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diff --git a/WebCore/platform/graphics/GlyphPageTreeNode.h b/WebCore/platform/graphics/GlyphPageTreeNode.h
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+/*
+ * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer. 
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution. 
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission. 
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef GlyphPageTreeNode_h
+#define GlyphPageTreeNode_h
+
+#include <wtf/HashMap.h>
+#include <wtf/PassRefPtr.h>
+#include <wtf/RefCounted.h>
+#include <wtf/unicode/Unicode.h>
+
+namespace WebCore {
+
+class FontData;
+class GlyphPageTreeNode;
+class SimpleFontData;
+
+typedef unsigned short Glyph;
+
+// Holds the glyph index and the corresponding SimpleFontData information for a given
+// character.
+struct GlyphData {
+    Glyph glyph;
+    const SimpleFontData* fontData;
+};
+
+// A GlyphPage contains a fixed-size set of GlyphData mappings for a contiguous
+// range of characters in the Unicode code space. GlyphPages are indexed
+// starting from 0 and incrementing for each 256 glyphs.
+//
+// One page may actually include glyphs from other fonts if the characters are
+// missing in the parimary font. It is owned by exactly one GlyphPageTreeNode,
+// although multiple nodes may reference it as their "page" if they are supposed
+// to be overriding the parent's node, but provide no additional information.
+struct GlyphPage : public RefCounted<GlyphPage> {
+    static PassRefPtr<GlyphPage> create(GlyphPageTreeNode* owner)
+    {
+        return adoptRef(new GlyphPage(owner));
+    }
+
+    static const size_t size = 256; // Covers Latin-1 in a single page.
+    GlyphData m_glyphs[size];
+    GlyphPageTreeNode* m_owner;
+
+    const GlyphData& glyphDataForCharacter(UChar32 c) const { return m_glyphs[c % size]; }
+    void setGlyphDataForCharacter(UChar32 c, Glyph g, const SimpleFontData* f)
+    {
+        setGlyphDataForIndex(c % size, g, f);
+    }
+    void setGlyphDataForIndex(unsigned index, Glyph g, const SimpleFontData* f)
+    {
+        ASSERT(index < size);
+        m_glyphs[index].glyph = g;
+        m_glyphs[index].fontData = f;
+    }
+    GlyphPageTreeNode* owner() const { return m_owner; }
+
+    // Implemented by the platform.
+    bool fill(unsigned offset, unsigned length, UChar* characterBuffer, unsigned bufferLength, const SimpleFontData*);
+
+private:
+    GlyphPage(GlyphPageTreeNode* owner)
+        : m_owner(owner)
+    {
+    }
+};
+
+// The glyph page tree is a data structure that maps (FontData, glyph page number)
+// to a GlyphPage.  Level 0 (the "root") is special. There is one root
+// GlyphPageTreeNode for each glyph page number.  The roots do not have a
+// GlyphPage associated with them, and their initializePage() function is never
+// called to fill the glyphs.
+//
+// Each root node maps a FontData pointer to another GlyphPageTreeNode at
+// level 1 (the "root child") that stores the actual glyphs for a specific font data.
+// These nodes will only have a GlyphPage if they have glyphs for that range.
+//
+// Levels greater than one correspond to subsequent levels of the fallback list
+// for that font. These levels override their parent's page of glyphs by
+// filling in holes with the new font (thus making a more complete page).
+//
+// A NULL FontData pointer corresponds to the system fallback
+// font. It is tracked separately from the regular pages and overrides so that
+// the glyph pages do not get polluted with these last-resort glyphs. The
+// system fallback page is not populated at construction like the other pages,
+// but on demand for each glyph, because the system may need to use different
+// fallback fonts for each. This lazy population is done by the Font.
+class GlyphPageTreeNode {
+public:
+    GlyphPageTreeNode()
+        : m_parent(0)
+        , m_level(0)
+        , m_isSystemFallback(false)
+        , m_systemFallbackChild(0)
+        , m_customFontCount(0)
+#ifndef NDEBUG
+        , m_pageNumber(0)
+#endif
+    {
+    }
+
+    ~GlyphPageTreeNode();
+
+    static HashMap<int, GlyphPageTreeNode*>* roots;
+    static GlyphPageTreeNode* pageZeroRoot;
+
+    static GlyphPageTreeNode* getRootChild(const FontData* fontData, unsigned pageNumber)
+    {
+        return getRoot(pageNumber)->getChild(fontData, pageNumber);
+    }
+
+    static void pruneTreeCustomFontData(const FontData*);
+    static void pruneTreeFontData(const SimpleFontData*);
+
+    void pruneCustomFontData(const FontData*);
+    void pruneFontData(const SimpleFontData*, unsigned level = 0);
+
+    GlyphPageTreeNode* parent() const { return m_parent; }
+    GlyphPageTreeNode* getChild(const FontData*, unsigned pageNumber);
+
+    // Returns a page of glyphs (or NULL if there are no glyphs in this page's character range).
+    GlyphPage* page() const { return m_page.get(); }
+
+    // Returns the level of this node. See class-level comment.
+    unsigned level() const { return m_level; }
+
+    // The system fallback font has special rules (see above).
+    bool isSystemFallback() const { return m_isSystemFallback; }
+
+    static size_t treeGlyphPageCount();
+    size_t pageCount() const;
+
+private:
+    static GlyphPageTreeNode* getRoot(unsigned pageNumber);
+    void initializePage(const FontData*, unsigned pageNumber);
+
+    GlyphPageTreeNode* m_parent;
+    RefPtr<GlyphPage> m_page;
+    unsigned m_level;
+    bool m_isSystemFallback;
+    HashMap<const FontData*, GlyphPageTreeNode*> m_children;
+    GlyphPageTreeNode* m_systemFallbackChild;
+    unsigned m_customFontCount;
+
+#ifndef NDEBUG
+    unsigned m_pageNumber;
+#endif
+};
+
+} // namespace WebCore
+
+#endif // GlyphPageTreeNode_h