C++ SVGTextMetrics::length方法代码示例

static void measureTextRenderer(RenderSVGInlineText* text, MeasureTextData* data, bool processRenderer)
{
    ASSERT(text);

    SVGTextLayoutAttributes* attributes = text->layoutAttributes();
    Vector<SVGTextMetrics>* textMetricsValues = &attributes->textMetricsValues();
    if (processRenderer) {
        if (data->allCharactersMap)
            attributes->clear();
        else
            textMetricsValues->clear();
    }

    SVGTextMetricsCalculator calculator(text);
    bool preserveWhiteSpace = text->style()->whiteSpace() == PRE;
    unsigned surrogatePairCharacters = 0;
    unsigned skippedCharacters = 0;
    unsigned textPosition = 0;
    unsigned textLength = calculator.textLength();

    SVGTextMetrics currentMetrics;
    for (; textPosition < textLength; textPosition += currentMetrics.length()) {
        currentMetrics = calculator.computeMetricsForCharacter(textPosition);
        if (!currentMetrics.length())
            break;

        bool characterIsWhiteSpace = calculator.characterIsWhiteSpace(textPosition);
        if (characterIsWhiteSpace && !preserveWhiteSpace && data->lastCharacterWasWhiteSpace) {
            if (processRenderer)
                textMetricsValues->append(SVGTextMetrics(SVGTextMetrics::SkippedSpaceMetrics));
            if (data->allCharactersMap)
                skippedCharacters += currentMetrics.length();
            continue;
        }

        if (processRenderer) {
            if (data->allCharactersMap) {
                const SVGCharacterDataMap::const_iterator it = data->allCharactersMap->find(data->valueListPosition + textPosition - skippedCharacters - surrogatePairCharacters + 1);
                if (it != data->allCharactersMap->end())
                    attributes->characterDataMap().set(textPosition + 1, it->value);
            }
            textMetricsValues->append(currentMetrics);
        }

        if (data->allCharactersMap && calculator.characterStartsSurrogatePair(textPosition))
            surrogatePairCharacters++;

        data->lastCharacterWasWhiteSpace = characterIsWhiteSpace;
    }

    if (!data->allCharactersMap)
        return;

    data->valueListPosition += textPosition - skippedCharacters;
}

SVGTextMetrics SVGTextMetricsCalculator::computeMetricsForCharacter(unsigned textPosition)
{
    if (m_bidiRun) {
        if (textPosition >= static_cast<unsigned>(m_bidiRun->stop())) {
            m_bidiRun = m_bidiRun->next();
            // New BiDi run means new reference position for measurements, so reset |m_totalWidth|.
            m_totalWidth = 0;
        }
        ASSERT(m_bidiRun);
        ASSERT(static_cast<int>(textPosition) < m_bidiRun->stop());
        m_textDirection = m_bidiRun->direction();
    }

    unsigned metricsLength = characterStartsSurrogatePair(textPosition) ? 2 : 1;
    SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(m_text, textPosition, metricsLength, m_textDirection);
    ASSERT(metrics.length() == metricsLength);

    unsigned startPosition = m_bidiRun ? m_bidiRun->start() : 0;
    ASSERT(startPosition <= textPosition);
    SVGTextMetrics complexStartToCurrentMetrics = SVGTextMetrics::measureCharacterRange(m_text, startPosition, textPosition - startPosition + metricsLength, m_textDirection);
    // Frequent case for Arabic text: when measuring a single character the arabic isolated form is taken
    // when laying out the glyph "in context" (with it's surrounding characters) it changes due to shaping.
    // So whenever currentWidth != currentMetrics.width(), we are processing a text run whose length is
    // not equal to the sum of the individual lengths of the glyphs, when measuring them isolated.
    float currentWidth = complexStartToCurrentMetrics.width() - m_totalWidth;
    if (currentWidth != metrics.width())
        metrics.setWidth(currentWidth);

    m_totalWidth = complexStartToCurrentMetrics.width();
    return metrics;
}

SVGTextMetrics SVGTextMetricsCalculator::computeMetricsForCharacterComplex(unsigned textPosition)
{
    unsigned metricsLength = characterStartsSurrogatePair(textPosition) ? 2 : 1;
    SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(m_text, textPosition, metricsLength, m_textDirection);
    ASSERT(metrics.length() == metricsLength);

    unsigned startPosition = m_bidiRun ? m_bidiRun->start() : 0;
    ASSERT(startPosition <= textPosition);
    SVGTextMetrics complexStartToCurrentMetrics = SVGTextMetrics::measureCharacterRange(m_text, startPosition, textPosition - startPosition + metricsLength, m_textDirection);
    // Frequent case for Arabic text: when measuring a single character the arabic isolated form is taken
    // when rendering the glyph "in context" (with it's surrounding characters) it changes due to shaping.
    // So whenever currentWidth != currentMetrics.width(), we are processing a text run whose length is
    // not equal to the sum of the individual lengths of the glyphs, when measuring them isolated.
    float currentWidth = complexStartToCurrentMetrics.width() - m_totalWidth;
    if (currentWidth != metrics.width())
        metrics.setWidth(currentWidth);

    m_totalWidth = complexStartToCurrentMetrics.width();
    return metrics;
}

void SVGTextLayoutEngine::advanceToNextLogicalCharacter(const SVGTextMetrics& logicalMetrics)
{
    ++m_logicalMetricsListOffset;
    m_logicalCharacterOffset += logicalMetrics.length();
}

void SVGTextLayoutEngine::advanceToNextVisualCharacter(const SVGTextMetrics& visualMetrics)
{
    ++m_visualMetricsListOffset;
    m_visualCharacterOffset += visualMetrics.length();
}