C++ RenderBoxModelObject::baselinePosition方法代码示例

void RenderMathMLSubSup::layout()
{
    RenderBlock::layout();
    
    if (m_kind != SubSup || !m_scripts)
        return;
    RenderBoxModelObject* base = this->base();
    RenderObject* superscriptWrapper = m_scripts->firstChild();
    RenderObject* subscriptWrapper = m_scripts->lastChild();
    if (!base || !superscriptWrapper || !subscriptWrapper || superscriptWrapper == subscriptWrapper)
        return;
    ASSERT(superscriptWrapper->isRenderMathMLBlock());
    ASSERT(subscriptWrapper->isRenderMathMLBlock());
    RenderObject* superscript = superscriptWrapper->firstChild();
    RenderObject* subscript = subscriptWrapper->firstChild();
    if (!superscript || !subscript)
        return;
    
    LineDirectionMode lineDirection = style()->isHorizontalWritingMode() ? HorizontalLine : VerticalLine;
    LayoutUnit baseBaseline = base->baselinePosition(AlphabeticBaseline, true, lineDirection);
    LayoutUnit baseExtendUnderBaseline = getBoxModelObjectHeight(base) - baseBaseline;
    LayoutUnit axis = style()->fontMetrics().xHeight() / 2;
    LayoutUnit superscriptHeight = getBoxModelObjectHeight(superscript);
    LayoutUnit subscriptHeight = getBoxModelObjectHeight(subscript);
    
    // Our layout rules are: Don't let the superscript go below the "axis" (half x-height above the
    // baseline), or the subscript above the axis. Also, don't let the superscript's top edge be
    // below the base's top edge, or the subscript's bottom edge above the base's bottom edge.
    //
    // FIXME: Check any subscriptshift or superscriptshift attributes, and maybe use more sophisticated
    // heuristics from TeX or elsewhere. See https://bugs.webkit.org/show_bug.cgi?id=79274#c5.
    
    // Above we did scriptsStyle->setVerticalAlign(TOP) for mscripts' style, so the superscript's
    // top edge will equal the top edge of the base's padding.
    LayoutUnit basePaddingTop = superscriptHeight + axis - baseBaseline;
    // If basePaddingTop is positive, it's indeed the base's padding-top that we need. If it's negative,
    // then we should instead use its absolute value to pad the bottom of the superscript, to get the
    // superscript's bottom edge down to the axis. First we compute how much more we need to shift the
    // subscript down, once its top edge is at the axis.
    LayoutUnit superPaddingBottom = max<LayoutUnit>(baseExtendUnderBaseline + axis - subscriptHeight, 0);
    if (basePaddingTop < 0) {
        superPaddingBottom += -basePaddingTop;
        basePaddingTop = 0;
    }
    
    setChildNeedsLayout(true, false);
    
    RenderObject* baseWrapper = firstChild();
    baseWrapper->style()->setPaddingTop(Length(basePaddingTop, Fixed));
    baseWrapper->setNeedsLayout(true, false);
    
    superscriptWrapper->style()->setPaddingBottom(Length(superPaddingBottom, Fixed));
    superscriptWrapper->setNeedsLayout(true, false);
    m_scripts->setNeedsLayout(true, false);
    
    RenderBlock::layout();
}

void RootInlineBox::ascentAndDescentForBox(InlineBox* box, GlyphOverflowAndFallbackFontsMap& textBoxDataMap, int& ascent, int& descent,
                                           bool& affectsAscent, bool& affectsDescent) const
{
    bool ascentDescentSet = false;

    // Replaced boxes will return 0 for the line-height if line-box-contain says they are
    // not to be included.
    if (box->renderer().isReplaced()) {
        if (lineStyle().lineBoxContain() & LineBoxContainReplaced) {
            ascent = box->baselinePosition(baselineType());
            descent = box->lineHeight() - ascent;
            
            // Replaced elements always affect both the ascent and descent.
            affectsAscent = true;
            affectsDescent = true;
        }
        return;
    }

    Vector<const SimpleFontData*>* usedFonts = 0;
    GlyphOverflow* glyphOverflow = 0;
    if (box->isInlineTextBox()) {
        GlyphOverflowAndFallbackFontsMap::iterator it = textBoxDataMap.find(toInlineTextBox(box));
        usedFonts = it == textBoxDataMap.end() ? 0 : &it->value.first;
        glyphOverflow = it == textBoxDataMap.end() ? 0 : &it->value.second;
    }
        
    bool includeLeading = includeLeadingForBox(box);
    bool includeFont = includeFontForBox(box);
    
    bool setUsedFont = false;
    bool setUsedFontWithLeading = false;

    const RenderStyle& boxLineStyle = box->lineStyle();
#if PLATFORM(IOS)
    if (usedFonts && !usedFonts->isEmpty() && (includeFont || (boxLineStyle.lineHeight().isNegative() && includeLeading)) && !box->renderer().document().settings()->alwaysUseBaselineOfPrimaryFont()) {
#else
    if (usedFonts && !usedFonts->isEmpty() && (includeFont || (boxLineStyle.lineHeight().isNegative() && includeLeading))) {
#endif
        usedFonts->append(boxLineStyle.font().primaryFont());
        for (size_t i = 0; i < usedFonts->size(); ++i) {
            const FontMetrics& fontMetrics = usedFonts->at(i)->fontMetrics();
            int usedFontAscent = fontMetrics.ascent(baselineType());
            int usedFontDescent = fontMetrics.descent(baselineType());
            int halfLeading = (fontMetrics.lineSpacing() - fontMetrics.height()) / 2;
            int usedFontAscentAndLeading = usedFontAscent + halfLeading;
            int usedFontDescentAndLeading = fontMetrics.lineSpacing() - usedFontAscentAndLeading;
            if (includeFont) {
                setAscentAndDescent(ascent, descent, usedFontAscent, usedFontDescent, ascentDescentSet);
                setUsedFont = true;
            }
            if (includeLeading) {
                setAscentAndDescent(ascent, descent, usedFontAscentAndLeading, usedFontDescentAndLeading, ascentDescentSet);
                setUsedFontWithLeading = true;
            }
            if (!affectsAscent)
                affectsAscent = usedFontAscent - box->logicalTop() > 0;
            if (!affectsDescent)
                affectsDescent = usedFontDescent + box->logicalTop() > 0;
        }
    }

    // If leading is included for the box, then we compute that box.
    if (includeLeading && !setUsedFontWithLeading) {
        int ascentWithLeading = box->baselinePosition(baselineType());
        int descentWithLeading = box->lineHeight() - ascentWithLeading;
        setAscentAndDescent(ascent, descent, ascentWithLeading, descentWithLeading, ascentDescentSet);
        
        // Examine the font box for inline flows and text boxes to see if any part of it is above the baseline.
        // If the top of our font box relative to the root box baseline is above the root box baseline, then
        // we are contributing to the maxAscent value. Descent is similar. If any part of our font box is below
        // the root box's baseline, then we contribute to the maxDescent value.
        affectsAscent = ascentWithLeading - box->logicalTop() > 0;
        affectsDescent = descentWithLeading + box->logicalTop() > 0; 
    }
    
    if (includeFontForBox(box) && !setUsedFont) {
        int fontAscent = boxLineStyle.fontMetrics().ascent(baselineType());
        int fontDescent = boxLineStyle.fontMetrics().descent(baselineType());
        setAscentAndDescent(ascent, descent, fontAscent, fontDescent, ascentDescentSet);
        affectsAscent = fontAscent - box->logicalTop() > 0;
        affectsDescent = fontDescent + box->logicalTop() > 0; 
    }

    if (includeGlyphsForBox(box) && glyphOverflow && glyphOverflow->computeBounds) {
        setAscentAndDescent(ascent, descent, glyphOverflow->top, glyphOverflow->bottom, ascentDescentSet);
        affectsAscent = glyphOverflow->top - box->logicalTop() > 0;
        affectsDescent = glyphOverflow->bottom + box->logicalTop() > 0; 
        glyphOverflow->top = std::min(glyphOverflow->top, std::max(0, glyphOverflow->top - boxLineStyle.fontMetrics().ascent(baselineType())));
        glyphOverflow->bottom = std::min(glyphOverflow->bottom, std::max(0, glyphOverflow->bottom - boxLineStyle.fontMetrics().descent(baselineType())));
    }

    if (includeMarginForBox(box)) {
        LayoutUnit ascentWithMargin = boxLineStyle.fontMetrics().ascent(baselineType());
        LayoutUnit descentWithMargin = boxLineStyle.fontMetrics().descent(baselineType());
        if (box->parent() && !box->renderer().isTextOrLineBreak()) {
            ascentWithMargin += box->boxModelObject()->borderAndPaddingBefore() + box->boxModelObject()->marginBefore();
            descentWithMargin += box->boxModelObject()->borderAndPaddingAfter() + box->boxModelObject()->marginAfter();
        }
        setAscentAndDescent(ascent, descent, ascentWithMargin, descentWithMargin, ascentDescentSet);
//.........这里部分代码省略.........