C++ SVGTextMetrics类代码示例

bool SVGTextLayoutEngine::currentLogicalCharacterMetrics(SVGTextLayoutAttributes*& logicalAttributes, SVGTextMetrics& logicalMetrics)
{
    const Vector<SVGTextMetrics>* textMetricsValues = &logicalAttributes->textMetricsValues();
    unsigned textMetricsSize = textMetricsValues->size();
    while (true) {
        if (m_logicalMetricsListOffset == textMetricsSize) {
            if (!currentLogicalCharacterAttributes(logicalAttributes))
                return false;

            textMetricsValues = &logicalAttributes->textMetricsValues();
            textMetricsSize = textMetricsValues->size();
            continue;
        }

        ASSERT(textMetricsSize);
        ASSERT(m_logicalMetricsListOffset < textMetricsSize);
        logicalMetrics = textMetricsValues->at(m_logicalMetricsListOffset);
        if (logicalMetrics.isEmpty() || (!logicalMetrics.width() && !logicalMetrics.height())) {
            advanceToNextLogicalCharacter(logicalMetrics);
            continue;
        }

        // Stop if we found the next valid logical text metrics object.
        return true;
    }

    ASSERT_NOT_REACHED();
    return true;
}

bool SVGTextQuery::endPositionOfCharacterCallback(Data* queryData, const SVGTextFragment& fragment) const
{
    EndPositionOfCharacterData* data = static_cast<EndPositionOfCharacterData*>(queryData);

    int startPosition = data->position;
    int endPosition = startPosition + 1;
    if (!mapStartEndPositionsIntoFragmentCoordinates(queryData, fragment, startPosition, endPosition))
        return false;

    data->endPosition = FloatPoint(fragment.x, fragment.y);

    SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(queryData->textRenderer, fragment.characterOffset, startPosition + 1);
    if (queryData->isVerticalText)
        data->endPosition.move(0, metrics.height());
    else
        data->endPosition.move(metrics.width(), 0);

    AffineTransform fragmentTransform;
    fragment.buildFragmentTransform(fragmentTransform, SVGTextFragment::TransformIgnoringTextLength);
    if (fragmentTransform.isIdentity())
        return true;

    data->endPosition = fragmentTransform.mapPoint(data->endPosition);
    return true;
}

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;
}

float SVGTextLayoutEngineBaseline::calculateGlyphAdvanceAndOrientation(bool isVerticalText, const SVGTextMetrics& metrics, float angle, float& xOrientationShift, float& yOrientationShift) const
{
    bool orientationIsMultiplyOf180Degrees = glyphOrientationIsMultiplyOf180Degrees(angle);

    // The function is based on spec requirements:
    //
    // Spec: If the 'glyph-orientation-horizontal' results in an orientation angle that is not a multiple of
    // of 180 degrees, then the current text position is incremented according to the vertical metrics of the glyph.
    //
    // Spec: If if the 'glyph-orientation-vertical' results in an orientation angle that is not a multiple of
    // 180 degrees, then the current text position is incremented according to the horizontal metrics of the glyph.

    const FontMetrics& fontMetrics = m_font.fontMetrics();

    float ascent = fontMetrics.floatAscent() / m_effectiveZoom;
    float descent = fontMetrics.floatDescent() / m_effectiveZoom;

    // Vertical orientation handling.
    if (isVerticalText) {
        float ascentMinusDescent = ascent - descent;

        if (!angle) {
            xOrientationShift = (ascentMinusDescent - metrics.width()) / 2;
            yOrientationShift = ascent;
        } else if (angle == 180) {
            xOrientationShift = (ascentMinusDescent + metrics.width()) / 2;
        } else if (angle == 270) {
            yOrientationShift = metrics.width();
            xOrientationShift = ascentMinusDescent;
        }

        // Vertical advance calculation.
        if (angle && !orientationIsMultiplyOf180Degrees)
            return metrics.width();

        return metrics.height();
    }

    // Horizontal orientation handling.
    if (angle == 90) {
        yOrientationShift = -metrics.width();
    } else if (angle == 180) {
        xOrientationShift = metrics.width();
        yOrientationShift = -ascent;
    } else if (angle == 270) {
        xOrientationShift = metrics.width();
    }

    // Horizontal advance calculation.
    if (angle && !orientationIsMultiplyOf180Degrees)
        return metrics.height();

    return metrics.width();
}

bool SVGTextQuery::subStringLengthCallback(Data* queryData, const SVGTextFragment& fragment) const
{
    SubStringLengthData* data = static_cast<SubStringLengthData*>(queryData);

    int startPosition = data->startPosition;
    int endPosition = startPosition + data->length;
    if (!mapStartEndPositionsIntoFragmentCoordinates(queryData, fragment, startPosition, endPosition))
        return false;

    SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(queryData->textRenderer, fragment.characterOffset + startPosition, endPosition - startPosition);
    data->subStringLength += queryData->isVerticalText ? metrics.height() : metrics.width();
    return false;
}

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;
}

static inline void calculateGlyphBoundaries(SVGTextQuery::Data* queryData, const SVGTextFragment& fragment, int startPosition, FloatRect& extent)
{
    float scalingFactor = queryData->textRenderer->scalingFactor();
    ASSERT(scalingFactor);

    extent.setLocation(FloatPoint(fragment.x, fragment.y - queryData->textRenderer->scaledFont().fontMetrics().floatAscent() / scalingFactor));

    if (startPosition) {
        SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(queryData->textRenderer, fragment.characterOffset, startPosition);
        if (queryData->isVerticalText)
            extent.move(0, metrics.height());
        else
            extent.move(metrics.width(), 0);
    }

    SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(queryData->textRenderer, fragment.characterOffset + startPosition, 1);
    extent.setSize(FloatSize(metrics.width(), metrics.height()));

    AffineTransform fragmentTransform;
    fragment.buildFragmentTransform(fragmentTransform, SVGTextFragment::TransformIgnoringTextLength);
    if (fragmentTransform.isIdentity())
        return;

    extent = fragmentTransform.mapRect(extent);
}

static FloatPoint calculateGlyphPositionWithoutTransform(const QueryData* queryData, const SVGTextFragment& fragment, int offsetInFragment)
{
    float glyphOffsetInDirection = 0;
    if (offsetInFragment) {
        SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(queryData->textLayoutObject, fragment.characterOffset, offsetInFragment, queryData->textBox->direction());
        if (queryData->isVerticalText)
            glyphOffsetInDirection = metrics.height();
        else
            glyphOffsetInDirection = metrics.width();
    }

    if (!queryData->textBox->isLeftToRightDirection()) {
        float fragmentExtent = queryData->isVerticalText ? fragment.height : fragment.width;
        glyphOffsetInDirection = fragmentExtent - glyphOffsetInDirection;
    }

    FloatPoint glyphPosition(fragment.x, fragment.y);
    if (queryData->isVerticalText)
        glyphPosition.move(0, glyphOffsetInDirection);
    else
        glyphPosition.move(glyphOffsetInDirection, 0);

    return glyphPosition;
}

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::layoutTextOnLineOrPath(SVGInlineTextBox* textBox, RenderSVGInlineText* text, const RenderStyle* style)
{
    SVGElement* lengthContext = static_cast<SVGElement*>(text->parent()->node());
    
    RenderObject* textParent = text->parent();
    bool definesTextLength = textParent ? parentDefinesTextLength(textParent) : false;

    const SVGRenderStyle* svgStyle = style->svgStyle();
    ASSERT(svgStyle);

    m_visualMetricsListOffset = 0;
    m_visualCharacterOffset = 0;

    Vector<SVGTextMetrics>& textMetricsValues = text->layoutAttributes().textMetricsValues();
    const UChar* characters = text->characters();

    const Font& font = style->font();
    SVGTextLayoutEngineSpacing spacingLayout(font);
    SVGTextLayoutEngineBaseline baselineLayout(font);

    bool didStartTextFragment = false;
    bool applySpacingToNextCharacter = false;

    float lastAngle = 0;
    float baselineShift = baselineLayout.calculateBaselineShift(svgStyle, lengthContext);
    baselineShift -= baselineLayout.calculateAlignmentBaselineShift(m_isVerticalText, text);

    // Main layout algorithm.
    while (true) {
        // Find the start of the current text box in this list, respecting ligatures.
        SVGTextMetrics visualMetrics = SVGTextMetrics::emptyMetrics();
        if (!currentVisualCharacterMetrics(textBox, text, visualMetrics))
            break;

        if (visualMetrics == SVGTextMetrics::emptyMetrics()) {
            advanceToNextVisualCharacter(visualMetrics);
            continue;
        }

        SVGTextLayoutAttributes logicalAttributes;
        if (!currentLogicalCharacterAttributes(logicalAttributes))
            break;

        SVGTextMetrics logicalMetrics = SVGTextMetrics::emptyMetrics();
        if (!currentLogicalCharacterMetrics(logicalAttributes, logicalMetrics))
            break;

        Vector<float>& xValues = logicalAttributes.xValues();
        Vector<float>& yValues = logicalAttributes.yValues();
        Vector<float>& dxValues = logicalAttributes.dxValues();
        Vector<float>& dyValues = logicalAttributes.dyValues();
        Vector<float>& rotateValues = logicalAttributes.rotateValues();

        float x = xValues.at(m_logicalCharacterOffset);
        float y = yValues.at(m_logicalCharacterOffset);

        // When we've advanced to the box start offset, determine using the original x/y values,
        // whether this character starts a new text chunk, before doing any further processing.
        if (m_visualCharacterOffset == textBox->start())
            textBox->setStartsNewTextChunk(logicalAttributes.context()->characterStartsNewTextChunk(m_logicalCharacterOffset));

        float angle = 0;
        if (!rotateValues.isEmpty()) {
            float newAngle = rotateValues.at(m_logicalCharacterOffset);
            if (newAngle != SVGTextLayoutAttributes::emptyValue())
                angle = newAngle;
        }

        // Calculate glyph orientation angle.
        const UChar* currentCharacter = characters + m_visualCharacterOffset;
        float orientationAngle = baselineLayout.calculateGlyphOrientationAngle(m_isVerticalText, svgStyle, *currentCharacter);

        // Calculate glyph advance & x/y orientation shifts.
        float xOrientationShift = 0;
        float yOrientationShift = 0;
        float glyphAdvance = baselineLayout.calculateGlyphAdvanceAndOrientation(m_isVerticalText, visualMetrics, orientationAngle, xOrientationShift, yOrientationShift);

        // Assign current text position to x/y values, if needed.
        updateCharacerPositionIfNeeded(x, y);

        // Apply dx/dy value adjustments to current text position, if needed.
        updateRelativePositionAdjustmentsIfNeeded(dxValues, dyValues);

        // Calculate SVG Fonts kerning, if needed.
        float kerning = spacingLayout.calculateSVGKerning(m_isVerticalText, visualMetrics.glyph());

        // Calculate CSS 'kerning', 'letter-spacing' and 'word-spacing' for next character, if needed.
        float spacing = spacingLayout.calculateCSSKerningAndSpacing(svgStyle, lengthContext, currentCharacter);

        float textPathOffset = 0;
        if (m_inPathLayout) {
            float scaledGlyphAdvance = glyphAdvance * m_textPathScaling;
            if (m_isVerticalText) {
                // If there's an absolute y position available, it marks the beginning of a new position along the path.
                if (y != SVGTextLayoutAttributes::emptyValue())
                    m_textPathCurrentOffset = y + m_textPathStartOffset;

                m_textPathCurrentOffset += m_dy - kerning;
                m_dy = 0;

//.........这里部分代码省略.........

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