rendering/mathml/RenderMathMLUnderOver.cpp

/*
 * Copyright (C) 2009 Alex Milowski (alex (at) milowski.com). All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"

#if ENABLE(MATHML)

#include "RenderMathMLUnderOver.h"

#include "FontSelector.h"
#include "MathMLNames.h"

namespace WebCore {

using namespace MathMLNames;

static const double gOverSpacingAdjustment = 0.5;

RenderMathMLUnderOver::RenderMathMLUnderOver(Node* expression)
    : RenderMathMLBlock(expression)
{
    Element* element = static_cast<Element*>(expression);
    // Determine what kind of under/over expression we have by element name

    if (element->hasLocalName(MathMLNames::munderTag))
        m_kind = Under;
    else if (element->hasLocalName(MathMLNames::moverTag))
        m_kind = Over;
    else if (element->hasLocalName(MathMLNames::munderoverTag))
        m_kind = UnderOver;
    else
        m_kind = Under;

}

void RenderMathMLUnderOver::addChild(RenderObject* child, RenderObject* beforeChild)
{
    RenderMathMLBlock* row = new (renderArena()) RenderMathMLBlock(node());
    RefPtr<RenderStyle> rowStyle = makeBlockStyle();
    row->setStyle(rowStyle.release());

    // look through the children for rendered elements counting the blocks so we know what child
    // we are adding
    int blocks = 0;
    RenderObject* current = this->firstChild();
    while (current) {
        blocks++;
        current = current->nextSibling();
    }

    switch (blocks) {
    case 0:
        // this is the base so just append it
        RenderBlock::addChild(row, beforeChild);
        break;
    case 1:
        // the under or over
        // FIXME: text-align: center does not work
        row->style()->setTextAlign(CENTER);
        if (m_kind == Over) {
            // add the over as first
            RenderBlock::addChild(row, firstChild());
        } else {
            // add the under as last
            RenderBlock::addChild(row, beforeChild);
        }
        break;
    case 2:
        // the under or over
        // FIXME: text-align: center does not work
        row->style()->setTextAlign(CENTER);
        if (m_kind == UnderOver) {
            // add the over as first
            RenderBlock::addChild(row, firstChild());
        } else {
            // we really shouldn't get here as only munderover should have three children
            RenderBlock::addChild(row, beforeChild);
        }
        break;
    default:
        // munderover shouldn't have more than three children.  In theory we shouldn't
        // get here if the MathML is correctly formed, but that isn't a guarantee.
        // We will treat this as another under element and they'll get something funky.
        RenderBlock::addChild(row, beforeChild);
    }
    row->addChild(child);
}

inline int getOffsetHeight(RenderObject* obj)
{
    if (obj->isBoxModelObject()) {
        RenderBoxModelObject* box = toRenderBoxModelObject(obj);
        return box->offsetHeight();
    }

    return 0;
}

void RenderMathMLUnderOver::stretchToHeight(int height)
{

    RenderObject* base = firstChild();
    if (!base)
        return;

    // For over or underover, the base is the sibling of the first child
    if (m_kind != Under)
        base = base->nextSibling();

    if (!base)
        return;

    // use the child of the row which is the actual base
    base = base->firstChild();

    if (base && base->isRenderMathMLBlock()) {
        RenderMathMLBlock* block = toRenderMathMLBlock(base);
        block->stretchToHeight(height);
        setNeedsLayout(true);
    }
}

void RenderMathMLUnderOver::layout()
{
    RenderBlock::layout();
    RenderObject* over = 0;
    RenderObject* base = 0;
    switch (m_kind) {
    case Over:
        // We need to calculate the baseline over the over versus the start of the base and
        // adjust the placement of the base.
        over = firstChild();
        if (over) {
            // FIXME: descending glyphs intrude into base (e.g. lowercase y over base)
            // FIXME: bases that ascend higher than the line box intrude into the over
            if (!over->firstChild()->isBoxModelObject())
                break;

            int overSpacing = static_cast<int>(gOverSpacingAdjustment * (getOffsetHeight(over) - toRenderBoxModelObject(over->firstChild())->baselinePosition(AlphabeticBaseline, true, HorizontalLine)));

            // base row wrapper
            base = over->nextSibling();
            if (base) {
                if (overSpacing > 0)
                    base->style()->setMarginTop(Length(-overSpacing, Fixed));
                else
                    base->style()->setMarginTop(Length(0, Fixed));
            }

        }
        break;
    case Under:
        // FIXME: Non-ascending glyphs in the under should be moved closer to the base

        // We need to calculate the baseline of the base versus the start of the under block and
        // adjust the placement of the under block.

        // base row wrapper
        base = firstChild();
        if (base) {
            int baseHeight = getOffsetHeight(base);
            // actual base
            base = base->firstChild();
            if (!base->isBoxModelObject())
                break;

            // FIXME: We need to look at the space between a single maximum height of
            //        the line boxes and the baseline and squeeze them together
            int underSpacing = baseHeight - toRenderBoxModelObject(base)->baselinePosition(AlphabeticBaseline, true, HorizontalLine);

            // adjust the base's intrusion into the under
            RenderObject* under = lastChild();
            if (under && underSpacing > 0)
                under->style()->setMarginTop(Length(-underSpacing, Fixed));
        }
        break;
    case UnderOver:
        // FIXME: Non-descending glyphs in the over should be moved closer to the base
        // FIXME: Non-ascending glyphs in the under should be moved closer to the base

        // We need to calculate the baseline of the over versus the start of the base and
        // adjust the placement of the base.

        over = firstChild();
        if (over) {
            // FIXME: descending glyphs intrude into base (e.g. lowercase y over base)
            // FIXME: bases that ascend higher than the line box intrude into the over
            if (!over->firstChild()->isBoxModelObject())
                break;
            int overSpacing = static_cast<int>(gOverSpacingAdjustment * (getOffsetHeight(over) - toRenderBoxModelObject(over->firstChild())->baselinePosition(AlphabeticBaseline, true, HorizontalLine)));

            // base row wrapper
            base = over->nextSibling();

            if (base) {
                if (overSpacing > 0)
                    base->style()->setMarginTop(Length(-overSpacing, Fixed));

                // We need to calculate the baseline of the base versus the start of the under block and
                // adjust the placement of the under block.

                int baseHeight = getOffsetHeight(base);
                // actual base
                base = base->firstChild();
                if (!base->isBoxModelObject())
                    break;

                // FIXME: We need to look at the space between a single maximum height of
                //        the line boxes and the baseline and squeeze them together
                int underSpacing = baseHeight - toRenderBoxModelObject(base)->baselinePosition(AlphabeticBaseline, true, HorizontalLine);

                RenderObject* under = lastChild();
                if (under && under->firstChild()->isRenderInline() && underSpacing > 0)
                    under->style()->setMarginTop(Length(-underSpacing, Fixed));

            }
        }
        break;
    }
    setNeedsLayout(true);
    RenderBlock::layout();
}

int RenderMathMLUnderOver::baselinePosition(FontBaseline, bool firstLine, LineDirectionMode direction, LinePositionMode linePositionMode) const
{
    RenderObject* current = firstChild();
    if (!current)
        return RenderBlock::baselinePosition(AlphabeticBaseline, firstLine, direction, linePositionMode);

    int baseline = 0;
    switch (m_kind) {
    case UnderOver:
    case Over:
        baseline += getOffsetHeight(current);
        current = current->nextSibling();
        if (current) {
            // actual base
            RenderObject* base = current->firstChild();
            if (!base || !base->isBoxModelObject())
                break;
            baseline += toRenderBoxModelObject(base)->baselinePosition(AlphabeticBaseline, firstLine, HorizontalLine, linePositionMode);
            // added the negative top margin
            baseline += current->style()->marginTop().value();
        }
        break;
    case Under:
        RenderObject* base = current->firstChild();
        if (base && base->isBoxModelObject())
            baseline += toRenderBoxModelObject(base)->baselinePosition(AlphabeticBaseline, true, HorizontalLine);
    }

    // FIXME: Where is the extra 2-3px adjusted for zoom coming from?
    float zoomFactor = style()->effectiveZoom();
    baseline += static_cast<int>((zoomFactor > 1.25 ? 2 : 3) * zoomFactor);
    return baseline;
}


int RenderMathMLUnderOver::nonOperatorHeight() const
{
    int nonOperators = 0;
    for (RenderObject* current = firstChild(); current; current = current->nextSibling()) {
        if (current->firstChild()->isRenderMathMLBlock()) {
            RenderMathMLBlock* block = toRenderMathMLBlock(current->firstChild());
            if (!block->isRenderMathMLOperator())
                nonOperators += getOffsetHeight(current);
        } else {
            nonOperators += getOffsetHeight(current);
        }
    }
    return nonOperators;
}

}


#endif // ENABLE(MATHML)