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 "platform/fonts/GlyphPage.h"
33#include <string.h>
34#include "wtf/HashMap.h"
35#include "wtf/OwnPtr.h"
36#include "wtf/PassRefPtr.h"
37#include "wtf/RefCounted.h"
38#include "wtf/unicode/Unicode.h"
39
40namespace blink {
41
42class FontData;
43class SimpleFontData;
44
45// The glyph page tree is a data structure that maps (FontData, glyph page number)
46// to a GlyphPage.  Level 0 (the "root") is special. There is one root
47// GlyphPageTreeNode for each glyph page number.  The roots do not have a
48// GlyphPage associated with them, and their initializePage() function is never
49// called to fill the glyphs.
50//
51// Each root node maps a FontData pointer to another GlyphPageTreeNode at
52// level 1 (the "root child") that stores the actual glyphs for a specific font data.
53// These nodes will only have a GlyphPage if they have glyphs for that range.
54//
55// Levels greater than one correspond to subsequent levels of the fallback list
56// for that font. These levels override their parent's page of glyphs by
57// filling in holes with the new font (thus making a more complete page).
58//
59// A NULL FontData pointer corresponds to the system fallback
60// font. It is tracked separately from the regular pages and overrides so that
61// the glyph pages do not get polluted with these last-resort glyphs. The
62// system fallback page is not populated at construction like the other pages,
63// but on demand for each glyph, because the system may need to use different
64// fallback fonts for each. This lazy population is done by the Font.
65class PLATFORM_EXPORT GlyphPageTreeNode {
66    WTF_MAKE_FAST_ALLOCATED; WTF_MAKE_NONCOPYABLE(GlyphPageTreeNode);
67public:
68    static GlyphPageTreeNode* getRootChild(const FontData* fontData, unsigned pageNumber)
69    {
70        return getRoot(pageNumber)->getChild(fontData, pageNumber);
71    }
72
73    static void pruneTreeCustomFontData(const FontData*);
74    static void pruneTreeFontData(const SimpleFontData*);
75
76    void pruneCustomFontData(const FontData*);
77    void pruneFontData(const SimpleFontData*, unsigned level = 0);
78
79    GlyphPageTreeNode* parent() const { return m_parent; }
80    GlyphPageTreeNode* getChild(const FontData*, unsigned pageNumber);
81
82    // Returns a page of glyphs (or NULL if there are no glyphs in this page's character range).
83    GlyphPage* page() const { return m_page.get(); }
84
85    // Returns the level of this node. See class-level comment.
86    unsigned level() const { return m_level; }
87
88    // The system fallback font has special rules (see above).
89    bool isSystemFallback() const { return m_isSystemFallback; }
90
91    static size_t treeGlyphPageCount();
92    size_t pageCount() const;
93
94private:
95    GlyphPageTreeNode()
96        : m_parent(0)
97        , m_level(0)
98        , m_isSystemFallback(false)
99        , m_customFontCount(0)
100#if ENABLE(ASSERT)
101        , m_pageNumber(0)
102#endif
103    {
104    }
105
106    static GlyphPageTreeNode* getRoot(unsigned pageNumber);
107    void initializePage(const FontData*, unsigned pageNumber);
108
109#ifndef NDEBUG
110    void showSubtree();
111#endif
112
113    static HashMap<int, GlyphPageTreeNode*>* roots;
114    static GlyphPageTreeNode* pageZeroRoot;
115
116    typedef HashMap<const FontData*, OwnPtr<GlyphPageTreeNode> > GlyphPageTreeNodeMap;
117
118    GlyphPageTreeNodeMap m_children;
119    GlyphPageTreeNode* m_parent;
120    RefPtr<GlyphPage> m_page;
121    unsigned m_level : 31;
122    bool m_isSystemFallback : 1;
123    unsigned m_customFontCount;
124    OwnPtr<GlyphPageTreeNode> m_systemFallbackChild;
125
126#if ENABLE(ASSERT)
127    unsigned m_pageNumber;
128#endif
129};
130
131} // namespace blink
132
133#endif // GlyphPageTreeNode_h
134