svgfont.cpp

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/**
 * Copyright (C) 2007, 2008 Nikolas Zimmermann <[e-mail]>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"

#if ENABLE(SVG_FONTS)
#include "Font.h"

#include "CSSFontSelector.h"
#include "GraphicsContext.h"
#include "RenderObject.h"
#include "SimpleFontData.h"
#include "SVGAltGlyphElement.h"
#include "SVGFontData.h"
#include "SVGGlyphElement.h"
#include "SVGGlyphMap.h"
#include "SVGFontElement.h"
#include "SVGFontFaceElement.h"
#include "SVGMissingGlyphElement.h"
#include "SVGPaintServer.h"
#include "SVGPaintServerSolid.h"
#include "XMLNames.h"

using namespace WTF::Unicode;

namespace WebCore {

static inline float convertEmUnitToPixel(float fontSize, float unitsPerEm, float value)
{
    if (unitsPerEm == 0.0f)
        return 0.0f;

    return value * fontSize / unitsPerEm;
}

static inline bool isVerticalWritingMode(const SVGRenderStyle* style)
{
    return style->writingMode() == WM_TBRL || style->writingMode() == WM_TB; 
}

// Helper functions to determine the arabic character forms (initial, medial, terminal, isolated)
enum ArabicCharShapingMode {
    SNone = 0,
    SRight = 1,
    SDual = 2
};

static const ArabicCharShapingMode s_arabicCharShapingMode[222] = {
    SRight, SRight, SRight, SRight, SDual , SRight, SDual , SRight, SDual , SDual , SDual , SDual , SDual , SRight,                 /* 0x0622 - 0x062F */
    SRight, SRight, SRight, SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SNone , SNone , SNone , SNone , SNone , /* 0x0630 - 0x063F */
    SNone , SDual , SDual , SDual , SDual , SDual , SDual , SRight, SDual , SDual , SNone , SNone , SNone , SNone , SNone , SNone , /* 0x0640 - 0x064F */
    SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , /* 0x0650 - 0x065F */
    SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , /* 0x0660 - 0x066F */
    SNone , SRight, SRight, SRight, SNone , SRight, SRight, SRight, SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , /* 0x0670 - 0x067F */
    SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, /* 0x0680 - 0x068F */
    SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, SDual , SDual , SDual , SDual , SDual , SDual , /* 0x0690 - 0x069F */
    SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , /* 0x06A0 - 0x06AF */
    SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , SDual , /* 0x06B0 - 0x06BF */
    SRight, SDual , SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, SRight, SDual , SRight, SDual , SRight, /* 0x06C0 - 0x06CF */
    SDual , SDual , SRight, SRight, SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , /* 0x06D0 - 0x06DF */
    SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , /* 0x06E0 - 0x06EF */
    SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SNone , SDual , SDual , SDual , SNone , SNone , SNone   /* 0x06F0 - 0x06FF */
};

static inline SVGGlyphIdentifier::ArabicForm processArabicFormDetection(const UChar& curChar, bool& lastCharShapesRight, SVGGlyphIdentifier::ArabicForm* prevForm)
{
    SVGGlyphIdentifier::ArabicForm curForm;

    ArabicCharShapingMode shapingMode = SNone;
    if (curChar >= 0x0622 && curChar <= 0x06FF)
        shapingMode = s_arabicCharShapingMode[curChar - 0x0622];

    // Use a simple state machine to identify the actual arabic form
    // It depends on the order of the arabic form enum:
    // enum ArabicForm { None = 0, Isolated, Terminal, Initial, Medial };

    if (lastCharShapesRight && shapingMode == SDual) {
        if (prevForm) {
            int correctedForm = (int) *prevForm + 1;
            ASSERT(correctedForm >= SVGGlyphIdentifier::None && correctedForm <= SVGGlyphIdentifier::Medial);
            *prevForm = static_cast<SVGGlyphIdentifier::ArabicForm>(correctedForm);
        }

        curForm = SVGGlyphIdentifier::Initial;
    } else
        curForm = shapingMode == SNone ? SVGGlyphIdentifier::None : SVGGlyphIdentifier::Isolated;

    lastCharShapesRight = shapingMode != SNone;
    return curForm;
}

static Vector<SVGGlyphIdentifier::ArabicForm> charactersWithArabicForm(const String& input, bool rtl)
{
    Vector<SVGGlyphIdentifier::ArabicForm> forms;
    unsigned length = input.length();

    bool containsArabic = false;
    for (unsigned i = 0; i < length; ++i) {
        if (isArabicChar(input[i])) {
            containsArabic = true;
            break;
        }
    }

    if (!containsArabic)
        return forms;

    bool lastCharShapesRight = false;

    // Start identifying arabic forms
    if (rtl) {
        for (int i = length - 1; i >= 0; --i)
            forms.prepend(processArabicFormDetection(input[i], lastCharShapesRight, forms.isEmpty() ? 0 : &forms.first()));
    } else {
        for (unsigned i = 0; i < length; ++i)
            forms.append(processArabicFormDetection(input[i], lastCharShapesRight, forms.isEmpty() ? 0 : &forms.last()));
    }

    return forms;
}

static inline bool isCompatibleArabicForm(const SVGGlyphIdentifier& identifier, const Vector<SVGGlyphIdentifier::ArabicForm>& chars, unsigned startPosition, unsigned endPosition)
{
    if (chars.isEmpty())
        return true;

    Vector<SVGGlyphIdentifier::ArabicForm>::const_iterator it = chars.begin() + startPosition;
    Vector<SVGGlyphIdentifier::ArabicForm>::const_iterator end = chars.begin() + endPosition;

    ASSERT(end <= chars.end());
    for (; it != end; ++it) {
        if (*it != static_cast<SVGGlyphIdentifier::ArabicForm>(identifier.arabicForm) && *it != SVGGlyphIdentifier::None)
            return false;
    }

    return true;
}

static inline bool isCompatibleGlyph(const SVGGlyphIdentifier& identifier, bool isVerticalText, const String& language,
                                     const Vector<SVGGlyphIdentifier::ArabicForm>& chars, unsigned startPosition, unsigned endPosition)
{
    bool valid = true;

    // Check wheter orientation if glyph fits within the request
    switch (identifier.orientation) {
    case SVGGlyphIdentifier::Vertical:
        valid = isVerticalText;
        break;
    case SVGGlyphIdentifier::Horizontal:
        valid = !isVerticalText;
        break;
    case SVGGlyphIdentifier::Both:
        break;
    }

    if (!valid)
        return false;

    // Check wheter languages are compatible
    if (!identifier.languages.isEmpty()) {
        // This glyph exists only in certain languages, if we're not specifying a
        // language on the referencing element we're unable to use this glyph.
        if (language.isEmpty())
            return false;

        // Split subcode from language, if existant.
        String languagePrefix;

        int subCodeSeparator = language.find('-');
        if (subCodeSeparator != -1)
            languagePrefix = language.left(subCodeSeparator);

        Vector<String>::const_iterator it = identifier.languages.begin();
        Vector<String>::const_iterator end = identifier.languages.end();

        bool found = false;
        for (; it != end; ++it) {
            const String& cur = *it;
            if (cur == language || cur == languagePrefix) {
                found = true;
                break;
            }
        }

        if (!found)
            return false;
    }

    // Check wheter arabic form is compatible
    return isCompatibleArabicForm(identifier, chars, startPosition, endPosition);
}

static inline const SVGFontData* svgFontAndFontFaceElementForFontData(const SimpleFontData* fontData, SVGFontFaceElement*& fontFace, SVGFontElement*& font)
{
    ASSERT(fontData->isCustomFont());
    ASSERT(fontData->isSVGFont());

    const SVGFontData* svgFontData = static_cast<const SVGFontData*>(fontData->svgFontData());

    fontFace = svgFontData->svgFontFaceElement();
    ASSERT(fontFace);

    font = fontFace->associatedFontElement();
    return svgFontData;
}

// Helper class to walk a text run. Lookup a SVGGlyphIdentifier for each character
// - also respecting possibly defined ligatures - and invoke a callback for each found glyph.
template<typename SVGTextRunData>
struct SVGTextRunWalker {
    typedef bool (*SVGTextRunWalkerCallback)(const SVGGlyphIdentifier&, SVGTextRunData&);
    typedef void (*SVGTextRunWalkerMissingGlyphCallback)(const TextRun&, SVGTextRunData&);

    SVGTextRunWalker(const SVGFontData* fontData, SVGFontElement* fontElement, SVGTextRunData& data,
                     SVGTextRunWalkerCallback callback, SVGTextRunWalkerMissingGlyphCallback missingGlyphCallback)
        : m_fontData(fontData)
        , m_fontElement(fontElement)
        , m_walkerData(data)
        , m_walkerCallback(callback)
        , m_walkerMissingGlyphCallback(missingGlyphCallback)
    {
    }

    void walk(const TextRun& run, bool isVerticalText, const String& language, int from, int to)
    {
        // Should hold true for SVG text, otherwhise sth. is wrong
        ASSERT(to - from == run.length());

        Vector<SVGGlyphIdentifier::ArabicForm> chars(charactersWithArabicForm(String(run.data(from), run.length()), run.rtl()));

        SVGGlyphIdentifier identifier;
        bool foundGlyph = false;
        int characterLookupRange;
        int endOfScanRange = to + m_walkerData.extraCharsAvailable;

        bool haveAltGlyph = false;
        SVGGlyphIdentifier altGlyphIdentifier;
        if (RenderObject* renderObject = run.referencingRenderObject()) {
            if (renderObject->node() && renderObject->node()->hasTagName(SVGNames::altGlyphTag)) {
                SVGGlyphElement* glyphElement = static_cast<SVGAltGlyphElement*>(renderObject->node())->glyphElement();
                if (glyphElement) {
                    haveAltGlyph = true;
                    altGlyphIdentifier = glyphElement->buildGlyphIdentifier();
                    altGlyphIdentifier.isValid = true;
                    altGlyphIdentifier.nameLength = to - from;
                }
            }
        }

        for (int i = from; i < to; ++i) {
            // If characterLookupRange is > 0, then the font defined ligatures (length of unicode property value > 1).
            // We have to check wheter the current character & the next character define a ligature. This needs to be
            // extended to the n-th next character (where n is 'characterLookupRange'), to check for any possible ligature.
            characterLookupRange = endOfScanRange - i;

            String lookupString(run.data(i), characterLookupRange);
            Vector<SVGGlyphIdentifier> glyphs;
            if (haveAltGlyph)
                glyphs.append(altGlyphIdentifier);
            else
                m_fontElement->getGlyphIdentifiersForString(lookupString, glyphs);

            Vector<SVGGlyphIdentifier>::iterator it = glyphs.begin();
            Vector<SVGGlyphIdentifier>::iterator end = glyphs.end();
            
            for (; it != end; ++it) {
                identifier = *it;
                if (identifier.isValid && isCompatibleGlyph(identifier, isVerticalText, language, chars, i, i + identifier.nameLength)) {
                    ASSERT(characterLookupRange > 0);
                    i += identifier.nameLength - 1;
                    m_walkerData.charsConsumed += identifier.nameLength;
                    m_walkerData.glyphName = identifier.glyphName;

                    foundGlyph = true;
                    SVGGlyphElement::inheritUnspecifiedAttributes(identifier, m_fontData);
                    break;
                }
            }

            if (!foundGlyph) {
                ++m_walkerData.charsConsumed;