Source/WebCore/rendering/RenderCombineText.cpp

/*
 * Copyright (C) 2011 Apple Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"
#include "RenderCombineText.h"

#include "TextRun.h"

namespace WebCore {

const float textCombineMargin = 1.1f; // Allow em + 10% margin

RenderCombineText::RenderCombineText(Node* node, PassRefPtr<StringImpl> string)
     : RenderText(node, string)
     , m_combinedTextWidth(0)
     , m_isCombined(false)
     , m_needsFontUpdate(false)
{
}

void RenderCombineText::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
{
    setStyleInternal(RenderStyle::clone(style()));
    RenderText::styleDidChange(diff, oldStyle);

    if (m_isCombined)
        RenderText::setTextInternal(originalText()); // This RenderCombineText has been combined once. Restore the original text for the next combineText().

    m_needsFontUpdate = true;
}

void RenderCombineText::setTextInternal(PassRefPtr<StringImpl> text)
{
    RenderText::setTextInternal(text);

    m_needsFontUpdate = true;
}

float RenderCombineText::width(unsigned from, unsigned length, const Font& font, float xPosition, HashSet<const SimpleFontData*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
{
    if (!characters())
        return 0;

    if (m_isCombined)
        return font.size();

    return RenderText::width(from, length, font, xPosition, fallbackFonts, glyphOverflow);
}

void RenderCombineText::adjustTextOrigin(FloatPoint& textOrigin, const FloatRect& boxRect) const
{
    if (m_isCombined)
        textOrigin.move(boxRect.height() / 2 - ceilf(m_combinedTextWidth) / 2, style()->font().pixelSize());
}

void RenderCombineText::charactersToRender(int start, const UChar*& characters, int& length) const
{
    if (m_isCombined) {
        length = originalText()->length();
        characters = originalText()->characters();
        return;
    }
 
    characters = text()->characters() + start;
}

void RenderCombineText::combineText()
{
    if (!m_needsFontUpdate)
        return;

    m_isCombined = false;
    m_needsFontUpdate = false;

    // CSS3 spec says text-combine works only in vertical writing mode.
    if (style()->isHorizontalWritingMode())
        return;

    TextRun run = TextRun(String(text()));
    FontDescription description = originalFont().fontDescription();
    float emWidth = description.computedSize() * textCombineMargin;
    bool shouldUpdateFont = false;

    description.setOrientation(Horizontal); // We are going to draw combined text horizontally.
    m_combinedTextWidth = originalFont().width(run);
    m_isCombined = m_combinedTextWidth <= emWidth;

    if (m_isCombined)
        shouldUpdateFont = style()->setFontDescription(description); // Need to change font orientation to horizontal.
    else {
        // Need to try compressed glyphs.
        static const FontWidthVariant widthVariants[] = { HalfWidth, ThirdWidth, QuarterWidth };
        for (size_t i = 0 ; i < WTF_ARRAY_LENGTH(widthVariants) ; ++i) {
            description.setWidthVariant(widthVariants[i]);
            Font compressedFont = Font(description, style()->font().letterSpacing(), style()->font().wordSpacing());
            compressedFont.update(style()->font().fontSelector());
            float runWidth = compressedFont.width(run);
            if (runWidth <= emWidth) {
                m_combinedTextWidth = runWidth;
                m_isCombined = true;

                // Replace my font with the new one.
                shouldUpdateFont = style()->setFontDescription(description);
                break;
            }
        }
    }

    if (!m_isCombined)
        shouldUpdateFont = style()->setFontDescription(originalFont().fontDescription());

    if (shouldUpdateFont)
        style()->font().update(style()->font().fontSelector());

    if (m_isCombined) {
        DEFINE_STATIC_LOCAL(String, objectReplacementCharacterString, (&objectReplacementCharacter, 1));
        RenderText::setTextInternal(objectReplacementCharacterString.impl());
    }
}

} // namespace WebCore