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      1 /*
      2  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
     14  *     its contributors may be used to endorse or promote products derived
     15  *     from this software without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #ifndef GlyphPageTreeNode_h
     30 #define GlyphPageTreeNode_h
     31 
     32 #include <string.h>
     33 #include <wtf/HashMap.h>
     34 #include <wtf/PassRefPtr.h>
     35 #include <wtf/RefCounted.h>
     36 #include <wtf/unicode/Unicode.h>
     37 
     38 #ifndef NDEBUG
     39 void showGlyphPageTrees();
     40 void showGlyphPageTree(unsigned pageNumber);
     41 #endif
     42 
     43 namespace WebCore {
     44 
     45 class FontData;
     46 class GlyphPageTreeNode;
     47 class SimpleFontData;
     48 
     49 typedef unsigned short Glyph;
     50 
     51 // Holds the glyph index and the corresponding SimpleFontData information for a given
     52 // character.
     53 struct GlyphData {
     54     GlyphData(Glyph g = 0, const SimpleFontData* f = 0)
     55         : glyph(g)
     56         , fontData(f)
     57     {
     58     }
     59     Glyph glyph;
     60     const SimpleFontData* fontData;
     61 };
     62 
     63 // A GlyphPage contains a fixed-size set of GlyphData mappings for a contiguous
     64 // range of characters in the Unicode code space. GlyphPages are indexed
     65 // starting from 0 and incrementing for each 256 glyphs.
     66 //
     67 // One page may actually include glyphs from other fonts if the characters are
     68 // missing in the primary font. It is owned by exactly one GlyphPageTreeNode,
     69 // although multiple nodes may reference it as their "page" if they are supposed
     70 // to be overriding the parent's node, but provide no additional information.
     71 class GlyphPage : public RefCounted<GlyphPage> {
     72 public:
     73     static PassRefPtr<GlyphPage> create(GlyphPageTreeNode* owner)
     74     {
     75         return adoptRef(new GlyphPage(owner));
     76     }
     77 
     78     static const size_t size = 256; // Covers Latin-1 in a single page.
     79 
     80     unsigned indexForCharacter(UChar32 c) const { return c % size; }
     81     GlyphData glyphDataForCharacter(UChar32 c) const
     82     {
     83         unsigned index = indexForCharacter(c);
     84         return GlyphData(m_glyphs[index], m_glyphFontData[index]);
     85     }
     86 
     87     GlyphData glyphDataForIndex(unsigned index) const
     88     {
     89         ASSERT(index < size);
     90         return GlyphData(m_glyphs[index], m_glyphFontData[index]);
     91     }
     92 
     93     Glyph glyphAt(unsigned index) const
     94     {
     95         ASSERT(index < size);
     96         return m_glyphs[index];
     97     }
     98 
     99     const SimpleFontData* fontDataForCharacter(UChar32 c) const
    100     {
    101         return m_glyphFontData[indexForCharacter(c)];
    102     }
    103 
    104     void setGlyphDataForCharacter(UChar32 c, Glyph g, const SimpleFontData* f)
    105     {
    106         setGlyphDataForIndex(indexForCharacter(c), g, f);
    107     }
    108     void setGlyphDataForIndex(unsigned index, Glyph g, const SimpleFontData* f)
    109     {
    110         ASSERT(index < size);
    111         m_glyphs[index] = g;
    112         m_glyphFontData[index] = f;
    113     }
    114     void setGlyphDataForIndex(unsigned index, const GlyphData& glyphData)
    115     {
    116         setGlyphDataForIndex(index, glyphData.glyph, glyphData.fontData);
    117     }
    118 
    119     void copyFrom(const GlyphPage& other)
    120     {
    121         memcpy(m_glyphs, other.m_glyphs, sizeof(m_glyphs));
    122         memcpy(m_glyphFontData, other.m_glyphFontData, sizeof(m_glyphFontData));
    123     }
    124 
    125     void clear()
    126     {
    127         memset(m_glyphs, 0, sizeof(m_glyphs));
    128         memset(m_glyphFontData, 0, sizeof(m_glyphFontData));
    129     }
    130 
    131     GlyphPageTreeNode* owner() const { return m_owner; }
    132 
    133     // Implemented by the platform.
    134     bool fill(unsigned offset, unsigned length, UChar* characterBuffer, unsigned bufferLength, const SimpleFontData*);
    135 
    136 private:
    137     GlyphPage(GlyphPageTreeNode* owner)
    138         : m_owner(owner)
    139     {
    140     }
    141 
    142     // Separate arrays, rather than array of GlyphData, to save space.
    143     Glyph m_glyphs[size];
    144     const SimpleFontData* m_glyphFontData[size];
    145 
    146     GlyphPageTreeNode* m_owner;
    147 };
    148 
    149 // The glyph page tree is a data structure that maps (FontData, glyph page number)
    150 // to a GlyphPage.  Level 0 (the "root") is special. There is one root
    151 // GlyphPageTreeNode for each glyph page number.  The roots do not have a
    152 // GlyphPage associated with them, and their initializePage() function is never
    153 // called to fill the glyphs.
    154 //
    155 // Each root node maps a FontData pointer to another GlyphPageTreeNode at
    156 // level 1 (the "root child") that stores the actual glyphs for a specific font data.
    157 // These nodes will only have a GlyphPage if they have glyphs for that range.
    158 //
    159 // Levels greater than one correspond to subsequent levels of the fallback list
    160 // for that font. These levels override their parent's page of glyphs by
    161 // filling in holes with the new font (thus making a more complete page).
    162 //
    163 // A NULL FontData pointer corresponds to the system fallback
    164 // font. It is tracked separately from the regular pages and overrides so that
    165 // the glyph pages do not get polluted with these last-resort glyphs. The
    166 // system fallback page is not populated at construction like the other pages,
    167 // but on demand for each glyph, because the system may need to use different
    168 // fallback fonts for each. This lazy population is done by the Font.
    169 class GlyphPageTreeNode {
    170 public:
    171     GlyphPageTreeNode()
    172         : m_parent(0)
    173         , m_level(0)
    174         , m_isSystemFallback(false)
    175         , m_customFontCount(0)
    176         , m_systemFallbackChild(0)
    177 #ifndef NDEBUG
    178         , m_pageNumber(0)
    179 #endif
    180     {
    181     }
    182 
    183     ~GlyphPageTreeNode();
    184 
    185     static HashMap<int, GlyphPageTreeNode*>* roots;
    186     static GlyphPageTreeNode* pageZeroRoot;
    187 
    188     static GlyphPageTreeNode* getRootChild(const FontData* fontData, unsigned pageNumber)
    189     {
    190         return getRoot(pageNumber)->getChild(fontData, pageNumber);
    191     }
    192 
    193     static void pruneTreeCustomFontData(const FontData*);
    194     static void pruneTreeFontData(const SimpleFontData*);
    195 
    196     void pruneCustomFontData(const FontData*);
    197     void pruneFontData(const SimpleFontData*, unsigned level = 0);
    198 
    199 #if PLATFORM(ANDROID)
    200     static void resetRoots();
    201     void resetChildren();
    202 #endif
    203 
    204     GlyphPageTreeNode* parent() const { return m_parent; }
    205     GlyphPageTreeNode* getChild(const FontData*, unsigned pageNumber);
    206 
    207     // Returns a page of glyphs (or NULL if there are no glyphs in this page's character range).
    208     GlyphPage* page() const { return m_page.get(); }
    209 
    210     // Returns the level of this node. See class-level comment.
    211     unsigned level() const { return m_level; }
    212 
    213     // The system fallback font has special rules (see above).
    214     bool isSystemFallback() const { return m_isSystemFallback; }
    215 
    216     static size_t treeGlyphPageCount();
    217     size_t pageCount() const;
    218 
    219 private:
    220     static GlyphPageTreeNode* getRoot(unsigned pageNumber);
    221     void initializePage(const FontData*, unsigned pageNumber);
    222 
    223 #ifndef NDEBUG
    224     void showSubtree();
    225 #endif
    226 
    227     GlyphPageTreeNode* m_parent;
    228     RefPtr<GlyphPage> m_page;
    229     unsigned m_level : 31;
    230     bool m_isSystemFallback : 1;
    231     unsigned m_customFontCount;
    232     HashMap<const FontData*, GlyphPageTreeNode*> m_children;
    233     GlyphPageTreeNode* m_systemFallbackChild;
    234 
    235 #ifndef NDEBUG
    236     unsigned m_pageNumber;
    237 
    238     friend void ::showGlyphPageTree(unsigned pageNumber);
    239 #endif
    240 };
    241 
    242 } // namespace WebCore
    243 
    244 #endif // GlyphPageTreeNode_h
    245