/*

 * Copyright (C) 2006 Apple Computer, 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/unicode/Unicode.h>

#include <wtf/Noncopyable.h>

#include <wtf/HashMap.h>

namespace WebCore {

class FontData;

class GlyphPageTreeNode;

typedef unsigned short Glyph;

// Holds the glyph index and the corresponding FontData information for a given

// character.

struct GlyphData {

    Glyph glyph;

    const FontData* 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 {

    GlyphPage()

        : m_owner(0)

    {

    }

    GlyphPage(GlyphPageTreeNode* owner)

        : m_owner(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 FontData* f)

    {

        setGlyphDataForIndex(c % size, g, f);

    }

    void setGlyphDataForIndex(unsigned index, Glyph g, const FontData* f)

    {

        m_glyphs[index].glyph = g;

        m_glyphs[index].fontData = f;

    }

    GlyphPageTreeNode* owner() const { return m_owner; }

    // Implemented by the platform.

    bool fill(UChar* characterBuffer, unsigned bufferLength, const FontData* fontData);

};

// 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_page(0)

        , m_level(0)

        , m_isSystemFallback(false)

        , m_systemFallbackChild(0)

#ifndef NDEBUG

        , m_pageNumber(0)

#endif

    {

    }

    static GlyphPageTreeNode* getRootChild(const FontData* fontData, unsigned pageNumber)

    {

        return getRoot(pageNumber)->getChild(fontData, pageNumber);

    }

    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; }

    // 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; }

private:

    static GlyphPageTreeNode* getRoot(unsigned pageNumber);

    void initializePage(const FontData*, unsigned pageNumber);

    GlyphPageTreeNode* m_parent;

    GlyphPage* m_page;

    unsigned m_level;

    bool m_isSystemFallback;

    HashMap<const FontData*, GlyphPageTreeNode*> m_children;

    GlyphPageTreeNode* m_systemFallbackChild;

#ifndef NDEBUG

    unsigned m_pageNumber;

#endif

};

} // namespace WebCore

#endif // GlyphPageTreeNode_h