svgfont.cpp

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                if (SVGMissingGlyphElement* element = m_fontElement->firstMissingGlyphElement()) {
                    // <missing-glyph> element support
                    identifier = SVGGlyphElement::buildGenericGlyphIdentifier(element);
                    SVGGlyphElement::inheritUnspecifiedAttributes(identifier, m_fontData);
                    identifier.isValid = true;
                } else {
                    // Fallback to system font fallback
                    TextRun subRun(run);
                    subRun.setText(subRun.data(i), 1);

                    (*m_walkerMissingGlyphCallback)(subRun, m_walkerData);
                    continue;
                }
            }

            if (!(*m_walkerCallback)(identifier, m_walkerData))
                break;

            foundGlyph = false;
        }
    }

private:
    const SVGFontData* m_fontData;
    SVGFontElement* m_fontElement;
    SVGTextRunData& m_walkerData;
    SVGTextRunWalkerCallback m_walkerCallback;
    SVGTextRunWalkerMissingGlyphCallback m_walkerMissingGlyphCallback;
};

// Callback & data structures to compute the width of text using SVG Fonts
struct SVGTextRunWalkerMeasuredLengthData {
    int at;
    int from;
    int to;
    int extraCharsAvailable;
    int charsConsumed;
    String glyphName;

    float scale;
    float length;
    const Font* font;
};

static bool floatWidthUsingSVGFontCallback(const SVGGlyphIdentifier& identifier, SVGTextRunWalkerMeasuredLengthData& data)
{
    if (data.at >= data.from && data.at < data.to)
        data.length += identifier.horizontalAdvanceX * data.scale;

    data.at++;
    return data.at < data.to;
}

static void floatWidthMissingGlyphCallback(const TextRun& run, SVGTextRunWalkerMeasuredLengthData& data)
{
    // Handle system font fallback
    FontDescription fontDescription(data.font->fontDescription());
    fontDescription.setFamily(FontFamily());
    Font font(fontDescription, 0, 0); // spacing handled by SVG text code.
    font.update(data.font->fontSelector());

    data.length += font.floatWidth(run);
}


SVGFontElement* Font::svgFont() const
{ 
    if (!isSVGFont())
        return 0;

    SVGFontElement* fontElement = 0;
    SVGFontFaceElement* fontFaceElement = 0;
    if (svgFontAndFontFaceElementForFontData(primaryFont(), fontFaceElement, fontElement))
        return fontElement;
    
    return 0;
}

static float floatWidthOfSubStringUsingSVGFont(const Font* font, const TextRun& run, int extraCharsAvailable, int from, int to, int& charsConsumed, String& glyphName)
{
    int newFrom = to > from ? from : to;
    int newTo = to > from ? to : from;

    from = newFrom;
    to = newTo;

    SVGFontElement* fontElement = 0;
    SVGFontFaceElement* fontFaceElement = 0;

    if (const SVGFontData* fontData = svgFontAndFontFaceElementForFontData(font->primaryFont(), fontFaceElement, fontElement)) {
        if (!fontElement)
            return 0.0f;

        SVGTextRunWalkerMeasuredLengthData data;

        data.font = font;
        data.at = from;
        data.from = from;
        data.to = to;
        data.extraCharsAvailable = extraCharsAvailable;
        data.charsConsumed = 0;
        data.scale = convertEmUnitToPixel(font->size(), fontFaceElement->unitsPerEm(), 1.0f);
        data.length = 0.0f;

        String language;
        bool isVerticalText = false; // Holds true for HTML text

        // TODO: language matching & svg glyphs should be possible for HTML text, too.
        if (RenderObject* renderObject = run.referencingRenderObject()) {
            isVerticalText = isVerticalWritingMode(renderObject->style()->svgStyle());

            if (SVGElement* element = static_cast<SVGElement*>(renderObject->node()))
                language = element->getAttribute(XMLNames::langAttr);
        }

        SVGTextRunWalker<SVGTextRunWalkerMeasuredLengthData> runWalker(fontData, fontElement, data, floatWidthUsingSVGFontCallback, floatWidthMissingGlyphCallback);
        runWalker.walk(run, isVerticalText, language, 0, run.length());
        charsConsumed = data.charsConsumed;
        glyphName = data.glyphName;
        return data.length;
    }

    return 0.0f;
}

float Font::floatWidthUsingSVGFont(const TextRun& run) const
{
    int charsConsumed;
    String glyphName;
    return floatWidthOfSubStringUsingSVGFont(this, run, 0, 0, run.length(), charsConsumed, glyphName);
}

float Font::floatWidthUsingSVGFont(const TextRun& run, int extraCharsAvailable, int& charsConsumed, String& glyphName) const
{
    return floatWidthOfSubStringUsingSVGFont(this, run, extraCharsAvailable, 0, run.length(), charsConsumed, glyphName);
}

// Callback & data structures to draw text using SVG Fonts
struct SVGTextRunWalkerDrawTextData {
    int extraCharsAvailable;
    int charsConsumed;
    String glyphName;
    Vector<SVGGlyphIdentifier> glyphIdentifiers;
    Vector<UChar> fallbackCharacters;
};

static bool drawTextUsingSVGFontCallback(const SVGGlyphIdentifier& identifier, SVGTextRunWalkerDrawTextData& data)
{
    data.glyphIdentifiers.append(identifier);
    return true;
}

static void drawTextMissingGlyphCallback(const TextRun& run, SVGTextRunWalkerDrawTextData& data)
{
    ASSERT(run.length() == 1);
    data.glyphIdentifiers.append(SVGGlyphIdentifier());
    data.fallbackCharacters.append(run[0]);
}

void Font::drawTextUsingSVGFont(GraphicsContext* context, const TextRun& run, 
                                const FloatPoint& point, int from, int to) const
{
    SVGFontElement* fontElement = 0;
    SVGFontFaceElement* fontFaceElement = 0;

    if (const SVGFontData* fontData = svgFontAndFontFaceElementForFontData(primaryFont(), fontFaceElement, fontElement)) {
        if (!fontElement)
            return;

        SVGTextRunWalkerDrawTextData data;
        FloatPoint currentPoint = point;
        float scale = convertEmUnitToPixel(size(), fontFaceElement->unitsPerEm(), 1.0f);

        SVGPaintServer* activePaintServer = run.activePaintServer();

        // If renderObject is not set, we're dealing for HTML text rendered using SVG Fonts.
        if (!run.referencingRenderObject()) {
            ASSERT(!activePaintServer);

            // TODO: We're only supporting simple filled HTML text so far.
            SVGPaintServerSolid* solidPaintServer = SVGPaintServer::sharedSolidPaintServer();
            solidPaintServer->setColor(context->fillColor());

            activePaintServer = solidPaintServer;
        }

        ASSERT(activePaintServer);

        int charsConsumed;
        String glyphName;
        bool isVerticalText = false;
        float xStartOffset = floatWidthOfSubStringUsingSVGFont(this, run, 0, run.rtl() ? to : 0, run.rtl() ? run.length() : from, charsConsumed, glyphName);
        FloatPoint glyphOrigin;

        String language;

        // TODO: language matching & svg glyphs should be possible for HTML text, too.
        if (run.referencingRenderObject()) {
            isVerticalText = isVerticalWritingMode(run.referencingRenderObject()->style()->svgStyle());    

            if (SVGElement* element = static_cast<SVGElement*>(run.referencingRenderObject()->node()))
                language = element->getAttribute(XMLNames::langAttr);
        }

        if (!isVerticalText) {
            glyphOrigin.setX(fontData->horizontalOriginX() * scale);
            glyphOrigin.setY(fontData->horizontalOriginY() * scale);
        }

        data.extraCharsAvailable = 0;
        data.charsConsumed = 0;

        SVGTextRunWalker<SVGTextRunWalkerDrawTextData> runWalker(fontData, fontElement, data, drawTextUsingSVGFontCallback, drawTextMissingGlyphCallback);
        runWalker.walk(run, isVerticalText, language, from, to);

        SVGPaintTargetType targetType = context->textDrawingMode() == cTextStroke ? ApplyToStrokeTargetType : ApplyToFillTargetType;

        unsigned numGlyphs = data.glyphIdentifiers.size();
        unsigned fallbackCharacterIndex = 0;
        for (unsigned i = 0; i < numGlyphs; ++i) {
            const SVGGlyphIdentifier& identifier = data.glyphIdentifiers[run.rtl() ? numGlyphs - i - 1 : i];
            if (identifier.isValid) {
                // FIXME: Support arbitary SVG content as glyph (currently limited to <glyph d="..."> situations).
                if (!identifier.pathData.isEmpty()) {
                    context->save();

                    if (isVerticalText) {
                        glyphOrigin.setX(identifier.verticalOriginX * scale);
                        glyphOrigin.setY(identifier.verticalOriginY * scale);
                    }

                    context->translate(xStartOffset + currentPoint.x() + glyphOrigin.x(), currentPoint.y() + glyphOrigin.y());
                    context->scale(FloatSize(scale, -scale));

                    context->beginPath();
                    context->addPath(identifier.pathData);

                    if (activePaintServer->setup(context, run.referencingRenderObject(), targetType)) {
                        // Spec: Any properties specified on a text elements which represents a length, such as the
                        // 'stroke-width' property, might produce surprising results since the length value will be
                        // processed in the coordinate system of the glyph. (TODO: What other lengths? miter-limit? dash-offset?)
                        if (targetType == ApplyToStrokeTargetType && scale != 0.0f)
                            context->setStrokeThickness(context->strokeThickness() / scale);

                        activePaintServer->renderPath(context, run.referencingRenderObject(), targetType);
                        activePaintServer->teardown(context, run.referencingRenderObject(), targetType);
                    }

                    context->restore();
                }

                if (isVerticalText)
                    currentPoint.move(0.0f, identifier.verticalAdvanceY * scale);
                else
                    currentPoint.move(identifier.horizontalAdvanceX * scale, 0.0f);
            } else {
                // Handle system font fallback
                FontDescription fontDescription(m_fontDescription);
                fontDescription.setFamily(FontFamily());
                Font font(fontDescription, 0, 0); // spacing handled by SVG text code.
                font.update(fontSelector());

                TextRun fallbackCharacterRun(run);
                fallbackCharacterRun.setText(&data.fallbackCharacters[run.rtl() ? data.fallbackCharacters.size() - fallbackCharacterIndex - 1 : fallbackCharacterIndex], 1);
                font.drawText(context, fallbackCharacterRun, currentPoint);

                if (isVerticalText)
                    currentPoint.move(0.0f, font.floatWidth(fallbackCharacterRun));
                else
                    currentPoint.move(font.floatWidth(fallbackCharacterRun), 0.0f);

                fallbackCharacterIndex++;
            }
        }
    }
}

FloatRect Font::selectionRectForTextUsingSVGFont(const TextRun& run, const IntPoint& point, int height, int from, int to) const
{
    int charsConsumed;
    String glyphName;

    return FloatRect(point.x() + floatWidthOfSubStringUsingSVGFont(this, run, 0, run.rtl() ? to : 0, run.rtl() ? run.length() : from, charsConsumed, glyphName),
                     point.y(), floatWidthOfSubStringUsingSVGFont(this, run, 0, from, to, charsConsumed, glyphName), height);
}

int Font::offsetForPositionForTextUsingSVGFont(const TextRun&, int, bool) const
{
    // TODO: Fix text selection when HTML text is drawn using a SVG Font
    // We need to integrate the SVG text selection code in the offsetForPosition() framework.
    // This will also fix a major issue, that SVG Text code can't select arabic strings properly.
    return 0;
}

}

#endif