/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2000 Dirk Mueller (mueller@kde.org)
 * Copyright (C) 2003-2021 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 "FontCascade.h"

#include "CharacterProperties.h"
#include "ComplexTextController.h"
#include "DisplayListRecorderImpl.h"
#include "FloatRect.h"
#include "FontCache.h"
#include "GlyphBuffer.h"
#include "GraphicsContext.h"
#include "InMemoryDisplayList.h"
#include "LayoutRect.h"
#include "TextRun.h"
#include "WidthIterator.h"
#include <wtf/MainThread.h>
#include <wtf/MathExtras.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/RobinHoodHashSet.h>
#include <wtf/text/AtomStringHash.h>
#include <wtf/text/StringBuilder.h>

namespace WebCore {

using namespace WTF::Unicode;

static bool useBackslashAsYenSignForFamily(const AtomString& family)
{
    if (family.isEmpty())
        return false;
    static const auto set = makeNeverDestroyed([] {
        MemoryCompactLookupOnlyRobinHoodHashSet<AtomString> set;
        auto add = [&set] (const char* name, std::initializer_list<UChar> unicodeName) {
            unsigned nameLength = strlen(name);
            set.add(AtomString { name, nameLength, AtomString::ConstructFromLiteral });
            unsigned unicodeNameLength = unicodeName.size();
            set.add(AtomString { unicodeName.begin(), unicodeNameLength });
        };
        add("MS PGothic", { 0xFF2D, 0xFF33, 0x0020, 0xFF30, 0x30B4, 0x30B7, 0x30C3, 0x30AF });
        add("MS PMincho", { 0xFF2D, 0xFF33, 0x0020, 0xFF30, 0x660E, 0x671D });
        add("MS Gothic", { 0xFF2D, 0xFF33, 0x0020, 0x30B4, 0x30B7, 0x30C3, 0x30AF });
        add("MS Mincho", { 0xFF2D, 0xFF33, 0x0020, 0x660E, 0x671D });
        add("Meiryo", { 0x30E1, 0x30A4, 0x30EA, 0x30AA });
        return set;
    }());
    return set.get().contains(family);
}

FontCascade::CodePath FontCascade::s_codePath = CodePath::Auto;

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

FontCascade::FontCascade()
{
}

FontCascade::FontCascade(FontCascadeDescription&& fd, float letterSpacing, float wordSpacing)
    : m_fontDescription(WTFMove(fd))
    , m_letterSpacing(letterSpacing)
    , m_wordSpacing(wordSpacing)
    , m_useBackslashAsYenSymbol(useBackslashAsYenSignForFamily(m_fontDescription.firstFamily()))
    , m_enableKerning(computeEnableKerning())
    , m_requiresShaping(computeRequiresShaping())
{
}

FontCascade::FontCascade(const FontCascade& other)
    : m_fontDescription(other.m_fontDescription)
    , m_fonts(other.m_fonts)
    , m_letterSpacing(other.m_letterSpacing)
    , m_wordSpacing(other.m_wordSpacing)
    , m_useBackslashAsYenSymbol(other.m_useBackslashAsYenSymbol)
    , m_enableKerning(computeEnableKerning())
    , m_requiresShaping(computeRequiresShaping())
{
}

FontCascade& FontCascade::operator=(const FontCascade& other)
{
    m_fontDescription = other.m_fontDescription;
    m_fonts = other.m_fonts;
    m_letterSpacing = other.m_letterSpacing;
    m_wordSpacing = other.m_wordSpacing;
    m_useBackslashAsYenSymbol = other.m_useBackslashAsYenSymbol;
    m_enableKerning = other.m_enableKerning;
    m_requiresShaping = other.m_requiresShaping;
    return *this;
}

bool FontCascade::operator==(const FontCascade& other) const
{
    if (isLoadingCustomFonts() || other.isLoadingCustomFonts())
        return false;

    if (m_fontDescription != other.m_fontDescription || m_letterSpacing != other.m_letterSpacing || m_wordSpacing != other.m_wordSpacing)
        return false;
    if (m_fonts == other.m_fonts)
        return true;
    if (!m_fonts || !other.m_fonts)
        return false;
    if (m_fonts->fontSelector() != other.m_fonts->fontSelector())
        return false;
    // Can these cases actually somehow occur? All fonts should get wiped out by full style recalc.
    if (m_fonts->fontSelectorVersion() != other.m_fonts->fontSelectorVersion())
        return false;
    if (m_fonts->generation() != other.m_fonts->generation())
        return false;
    return true;
}

bool FontCascade::isCurrent(const FontSelector& fontSelector) const
{
    if (!m_fonts)
        return false;
    if (m_fonts->generation() != fontSelector.fontCache().generation())
        return false;
    if (m_fonts->fontSelectorVersion() != fontSelector.version())
        return false;

    return true;
}

void FontCascade::updateFonts(Ref<FontCascadeFonts>&& fonts) const
{
    m_fonts = WTFMove(fonts);
    m_useBackslashAsYenSymbol = useBackslashAsYenSignForFamily(firstFamily());
    m_enableKerning = computeEnableKerning();
    m_requiresShaping = computeRequiresShaping();
}

void FontCascade::update(RefPtr<FontSelector>&& fontSelector) const
{
    FontCache::fontCacheFallingBackToSingleton(fontSelector).updateFontCascade(*this, WTFMove(fontSelector));
}

GlyphBuffer FontCascade::layoutText(CodePath codePathToUse, const TextRun& run, unsigned from, unsigned to, ForTextEmphasisOrNot forTextEmphasis) const
{
    if (codePathToUse != CodePath::Complex)
        return layoutSimpleText(run, from, to, forTextEmphasis);

    return layoutComplexText(run, from, to, forTextEmphasis);
}

FloatSize FontCascade::drawText(GraphicsContext& context, const TextRun& run, const FloatPoint& point, unsigned from, std::optional<unsigned> to, CustomFontNotReadyAction customFontNotReadyAction) const
{
    unsigned destination = to.value_or(run.length());
    auto glyphBuffer = layoutText(codePath(run, from, to), run, from, destination);
    glyphBuffer.flatten();

    if (glyphBuffer.isEmpty())
        return FloatSize();

    FloatPoint startPoint = point + WebCore::size(glyphBuffer.initialAdvance());
    drawGlyphBuffer(context, glyphBuffer, startPoint, customFontNotReadyAction);
    return startPoint - point;
}

void FontCascade::drawEmphasisMarks(GraphicsContext& context, const TextRun& run, const AtomString& mark, const FloatPoint& point, unsigned from, std::optional<unsigned> to) const
{
    if (isLoadingCustomFonts())
        return;

    unsigned destination = to.value_or(run.length());

    auto glyphBuffer = layoutText(codePath(run, from, to), run, from, destination, ForTextEmphasisOrNot::ForTextEmphasis);
    glyphBuffer.flatten();

    if (glyphBuffer.isEmpty())
        return;

    FloatPoint startPoint = point + WebCore::size(glyphBuffer.initialAdvance());
    drawEmphasisMarks(context, glyphBuffer, mark, startPoint);
}

std::unique_ptr<DisplayList::InMemoryDisplayList> FontCascade::displayListForTextRun(GraphicsContext& context, const TextRun& run, unsigned from, std::optional<unsigned> to, CustomFontNotReadyAction customFontNotReadyAction) const
{
    ASSERT(!context.paintingDisabled());
    unsigned destination = to.value_or(run.length());
    
    // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
    CodePath codePathToUse = codePath(run);
    if (codePathToUse != CodePath::Complex && (enableKerning() || requiresShaping()) && (from || destination != run.length()))
        codePathToUse = CodePath::Complex;

    auto glyphBuffer = layoutText(codePathToUse, run, from, destination);
    glyphBuffer.flatten();

    if (glyphBuffer.isEmpty())
        return nullptr;
    
    std::unique_ptr<DisplayList::InMemoryDisplayList> displayList = makeUnique<DisplayList::InMemoryDisplayList>();
    DisplayList::RecorderImpl recordingContext(*displayList, context.state(), FloatRect(), AffineTransform(), nullptr, DrawGlyphsRecorder::DeconstructDrawGlyphs::No);
    
    FloatPoint startPoint = toFloatPoint(WebCore::size(glyphBuffer.initialAdvance()));
    drawGlyphBuffer(recordingContext, glyphBuffer, startPoint, customFontNotReadyAction);
    
    displayList->shrinkToFit();
    return displayList;
}
    
float FontCascade::widthOfTextRange(const TextRun& run, unsigned from, unsigned to, HashSet<const Font*>* fallbackFonts, float* outWidthBeforeRange, float* outWidthAfterRange) const
{
    ASSERT(from <= to);
    ASSERT(to <= run.length());

    if (!run.length())
        return 0;

    float offsetBeforeRange = 0;
    float offsetAfterRange = 0;
    float totalWidth = 0;

    auto codePathToUse = codePath(run);
    if (codePathToUse == CodePath::Complex) {
        ComplexTextController complexIterator(*this, run, false, fallbackFonts);
        complexIterator.advance(from, nullptr, IncludePartialGlyphs, fallbackFonts);
        offsetBeforeRange = complexIterator.runWidthSoFar();
        complexIterator.advance(to, nullptr, IncludePartialGlyphs, fallbackFonts);
        offsetAfterRange = complexIterator.runWidthSoFar();
        complexIterator.advance(run.length(), nullptr, IncludePartialGlyphs, fallbackFonts);
        totalWidth = complexIterator.runWidthSoFar();
    } else {
        WidthIterator simpleIterator(*this, run, fallbackFonts);
        GlyphBuffer glyphBuffer;
        simpleIterator.advance(from, glyphBuffer);
        offsetBeforeRange = simpleIterator.runWidthSoFar();
        simpleIterator.advance(to, glyphBuffer);
        offsetAfterRange = simpleIterator.runWidthSoFar();
        simpleIterator.advance(run.length(), glyphBuffer);
        totalWidth = simpleIterator.runWidthSoFar();
        simpleIterator.finalize(glyphBuffer);
        // FIXME: Finalizing the WidthIterator can affect the total width.
        // We might need to adjust the various widths we've measured to account for that.
    }

    if (outWidthBeforeRange)
        *outWidthBeforeRange = offsetBeforeRange;

    if (outWidthAfterRange)
        *outWidthAfterRange = totalWidth - offsetAfterRange;

    return offsetAfterRange - offsetBeforeRange;
}

float FontCascade::width(const TextRun& run, HashSet<const Font*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
{
    if (!run.length())
        return 0;

    CodePath codePathToUse = codePath(run);
    if (codePathToUse != CodePath::Complex) {
        // 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 (!canReturnFallbackFontsForComplexText())
            fallbackFonts = nullptr;
        // The simple path can optimize the case where glyph overflow is not observable.
        if (codePathToUse != CodePath::SimpleWithGlyphOverflow && (glyphOverflow && !glyphOverflow->computeBounds))
            glyphOverflow = nullptr;
    }

    bool hasWordSpacingOrLetterSpacing = wordSpacing() || letterSpacing();
    float* cacheEntry = m_fonts->widthCache().add(run, std::numeric_limits<float>::quiet_NaN(), enableKerning() || requiresShaping(), hasWordSpacingOrLetterSpacing, glyphOverflow);
    if (cacheEntry && !std::isnan(*cacheEntry))
        return *cacheEntry;

    HashSet<const Font*> localFallbackFonts;
    if (!fallbackFonts)
        fallbackFonts = &localFallbackFonts;

    float result;
    if (codePathToUse == CodePath::Complex)
        result = floatWidthForComplexText(run, fallbackFonts, glyphOverflow);
    else
        result = floatWidthForSimpleText(run, fallbackFonts, glyphOverflow);

    if (cacheEntry && fallbackFonts->isEmpty())
        *cacheEntry = result;
    return result;
}

float FontCascade::widthForSimpleText(StringView text, TextDirection textDirection) const
{
    if (text.isNull() || text.isEmpty())
        return 0;
    ASSERT(codePath(TextRun(text)) != CodePath::Complex);
    float* cacheEntry = m_fonts->widthCache().add(text, std::numeric_limits<float>::quiet_NaN());
    if (cacheEntry && !std::isnan(*cacheEntry))
        return *cacheEntry;

    GlyphBuffer glyphBuffer;
    float beforeWidth = 0;
    auto& font = primaryFont();
    for (unsigned i = 0; i < text.length(); ++i) {
        auto glyph = glyphDataForCharacter(text[i], false).glyph;
        auto glyphWidth = font.widthForGlyph(glyph);
        beforeWidth += glyphWidth;
        glyphBuffer.add(glyph, font, glyphWidth, i);
    }

    auto initialAdvance = font.applyTransforms(glyphBuffer, 0, 0, enableKerning(), requiresShaping(), fontDescription().computedLocale(), text, textDirection);
    // This is needed only to match the result of the slow path.
    // Same glyph widths but different floating point arithmetic can produce different run width.
    float afterWidth = 0;
    for (size_t i = 0; i < glyphBuffer.size(); ++i)
        afterWidth += WebCore::width(glyphBuffer.advanceAt(i));
    auto additionalAdvance = afterWidth - beforeWidth;

    auto finalWidth = beforeWidth + additionalAdvance;
    finalWidth += WebCore::width(initialAdvance);

    if (cacheEntry)
        *cacheEntry = finalWidth;
    return finalWidth;
}

GlyphData FontCascade::glyphDataForCharacter(UChar32 c, bool mirror, FontVariant variant) const
{
    if (variant == AutoVariant) {
        if (m_fontDescription.variantCaps() == FontVariantCaps::Small) {
            UChar32 upperC = u_toupper(c);
            if (upperC != c) {
                c = upperC;
                variant = SmallCapsVariant;
            } else
                variant = NormalVariant;
        } else
            variant = NormalVariant;
    }

    if (mirror)
        c = u_charMirror(c);

    return m_fonts->glyphDataForCharacter(c, m_fontDescription, variant);
}

// For font families where any of the fonts don't have a valid entry in the OS/2 table
// for avgCharWidth, fallback to the legacy webkit behavior of getting the avgCharWidth
// from the width of a '0'. This only seems to apply to a fixed number of Mac fonts,
// but, in order to get similar rendering across platforms, we do this check for
// all platforms.
bool FontCascade::hasValidAverageCharWidth() const
{
    const AtomString& family = firstFamily();
    if (family.isEmpty())
        return false;

#if PLATFORM(COCOA)
    // Internal fonts on macOS and iOS also have an invalid entry in the table for avgCharWidth.
    if (primaryFontIsSystemFont())
        return false;
#endif

    static const auto map = makeNeverDestroyed(MemoryCompactLookupOnlyRobinHoodHashSet<AtomString> {
        "American Typewriter"_s,
        "Arial Hebrew"_s,
        "Chalkboard"_s,
        "Cochin"_s,
        "Corsiva Hebrew"_s,
        "Courier"_s,
        "Euphemia UCAS"_s,
        "Geneva"_s,
        "Gill Sans"_s,
        "Hei"_s,
        "Helvetica"_s,
        "Hoefler Text"_s,
        "InaiMathi"_s,
        "Kai"_s,
        "Lucida Grande"_s,
        "Marker Felt"_s,
        "Monaco"_s,
        "Mshtakan"_s,
        "New Peninim MT"_s,
        "Osaka"_s,
        "Raanana"_s,
        "STHeiti"_s,
        "Symbol"_s,
        "Times"_s,
        "Apple Braille"_s,
        "Apple LiGothic"_s,
        "Apple LiSung"_s,
        "Apple Symbols"_s,
        "AppleGothic"_s,
        "AppleMyungjo"_s,
        "#GungSeo"_s,
        "#HeadLineA"_s,
        "#PCMyungjo"_s,
        "#PilGi"_s,
    });
    return !map.get().contains(family);
}

bool FontCascade::fastAverageCharWidthIfAvailable(float& width) const
{
    bool success = hasValidAverageCharWidth();
    if (success)
        width = roundf(primaryFont().avgCharWidth()); // FIXME: primaryFont() might not correspond to firstFamily().
    return success;
}

void FontCascade::adjustSelectionRectForText(const TextRun& run, LayoutRect& selectionRect, unsigned from, std::optional<unsigned> to) const
{
    unsigned destination = to.value_or(run.length());
    if (codePath(run, from, to) != CodePath::Complex)
        return adjustSelectionRectForSimpleText(run, selectionRect, from, destination);

    return adjustSelectionRectForComplexText(run, selectionRect, from, destination);
}

int FontCascade::offsetForPosition(const TextRun& run, float x, bool includePartialGlyphs) const
{
    if (codePath(run, x) != CodePath::Complex)
        return offsetForPositionForSimpleText(run, x, includePartialGlyphs);

    return offsetForPositionForComplexText(run, x, includePartialGlyphs);
}

template <typename CharacterType>
static inline String normalizeSpacesInternal(const CharacterType* characters, unsigned length)
{
    StringBuilder normalized;
    normalized.reserveCapacity(length);

    for (unsigned i = 0; i < length; ++i)
        normalized.append(FontCascade::normalizeSpaces(characters[i]));

    return normalized.toString();
}

String FontCascade::normalizeSpaces(const LChar* characters, unsigned length)
{
    return normalizeSpacesInternal(characters, length);
}

String FontCascade::normalizeSpaces(const UChar* characters, unsigned length)
{
    return normalizeSpacesInternal(characters, length);
}

static bool shouldUseFontSmoothing = true;

void FontCascade::setShouldUseSmoothing(bool shouldUseSmoothing)
{
    ASSERT(isMainThread());
    shouldUseFontSmoothing = shouldUseSmoothing;
}

bool FontCascade::shouldUseSmoothing()
{
    return shouldUseFontSmoothing;
}

#if !USE(CORE_TEXT) || PLATFORM(WIN)
bool FontCascade::isSubpixelAntialiasingAvailable()
{
    return false;
}
#endif

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

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

FontCascade::CodePath FontCascade::codePath(const TextRun& run, std::optional<unsigned> from, std::optional<unsigned> to) const
{
    if (s_codePath != CodePath::Auto)
        return s_codePath;

#if !USE(FREETYPE)
    // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
    if ((enableKerning() || requiresShaping()) && (from.value_or(0) || to.value_or(run.length()) != run.length()))
        return CodePath::Complex;
#else
    UNUSED_PARAM(from);
    UNUSED_PARAM(to);
#endif

#if PLATFORM(COCOA) || USE(FREETYPE)
    // Because Font::applyTransforms() doesn't know which features to enable/disable in the simple code path, it can't properly handle feature or variant settings.
    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=150791: @font-face features should also cause this to be complex.
    if (m_fontDescription.featureSettings().size() > 0 || !m_fontDescription.variantSettings().isAllNormal())
        return CodePath::Complex;

#else

    if (run.length() > 1 && (enableKerning() || requiresShaping()))
        return CodePath::Complex;
#endif

    if (!run.characterScanForCodePath())
        return CodePath::Simple;

    if (run.is8Bit())
        return CodePath::Simple;

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

FontCascade::CodePath FontCascade::characterRangeCodePath(const UChar* characters, unsigned len)
{
    // FIXME: Should use a UnicodeSet in ports where ICU is used. Note that we 
    // can't simply use UnicodeCharacter Property/class because some characters
    // are not 'combining', but still need to go to the complex path.
    // Alternatively, we may as well consider binary search over a sorted
    // list of ranges.
    CodePath result = CodePath::Simple;
    bool previousCharacterIsEmojiGroupCandidate = false;
    for (unsigned i = 0; i < len; i++) {
        const UChar c = characters[i];
        if (c == zeroWidthJoiner && previousCharacterIsEmojiGroupCandidate)
            return CodePath::Complex;
        
        previousCharacterIsEmojiGroupCandidate = false;
        if (c < 0x2E5) // U+02E5 through U+02E9 (Modifier Letters : Tone letters)  
            continue;
        if (c <= 0x2E9) 
            return CodePath::Complex;

        if (c < 0x300) // U+0300 through U+036F Combining diacritical marks
            continue;
        if (c <= 0x36F)
            return CodePath::Complex;

        if (c < 0x0591 || c == 0x05BE) // U+0591 through U+05CF excluding U+05BE Hebrew combining marks, Hebrew punctuation Paseq, Sof Pasuq and Nun Hafukha
            continue;
        if (c <= 0x05CF)
            return CodePath::Complex;

        // U+0600 through U+109F Arabic, Syriac, Thaana, NKo, Samaritan, Mandaic,
        // Devanagari, Bengali, Gurmukhi, Gujarati, Oriya, Tamil, Telugu, Kannada, 
        // Malayalam, Sinhala, Thai, Lao, Tibetan, Myanmar
        if (c < 0x0600) 
            continue;
        if (c <= 0x109F)
            return CodePath::Complex;

        // U+1100 through U+11FF Hangul Jamo (only Ancient Korean should be left here if you precompose;
        // Modern Korean will be precomposed as a result of step A)
        if (c < 0x1100)
            continue;
        if (c <= 0x11FF)
            return CodePath::Complex;

        if (c < 0x135D) // U+135D through U+135F Ethiopic combining marks
            continue;
        if (c <= 0x135F)
            return CodePath::Complex;

        if (c < 0x1700) // U+1780 through U+18AF Tagalog, Hanunoo, Buhid, Taghanwa,Khmer, Mongolian
            continue;
        if (c <= 0x18AF)
            return CodePath::Complex;

        if (c < 0x1900) // U+1900 through U+194F Limbu (Unicode 4.0)
            continue;
        if (c <= 0x194F)
            return CodePath::Complex;

        if (c < 0x1980) // U+1980 through U+19DF New Tai Lue
            continue;
        if (c <= 0x19DF)
            return CodePath::Complex;

        if (c < 0x1A00) // U+1A00 through U+1CFF Buginese, Tai Tham, Balinese, Batak, Lepcha, Vedic
            continue;
        if (c <= 0x1CFF)
            return CodePath::Complex;

        if (c < 0x1DC0) // U+1DC0 through U+1DFF Comining diacritical mark supplement
            continue;
        if (c <= 0x1DFF)
            return CodePath::Complex;

        // U+1E00 through U+2000 characters with diacritics and stacked diacritics
        if (c <= 0x2000) {
            result = CodePath::SimpleWithGlyphOverflow;
            continue;
        }

        if (c < 0x20D0) // U+20D0 through U+20FF Combining marks for symbols
            continue;
        if (c <= 0x20FF)
            return CodePath::Complex;

        if (c < 0x26F9)
            continue;
        if (c < 0x26FA)
            return CodePath::Complex;

        if (c < 0x2CEF) // U+2CEF through U+2CF1 Combining marks for Coptic
            continue;
        if (c <= 0x2CF1)
            return CodePath::Complex;

        if (c < 0x302A) // U+302A through U+302F Ideographic and Hangul Tone marks
            continue;
        if (c <= 0x302F)
            return CodePath::Complex;

        if (c < 0x3099)
            continue;
        if (c < 0x309D)
            return CodePath::Complex; // KATAKANA-HIRAGANA (SEMI-)VOICED SOUND MARKS require character composition

        if (c < 0xA67C) // U+A67C through U+A67D Combining marks for old Cyrillic
            continue;
        if (c <= 0xA67D)
            return CodePath::Complex;

        if (c < 0xA6F0) // U+A6F0 through U+A6F1 Combining mark for Bamum
            continue;
        if (c <= 0xA6F1)
            return CodePath::Complex;

        // U+A800 through U+ABFF Nagri, Phags-pa, Saurashtra, Devanagari Extended,
        // Hangul Jamo Ext. A, Javanese, Myanmar Extended A, Tai Viet, Meetei Mayek,
        if (c < 0xA800) 
            continue;
        if (c <= 0xABFF)
            return CodePath::Complex;

        if (c < 0xD7B0) // U+D7B0 through U+D7FF Hangul Jamo Ext. B
            continue;
        if (c <= 0xD7FF)
            return CodePath::Complex;

        if (c <= 0xDBFF) {
            // High surrogate

            if (i == len - 1)
                continue;

            UChar next = characters[++i];
            if (!U16_IS_TRAIL(next))
                continue;

            UChar32 supplementaryCharacter = U16_GET_SUPPLEMENTARY(c, next);

            if (supplementaryCharacter < 0x10A00)
                continue;
            if (supplementaryCharacter < 0x10A60) // Kharoshthi
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11000)
                continue;
            if (supplementaryCharacter < 0x11080) // Brahmi
                return CodePath::Complex;
            if (supplementaryCharacter < 0x110D0) // Kaithi
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11100)
                continue;
            if (supplementaryCharacter < 0x11150) // Chakma
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11180) // Mahajani
                return CodePath::Complex;
            if (supplementaryCharacter < 0x111E0) // Sharada
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11200)
                continue;
            if (supplementaryCharacter < 0x11250) // Khojki
                return CodePath::Complex;
            if (supplementaryCharacter < 0x112B0)
                continue;
            if (supplementaryCharacter < 0x11300) // Khudawadi
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11380) // Grantha
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11400)
                continue;
            if (supplementaryCharacter < 0x11480) // Newa
                return CodePath::Complex;
            if (supplementaryCharacter < 0x114E0) // Tirhuta
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11580)
                continue;
            if (supplementaryCharacter < 0x11600) // Siddham
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11660) // Modi
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11680)
                continue;
            if (supplementaryCharacter < 0x116D0) // Takri
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11700)
                continue;
            if (supplementaryCharacter < 0x11C00) // Ahom, Dogra, Dives Akuru, Nandinagari, Zanabazar Square, Soyombo, Warang Citi, Pau Cin Hau
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11C70) // Bhaiksuki
                return CodePath::Complex;
            if (supplementaryCharacter < 0x11CC0) // Marchen
                return CodePath::Complex;
            if (supplementaryCharacter < 0x1E900)
                continue;
            if (supplementaryCharacter < 0x1E960) // Adlam
                return CodePath::Complex;
            if (supplementaryCharacter < 0x1F1E6) // U+1F1E6 through U+1F1FF Regional Indicator Symbols
                continue;
            if (supplementaryCharacter <= 0x1F1FF)
                return CodePath::Complex;

            if (isEmojiFitzpatrickModifier(supplementaryCharacter))
                return CodePath::Complex;
            if (isEmojiGroupCandidate(supplementaryCharacter)) {
                previousCharacterIsEmojiGroupCandidate = true;
                continue;
            }

            if (supplementaryCharacter < 0xE0000)
                continue;
            if (supplementaryCharacter < 0xE0080) // Tags
                return CodePath::Complex;
            if (supplementaryCharacter < 0xE0100) // U+E0100 through U+E01EF Unicode variation selectors.
                continue;
            if (supplementaryCharacter <= 0xE01EF)
                return CodePath::Complex;

            // FIXME: Check for Brahmi (U+11000 block), Kaithi (U+11080 block) and other complex scripts
            // in plane 1 or higher.

            continue;
        }

        if (c < 0xFE00) // U+FE00 through U+FE0F Unicode variation selectors
            continue;
        if (c <= 0xFE0F)
            return CodePath::Complex;

        if (c < 0xFE20) // U+FE20 through U+FE2F Combining half marks
            continue;
        if (c <= 0xFE2F)
            return CodePath::Complex;
    }
    return result;
}

bool FontCascade::isCJKIdeograph(UChar32 c)
{
    // The basic CJK Unified Ideographs block.
    if (c >= 0x4E00 && c <= 0x9FFF)
        return true;
    
    // CJK Unified Ideographs Extension A.
    if (c >= 0x3400 && c <= 0x4DBF)
        return true;
    
    // CJK Radicals Supplement.
    if (c >= 0x2E80 && c <= 0x2EFF)
        return true;
    
    // Kangxi Radicals.
    if (c >= 0x2F00 && c <= 0x2FDF)
        return true;
    
    // CJK Strokes.
    if (c >= 0x31C0 && c <= 0x31EF)
        return true;
    
    // CJK Compatibility Ideographs.
    if (c >= 0xF900 && c <= 0xFAFF)
        return true;

    // CJK Unified Ideographs Extension B.
    if (c >= 0x20000 && c <= 0x2A6DF)
        return true;

    // CJK Unified Ideographs Extension C.
    if (c >= 0x2A700 && c <= 0x2B73F)
        return true;
    
    // CJK Unified Ideographs Extension D.
    if (c >= 0x2B740 && c <= 0x2B81F)
        return true;
    
    // CJK Compatibility Ideographs Supplement.
    if (c >= 0x2F800 && c <= 0x2FA1F)
        return true;

    return false;
}

bool FontCascade::isCJKIdeographOrSymbol(UChar32 c)
{
    // 0x2C7 Caron, Mandarin Chinese 3rd Tone
    // 0x2CA Modifier Letter Acute Accent, Mandarin Chinese 2nd Tone
    // 0x2CB Modifier Letter Grave Access, Mandarin Chinese 4th Tone 
    // 0x2D9 Dot Above, Mandarin Chinese 5th Tone 
    if ((c == 0x2C7) || (c == 0x2CA) || (c == 0x2CB) || (c == 0x2D9))
        return true;

    if ((c == 0x2020) || (c == 0x2021) || (c == 0x2030) || (c == 0x203B) || (c == 0x203C)
        || (c == 0x2042) || (c == 0x2047) || (c == 0x2048) || (c == 0x2049) || (c == 0x2051)
        || (c == 0x20DD) || (c == 0x20DE) || (c == 0x2100) || (c == 0x2103) || (c == 0x2105)
        || (c == 0x2109) || (c == 0x210A) || (c == 0x2113) || (c == 0x2116) || (c == 0x2121)
        || (c == 0x212B) || (c == 0x213B) || (c == 0x2150) || (c == 0x2151) || (c == 0x2152))
        return true;

    if (c >= 0x2156 && c <= 0x215A)
        return true;

    if (c >= 0x2160 && c <= 0x216B)
        return true;

    if (c >= 0x2170 && c <= 0x217B)
        return true;

    if ((c == 0x217F) || (c == 0x2189) || (c == 0x2307) || (c == 0x2312) || (c == 0x23BE) || (c == 0x23BF))
        return true;

    if (c >= 0x23C0 && c <= 0x23CC)
        return true;

    if ((c == 0x23CE) || (c == 0x2423))
        return true;

    if (c >= 0x2460 && c <= 0x2492)
        return true;

    if (c >= 0x249C && c <= 0x24FF)
        return true;

    if ((c == 0x25A0) || (c == 0x25A1) || (c == 0x25A2) || (c == 0x25AA) || (c == 0x25AB))
        return true;

    if ((c == 0x25B1) || (c == 0x25B2) || (c == 0x25B3) || (c == 0x25B6) || (c == 0x25B7) || (c == 0x25BC) || (c == 0x25BD))
        return true;
    
    if ((c == 0x25C0) || (c == 0x25C1) || (c == 0x25C6) || (c == 0x25C7) || (c == 0x25C9) || (c == 0x25CB) || (c == 0x25CC))
        return true;

    if (c >= 0x25CE && c <= 0x25D3)
        return true;

    if (c >= 0x25E2 && c <= 0x25E6)
        return true;

    if (c == 0x25EF)
        return true;

    if (c >= 0x2600 && c <= 0x2603)
        return true;

    if ((c == 0x2605) || (c == 0x2606) || (c == 0x260E) || (c == 0x2616) || (c == 0x2617) || (c == 0x2640) || (c == 0x2642))
        return true;

    if (c >= 0x2660 && c <= 0x266F)
        return true;

    if (c >= 0x2672 && c <= 0x267D)
        return true;

    if ((c == 0x26A0) || (c == 0x26BD) || (c == 0x26BE) || (c == 0x2713) || (c == 0x271A) || (c == 0x273F) || (c == 0x2740) || (c == 0x2756))
        return true;

    if (c >= 0x2776 && c <= 0x277F)
        return true;

    if (c == 0x2B1A)
        return true;

    // Ideographic Description Characters.
    if (c >= 0x2FF0 && c <= 0x2FFF)
        return true;

    // CJK Symbols and Punctuation, excluding 0x3030.
    if (c >= 0x3000 && c < 0x3030)
        return true;

    if (c > 0x3030 && c <= 0x303F)
        return true;

    // Hiragana
    if (c >= 0x3040 && c <= 0x309F)
        return true;

    // Katakana 
    if (c >= 0x30A0 && c <= 0x30FF)
        return true;

    // Bopomofo
    if (c >= 0x3100 && c <= 0x312F)
        return true;

    if (c >= 0x3190 && c <= 0x319F)
        return true;

    // Bopomofo Extended
    if (c >= 0x31A0 && c <= 0x31BF)
        return true;

    // Enclosed CJK Letters and Months.
    if (c >= 0x3200 && c <= 0x32FF)
        return true;
    
    // CJK Compatibility.
    if (c >= 0x3300 && c <= 0x33FF)
        return true;

    if (c >= 0xF860 && c <= 0xF862)
        return true;

    // CJK Compatibility Forms.
    if (c >= 0xFE30 && c <= 0xFE4F)
        return true;

    if ((c == 0xFE10) || (c == 0xFE11) || (c == 0xFE12) || (c == 0xFE19))
        return true;

    if ((c == 0xFF0D) || (c == 0xFF1B) || (c == 0xFF1C) || (c == 0xFF1E))
        return false;

    // Halfwidth and Fullwidth Forms
    // Usually only used in CJK
    if (c >= 0xFF00 && c <= 0xFFEF)
        return true;

    // Emoji.
    if (c == 0x1F100)
        return true;

    if (c >= 0x1F110 && c <= 0x1F129)
        return true;

    if (c >= 0x1F130 && c <= 0x1F149)
        return true;

    if (c >= 0x1F150 && c <= 0x1F169)
        return true;

    if (c >= 0x1F170 && c <= 0x1F189)
        return true;

    if (c >= 0x1F200 && c <= 0x1F6C5)
        return true;

    return isCJKIdeograph(c);
}

std::pair<unsigned, bool> FontCascade::expansionOpportunityCountInternal(const LChar* characters, unsigned length, TextDirection direction, ExpansionBehavior expansionBehavior)
{
    unsigned count = 0;
    bool isAfterExpansion = (expansionBehavior & LeftExpansionMask) == ForbidLeftExpansion;
    if ((expansionBehavior & LeftExpansionMask) == ForceLeftExpansion) {
        ++count;
        isAfterExpansion = true;
    }
    if (direction == TextDirection::LTR) {
        for (unsigned i = 0; i < length; ++i) {
            if (treatAsSpace(characters[i])) {
                count++;
                isAfterExpansion = true;
            } else
                isAfterExpansion = false;
        }
    } else {
        for (unsigned i = length; i > 0; --i) {
            if (treatAsSpace(characters[i - 1])) {
                count++;
                isAfterExpansion = true;
            } else
                isAfterExpansion = false;
        }
    }
    if (!isAfterExpansion && (expansionBehavior & RightExpansionMask) == ForceRightExpansion) {
        ++count;
        isAfterExpansion = true;
    } else if (isAfterExpansion && (expansionBehavior & RightExpansionMask) == ForbidRightExpansion) {
        ASSERT(count);
        --count;
        isAfterExpansion = false;
    }
    return std::make_pair(count, isAfterExpansion);
}

std::pair<unsigned, bool> FontCascade::expansionOpportunityCountInternal(const UChar* characters, unsigned length, TextDirection direction, ExpansionBehavior expansionBehavior)
{
    static bool expandAroundIdeographs = canExpandAroundIdeographsInComplexText();
    unsigned count = 0;
    bool isAfterExpansion = (expansionBehavior & LeftExpansionMask) == ForbidLeftExpansion;
    if ((expansionBehavior & LeftExpansionMask) == ForceLeftExpansion) {
        ++count;
        isAfterExpansion = true;
    }
    if (direction == TextDirection::LTR) {
        for (unsigned i = 0; i < length; ++i) {
            UChar32 character = characters[i];
            if (treatAsSpace(character)) {
                count++;
                isAfterExpansion = true;
                continue;
            }
            if (U16_IS_LEAD(character) && i + 1 < length && U16_IS_TRAIL(characters[i + 1])) {
                character = U16_GET_SUPPLEMENTARY(character, characters[i + 1]);
                i++;
            }
            if (expandAroundIdeographs && isCJKIdeographOrSymbol(character)) {
                if (!isAfterExpansion)
                    count++;
                count++;
                isAfterExpansion = true;
                continue;
            }
            isAfterExpansion = false;
        }
    } else {
        for (unsigned i = length; i > 0; --i) {
            UChar32 character = characters[i - 1];
            if (treatAsSpace(character)) {
                count++;
                isAfterExpansion = true;
                continue;
            }
            if (U16_IS_TRAIL(character) && i > 1 && U16_IS_LEAD(characters[i - 2])) {
                character = U16_GET_SUPPLEMENTARY(characters[i - 2], character);
                i--;
            }
            if (expandAroundIdeographs && isCJKIdeographOrSymbol(character)) {
                if (!isAfterExpansion)
                    count++;
                count++;
                isAfterExpansion = true;
                continue;
            }
            isAfterExpansion = false;
        }
    }
    if (!isAfterExpansion && (expansionBehavior & RightExpansionMask) == ForceRightExpansion) {
        ++count;
        isAfterExpansion = true;
    } else if (isAfterExpansion && (expansionBehavior & RightExpansionMask) == ForbidRightExpansion) {
        ASSERT(count);
        --count;
        isAfterExpansion = false;
    }
    return std::make_pair(count, isAfterExpansion);
}

std::pair<unsigned, bool> FontCascade::expansionOpportunityCount(StringView stringView, TextDirection direction, ExpansionBehavior expansionBehavior)
{
    // For each character, iterating from left to right:
    //   If it is recognized as a space, insert an opportunity after it
    //   If it is an ideograph, insert one opportunity before it and one opportunity after it
    // Do this such a way so that there are not two opportunities next to each other.
    if (stringView.is8Bit())
        return expansionOpportunityCountInternal(stringView.characters8(), stringView.length(), direction, expansionBehavior);
    return expansionOpportunityCountInternal(stringView.characters16(), stringView.length(), direction, expansionBehavior);
}

bool FontCascade::leftExpansionOpportunity(StringView stringView, TextDirection direction)
{
    if (!stringView.length())
        return false;

    UChar32 initialCharacter;
    if (direction == TextDirection::LTR) {
        initialCharacter = stringView[0];
        if (U16_IS_LEAD(initialCharacter) && stringView.length() > 1 && U16_IS_TRAIL(stringView[1]))
            initialCharacter = U16_GET_SUPPLEMENTARY(initialCharacter, stringView[1]);
    } else {
        initialCharacter = stringView[stringView.length() - 1];
        if (U16_IS_TRAIL(initialCharacter) && stringView.length() > 1 && U16_IS_LEAD(stringView[stringView.length() - 2]))
            initialCharacter = U16_GET_SUPPLEMENTARY(stringView[stringView.length() - 2], initialCharacter);
    }

    return canExpandAroundIdeographsInComplexText() && isCJKIdeographOrSymbol(initialCharacter);
}

bool FontCascade::rightExpansionOpportunity(StringView stringView, TextDirection direction)
{
    if (!stringView.length())
        return false;

    UChar32 finalCharacter;
    if (direction == TextDirection::LTR) {
        finalCharacter = stringView[stringView.length() - 1];
        if (U16_IS_TRAIL(finalCharacter) && stringView.length() > 1 && U16_IS_LEAD(stringView[stringView.length() - 2]))
            finalCharacter = U16_GET_SUPPLEMENTARY(stringView[stringView.length() - 2], finalCharacter);
    } else {
        finalCharacter = stringView[0];
        if (U16_IS_LEAD(finalCharacter) && stringView.length() > 1 && U16_IS_TRAIL(stringView[1]))
            finalCharacter = U16_GET_SUPPLEMENTARY(finalCharacter, stringView[1]);
    }

    return treatAsSpace(finalCharacter) || (canExpandAroundIdeographsInComplexText() && isCJKIdeographOrSymbol(finalCharacter));
}

bool FontCascade::canReceiveTextEmphasis(UChar32 c)
{
    if (U_GET_GC_MASK(c) & (U_GC_Z_MASK | U_GC_CN_MASK | U_GC_CC_MASK | U_GC_CF_MASK))
        return false;

    // Additional word-separator characters listed in CSS Text Level 3 Editor's Draft 3 November 2010.
    if (c == ethiopicWordspace || c == aegeanWordSeparatorLine || c == aegeanWordSeparatorDot
        || c == ugariticWordDivider || c == tibetanMarkIntersyllabicTsheg || c == tibetanMarkDelimiterTshegBstar)
        return false;

    return true;
}

bool FontCascade::isLoadingCustomFonts() const
{
    return m_fonts && m_fonts->isLoadingCustomFonts();
}

enum class GlyphUnderlineType : uint8_t {
    SkipDescenders,
    SkipGlyph,
    DrawOverGlyph
};
    
static GlyphUnderlineType computeUnderlineType(const TextRun& textRun, const GlyphBuffer& glyphBuffer, unsigned index)
{
    // In general, we want to skip descenders. However, skipping descenders on CJK characters leads to undesirable renderings,
    // so we want to draw through CJK characters (on a character-by-character basis).
    // FIXME: The CSS spec says this should instead be done by the user-agent stylesheet using the lang= attribute.
    UChar32 baseCharacter;
    auto offsetInString = glyphBuffer.checkedStringOffsetAt(index, textRun.length());
    if (!offsetInString)
        return GlyphUnderlineType::SkipDescenders;
    
    if (textRun.is8Bit())
        baseCharacter = textRun.characters8()[offsetInString.value()];
    else
        U16_GET(textRun.characters16(), 0, static_cast<unsigned>(offsetInString.value()), textRun.length(), baseCharacter);
    
    // u_getIntPropertyValue with UCHAR_IDEOGRAPHIC doesn't return true for Japanese or Korean codepoints.
    // Instead, we can use the "Unicode allocation block" for the character.
    UBlockCode blockCode = ublock_getCode(baseCharacter);
    switch (blockCode) {
    case UBLOCK_CJK_RADICALS_SUPPLEMENT:
    case UBLOCK_CJK_SYMBOLS_AND_PUNCTUATION:
    case UBLOCK_ENCLOSED_CJK_LETTERS_AND_MONTHS:
    case UBLOCK_CJK_COMPATIBILITY:
    case UBLOCK_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A:
    case UBLOCK_CJK_UNIFIED_IDEOGRAPHS:
    case UBLOCK_CJK_COMPATIBILITY_IDEOGRAPHS:
    case UBLOCK_CJK_COMPATIBILITY_FORMS:
    case UBLOCK_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_B:
    case UBLOCK_CJK_COMPATIBILITY_IDEOGRAPHS_SUPPLEMENT:
    case UBLOCK_CJK_STROKES:
    case UBLOCK_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_C:
    case UBLOCK_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_D:
    case UBLOCK_IDEOGRAPHIC_DESCRIPTION_CHARACTERS:
    case UBLOCK_LINEAR_B_IDEOGRAMS:
    case UBLOCK_ENCLOSED_IDEOGRAPHIC_SUPPLEMENT:
    case UBLOCK_HIRAGANA:
    case UBLOCK_KATAKANA:
    case UBLOCK_BOPOMOFO:
    case UBLOCK_BOPOMOFO_EXTENDED:
    case UBLOCK_HANGUL_JAMO:
    case UBLOCK_HANGUL_COMPATIBILITY_JAMO:
    case UBLOCK_HANGUL_SYLLABLES:
    case UBLOCK_HANGUL_JAMO_EXTENDED_A:
    case UBLOCK_HANGUL_JAMO_EXTENDED_B:
        return GlyphUnderlineType::DrawOverGlyph;
    default:
        return GlyphUnderlineType::SkipDescenders;
    }
}

// FIXME: This function may not work if the emphasis mark uses a complex script, but none of the
// standard emphasis marks do so.
std::optional<GlyphData> FontCascade::getEmphasisMarkGlyphData(const AtomString& mark) const
{
    if (mark.isEmpty())
        return std::nullopt;

    UChar32 character;
    if (!mark.is8Bit()) {
        size_t i = 0;
        U16_NEXT(mark.characters16(), i, mark.length(), character);
        ASSERT(U16_IS_SINGLE(character)); // The CSS parser replaces unpaired surrogates with the object replacement character.
    } else
        character = mark[0];

    std::optional<GlyphData> glyphData(glyphDataForCharacter(character, false, EmphasisMarkVariant));
    return glyphData.value().isValid() ? glyphData : std::nullopt;
}

int FontCascade::emphasisMarkAscent(const AtomString& mark) const
{
    std::optional<GlyphData> markGlyphData = getEmphasisMarkGlyphData(mark);
    if (!markGlyphData)
        return 0;

    const Font* markFontData = markGlyphData.value().font;
    ASSERT(markFontData);
    if (!markFontData)
        return 0;

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

int FontCascade::emphasisMarkDescent(const AtomString& mark) const
{
    std::optional<GlyphData> markGlyphData = getEmphasisMarkGlyphData(mark);
    if (!markGlyphData)
        return 0;

    const Font* markFontData = markGlyphData.value().font;
    ASSERT(markFontData);
    if (!markFontData)
        return 0;

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

int FontCascade::emphasisMarkHeight(const AtomString& mark) const
{
    std::optional<GlyphData> markGlyphData = getEmphasisMarkGlyphData(mark);
    if (!markGlyphData)
        return 0;

    const Font* markFontData = markGlyphData.value().font;
    ASSERT(markFontData);
    if (!markFontData)
        return 0;

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

GlyphBuffer FontCascade::layoutSimpleText(const TextRun& run, unsigned from, unsigned to, ForTextEmphasisOrNot forTextEmphasis) const
{
    GlyphBuffer glyphBuffer;

    WidthIterator it(*this, 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(from, localGlyphBuffer);
    float beforeWidth = it.runWidthSoFar();
    it.advance(to, glyphBuffer);

    if (glyphBuffer.isEmpty())
        return glyphBuffer;

    float afterWidth = it.runWidthSoFar();

    float initialAdvance = 0;
    if (run.rtl()) {
        it.advance(run.length(), localGlyphBuffer);
        it.finalize(localGlyphBuffer);
        initialAdvance = it.runWidthSoFar() - afterWidth;
    } else {
        it.finalize(localGlyphBuffer);
        initialAdvance = beforeWidth;
    }
    glyphBuffer.expandInitialAdvance(initialAdvance);

    // The glyph buffer is currently in logical order,
    // but we need to return the results in visual order.
    if (run.rtl())
        glyphBuffer.reverse(0, glyphBuffer.size());

    return glyphBuffer;
}

GlyphBuffer FontCascade::layoutComplexText(const TextRun& run, unsigned from, unsigned to, ForTextEmphasisOrNot forTextEmphasis) const
{
    GlyphBuffer glyphBuffer;

    ComplexTextController controller(*this, run, false, 0, forTextEmphasis);
    GlyphBuffer dummyGlyphBuffer;
    controller.advance(from, &dummyGlyphBuffer);
    controller.advance(to, &glyphBuffer);

    if (glyphBuffer.isEmpty())
        return glyphBuffer;

    if (run.rtl()) {
        // Exploit the fact that the sum of the paint advances is equal to
        // the sum of the layout advances.
        FloatSize initialAdvance = controller.totalAdvance();
        for (unsigned i = 0; i < dummyGlyphBuffer.size(); ++i)
            initialAdvance -= WebCore::size(dummyGlyphBuffer.advanceAt(i));
        for (unsigned i = 0; i < glyphBuffer.size(); ++i)
            initialAdvance -= WebCore::size(glyphBuffer.advanceAt(i));
        // FIXME: Shouldn't we subtract the other initial advance?
        glyphBuffer.reverse(0, glyphBuffer.size());
        glyphBuffer.setInitialAdvance(makeGlyphBufferAdvance(initialAdvance));
    } else {
        FloatSize initialAdvance = WebCore::size(dummyGlyphBuffer.initialAdvance());
        for (unsigned i = 0; i < dummyGlyphBuffer.size(); ++i)
            initialAdvance += WebCore::size(dummyGlyphBuffer.advanceAt(i));
        // FIXME: Shouldn't we add the other initial advance?
        glyphBuffer.setInitialAdvance(makeGlyphBufferAdvance(initialAdvance));
    }

    return glyphBuffer;
}

inline bool shouldDrawIfLoading(const Font& font, FontCascade::CustomFontNotReadyAction customFontNotReadyAction)
{
    // Don't draw anything while we are using custom fonts that are in the process of loading,
    // except if the 'customFontNotReadyAction' argument is set to UseFallbackIfFontNotReady
    // (in which case "font" will be a fallback font).
    return !font.isInterstitial() || font.visibility() == Font::Visibility::Visible || customFontNotReadyAction == FontCascade::CustomFontNotReadyAction::UseFallbackIfFontNotReady;
}

// This function assumes the GlyphBuffer's initial advance has already been incorporated into the start point.
void FontCascade::drawGlyphBuffer(GraphicsContext& context, const GlyphBuffer& glyphBuffer, FloatPoint& point, CustomFontNotReadyAction customFontNotReadyAction) const
{
    ASSERT(glyphBuffer.isFlattened());
    const Font* fontData = &glyphBuffer.fontAt(0);
    FloatPoint startPoint = point;
    float nextX = startPoint.x() + WebCore::width(glyphBuffer.advanceAt(0));
    float nextY = startPoint.y() + height(glyphBuffer.advanceAt(0));
    unsigned lastFrom = 0;
    unsigned nextGlyph = 1;
    while (nextGlyph < glyphBuffer.size()) {
        const Font& nextFontData = glyphBuffer.fontAt(nextGlyph);

        if (&nextFontData != fontData) {
            if (shouldDrawIfLoading(*fontData, customFontNotReadyAction))
                context.drawGlyphs(*fontData, glyphBuffer.glyphs(lastFrom), glyphBuffer.advances(lastFrom), nextGlyph - lastFrom, startPoint, m_fontDescription.fontSmoothing());

            lastFrom = nextGlyph;
            fontData = &nextFontData;
            startPoint.setX(nextX);
            startPoint.setY(nextY);
        }
        nextX += WebCore::width(glyphBuffer.advanceAt(nextGlyph));
        nextY += height(glyphBuffer.advanceAt(nextGlyph));
        nextGlyph++;
    }

    if (shouldDrawIfLoading(*fontData, customFontNotReadyAction))
        context.drawGlyphs(*fontData, glyphBuffer.glyphs(lastFrom), glyphBuffer.advances(lastFrom), nextGlyph - lastFrom, startPoint, m_fontDescription.fontSmoothing());
    point.setX(nextX);
}

inline static float offsetToMiddleOfGlyph(const Font& fontData, Glyph glyph)
{
    if (fontData.platformData().orientation() == FontOrientation::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 offsetToMiddleOfGlyphAtIndex(const GlyphBuffer& glyphBuffer, unsigned i)
{
    return offsetToMiddleOfGlyph(glyphBuffer.fontAt(i), glyphBuffer.glyphAt(i));
}

void FontCascade::drawEmphasisMarks(GraphicsContext& context, const GlyphBuffer& glyphBuffer, const AtomString& mark, const FloatPoint& point) const
{
    ASSERT(glyphBuffer.isFlattened());
    std::optional<GlyphData> markGlyphData = getEmphasisMarkGlyphData(mark);
    if (!markGlyphData)
        return;

    const Font* markFontData = markGlyphData.value().font;
    ASSERT(markFontData);
    if (!markFontData)
        return;

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

    // FIXME: This needs to take the initial advance into account.
    // The problem might actually be harder for complex text, though.
    // Putting a mark over every glyph probably isn't great in complex scripts.
    float middleOfLastGlyph = offsetToMiddleOfGlyphAtIndex(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 = offsetToMiddleOfGlyphAtIndex(glyphBuffer, i + 1);
        float advance = WebCore::width(glyphBuffer.advanceAt(i)) - 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, markBuffer, startPoint, CustomFontNotReadyAction::DoNotPaintIfFontNotReady);
}

float FontCascade::floatWidthForSimpleText(const TextRun& run, HashSet<const Font*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
{
    WidthIterator it(*this, run, fallbackFonts, glyphOverflow);
    GlyphBuffer glyphBuffer;
    it.advance(run.length(), glyphBuffer);
    it.finalize(glyphBuffer);

    if (glyphOverflow) {
        glyphOverflow->top = std::max<int>(glyphOverflow->top, ceilf(-it.minGlyphBoundingBoxY()) - (glyphOverflow->computeBounds ? 0 : fontMetrics().ascent()));
        glyphOverflow->bottom = std::max<int>(glyphOverflow->bottom, ceilf(it.maxGlyphBoundingBoxY()) - (glyphOverflow->computeBounds ? 0 : fontMetrics().descent()));
        glyphOverflow->left = ceilf(it.firstGlyphOverflow());
        glyphOverflow->right = ceilf(it.lastGlyphOverflow());
    }

    return it.runWidthSoFar();
}

float FontCascade::floatWidthForComplexText(const TextRun& run, HashSet<const Font*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
{
    ComplexTextController controller(*this, run, true, fallbackFonts);
    if (glyphOverflow) {
        glyphOverflow->top = std::max<int>(glyphOverflow->top, ceilf(-controller.minGlyphBoundingBoxY()) - (glyphOverflow->computeBounds ? 0 : fontMetrics().ascent()));
        glyphOverflow->bottom = std::max<int>(glyphOverflow->bottom, ceilf(controller.maxGlyphBoundingBoxY()) - (glyphOverflow->computeBounds ? 0 : fontMetrics().descent()));
        glyphOverflow->left = std::max<int>(0, ceilf(-controller.minGlyphBoundingBoxX()));
        glyphOverflow->right = std::max<int>(0, ceilf(controller.maxGlyphBoundingBoxX() - controller.totalAdvance().width()));
    }
    return controller.totalAdvance().width();
}

void FontCascade::adjustSelectionRectForSimpleText(const TextRun& run, LayoutRect& selectionRect, unsigned from, unsigned to) const
{
    GlyphBuffer glyphBuffer;
    WidthIterator it(*this, run);
    it.advance(from, glyphBuffer);
    float beforeWidth = it.runWidthSoFar();
    it.advance(to, glyphBuffer);
    float afterWidth = it.runWidthSoFar();

    if (run.rtl()) {
        it.advance(run.length(), glyphBuffer);
        it.finalize(glyphBuffer);
        float totalWidth = it.runWidthSoFar();
        selectionRect.move(totalWidth - afterWidth, 0);
    } else {
        it.finalize(glyphBuffer);
        selectionRect.move(beforeWidth, 0);
    }
    selectionRect.setWidth(LayoutUnit::fromFloatCeil(afterWidth - beforeWidth));
}

void FontCascade::adjustSelectionRectForComplexText(const TextRun& run, LayoutRect& selectionRect, unsigned from, unsigned to) const
{
    ComplexTextController controller(*this, run);
    controller.advance(from);
    float beforeWidth = controller.runWidthSoFar();
    controller.advance(to);
    float afterWidth = controller.runWidthSoFar();

    if (run.rtl())
        selectionRect.move(controller.totalAdvance().width() - afterWidth, 0);
    else
        selectionRect.move(beforeWidth, 0);
    selectionRect.setWidth(LayoutUnit::fromFloatCeil(afterWidth - beforeWidth));
}

int FontCascade::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.currentCharacterIndex();
            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.currentCharacterIndex();
            float w;
            if (!it.advanceOneCharacter(w, localGlyphBuffer))
                break;
            delta -= w;
            if (includePartialGlyphs) {
                if (delta + w / 2 <= 0)
                    break;
            } else {
                if (delta <= 0)
                    break;
            }
        }
    }

    it.finalize(localGlyphBuffer);
    return offset;
}

int FontCascade::offsetForPositionForComplexText(const TextRun& run, float x, bool includePartialGlyphs) const
{
    ComplexTextController controller(*this, run);
    return controller.offsetForPosition(x, includePartialGlyphs);
}

#if !PLATFORM(COCOA) && !USE(HARFBUZZ)
// FIXME: Unify this with the macOS and iOS implementation.
const Font* FontCascade::fontForCombiningCharacterSequence(const UChar* characters, size_t length) const
{
    UChar32 baseCharacter;
    size_t baseCharacterLength = 0;
    U16_NEXT(characters, baseCharacterLength, length, baseCharacter);
    GlyphData baseCharacterGlyphData = glyphDataForCharacter(baseCharacter, false, NormalVariant);

    if (!baseCharacterGlyphData.glyph)
        return nullptr;
    return baseCharacterGlyphData.font;
}
#endif

struct GlyphIterationState {
    FloatPoint startingPoint;
    FloatPoint currentPoint;
    float y1;
    float y2;
    float minX;
    float maxX;
};

static std::optional<float> findIntersectionPoint(float y, FloatPoint p1, FloatPoint p2)
{
    if ((p1.y() < y && p2.y() > y) || (p1.y() > y && p2.y() < y))
        return p1.x() + (y - p1.y()) * (p2.x() - p1.x()) / (p2.y() - p1.y());
    return std::nullopt;
}

static void updateX(GlyphIterationState& state, float x)
{
    state.minX = std::min(state.minX, x);
    state.maxX = std::max(state.maxX, x);
}

// This function is called by CGPathApply and is therefore invoked for each
// contour in a glyph. This function models each contours as a straight line
// and calculates the intersections between each pseudo-contour and
// two horizontal lines (the upper and lower bounds of an underline) found in
// GlyphIterationState::y1 and GlyphIterationState::y2. It keeps track of the
// leftmost and rightmost intersection in GlyphIterationState::minX and
// GlyphIterationState::maxX.
static void findPathIntersections(GlyphIterationState& state, const PathElement& element)
{
    bool doIntersection = false;
    FloatPoint point = FloatPoint();
    switch (element.type) {
    case PathElement::Type::MoveToPoint:
        state.startingPoint = element.points[0];
        state.currentPoint = element.points[0];
        break;
    case PathElement::Type::AddLineToPoint:
        doIntersection = true;
        point = element.points[0];
        break;
    case PathElement::Type::AddQuadCurveToPoint:
        doIntersection = true;
        point = element.points[1];
        break;
    case PathElement::Type::AddCurveToPoint:
        doIntersection = true;
        point = element.points[2];
        break;
    case PathElement::Type::CloseSubpath:
        doIntersection = true;
        point = state.startingPoint;
        break;
    }
    if (!doIntersection)
        return;
    if (auto intersectionPoint = findIntersectionPoint(state.y1, state.currentPoint, point))
        updateX(state, *intersectionPoint);
    if (auto intersectionPoint = findIntersectionPoint(state.y2, state.currentPoint, point))
        updateX(state, *intersectionPoint);
    if ((state.currentPoint.y() >= state.y1 && state.currentPoint.y() <= state.y2)
        || (state.currentPoint.y() <= state.y1 && state.currentPoint.y() >= state.y2))
        updateX(state, state.currentPoint.x());
    state.currentPoint = point;
}

class GlyphToPathTranslator {
public:
    GlyphToPathTranslator(const TextRun& textRun, const GlyphBuffer& glyphBuffer, const FloatPoint& textOrigin)
        : m_index(0)
        , m_textRun(textRun)
        , m_glyphBuffer(glyphBuffer)
        , m_fontData(&glyphBuffer.fontAt(m_index))
        , m_translation(AffineTransform::translation(textOrigin.x(), textOrigin.y()))
    {
#if USE(CG)
        m_translation.flipY();
#endif
    }

    bool containsMorePaths() { return m_index != m_glyphBuffer.size(); }
    Path path();
    std::pair<float, float> extents();
    GlyphUnderlineType underlineType();
    void advance();

private:
    unsigned m_index;
    const TextRun& m_textRun;
    const GlyphBuffer& m_glyphBuffer;
    const Font* m_fontData;
    AffineTransform m_translation;
};

Path GlyphToPathTranslator::path()
{
    Path path = m_fontData->pathForGlyph(m_glyphBuffer.glyphAt(m_index));
    path.transform(m_translation);
    return path;
}

std::pair<float, float> GlyphToPathTranslator::extents()
{
    auto beginning = m_translation.mapPoint(FloatPoint(0, 0));
    auto advance = m_glyphBuffer.advanceAt(m_index);
    auto end = m_translation.mapSize(size(advance));
    return std::make_pair(beginning.x(), beginning.x() + end.width());
}

auto GlyphToPathTranslator::underlineType() -> GlyphUnderlineType
{
    return computeUnderlineType(m_textRun, m_glyphBuffer, m_index);
}

void GlyphToPathTranslator::advance()
{
    GlyphBufferAdvance advance = m_glyphBuffer.advanceAt(m_index);
    m_translation.translate(size(advance));
    ++m_index;
    if (m_index < m_glyphBuffer.size())
        m_fontData = &m_glyphBuffer.fontAt(m_index);
}

DashArray FontCascade::dashesForIntersectionsWithRect(const TextRun& run, const FloatPoint& textOrigin, const FloatRect& lineExtents) const
{
    if (isLoadingCustomFonts())
        return DashArray();

    auto glyphBuffer = layoutText(codePath(run), run, 0, run.length());

    if (!glyphBuffer.size())
        return DashArray();

    FloatPoint origin = textOrigin + WebCore::size(glyphBuffer.initialAdvance());
    GlyphToPathTranslator translator(run, glyphBuffer, origin);
    DashArray result;
    for (unsigned index = 0; translator.containsMorePaths(); ++index, translator.advance()) {
        GlyphIterationState info = { FloatPoint(0, 0), FloatPoint(0, 0), lineExtents.y(), lineExtents.y() + lineExtents.height(), lineExtents.x() + lineExtents.width(), lineExtents.x() };
        switch (translator.underlineType()) {
        case GlyphUnderlineType::SkipDescenders: {
            Path path = translator.path();
            path.apply([&](const PathElement& element) {
                findPathIntersections(info, element);
            });
            if (info.minX < info.maxX) {
                result.append(info.minX - lineExtents.x());
                result.append(info.maxX - lineExtents.x());
            }
            break;
        }
        case GlyphUnderlineType::SkipGlyph: {
            std::pair<float, float> extents = translator.extents();
            result.append(extents.first - lineExtents.x());
            result.append(extents.second - lineExtents.x());
            break;
        }
        case GlyphUnderlineType::DrawOverGlyph:
            // Nothing to do
            break;
        }
    }
    return result;
}

}