C++ NodeRenderingContext类代码示例

bool HTMLSummaryElement::childShouldCreateRenderer(const NodeRenderingContext& childContext) const
{
    if (childContext.node()->isPseudoElement())
        return HTMLElement::childShouldCreateRenderer(childContext);

    return childContext.isOnEncapsulationBoundary() && HTMLElement::childShouldCreateRenderer(childContext);
}

bool HTMLDetailsElement::childShouldCreateRenderer(const NodeRenderingContext& childContext) const
{
    if (!childContext.isOnEncapsulationBoundary())
        return false;

    if (m_isOpen)
        return HTMLElement::childShouldCreateRenderer(childContext);

    if (!childContext.node()->hasTagName(summaryTag))
        return false;

    return childContext.node() == findMainSummary() && HTMLElement::childShouldCreateRenderer(childContext);
}

bool HTMLFormElement::rendererIsNeeded(const NodeRenderingContext& context)
{
    if (!m_wasDemoted)
        return HTMLElement::rendererIsNeeded(context);

    ContainerNode* node = parentNode();
    RenderObject* parentRenderer = node->renderer();
    // FIXME: Shouldn't we also check for table caption (see |formIsTablePart| below).
    bool parentIsTableElementPart = (parentRenderer->isTable() && node->hasTagName(tableTag))
        || (parentRenderer->isTableRow() && node->hasTagName(trTag))
        || (parentRenderer->isTableSection() && node->hasTagName(tbodyTag))
        || (parentRenderer->isRenderTableCol() && node->hasTagName(colTag))
        || (parentRenderer->isTableCell() && node->hasTagName(trTag));

    if (!parentIsTableElementPart)
        return true;

    EDisplay display = context.style()->display();
    bool formIsTablePart = display == TABLE || display == INLINE_TABLE || display == TABLE_ROW_GROUP
        || display == TABLE_HEADER_GROUP || display == TABLE_FOOTER_GROUP || display == TABLE_ROW
        || display == TABLE_COLUMN_GROUP || display == TABLE_COLUMN || display == TABLE_CELL
        || display == TABLE_CAPTION;

    return formIsTablePart;
}

bool Text::textRendererIsNeeded(const NodeRenderingContext& context)
{
    if (isEditingText())
        return true;

    if (!length())
        return false;

    if (context.style()->display() == NONE)
        return false;

    if (!containsOnlyWhitespace())
        return true;

    RenderObject* parent = context.parentRenderer();
    if (!parent->canHaveWhitespaceChildren())
        return false;

    if (context.style()->preserveNewline()) // pre/pre-wrap/pre-line always make renderers.
        return true;

    RenderObject* prev = context.previousRenderer();
    if (prev && prev->isBR()) // <span><br/> <br/></span>
        return false;

    if (parent->isRenderInline()) {
        // <span><div/> <div/></span>
        if (prev && !prev->isInline())
            return false;
    } else {
        if (parent->isRenderBlock() && !parent->childrenInline() && (!prev || !prev->isInline()))
            return false;

        // Avoiding creation of a Renderer for the text node is a non-essential memory optimization.
        // So to avoid blowing up on very wide DOMs, we limit the number of siblings to visit.
        unsigned maxSiblingsToVisit = 50;

        RenderObject* first = parent->firstChild();
        while (first && first->isFloatingOrOutOfFlowPositioned() && maxSiblingsToVisit--)
            first = first->nextSibling();
        if (!first || context.nextRenderer() == first)
            // Whitespace at the start of a block just goes away.  Don't even
            // make a render object for this text.
            return false;
    }
    return true;
}

bool Text::textRendererIsNeeded(const NodeRenderingContext& context)
{
    if (isEditingText())
        return true;

    if (!length())
        return false;

    if (context.style()->display() == NONE)
        return false;

    bool onlyWS = containsOnlyWhitespace();
    if (!onlyWS)
        return true;

    RenderObject* parent = context.parentRenderer();
    if (parent->isTable() || parent->isTableRow() || parent->isTableSection() || parent->isRenderTableCol() || parent->isFrameSet())
        return false;
    
    if (context.style()->preserveNewline()) // pre/pre-wrap/pre-line always make renderers.
        return true;
    
    RenderObject* prev = context.previousRenderer();
    if (prev && prev->isBR()) // <span><br/> <br/></span>
        return false;
        
    if (parent->isRenderInline()) {
        // <span><div/> <div/></span>
        if (prev && !prev->isInline())
            return false;
    } else {
        if (parent->isRenderBlock() && !parent->childrenInline() && (!prev || !prev->isInline()))
            return false;
        
        RenderObject* first = parent->firstChild();
        while (first && first->isFloatingOrOutOfFlowPositioned())
            first = first->nextSibling();
        if (!first || context.nextRenderer() == first) {
            // Whitespace at the start of a block just goes away.  Don't even
            // make a render object for this text.
            return false;
        }
    }
    
    return true;
}

bool SVGSwitchElement::childShouldCreateRenderer(const NodeRenderingContext& childContext) const
{
    // FIXME: This function does not do what the comment below implies it does.
    // It will create a renderer for any valid SVG element children, not just the first one.
    for (Node* node = firstChild(); node; node = node->nextSibling()) {
        if (!node->isSVGElement())
            continue;

        SVGElement* element = toSVGElement(node);
        if (!element || !element->isValid())
            continue;

        return node == childContext.node(); // Only allow this child if it's the first valid child
    }

    return false;
}

bool SVGTextElement::childShouldCreateRenderer(const NodeRenderingContext& childContext) const
{
    if (childContext.node()->isTextNode()
        || childContext.node()->hasTagName(SVGNames::aTag)
#if ENABLE(SVG_FONTS)
        || childContext.node()->hasTagName(SVGNames::altGlyphTag)
#endif
        || childContext.node()->hasTagName(SVGNames::textPathTag)
        || childContext.node()->hasTagName(SVGNames::trefTag)
        || childContext.node()->hasTagName(SVGNames::tspanTag))
        return true;

    return false;
}

bool SVGDocument::childShouldCreateRenderer(const NodeRenderingContext& childContext) const
{
    if (childContext.node()->hasTagName(SVGNames::svgTag))
        return toSVGSVGElement(childContext.node())->isValid();
    return true;
}

bool HTMLIFrameElement::rendererIsNeeded(const NodeRenderingContext& context)
{
    return isURLAllowed() && context.style()->display() != NONE;
}

bool HTMLFrameSetElement::rendererIsNeeded(const NodeRenderingContext& context)
{
    // For compatibility, frames render even when display: none is set.
    // However, we delay creating a renderer until stylesheets have loaded. 
    return context.style()->isStyleAvailable();
}

bool SVGAltGlyphElement::childShouldCreateRenderer(const NodeRenderingContext& childContext) const
{
    if (childContext.node()->isTextNode())
        return true;
    return false;
}

bool PseudoElement::rendererIsNeeded(const NodeRenderingContext& context)
{
    return pseudoElementRendererIsNeeded(context.style());
}