegmented() const;
 
     const GlyphData& missingGlyphData() const { return m_missingGlyphData; }
     void setMissingGlyphData(const GlyphData& glyphData) { m_missingGlyphData = glyphData; }
 
+    void beginLoadIfNeeded() const;
+
 #ifndef NDEBUG
     virtual String description() const;
 #endif
@@ -190,8 +194,11 @@ public:
         return false;
     }
 
+    void setCSSFontFaceSource(CSSFontFaceSource* source) { m_fontFaceSource = source; }
+    void clearCSSFontFaceSource() { m_fontFaceSource = 0; }
+
 private:
-    SimpleFontData(const FontPlatformData&, bool isCustomFont = false, bool isLoading = false, bool isTextOrientationFallback = false);
+    SimpleFontData(const FontPlatformData&, bool isCustomFont = false, bool isLoadingFallback = false, bool isTextOrientationFallback = false);
 
     SimpleFontData(PassOwnPtr<AdditionalFontData> , float fontSize, bool syntheticBold, bool syntheticItalic);
 
@@ -217,7 +224,7 @@ private:
 
     bool m_treatAsFixedPitch;
     bool m_isCustomFont;  // Whether or not we are custom font loaded via @font-face
-    bool m_isLoading; // Whether or not this custom font is still in the act of loading.
+    bool m_isLoadingFallback; // Whether or not this is a temporary font data for a custom font which is not yet loaded.
 
     bool m_isTextOrientationFallback;
     bool m_isBrokenIdeographFallback;
@@ -258,6 +265,9 @@ private:
 
     mutable OwnPtr<DerivedFontData> m_derivedFontData;
 
+    mutable bool m_isUsed;

[eseidel, 2013/09/10 15:07:26]

I see.  Normally we don't have non-used SimpleFontDatas, but I guess we can for
custom fonts?  I wonder if we should have some sort of subclass of
SimpleFontData in that case.

Alternatively we shoudl consider moving all of the custom-font related memebers
into a helper object which is held by SimpleFontData.  Then it would be clear
that they're ignored by non-custom fonts.

m_customFontData.isUsed
m_customFontData.fontFaceSource
m_customFontData.isLoadingFallback

etc.

We could possibly even make this an OwnPtr to reduce the size of SimpleFontData.
 I think we only have a few hundred SimpleFontData objects per renderer, so I
doubt it matters too much.

[Kunihiko Sakamoto, 2013/09/11 13:28:09]

Thanks for the suggestion. Moved these fields to a helper object.

+    CSSFontFaceSource* m_fontFaceSource;
+
 #if OS(DARWIN)
     float m_syntheticBoldOffset;