android-5.0.1_r1/s

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2000 Dirk Mueller (mueller@kde.org)
 * Copyright (C) 2003, 2006, 2010, 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 "platform/fonts/Font.h"

#include "platform/LayoutUnit.h"
#include "platform/fonts/Character.h"
#include "platform/fonts/FontCache.h"
#include "platform/fonts/FontFallbackList.h"
#include "platform/fonts/FontPlatformFeatures.h"
#include "platform/fonts/GlyphBuffer.h"
#include "platform/fonts/GlyphPageTreeNode.h"
#include "platform/fonts/SimpleFontData.h"
#include "platform/fonts/WidthIterator.h"
#include "platform/geometry/FloatRect.h"
#include "platform/text/TextRun.h"
#include "wtf/MainThread.h"
#include "wtf/StdLibExtras.h"
#include "wtf/unicode/CharacterNames.h"
#include "wtf/unicode/Unicode.h"

using namespace WTF;
using namespace Unicode;
using namespace std;

namespace WebCore {

CodePath Font::s_codePath = AutoPath;

// ============================================================================================
// Font Implementation (Cross-Platform Portion)
// ============================================================================================

Font::Font()
{
}

Font::Font(const FontDescription& fd)
    : m_fontDescription(fd)
{
}

Font::Font(const Font& other)
    : m_fontDescription(other.m_fontDescription)
    , m_fontFallbackList(other.m_fontFallbackList)
{
}

Font& Font::operator=(const Font& other)
{
    m_fontDescription = other.m_fontDescription;
    m_fontFallbackList = other.m_fontFallbackList;
    return *this;
}

bool Font::operator==(const Font& other) const
{
    // Our FontData don't have to be checked, since checking the font description will be fine.
    // FIXME: This does not work if the font was made with the FontPlatformData constructor.
    if (loadingCustomFonts() || other.loadingCustomFonts())
        return false;

    FontSelector* first = m_fontFallbackList ? m_fontFallbackList->fontSelector() : 0;
    FontSelector* second = other.m_fontFallbackList ? other.m_fontFallbackList->fontSelector() : 0;

    return first == second
        && m_fontDescription == other.m_fontDescription
        && (m_fontFallbackList ? m_fontFallbackList->fontSelectorVersion() : 0) == (other.m_fontFallbackList ? other.m_fontFallbackList->fontSelectorVersion() : 0)
        && (m_fontFallbackList ? m_fontFallbackList->generation() : 0) == (other.m_fontFallbackList ? other.m_fontFallbackList->generation() : 0);
}

void Font::update(PassRefPtrWillBeRawPtr<FontSelector> fontSelector) const
{
    // FIXME: It is pretty crazy that we are willing to just poke into a RefPtr, but it ends up
    // being reasonably safe (because inherited fonts in the render tree pick up the new
    // style anyway. Other copies are transient, e.g., the state in the GraphicsContext, and
    // won't stick around long enough to get you in trouble). Still, this is pretty disgusting,
    // and could eventually be rectified by using RefPtrs for Fonts themselves.
    if (!m_fontFallbackList)
        m_fontFallbackList = FontFallbackList::create();
    m_fontFallbackList->invalidate(fontSelector);
}

void Font::drawText(GraphicsContext* context, const TextRunPaintInfo& runInfo, const FloatPoint& point, CustomFontNotReadyAction customFontNotReadyAction) const
{
    // Don't draw anything while we are using custom fonts that are in the process of loading,
    // except if the 'force' argument is set to true (in which case it will use a fallback
    // font).
    if (shouldSkipDrawing() && customFontNotReadyAction == DoNotPaintIfFontNotReady)
        return;

    CodePath codePathToUse = codePath(runInfo.run);
    // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
    if (codePathToUse != ComplexPath && fontDescription().typesettingFeatures() && (runInfo.from || runInfo.to != runInfo.run.length()))
        codePathToUse = ComplexPath;

    if (codePathToUse != ComplexPath)
        return drawSimpleText(context, runInfo, point);

    return drawComplexText(context, runInfo, point);
}

void Font::drawEmphasisMarks(GraphicsContext* context, const TextRunPaintInfo& runInfo, const AtomicString& mark, const FloatPoint& point) const
{
    if (shouldSkipDrawing())
        return;

    CodePath codePathToUse = codePath(runInfo.run);
    // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
    if (codePathToUse != ComplexPath && fontDescription().typesettingFeatures() && (runInfo.from || runInfo.to != runInfo.run.length()))
        codePathToUse = ComplexPath;

    if (codePathToUse != ComplexPath)
        drawEmphasisMarksForSimpleText(context, runInfo, mark, point);
    else
        drawEmphasisMarksForComplexText(context, runInfo, mark, point);
}

static inline void updateGlyphOverflowFromBounds(const IntRectExtent& glyphBounds,
    const FontMetrics& fontMetrics, GlyphOverflow* glyphOverflow)
{
    glyphOverflow->top = max<int>(glyphOverflow->top,
        glyphBounds.top() - (glyphOverflow->computeBounds ? 0 : fontMetrics.ascent()));
    glyphOverflow->bottom = max<int>(glyphOverflow->bottom,
        glyphBounds.bottom() - (glyphOverflow->computeBounds ? 0 : fontMetrics.descent()));
    glyphOverflow->left = glyphBounds.left();
    glyphOverflow->right = glyphBounds.right();
}

float Font::width(const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
{
    CodePath codePathToUse = codePath(run);
    if (codePathToUse != ComplexPath) {
        // The complex path is more restrictive about returning fallback fonts than the simple path, so we need an explicit test to make their behaviors match.
        if (!FontPlatformFeatures::canReturnFallbackFontsForComplexText())
            fallbackFonts = 0;
        // The simple path can optimize the case where glyph overflow is not observable.
        if (codePathToUse != SimpleWithGlyphOverflowPath && (glyphOverflow && !glyphOverflow->computeBounds))
            glyphOverflow = 0;
    }

    bool hasKerningOrLigatures = fontDescription().typesettingFeatures() & (Kerning | Ligatures);
    bool hasWordSpacingOrLetterSpacing = fontDescription().wordSpacing() || fontDescription().letterSpacing();
    bool isCacheable = (codePathToUse == ComplexPath || hasKerningOrLigatures)
        && !hasWordSpacingOrLetterSpacing // Word spacing and letter spacing can change the width of a word.
        && !run.allowTabs(); // If we allow tabs and a tab occurs inside a word, the width of the word varies based on its position on the line.

    WidthCacheEntry* cacheEntry = isCacheable
        ? m_fontFallbackList->widthCache().add(run, WidthCacheEntry())
        : 0;
    if (cacheEntry && cacheEntry->isValid()) {
        if (glyphOverflow)
            updateGlyphOverflowFromBounds(cacheEntry->glyphBounds, fontMetrics(), glyphOverflow);
        return cacheEntry->width;
    }

    float result;
    IntRectExtent glyphBounds;
    if (codePathToUse == ComplexPath) {
        result = floatWidthForComplexText(run, fallbackFonts, &glyphBounds);
    } else {
        result = floatWidthForSimpleText(run, fallbackFonts,
            glyphOverflow || isCacheable ? &glyphBounds : 0);
    }

    if (cacheEntry && (!fallbackFonts || fallbackFonts->isEmpty())) {
        cacheEntry->glyphBounds = glyphBounds;
        cacheEntry->width = result;
    }

    if (glyphOverflow)
        updateGlyphOverflowFromBounds(glyphBounds, fontMetrics(), glyphOverflow);
    return result;
}

float Font::width(const TextRun& run, int& charsConsumed, Glyph& glyphId) const
{
#if ENABLE(SVG_FONTS)
    if (TextRun::RenderingContext* renderingContext = run.renderingContext())
        return renderingContext->floatWidthUsingSVGFont(*this, run, charsConsumed, glyphId);
#endif

    charsConsumed = run.length();
    glyphId = 0;
    return width(run);
}

FloatRect Font::selectionRectForText(const TextRun& run, const FloatPoint& point, int h, int from, int to, bool accountForGlyphBounds) const
{
    to = (to == -1 ? run.length() : to);

    CodePath codePathToUse = codePath(run);
    // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
    if (codePathToUse != ComplexPath && fontDescription().typesettingFeatures() && (from || to != run.length()))
        codePathToUse = ComplexPath;

    if (codePathToUse != ComplexPath)
        return selectionRectForSimpleText(run, point, h, from, to, accountForGlyphBounds);

    return selectionRectForComplexText(run, point, h, from, to);
}

int Font::offsetForPosition(const TextRun& run, float x, bool includePartialGlyphs) const
{
    // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
    if (codePath(run) != ComplexPath && !fontDescription().typesettingFeatures())
        return offsetForPositionForSimpleText(run, x, includePartialGlyphs);

    return offsetForPositionForComplexText(run, x, includePartialGlyphs);
}

void Font::setCodePath(CodePath p)
{
    s_codePath = p;
}

CodePath Font::codePath()
{
    return s_codePath;
}

CodePath Font::codePath(const TextRun& run) const
{
    if (s_codePath != AutoPath)
        return s_codePath;

#if ENABLE(SVG_FONTS)
    if (run.renderingContext())
        return SimplePath;
#endif

    if (m_fontDescription.featureSettings() && m_fontDescription.featureSettings()->size() > 0 && m_fontDescription.letterSpacing() == 0)
        return ComplexPath;

    if (run.length() > 1 && !WidthIterator::supportsTypesettingFeatures(*this))
        return ComplexPath;

    if (!run.characterScanForCodePath())
        return SimplePath;

    if (run.is8Bit())
        return SimplePath;

    // Start from 0 since drawing and highlighting also measure the characters before run->from.
    return Character::characterRangeCodePath(run.characters16(), run.length());
}

void Font::willUseFontData(UChar32 character) const
{
    const FontFamily& family = fontDescription().family();
    if (m_fontFallbackList && m_fontFallbackList->fontSelector() && !family.familyIsEmpty())
        m_fontFallbackList->fontSelector()->willUseFontData(fontDescription(), family.family(), character);
}

static inline bool isInRange(UChar32 character, UChar32 lowerBound, UChar32 upperBound)
{
    return character >= lowerBound && character <= upperBound;
}

static bool shouldIgnoreRotation(UChar32 character)
{
    if (character == 0x000A7 || character == 0x000A9 || character == 0x000AE)
        return true;

    if (character == 0x000B6 || character == 0x000BC || character == 0x000BD || character == 0x000BE)
        return true;

    if (isInRange(character, 0x002E5, 0x002EB))
        return true;

    if (isInRange(character, 0x01100, 0x011FF) || isInRange(character, 0x01401, 0x0167F) || isInRange(character, 0x01800, 0x018FF))
        return true;

    if (character == 0x02016 || character == 0x02018 || character == 0x02019 || character == 0x02020 || character == 0x02021
        || character == 0x2030 || character == 0x02031)
        return true;

    if (isInRange(character, 0x0203B, 0x0203D) || character == 0x02042 || character == 0x02044 || character == 0x02047
        || character == 0x02048 || character == 0x02049 || character == 0x2051)
        return true;

    if (isInRange(character, 0x02065, 0x02069) || isInRange(character, 0x020DD, 0x020E0)
        || isInRange(character, 0x020E2, 0x020E4) || isInRange(character, 0x02100, 0x02117)
        || isInRange(character, 0x02119, 0x02131) || isInRange(character, 0x02133, 0x0213F))
        return true;

    if (isInRange(character, 0x02145, 0x0214A) || character == 0x0214C || character == 0x0214D
        || isInRange(character, 0x0214F, 0x0218F))
        return true;

    if (isInRange(character, 0x02300, 0x02307) || isInRange(character, 0x0230C, 0x0231F)
        || isInRange(character, 0x02322, 0x0232B) || isInRange(character, 0x0237D, 0x0239A)
        || isInRange(character, 0x023B4, 0x023B6) || isInRange(character, 0x023BA, 0x023CF)
        || isInRange(character, 0x023D1, 0x023DB) || isInRange(character, 0x023E2, 0x024FF))
        return true;

    if (isInRange(character, 0x025A0, 0x02619) || isInRange(character, 0x02620, 0x02767)
        || isInRange(character, 0x02776, 0x02793) || isInRange(character, 0x02B12, 0x02B2F)
        || isInRange(character, 0x02B4D, 0x02BFF) || isInRange(character, 0x02E80, 0x03007))
        return true;

    if (character == 0x03012 || character == 0x03013 || isInRange(character, 0x03020, 0x0302F)
        || isInRange(character, 0x03031, 0x0309F) || isInRange(character, 0x030A1, 0x030FB)
        || isInRange(character, 0x030FD, 0x0A4CF))
        return true;

    if (isInRange(character, 0x0A840, 0x0A87F) || isInRange(character, 0x0A960, 0x0A97F)
        || isInRange(character, 0x0AC00, 0x0D7FF) || isInRange(character, 0x0E000, 0x0FAFF))
        return true;

    if (isInRange(character, 0x0FE10, 0x0FE1F) || isInRange(character, 0x0FE30, 0x0FE48)
        || isInRange(character, 0x0FE50, 0x0FE57) || isInRange(character, 0x0FE5F, 0x0FE62)
        || isInRange(character, 0x0FE67, 0x0FE6F))
        return true;

    if (isInRange(character, 0x0FF01, 0x0FF07) || isInRange(character, 0x0FF0A, 0x0FF0C)
        || isInRange(character, 0x0FF0E, 0x0FF19) || isInRange(character, 0x0FF1F, 0x0FF3A))
        return true;

    if (character == 0x0FF3C || character == 0x0FF3E)
        return true;

    if (isInRange(character, 0x0FF40, 0x0FF5A) || isInRange(character, 0x0FFE0, 0x0FFE2)
        || isInRange(character, 0x0FFE4, 0x0FFE7) || isInRange(character, 0x0FFF0, 0x0FFF8)
        || character == 0x0FFFD)
        return true;

    if (isInRange(character, 0x13000, 0x1342F) || isInRange(character, 0x1B000, 0x1B0FF)
        || isInRange(character, 0x1D000, 0x1D1FF) || isInRange(character, 0x1D300, 0x1D37F)
        || isInRange(character, 0x1F000, 0x1F64F) || isInRange(character, 0x1F680, 0x1F77F))
        return true;

    if (isInRange(character, 0x20000, 0x2FFFD) || isInRange(character, 0x30000, 0x3FFFD))
        return true;

    return false;
}

static inline std::pair<GlyphData, GlyphPage*> glyphDataAndPageForNonCJKCharacterWithGlyphOrientation(UChar32 character, NonCJKGlyphOrientation orientation, GlyphData& data, GlyphPage* page, unsigned pageNumber)
{
    if (orientation == NonCJKGlyphOrientationUpright || shouldIgnoreRotation(character)) {
        RefPtr<SimpleFontData> uprightFontData = data.fontData->uprightOrientationFontData();
        GlyphPageTreeNode* uprightNode = GlyphPageTreeNode::getRootChild(uprightFontData.get(), pageNumber);
        GlyphPage* uprightPage = uprightNode->page();
        if (uprightPage) {
            GlyphData uprightData = uprightPage->glyphDataForCharacter(character);
            // If the glyphs are the same, then we know we can just use the horizontal glyph rotated vertically to be upright.
            if (data.glyph == uprightData.glyph)
                return make_pair(data, page);
            // The glyphs are distinct, meaning that the font has a vertical-right glyph baked into it. We can't use that
            // glyph, so we fall back to the upright data and use the horizontal glyph.
            if (uprightData.fontData)
                return make_pair(uprightData, uprightPage);
        }
    } else if (orientation == NonCJKGlyphOrientationVerticalRight) {
        RefPtr<SimpleFontData> verticalRightFontData = data.fontData->verticalRightOrientationFontData();
        GlyphPageTreeNode* verticalRightNode = GlyphPageTreeNode::getRootChild(verticalRightFontData.get(), pageNumber);
        GlyphPage* verticalRightPage = verticalRightNode->page();
        if (verticalRightPage) {
            GlyphData verticalRightData = verticalRightPage->glyphDataForCharacter(character);
            // If the glyphs are distinct, we will make the assumption that the font has a vertical-right glyph baked
            // into it.
            if (data.glyph != verticalRightData.glyph)
                return make_pair(data, page);
            // The glyphs are identical, meaning that we should just use the horizontal glyph.
            if (verticalRightData.fontData)
                return make_pair(verticalRightData, verticalRightPage);
        }
    }
    return make_pair(data, page);
}

std::pair<GlyphData, GlyphPage*> Font::glyphDataAndPageForCharacter(UChar32 c, bool mirror, FontDataVariant variant) const
{
    ASSERT(isMainThread());

    if (variant == AutoVariant) {
        if (m_fontDescription.variant() == FontVariantSmallCaps && !primaryFont()->isSVGFont()) {
            UChar32 upperC = toUpper(c);
            if (upperC != c) {
                c = upperC;
                variant = SmallCapsVariant;
            } else {
                variant = NormalVariant;
            }
        } else {
            variant = NormalVariant;
        }
    }

    if (mirror)
        c = mirroredChar(c);

    unsigned pageNumber = (c / GlyphPage::size);

    GlyphPageTreeNode* node = pageNumber ? m_fontFallbackList->m_pages.get(pageNumber) : m_fontFallbackList->m_pageZero;
    if (!node) {
        node = GlyphPageTreeNode::getRootChild(fontDataAt(0), pageNumber);
        if (pageNumber)
            m_fontFallbackList->m_pages.set(pageNumber, node);
        else
            m_fontFallbackList->m_pageZero = node;
    }

    GlyphPage* page = 0;
    if (variant == NormalVariant) {
        // Fastest loop, for the common case (normal variant).
        while (true) {
            page = node->page();
            if (page) {
                GlyphData data = page->glyphDataForCharacter(c);
                if (data.fontData && (data.fontData->platformData().orientation() == Horizontal || data.fontData->isTextOrientationFallback()))
                    return make_pair(data, page);

                if (data.fontData) {
                    if (Character::isCJKIdeographOrSymbol(c)) {
                        if (!data.fontData->hasVerticalGlyphs()) {
                            // Use the broken ideograph font data. The broken ideograph font will use the horizontal width of glyphs
                            // to make sure you get a square (even for broken glyphs like symbols used for punctuation).
                            variant = BrokenIdeographVariant;
                            break;
                        }
                    } else {
                        return glyphDataAndPageForNonCJKCharacterWithGlyphOrientation(c, m_fontDescription.nonCJKGlyphOrientation(), data, page, pageNumber);
                    }

                    return make_pair(data, page);
                }

                if (node->isSystemFallback())
                    break;
            }

            // Proceed with the fallback list.
            node = node->getChild(fontDataAt(node->level()), pageNumber);
            if (pageNumber)
                m_fontFallbackList->m_pages.set(pageNumber, node);
            else
                m_fontFallbackList->m_pageZero = node;
        }
    }
    if (variant != NormalVariant) {
        while (true) {
            page = node->page();
            if (page) {
                GlyphData data = page->glyphDataForCharacter(c);
                if (data.fontData) {
                    // The variantFontData function should not normally return 0.
                    // But if it does, we will just render the capital letter big.
                    RefPtr<SimpleFontData> variantFontData = data.fontData->variantFontData(m_fontDescription, variant);
                    if (!variantFontData)
                        return make_pair(data, page);

                    GlyphPageTreeNode* variantNode = GlyphPageTreeNode::getRootChild(variantFontData.get(), pageNumber);
                    GlyphPage* variantPage = variantNode->page();
                    if (variantPage) {
                        GlyphData data = variantPage->glyphDataForCharacter(c);
                        if (data.fontData)
                            return make_pair(data, variantPage);
                    }

                    // Do not attempt system fallback off the variantFontData. This is the very unlikely case that
                    // a font has the lowercase character but the small caps font does not have its uppercase version.
                    return make_pair(variantFontData->missingGlyphData(), page);
                }

                if (node->isSystemFallback())
                    break;
            }

            // Proceed with the fallback list.
            node = node->getChild(fontDataAt(node->level()), pageNumber);
            if (pageNumber)
                m_fontFallbackList->m_pages.set(pageNumber, node);
            else
                m_fontFallbackList->m_pageZero = node;
        }
    }

    ASSERT(page);
    ASSERT(node->isSystemFallback());

    // System fallback is character-dependent. When we get here, we
    // know that the character in question isn't in the system fallback
    // font's glyph page. Try to lazily create it here.

    // FIXME: Unclear if this should normalizeSpaces above 0xFFFF.
    // Doing so changes fast/text/international/plane2-diffs.html
    UChar32 characterToRender = c;
    if (characterToRender <=  0xFFFF)
        characterToRender = Character::normalizeSpaces(characterToRender);
    const SimpleFontData* fontDataToSubstitute = fontDataAt(0)->fontDataForCharacter(characterToRender);
    RefPtr<SimpleFontData> characterFontData = FontCache::fontCache()->fallbackFontForCharacter(m_fontDescription, characterToRender, fontDataToSubstitute);
    if (characterFontData) {
        if (characterFontData->platformData().orientation() == Vertical && !characterFontData->hasVerticalGlyphs() && Character::isCJKIdeographOrSymbol(c))
            variant = BrokenIdeographVariant;
        if (variant != NormalVariant)
            characterFontData = characterFontData->variantFontData(m_fontDescription, variant);
    }
    if (characterFontData) {
        // Got the fallback glyph and font.
        GlyphPage* fallbackPage = GlyphPageTreeNode::getRootChild(characterFontData.get(), pageNumber)->page();
        GlyphData data = fallbackPage && fallbackPage->glyphForCharacter(c) ? fallbackPage->glyphDataForCharacter(c) : characterFontData->missingGlyphData();
        // Cache it so we don't have to do system fallback again next time.
        if (variant == NormalVariant) {
            page->setGlyphDataForCharacter(c, data.glyph, data.fontData);
            data.fontData->setMaxGlyphPageTreeLevel(max(data.fontData->maxGlyphPageTreeLevel(), node->level()));
            if (!Character::isCJKIdeographOrSymbol(c) && data.fontData->platformData().orientation() != Horizontal && !data.fontData->isTextOrientationFallback())
                return glyphDataAndPageForNonCJKCharacterWithGlyphOrientation(c, m_fontDescription.nonCJKGlyphOrientation(), data, page, pageNumber);
        }
        return make_pair(data, page);
    }

    // Even system fallback can fail; use the missing glyph in that case.
    // FIXME: It would be nicer to use the missing glyph from the last resort font instead.
    GlyphData data = primaryFont()->missingGlyphData();
    if (variant == NormalVariant) {
        page->setGlyphDataForCharacter(c, data.glyph, data.fontData);
        data.fontData->setMaxGlyphPageTreeLevel(max(data.fontData->maxGlyphPageTreeLevel(), node->level()));
    }
    return make_pair(data, page);
}

bool Font::primaryFontHasGlyphForCharacter(UChar32 character) const
{
    unsigned pageNumber = (character / GlyphPage::size);

    GlyphPageTreeNode* node = GlyphPageTreeNode::getRootChild(primaryFont(), pageNumber);
    GlyphPage* page = node->page();

    return page && page->glyphForCharacter(character);
}

// FIXME: This function may not work if the emphasis mark uses a complex script, but none of the
// standard emphasis marks do so.
bool Font::getEmphasisMarkGlyphData(const AtomicString& mark, GlyphData& glyphData) const
{
    if (mark.isEmpty())
        return false;

    UChar32 character = mark[0];

    if (U16_IS_SURROGATE(character)) {
        if (!U16_IS_SURROGATE_LEAD(character))
            return false;

        if (mark.length() < 2)
            return false;

        UChar low = mark[1];
        if (!U16_IS_TRAIL(low))
            return false;

        character = U16_GET_SUPPLEMENTARY(character, low);
    }

    glyphData = glyphDataForCharacter(character, false, EmphasisMarkVariant);
    return true;
}

int Font::emphasisMarkAscent(const AtomicString& mark) const
{
    FontCachePurgePreventer purgePreventer;

    GlyphData markGlyphData;
    if (!getEmphasisMarkGlyphData(mark, markGlyphData))
        return 0;

    const SimpleFontData* markFontData = markGlyphData.fontData;
    ASSERT(markFontData);
    if (!markFontData)
        return 0;

    return markFontData->fontMetrics().ascent();
}

int Font::emphasisMarkDescent(const AtomicString& mark) const
{
    FontCachePurgePreventer purgePreventer;

    GlyphData markGlyphData;
    if (!getEmphasisMarkGlyphData(mark, markGlyphData))
        return 0;

    const SimpleFontData* markFontData = markGlyphData.fontData;
    ASSERT(markFontData);
    if (!markFontData)
        return 0;

    return markFontData->fontMetrics().descent();
}

int Font::emphasisMarkHeight(const AtomicString& mark) const
{
    FontCachePurgePreventer purgePreventer;

    GlyphData markGlyphData;
    if (!getEmphasisMarkGlyphData(mark, markGlyphData))
        return 0;

    const SimpleFontData* markFontData = markGlyphData.fontData;
    ASSERT(markFontData);
    if (!markFontData)
        return 0;

    return markFontData->fontMetrics().height();
}

float Font::getGlyphsAndAdvancesForSimpleText(const TextRunPaintInfo& runInfo, GlyphBuffer& glyphBuffer, ForTextEmphasisOrNot forTextEmphasis) const
{
    float initialAdvance;

    WidthIterator it(this, runInfo.run, 0, false, forTextEmphasis);
    // FIXME: Using separate glyph buffers for the prefix and the suffix is incorrect when kerning or
    // ligatures are enabled.
    GlyphBuffer localGlyphBuffer;
    it.advance(runInfo.from, &localGlyphBuffer);
    float beforeWidth = it.m_runWidthSoFar;
    it.advance(runInfo.to, &glyphBuffer);

    if (glyphBuffer.isEmpty())
        return 0;

    float afterWidth = it.m_runWidthSoFar;

    if (runInfo.run.rtl()) {
        float finalRoundingWidth = it.m_finalRoundingWidth;
        it.advance(runInfo.run.length(), &localGlyphBuffer);
        initialAdvance = finalRoundingWidth + it.m_runWidthSoFar - afterWidth;
        glyphBuffer.reverse();
    } else {
        initialAdvance = beforeWidth;
    }

    return initialAdvance;
}

void Font::drawSimpleText(GraphicsContext* context, const TextRunPaintInfo& runInfo, const FloatPoint& point) const
{
    // This glyph buffer holds our glyphs+advances+font data for each glyph.
    GlyphBuffer glyphBuffer;

    float startX = point.x() + getGlyphsAndAdvancesForSimpleText(runInfo, glyphBuffer);

    if (glyphBuffer.isEmpty())
        return;

    FloatPoint startPoint(startX, point.y());
    drawGlyphBuffer(context, runInfo, glyphBuffer, startPoint);
}

void Font::drawEmphasisMarksForSimpleText(GraphicsContext* context, const TextRunPaintInfo& runInfo, const AtomicString& mark, const FloatPoint& point) const
{
    GlyphBuffer glyphBuffer;
    float initialAdvance = getGlyphsAndAdvancesForSimpleText(runInfo, glyphBuffer, ForTextEmphasis);

    if (glyphBuffer.isEmpty())
        return;

    drawEmphasisMarks(context, runInfo, glyphBuffer, mark, FloatPoint(point.x() + initialAdvance, point.y()));
}

void Font::drawGlyphBuffer(GraphicsContext* context, const TextRunPaintInfo& runInfo, const GlyphBuffer& glyphBuffer, const FloatPoint& point) const
{
    // Draw each contiguous run of glyphs that use the same font data.
    const SimpleFontData* fontData = glyphBuffer.fontDataAt(0);
    FloatPoint startPoint(point);
    FloatPoint nextPoint = startPoint + glyphBuffer.advanceAt(0);
    unsigned lastFrom = 0;
    unsigned nextGlyph = 1;
#if ENABLE(SVG_FONTS)
    TextRun::RenderingContext* renderingContext = runInfo.run.renderingContext();
#endif
    while (nextGlyph < glyphBuffer.size()) {
        const SimpleFontData* nextFontData = glyphBuffer.fontDataAt(nextGlyph);

        if (nextFontData != fontData) {
#if ENABLE(SVG_FONTS)
            if (renderingContext && fontData->isSVGFont())
                renderingContext->drawSVGGlyphs(context, runInfo.run, fontData, glyphBuffer, lastFrom, nextGlyph - lastFrom, startPoint);
            else
#endif
                drawGlyphs(context, fontData, glyphBuffer, lastFrom, nextGlyph - lastFrom, startPoint, runInfo.bounds);

            lastFrom = nextGlyph;
            fontData = nextFontData;
            startPoint = nextPoint;
        }
        nextPoint += glyphBuffer.advanceAt(nextGlyph);
        nextGlyph++;
    }

#if ENABLE(SVG_FONTS)
    if (renderingContext && fontData->isSVGFont())
        renderingContext->drawSVGGlyphs(context, runInfo.run, fontData, glyphBuffer, lastFrom, nextGlyph - lastFrom, startPoint);
    else
#endif
        drawGlyphs(context, fontData, glyphBuffer, lastFrom, nextGlyph - lastFrom, startPoint, runInfo.bounds);
}

inline static float offsetToMiddleOfGlyph(const SimpleFontData* fontData, Glyph glyph)
{
    if (fontData->platformData().orientation() == Horizontal) {
        FloatRect bounds = fontData->boundsForGlyph(glyph);
        return bounds.x() + bounds.width() / 2;
    }
    // FIXME: Use glyph bounds once they make sense for vertical fonts.
    return fontData->widthForGlyph(glyph) / 2;
}

inline static float offsetToMiddleOfAdvanceAtIndex(const GlyphBuffer& glyphBuffer, size_t i)
{
    return glyphBuffer.advanceAt(i).width() / 2;
}

void Font::drawEmphasisMarks(GraphicsContext* context, const TextRunPaintInfo& runInfo, const GlyphBuffer& glyphBuffer, const AtomicString& mark, const FloatPoint& point) const
{
    FontCachePurgePreventer purgePreventer;

    GlyphData markGlyphData;
    if (!getEmphasisMarkGlyphData(mark, markGlyphData))
        return;

    const SimpleFontData* markFontData = markGlyphData.fontData;
    ASSERT(markFontData);
    if (!markFontData)
        return;

    Glyph markGlyph = markGlyphData.glyph;
    Glyph spaceGlyph = markFontData->spaceGlyph();

    float middleOfLastGlyph = offsetToMiddleOfAdvanceAtIndex(glyphBuffer, 0);
    FloatPoint startPoint(point.x() + middleOfLastGlyph - offsetToMiddleOfGlyph(markFontData, markGlyph), point.y());

    GlyphBuffer markBuffer;
    for (unsigned i = 0; i + 1 < glyphBuffer.size(); ++i) {
        float middleOfNextGlyph = offsetToMiddleOfAdvanceAtIndex(glyphBuffer, i + 1);
        float advance = glyphBuffer.advanceAt(i).width() - middleOfLastGlyph + middleOfNextGlyph;
        markBuffer.add(glyphBuffer.glyphAt(i) ? markGlyph : spaceGlyph, markFontData, advance);
        middleOfLastGlyph = middleOfNextGlyph;
    }
    markBuffer.add(glyphBuffer.glyphAt(glyphBuffer.size() - 1) ? markGlyph : spaceGlyph, markFontData, 0);

    drawGlyphBuffer(context, runInfo, markBuffer, startPoint);
}

float Font::floatWidthForSimpleText(const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, IntRectExtent* glyphBounds) const
{
    WidthIterator it(this, run, fallbackFonts, glyphBounds);
    GlyphBuffer glyphBuffer;
    it.advance(run.length(), (fontDescription().typesettingFeatures() & (Kerning | Ligatures)) ? &glyphBuffer : 0);

    if (glyphBounds) {
        glyphBounds->setTop(floorf(-it.minGlyphBoundingBoxY()));
        glyphBounds->setBottom(ceilf(it.maxGlyphBoundingBoxY()));
        glyphBounds->setLeft(floorf(it.firstGlyphOverflow()));
        glyphBounds->setRight(ceilf(it.lastGlyphOverflow()));
    }

    return it.m_runWidthSoFar;
}

FloatRect Font::pixelSnappedSelectionRect(float fromX, float toX, float y, float height)
{
    // Using roundf() rather than ceilf() for the right edge as a compromise to
    // ensure correct caret positioning.
    // Use LayoutUnit::epsilon() to ensure that values that cannot be stored as
    // an integer are floored to n and not n-1 due to floating point imprecision.
    float pixelAlignedX = floorf(fromX + LayoutUnit::epsilon());
    return FloatRect(pixelAlignedX, y, roundf(toX) - pixelAlignedX, height);
}

FloatRect Font::selectionRectForSimpleText(const TextRun& run, const FloatPoint& point, int h, int from, int to, bool accountForGlyphBounds) const
{
    GlyphBuffer glyphBuffer;
    WidthIterator it(this, run, 0, accountForGlyphBounds);
    it.advance(from, &glyphBuffer);
    float fromX = it.m_runWidthSoFar;
    it.advance(to, &glyphBuffer);
    float toX = it.m_runWidthSoFar;

    if (run.rtl()) {
        it.advance(run.length(), &glyphBuffer);
        float totalWidth = it.m_runWidthSoFar;
        float beforeWidth = fromX;
        float afterWidth = toX;
        fromX = totalWidth - afterWidth;
        toX = totalWidth - beforeWidth;
    }

    return pixelSnappedSelectionRect(point.x() + fromX, point.x() + toX,
        accountForGlyphBounds ? it.minGlyphBoundingBoxY() : point.y(),
        accountForGlyphBounds ? it.maxGlyphBoundingBoxY() - it.minGlyphBoundingBoxY() : h);
}

int Font::offsetForPositionForSimpleText(const TextRun& run, float x, bool includePartialGlyphs) const
{
    float delta = x;

    WidthIterator it(this, run);
    GlyphBuffer localGlyphBuffer;
    unsigned offset;
    if (run.rtl()) {
        delta -= floatWidthForSimpleText(run);
        while (1) {
            offset = it.m_currentCharacter;
            float w;
            if (!it.advanceOneCharacter(w, localGlyphBuffer))
                break;
            delta += w;
            if (includePartialGlyphs) {
                if (delta - w / 2 >= 0)
                    break;
            } else {
                if (delta >= 0)
                    break;
            }
        }
    } else {
        while (1) {
            offset = it.m_currentCharacter;
            float w;
            if (!it.advanceOneCharacter(w, localGlyphBuffer))
                break;
            delta -= w;
            if (includePartialGlyphs) {
                if (delta + w / 2 <= 0)
                    break;
            } else {
                if (delta <= 0)
                    break;
            }
        }
    }

    return offset;
}

}