Quelle gfxFont.cpp Sprache: C

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "gfxFont.h"

#include "mozilla/BinarySearch.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/FontPropertyTypes.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/IntegerRange.h"
#include "mozilla/intl/Segmenter.h"
#include "mozilla/MathAlgorithms.h"
#include "mozilla/StaticPrefs_gfx.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/SVGContextPaint.h"

#include "mozilla/Logging.h"

#include "nsITimer.h"

#include "gfxGlyphExtents.h"
#include "gfxPlatform.h"
#include "gfxTextRun.h"
#include "nsGkAtoms.h"

#include "gfxTypes.h"
#include "gfxContext.h"
#include "gfxFontMissingGlyphs.h"
#include "gfxGraphiteShaper.h"
#include "gfxHarfBuzzShaper.h"
#include "gfxUserFontSet.h"
#include "nsCRT.h"
#include "nsContentUtils.h"
#include "nsSpecialCasingData.h"
#include "nsTextRunTransformations.h"
#include "nsUGenCategory.h"
#include "nsUnicodeProperties.h"
#include "nsStyleConsts.h"
#include "mozilla/AppUnits.h"
#include "mozilla/HashTable.h"
#include "mozilla/Likely.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Preferences.h"
#include "mozilla/Services.h"
#include "mozilla/glean/GfxMetrics.h"
#include "gfxMathTable.h"
#include "gfxSVGGlyphs.h"
#include "gfx2DGlue.h"
#include "TextDrawTarget.h"

#include "ThebesRLBox.h"

#include "GreekCasing.h"

#include "cairo.h"
#ifdef XP_WIN
#  include "cairo-win32.h"
#  include "gfxWindowsPlatform.h"
#endif

#include "harfbuzz/hb.h"
#include "harfbuzz/hb-ot.h"

#include <algorithm>
#include <limits>
#include <cmath>

using namespace mozilla;
using namespace mozilla::gfx;
using namespace mozilla::unicode;
using mozilla::services::GetObserverService;

gfxFontCache* gfxFontCache::gGlobalCache = nullptr;

#ifdef DEBUG_roc
#  define DEBUG_TEXT_RUN_STORAGE_METRICS
#endif

#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
uint32_t gTextRunStorageHighWaterMark = 0;
uint32_t gTextRunStorage = 0;
uint32_t gFontCount = 0;
uint32_t gGlyphExtentsCount = 0;
uint32_t gGlyphExtentsWidthsTotalSize = 0;
uint32_t gGlyphExtentsSetupEagerSimple = 0;
uint32_t gGlyphExtentsSetupEagerTight = 0;
uint32_t gGlyphExtentsSetupLazyTight = 0;
uint32_t gGlyphExtentsSetupFallBackToTight = 0;
#endif

#define LOG_FONTINIT(args) \
  MOZ_LOG(gfxPlatform::GetLog(eGfxLog_fontinit), LogLevel::Debug, args)
#define LOG_FONTINIT_ENABLED() \
  MOZ_LOG_TEST(gfxPlatform::GetLog(eGfxLog_fontinit), LogLevel::Debug)

/*
* gfxFontCache - global cache of gfxFont instances.
* Expires unused fonts after a short interval;
* notifies fonts to age their cached shaped-word records;
* observes memory-pressure notification and tells fonts to clear their
* shaped-word caches to free up memory.
*/

MOZ_DEFINE_MALLOC_SIZE_OF(FontCacheMallocSizeOf)

NS_IMPL_ISUPPORTS(gfxFontCache::MemoryReporter, nsIMemoryReporter)

/*virtual*/
gfxTextRunFactory::~gfxTextRunFactory() {
  // Should not be dropped by stylo
  MOZ_ASSERT(!Servo_IsWorkerThread());
}

NS_IMETHODIMP
gfxFontCache::MemoryReporter::CollectReports(
    nsIHandleReportCallback* aHandleReport, nsISupports* aData,
    bool aAnonymize) {
  FontCacheSizes sizes;

  gfxFontCache::GetCache()->AddSizeOfIncludingThis(&FontCacheMallocSizeOf,
                                                   &sizes);

  MOZ_COLLECT_REPORT("explicit/gfx/font-cache", KIND_HEAP, UNITS_BYTES,
                     sizes.mFontInstances,
                     "Memory used for active font instances.");

  MOZ_COLLECT_REPORT("explicit/gfx/font-shaped-words", KIND_HEAP, UNITS_BYTES,
                     sizes.mShapedWords,
                     "Memory used to cache shaped glyph data.");

  return NS_OK;
}

NS_IMPL_ISUPPORTS(gfxFontCache::Observer, nsIObserver)

NS_IMETHODIMP
gfxFontCache::Observer::Observe(nsISupports* aSubject, const char* aTopic,
                                const char16_t* someData) {
  if (!nsCRT::strcmp(aTopic, "memory-pressure")) {
    gfxFontCache* fontCache = gfxFontCache::GetCache();
    if (fontCache) {
      fontCache->FlushShapedWordCaches();
    }
  } else {
    MOZ_ASSERT_UNREACHABLE("unexpected notification topic");
  }
  return NS_OK;
}

nsresult gfxFontCache::Init() {
  NS_ASSERTION(!gGlobalCache, "Where did this come from?");
  gGlobalCache = new gfxFontCache(GetMainThreadSerialEventTarget());
  if (!gGlobalCache) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  RegisterStrongMemoryReporter(new MemoryReporter());
  return NS_OK;
}

void gfxFontCache::Shutdown() {
  delete gGlobalCache;
  gGlobalCache = nullptr;

#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
  printf("Textrun storage high water mark=%d\n", gTextRunStorageHighWaterMark);
  printf("Total number of fonts=%d\n", gFontCount);
  printf("Total glyph extents allocated=%d (size %d)\n", gGlyphExtentsCount,
         int(gGlyphExtentsCount * sizeof(gfxGlyphExtents)));
  printf("Total glyph extents width-storage size allocated=%d\n",
         gGlyphExtentsWidthsTotalSize);
  printf("Number of simple glyph extents eagerly requested=%d\n",
         gGlyphExtentsSetupEagerSimple);
  printf("Number of tight glyph extents eagerly requested=%d\n",
         gGlyphExtentsSetupEagerTight);
  printf("Number of tight glyph extents lazily requested=%d\n",
         gGlyphExtentsSetupLazyTight);
  printf("Number of simple glyph extent setups that fell back to tight=%d\n",
         gGlyphExtentsSetupFallBackToTight);
#endif
}

gfxFontCache::gfxFontCache(nsIEventTarget* aEventTarget)
    : ExpirationTrackerImpl<gfxFont, 3, Lock, AutoLock>(
          FONT_TIMEOUT_SECONDS * 1000, "gfxFontCache", aEventTarget) {
  nsCOMPtr<nsIObserverService> obs = GetObserverService();
  if (obs) {
    obs->AddObserver(new Observer, "memory-pressure", false);
  }

  nsIEventTarget* target = nullptr;
  if (XRE_IsContentProcess() && NS_IsMainThread()) {
    target = aEventTarget;
  }

  // Create the timer used to expire shaped-word records from each font's
  // cache after a short period of non-use. We have a single timer in
  // gfxFontCache that loops over all fonts known to the cache, to avoid
  // the overhead of individual timers in each font instance.
  // The timer will be started any time shaped word records are cached
  // (and pauses itself when all caches become empty).
  mWordCacheExpirationTimer = NS_NewTimer(target);
}

gfxFontCache::~gfxFontCache() {
  // Ensure the user font cache releases its references to font entries,
  // so they aren't kept alive after the font instances and font-list
  // have been shut down.
  gfxUserFontSet::UserFontCache::Shutdown();

  if (mWordCacheExpirationTimer) {
    mWordCacheExpirationTimer->Cancel();
    mWordCacheExpirationTimer = nullptr;
  }

  // Expire everything manually so we don't leak them.
  Flush();
}

bool gfxFontCache::HashEntry::KeyEquals(const KeyTypePointer aKey) const {
  const gfxCharacterMap* fontUnicodeRangeMap = mFont->GetUnicodeRangeMap();
  return aKey->mFontEntry == mFont->GetFontEntry() &&
         aKey->mStyle->Equals(*mFont->GetStyle()) &&
         ((!aKey->mUnicodeRangeMap && !fontUnicodeRangeMap) ||
          (aKey->mUnicodeRangeMap && fontUnicodeRangeMap &&
           aKey->mUnicodeRangeMap->Equals(fontUnicodeRangeMap)));
}

already_AddRefed<gfxFont> gfxFontCache::Lookup(
    const gfxFontEntry* aFontEntry, const gfxFontStyle* aStyle,
    const gfxCharacterMap* aUnicodeRangeMap) {
  MutexAutoLock lock(mMutex);

  Key key(aFontEntry, aStyle, aUnicodeRangeMap);
  HashEntry* entry = mFonts.GetEntry(key);

  glean::fontlist::font_cache_hit
      .EnumGet(
          static_cast<glean::fontlist::FontCacheHitLabel>(entry != nullptr))
      .Add();

  if (!entry) {
    return nullptr;
  }

  RefPtr<gfxFont> font = entry->mFont;
  if (font->GetExpirationState()->IsTracked()) {
    RemoveObjectLocked(font, lock);
  }
  return font.forget();
}

already_AddRefed<gfxFont> gfxFontCache::MaybeInsert(gfxFont* aFont) {
  MOZ_ASSERT(aFont);
  MutexAutoLock lock(mMutex);

  Key key(aFont->GetFontEntry(), aFont->GetStyle(),
          aFont->GetUnicodeRangeMap());
  HashEntry* entry = mFonts.PutEntry(key);
  if (!entry) {
    return do_AddRef(aFont);
  }

  // If it is null, then we are inserting a new entry. Otherwise we are
  // attempting to replace an existing font, probably due to a thread race, in
  // which case stick with the original font.
  if (!entry->mFont) {
    entry->mFont = aFont;
    // Assert that we can find the entry we just put in (this fails if the key
    // has a NaN float value in it, e.g. 'sizeAdjust').
    MOZ_ASSERT(entry == mFonts.GetEntry(key));
  } else {
    MOZ_ASSERT(entry->mFont != aFont);
    aFont->Destroy();
    if (entry->mFont->GetExpirationState()->IsTracked()) {
      RemoveObjectLocked(entry->mFont, lock);
    }
  }

  return do_AddRef(entry->mFont);
}

bool gfxFontCache::MaybeDestroy(gfxFont* aFont) {
  MOZ_ASSERT(aFont);
  MutexAutoLock lock(mMutex);

  // If the font has a non-zero refcount, then we must have lost the race with
  // gfxFontCache::Lookup and the same font was reacquired.
  if (aFont->GetRefCount() > 0) {
    return false;
  }

  Key key(aFont->GetFontEntry(), aFont->GetStyle(),
          aFont->GetUnicodeRangeMap());
  HashEntry* entry = mFonts.GetEntry(key);
  if (!entry || entry->mFont != aFont) {
    MOZ_ASSERT(!aFont->GetExpirationState()->IsTracked());
    return true;
  }

  // If the font is being tracked, we must have then also lost another race with
  // gfxFontCache::MaybeDestroy which re-added it to the tracker.
  if (aFont->GetExpirationState()->IsTracked()) {
    return false;
  }

  // Typically this won't fail, but it may during startup/shutdown if the timer
  // service is not available.
  nsresult rv = AddObjectLocked(aFont, lock);
  if (NS_SUCCEEDED(rv)) {
    return false;
  }

  mFonts.RemoveEntry(entry);
  return true;
}

void gfxFontCache::NotifyExpiredLocked(gfxFont* aFont, const AutoLock& aLock) {
  MOZ_ASSERT(aFont->GetRefCount() == 0);

  RemoveObjectLocked(aFont, aLock);
  mTrackerDiscard.AppendElement(aFont);

  Key key(aFont->GetFontEntry(), aFont->GetStyle(),
          aFont->GetUnicodeRangeMap());
  HashEntry* entry = mFonts.GetEntry(key);
  if (!entry || entry->mFont != aFont) {
    MOZ_ASSERT_UNREACHABLE("Invalid font?");
    return;
  }

  mFonts.RemoveEntry(entry);
}

void gfxFontCache::NotifyHandlerEnd() {
  nsTArray<gfxFont*> discard;
  {
    MutexAutoLock lock(mMutex);
    discard = std::move(mTrackerDiscard);
  }
  DestroyDiscard(discard);
}

void gfxFontCache::DestroyDiscard(nsTArray<gfxFont*>& aDiscard) {
  for (auto& font : aDiscard) {
    NS_ASSERTION(font->GetRefCount() == 0,
                 "Destroying with refs outside cache!");
    font->ClearCachedWords();
    font->Destroy();
  }
  aDiscard.Clear();
}

void gfxFontCache::Flush() {
  nsTArray<gfxFont*> discard;
  {
    MutexAutoLock lock(mMutex);
    discard.SetCapacity(mFonts.Count());
    for (auto iter = mFonts.Iter(); !iter.Done(); iter.Next()) {
      HashEntry* entry = static_cast<HashEntry*>(iter.Get());
      if (!entry || !entry->mFont) {
        MOZ_ASSERT_UNREACHABLE("Invalid font?");
        continue;
      }

      if (entry->mFont->GetRefCount() == 0) {
        // If we are not tracked, then we must have won the race with
        // gfxFont::MaybeDestroy and it is waiting on the mutex. To avoid a
        // double free, we let gfxFont::MaybeDestroy handle the freeing when it
        // acquires the mutex and discovers there is no matching entry in the
        // hashtable.
        if (entry->mFont->GetExpirationState()->IsTracked()) {
          RemoveObjectLocked(entry->mFont, lock);
          discard.AppendElement(entry->mFont);
        }
      } else {
        MOZ_ASSERT(!entry->mFont->GetExpirationState()->IsTracked());
      }
    }
    MOZ_ASSERT(IsEmptyLocked(lock),
               "Cache tracker still has fonts after flush!");
    mFonts.Clear();
  }
  DestroyDiscard(discard);
}

/*static*/
void gfxFontCache::WordCacheExpirationTimerCallback(nsITimer* aTimer,
                                                    void* aCache) {
  gfxFontCache* cache = static_cast<gfxFontCache*>(aCache);
  cache->AgeCachedWords();
}

void gfxFontCache::AgeCachedWords() {
  bool allEmpty = true;
  {
    MutexAutoLock lock(mMutex);
    for (const auto& entry : mFonts) {
      allEmpty = entry.mFont->AgeCachedWords() && allEmpty;
    }
  }
  if (allEmpty) {
    PauseWordCacheExpirationTimer();
  }
}

void gfxFontCache::FlushShapedWordCaches() {
  {
    MutexAutoLock lock(mMutex);
    for (const auto& entry : mFonts) {
      entry.mFont->ClearCachedWords();
    }
  }
  PauseWordCacheExpirationTimer();
}

void gfxFontCache::NotifyGlyphsChanged() {
  MutexAutoLock lock(mMutex);
  for (const auto& entry : mFonts) {
    entry.mFont->NotifyGlyphsChanged();
  }
}

void gfxFontCache::AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
                                          FontCacheSizes* aSizes) const {
  // TODO: add the overhead of the expiration tracker (generation arrays)

  MutexAutoLock lock(*const_cast<Mutex*>(&mMutex));
  aSizes->mFontInstances += mFonts.ShallowSizeOfExcludingThis(aMallocSizeOf);
  for (const auto& entry : mFonts) {
    entry.mFont->AddSizeOfExcludingThis(aMallocSizeOf, aSizes);
  }
}

void gfxFontCache::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
                                          FontCacheSizes* aSizes) const {
  aSizes->mFontInstances += aMallocSizeOf(this);
  AddSizeOfExcludingThis(aMallocSizeOf, aSizes);
}

#define MAX_SSXX_VALUE 99
#define MAX_CVXX_VALUE 99

static void LookupAlternateValues(const gfxFontFeatureValueSet& aFeatureLookup,
                                  const nsACString& aFamily,
                                  const StyleVariantAlternates& aAlternates,
                                  nsTArray<gfxFontFeature>& aFontFeatures) {
  using Tag = StyleVariantAlternates::Tag;

  // historical-forms gets handled in nsFont::AddFontFeaturesToStyle.
  if (aAlternates.IsHistoricalForms()) {
    return;
  }

  gfxFontFeature feature;
  if (aAlternates.IsCharacterVariant()) {
    for (auto& ident : aAlternates.AsCharacterVariant().AsSpan()) {
      Span<const uint32_t> values = aFeatureLookup.GetFontFeatureValuesFor(
          aFamily, NS_FONT_VARIANT_ALTERNATES_CHARACTER_VARIANT,
          ident.AsAtom());
      // nothing defined, skip
      if (values.IsEmpty()) {
        continue;
      }
      NS_ASSERTION(values.Length() <= 2,
                   "too many values allowed for character-variant");
      // character-variant(12 3) ==> 'cv12' = 3
      uint32_t nn = values[0];
      // ignore values greater than 99
      if (nn == 0 || nn > MAX_CVXX_VALUE) {
        continue;
      }
      feature.mValue = values.Length() > 1 ? values[1] : 1;
      feature.mTag = HB_TAG('c', 'v', ('0' + nn / 10), ('0' + nn % 10));
      aFontFeatures.AppendElement(feature);
    }
    return;
  }

  if (aAlternates.IsStyleset()) {
    for (auto& ident : aAlternates.AsStyleset().AsSpan()) {
      Span<const uint32_t> values = aFeatureLookup.GetFontFeatureValuesFor(
          aFamily, NS_FONT_VARIANT_ALTERNATES_STYLESET, ident.AsAtom());

      // styleset(1 2 7) ==> 'ss01' = 1, 'ss02' = 1, 'ss07' = 1
      feature.mValue = 1;
      for (uint32_t nn : values) {
        if (nn == 0 || nn > MAX_SSXX_VALUE) {
          continue;
        }
        feature.mTag = HB_TAG('s', 's', ('0' + nn / 10), ('0' + nn % 10));
        aFontFeatures.AppendElement(feature);
      }
    }
    return;
  }

  uint32_t constant = 0;
  nsAtom* name = nullptr;
  switch (aAlternates.tag) {
    case Tag::Swash:
      constant = NS_FONT_VARIANT_ALTERNATES_SWASH;
      name = aAlternates.AsSwash().AsAtom();
      break;
    case Tag::Stylistic:
      constant = NS_FONT_VARIANT_ALTERNATES_STYLISTIC;
      name = aAlternates.AsStylistic().AsAtom();
      break;
    case Tag::Ornaments:
      constant = NS_FONT_VARIANT_ALTERNATES_ORNAMENTS;
      name = aAlternates.AsOrnaments().AsAtom();
      break;
    case Tag::Annotation:
      constant = NS_FONT_VARIANT_ALTERNATES_ANNOTATION;
      name = aAlternates.AsAnnotation().AsAtom();
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("Unknown font-variant-alternates value!");
      return;
  }

  Span<const uint32_t> values =
      aFeatureLookup.GetFontFeatureValuesFor(aFamily, constant, name);
  if (values.IsEmpty()) {
    return;
  }
  MOZ_ASSERT(values.Length() == 1,
             "too many values for font-specific font-variant-alternates");

  feature.mValue = values[0];
  switch (aAlternates.tag) {
    case Tag::Swash:  // swsh, cswh
      feature.mTag = HB_TAG('s', 'w', 's', 'h');
      aFontFeatures.AppendElement(feature);
      feature.mTag = HB_TAG('c', 's', 'w', 'h');
      break;
    case Tag::Stylistic:  // salt
      feature.mTag = HB_TAG('s', 'a', 'l', 't');
      break;
    case Tag::Ornaments:  // ornm
      feature.mTag = HB_TAG('o', 'r', 'n', 'm');
      break;
    case Tag::Annotation:  // nalt
      feature.mTag = HB_TAG('n', 'a', 'l', 't');
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("how?");
      return;
  }
  aFontFeatures.AppendElement(feature);
}

/* static */
void gfxFontShaper::MergeFontFeatures(
    const gfxFontStyle* aStyle, const nsTArray<gfxFontFeature>& aFontFeatures,
    bool aDisableLigatures, const nsACString& aFamilyName, bool aAddSmallCaps,
    void (*aHandleFeature)(uint32_t, uint32_t, void*),
    void* aHandleFeatureData) {
  const nsTArray<gfxFontFeature>& styleRuleFeatures = aStyle->featureSettings;

  // Bail immediately if nothing to do, which is the common case.
  if (styleRuleFeatures.IsEmpty() && aFontFeatures.IsEmpty() &&
      !aDisableLigatures &&
      aStyle->variantCaps == NS_FONT_VARIANT_CAPS_NORMAL &&
      aStyle->variantSubSuper == NS_FONT_VARIANT_POSITION_NORMAL &&
      aStyle->variantAlternates.IsEmpty()) {
    return;
  }

  AutoTArray<gfxFontFeature, 32> mergedFeatures;

  struct FeatureTagCmp {
    bool Equals(const gfxFontFeature& a, const gfxFontFeature& b) const {
      return a.mTag == b.mTag;
    }
    bool LessThan(const gfxFontFeature& a, const gfxFontFeature& b) const {
      return a.mTag < b.mTag;
    }
  } cmp;

  auto addOrReplace = [&](const gfxFontFeature& aFeature) {
    auto index = mergedFeatures.BinaryIndexOf(aFeature, cmp);
    if (index == nsTArray<gfxFontFeature>::NoIndex) {
      mergedFeatures.InsertElementSorted(aFeature, cmp);
    } else {
      mergedFeatures[index].mValue = aFeature.mValue;
    }
  };

  // add feature values from font
  for (const gfxFontFeature& feature : aFontFeatures) {
    addOrReplace(feature);
  }

  // font-variant-caps - handled here due to the need for fallback handling
  // petite caps cases can fallback to appropriate smallcaps
  uint32_t variantCaps = aStyle->variantCaps;
  switch (variantCaps) {
    case NS_FONT_VARIANT_CAPS_NORMAL:
      break;

    case NS_FONT_VARIANT_CAPS_ALLSMALL:
      addOrReplace(gfxFontFeature{HB_TAG('c', '2', 's', 'c'), 1});
      // fall through to the small-caps case
      [[fallthrough]];

    case NS_FONT_VARIANT_CAPS_SMALLCAPS:
      addOrReplace(gfxFontFeature{HB_TAG('s', 'm', 'c', 'p'), 1});
      break;

    case NS_FONT_VARIANT_CAPS_ALLPETITE:
      addOrReplace(gfxFontFeature{aAddSmallCaps ? HB_TAG('c', '2', 's', 'c')
                                                : HB_TAG('c', '2', 'p', 'c'),
                                  1});
      // fall through to the petite-caps case
      [[fallthrough]];

    case NS_FONT_VARIANT_CAPS_PETITECAPS:
      addOrReplace(gfxFontFeature{aAddSmallCaps ? HB_TAG('s', 'm', 'c', 'p')
                                                : HB_TAG('p', 'c', 'a', 'p'),
                                  1});
      break;

    case NS_FONT_VARIANT_CAPS_TITLING:
      addOrReplace(gfxFontFeature{HB_TAG('t', 'i', 't', 'l'), 1});
      break;

    case NS_FONT_VARIANT_CAPS_UNICASE:
      addOrReplace(gfxFontFeature{HB_TAG('u', 'n', 'i', 'c'), 1});
      break;

    default:
      MOZ_ASSERT_UNREACHABLE("Unexpected variantCaps");
      break;
  }

  // font-variant-position - handled here due to the need for fallback
  switch (aStyle->variantSubSuper) {
    case NS_FONT_VARIANT_POSITION_NORMAL:
      break;
    case NS_FONT_VARIANT_POSITION_SUPER:
      addOrReplace(gfxFontFeature{HB_TAG('s', 'u', 'p', 's'), 1});
      break;
    case NS_FONT_VARIANT_POSITION_SUB:
      addOrReplace(gfxFontFeature{HB_TAG('s', 'u', 'b', 's'), 1});
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("Unexpected variantSubSuper");
      break;
  }

  // add font-specific feature values from style rules
  if (aStyle->featureValueLookup && !aStyle->variantAlternates.IsEmpty()) {
    AutoTArray<gfxFontFeature, 4> featureList;

    // insert list of alternate feature settings
    for (auto& alternate : aStyle->variantAlternates.AsSpan()) {
      LookupAlternateValues(*aStyle->featureValueLookup, aFamilyName, alternate,
                            featureList);
    }

    for (const gfxFontFeature& feature : featureList) {
      addOrReplace(gfxFontFeature{feature.mTag, feature.mValue});
    }
  }

  auto disableOptionalLigatures = [&]() -> void {
    addOrReplace(gfxFontFeature{HB_TAG('l', 'i', 'g', 'a'), 0});
    addOrReplace(gfxFontFeature{HB_TAG('c', 'l', 'i', 'g'), 0});
    addOrReplace(gfxFontFeature{HB_TAG('d', 'l', 'i', 'g'), 0});
    addOrReplace(gfxFontFeature{HB_TAG('h', 'l', 'i', 'g'), 0});
  };

  // Add features that are already resolved to tags & values in the style.
  if (styleRuleFeatures.IsEmpty()) {
    // Disable optional ligatures if non-zero letter-spacing is in effect.
    if (aDisableLigatures) {
      disableOptionalLigatures();
    }
  } else {
    for (const gfxFontFeature& feature : styleRuleFeatures) {
      // A dummy feature (0,0) is used as a sentinel to separate features
      // originating from font-variant-* or other high-level properties from
      // those directly specified as font-feature-settings. The high-level
      // features may be overridden by aDisableLigatures, while low-level
      // features specified directly as tags will come last and therefore
      // take precedence over everything else.
      if (feature.mTag) {
        addOrReplace(gfxFontFeature{feature.mTag, feature.mValue});
      } else if (aDisableLigatures) {
        // Handle ligature-disabling setting at the boundary between high-
        // and low-level features.
        disableOptionalLigatures();
      }
    }
  }

  for (const auto& f : mergedFeatures) {
    aHandleFeature(f.mTag, f.mValue, aHandleFeatureData);
  }
}

void gfxShapedText::SetupClusterBoundaries(uint32_t aOffset,
                                           const char16_t* aString,
                                           uint32_t aLength) {
  if (aLength == 0) {
    return;
  }

  CompressedGlyph* const glyphs = GetCharacterGlyphs() + aOffset;
  CompressedGlyph extendCluster = CompressedGlyph::MakeComplex(false, true);

  // GraphemeClusterBreakIteratorUtf16 won't be able to tell us if the string
  // _begins_ with a cluster-extender, so we handle that here
  uint32_t ch = aString[0];
  if (aLength > 1 && NS_IS_SURROGATE_PAIR(ch, aString[1])) {
    ch = SURROGATE_TO_UCS4(ch, aString[1]);
  }
  if (IsClusterExtender(ch)) {
    glyphs[0] = extendCluster;
  }

  intl::GraphemeClusterBreakIteratorUtf16 iter(
      Span<const char16_t>(aString, aLength));
  uint32_t pos = 0;

  const char16_t kIdeographicSpace = 0x3000;
  // Special case for Bengali: although Virama normally clusters with the
  // preceding letter, we *also* want to cluster it with a following Ya
  // so that when the Virama+Ya form ya-phala, this is not separated from the
  // preceding letter by any letter-spacing or justification.
  const char16_t kBengaliVirama = 0x09CD;
  const char16_t kBengaliYa = 0x09AF;
  bool prevWasHyphen = false;
  while (pos < aLength) {
    const char16_t ch = aString[pos];
    if (prevWasHyphen) {
      if (nsContentUtils::IsAlphanumeric(ch)) {
        glyphs[pos].SetCanBreakBefore(
            CompressedGlyph::FLAG_BREAK_TYPE_EMERGENCY_WRAP);
      }
      prevWasHyphen = false;
    }
    if (ch == char16_t(' ') || ch == kIdeographicSpace) {
      glyphs[pos].SetIsSpace();
    } else if (nsContentUtils::IsHyphen(ch) && pos &&
               nsContentUtils::IsAlphanumeric(aString[pos - 1])) {
      prevWasHyphen = true;
    } else if (ch == kBengaliYa) {
      // Unless we're at the start, check for a preceding virama.
      if (pos > 0 && aString[pos - 1] == kBengaliVirama) {
        glyphs[pos] = extendCluster;
      }
    }
    // advance iter to the next cluster-start (or end of text)
    const uint32_t nextPos = *iter.Next();
    // step past the first char of the cluster
    ++pos;
    // mark all the rest as cluster-continuations
    for (; pos < nextPos; ++pos) {
      glyphs[pos] = extendCluster;
    }
  }
}

void gfxShapedText::SetupClusterBoundaries(uint32_t aOffset,
                                           const uint8_t* aString,
                                           uint32_t aLength) {
  CompressedGlyph* glyphs = GetCharacterGlyphs() + aOffset;
  uint32_t pos = 0;
  bool prevWasHyphen = false;
  while (pos < aLength) {
    uint8_t ch = aString[pos];
    if (prevWasHyphen) {
      if (nsContentUtils::IsAlphanumeric(ch)) {
        glyphs->SetCanBreakBefore(
            CompressedGlyph::FLAG_BREAK_TYPE_EMERGENCY_WRAP);
      }
      prevWasHyphen = false;
    }
    if (ch == uint8_t(' ')) {
      glyphs->SetIsSpace();
    } else if (ch == uint8_t('-') && pos &&
               nsContentUtils::IsAlphanumeric(aString[pos - 1])) {
      prevWasHyphen = true;
    }
    ++pos;
    ++glyphs;
  }
}

gfxShapedText::DetailedGlyph* gfxShapedText::AllocateDetailedGlyphs(
    uint32_t aIndex, uint32_t aCount) {
  NS_ASSERTION(aIndex < GetLength(), "Index out of range");

  if (!mDetailedGlyphs) {
    mDetailedGlyphs = MakeUnique<DetailedGlyphStore>();
  }

  return mDetailedGlyphs->Allocate(aIndex, aCount);
}

void gfxShapedText::SetDetailedGlyphs(uint32_t aIndex, uint32_t aGlyphCount,
                                      const DetailedGlyph* aGlyphs) {
  CompressedGlyph& g = GetCharacterGlyphs()[aIndex];

  MOZ_ASSERT(aIndex > 0 || g.IsLigatureGroupStart(),
             "First character can't be a ligature continuation!");

  if (aGlyphCount > 0) {
    DetailedGlyph* details = AllocateDetailedGlyphs(aIndex, aGlyphCount);
    memcpy(details, aGlyphs, sizeof(DetailedGlyph) * aGlyphCount);
  }

  g.SetGlyphCount(aGlyphCount);
}

#define ZWNJ 0x200C
#define ZWJ 0x200D
static inline bool IsIgnorable(uint32_t aChar) {
  return (IsDefaultIgnorable(aChar)) || aChar == ZWNJ || aChar == ZWJ;
}

void gfxShapedText::SetMissingGlyph(uint32_t aIndex, uint32_t aChar,
                                    gfxFont* aFont) {
  CompressedGlyph& g = GetCharacterGlyphs()[aIndex];
  uint8_t category = GetGeneralCategory(aChar);
  if (category >= HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK &&
      category <= HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) {
    g.SetComplex(false, true);
  }

  // Leaving advance as zero will prevent drawing the hexbox for ignorables.
  int32_t advance = 0;
  if (!IsIgnorable(aChar)) {
    gfxFloat width =
        std::max(aFont->GetMetrics(nsFontMetrics::eHorizontal).aveCharWidth,
                 gfxFloat(gfxFontMissingGlyphs::GetDesiredMinWidth(
                     aChar, mAppUnitsPerDevUnit)));
    advance = int32_t(width * mAppUnitsPerDevUnit);
  }
  DetailedGlyph detail = {aChar, advance, gfx::Point()};
  SetDetailedGlyphs(aIndex, 1, &detail);
  g.SetMissing();
}

bool gfxShapedText::FilterIfIgnorable(uint32_t aIndex, uint32_t aCh) {
  if (IsIgnorable(aCh)) {
    // There are a few default-ignorables of Letter category (currently,
    // just the Hangul filler characters) that we'd better not discard
    // if they're followed by additional characters in the same cluster.
    // Some fonts use them to carry the width of a whole cluster of
    // combining jamos; see bug 1238243.
    auto* charGlyphs = GetCharacterGlyphs();
    if (GetGenCategory(aCh) == nsUGenCategory::kLetter &&
        aIndex + 1 < GetLength() && !charGlyphs[aIndex + 1].IsClusterStart()) {
      return false;
    }
    // A compressedGlyph that is set to MISSING but has no DetailedGlyphs list
    // will be zero-width/invisible, which is what we want here.
    CompressedGlyph& g = charGlyphs[aIndex];
    g.SetComplex(g.IsClusterStart(), g.IsLigatureGroupStart()).SetMissing();
    return true;
  }
  return false;
}

void gfxShapedText::ApplyTrackingToClusters(gfxFloat aTrackingAdjustment,
                                            uint32_t aOffset,
                                            uint32_t aLength) {
  int32_t appUnitAdjustment =
      NS_round(aTrackingAdjustment * gfxFloat(mAppUnitsPerDevUnit));
  CompressedGlyph* charGlyphs = GetCharacterGlyphs();
  for (uint32_t i = aOffset; i < aOffset + aLength; ++i) {
    CompressedGlyph* glyphData = charGlyphs + i;
    if (glyphData->IsSimpleGlyph()) {
      // simple glyphs ==> just add the advance
      int32_t advance = glyphData->GetSimpleAdvance();
      if (advance > 0) {
        advance = std::max(0, advance + appUnitAdjustment);
        if (CompressedGlyph::IsSimpleAdvance(advance)) {
          glyphData->SetSimpleGlyph(advance, glyphData->GetSimpleGlyph());
        } else {
          // rare case, tested by making this the default
          uint32_t glyphIndex = glyphData->GetSimpleGlyph();
          // convert the simple CompressedGlyph to an empty complex record
          glyphData->SetComplex(true, true);
          // then set its details (glyph ID with its new advance)
          DetailedGlyph detail = {glyphIndex, advance, gfx::Point()};
          SetDetailedGlyphs(i, 1, &detail);
        }
      }
    } else {
      // complex glyphs ==> add offset at cluster/ligature boundaries
      uint32_t detailedLength = glyphData->GetGlyphCount();
      if (detailedLength) {
        DetailedGlyph* details = GetDetailedGlyphs(i);
        if (!details) {
          continue;
        }
        auto& advance = IsRightToLeft() ? details[0].mAdvance
                                        : details[detailedLength - 1].mAdvance;
        if (advance > 0) {
          advance = std::max(0, advance + appUnitAdjustment);
        }
      }
    }
  }
}

size_t gfxShapedWord::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
  size_t total = aMallocSizeOf(this);
  if (mDetailedGlyphs) {
    total += mDetailedGlyphs->SizeOfIncludingThis(aMallocSizeOf);
  }
  return total;
}

float gfxFont::AngleForSyntheticOblique() const {
  // First check conditions that mean no synthetic slant should be used:
  if (mStyle.style == FontSlantStyle::NORMAL) {
    return 0.0f;  // Requested style is 'normal'.
  }
  if (!mStyle.allowSyntheticStyle) {
    return 0.0f;  // Synthetic obliquing is disabled.
  }
  if (!mFontEntry->MayUseSyntheticSlant()) {
    return 0.0f;  // The resource supports "real" slant, so don't synthesize.
  }

  // If style calls for italic, and face doesn't support it, use default
  // oblique angle as a simulation.
  if (mStyle.style.IsItalic()) {
    return mFontEntry->SupportsItalic()
               ? 0.0f
               : FontSlantStyle::DEFAULT_OBLIQUE_DEGREES;
  }

  // OK, we're going to use synthetic oblique: return the requested angle.
  return mStyle.style.ObliqueAngle();
}

float gfxFont::SkewForSyntheticOblique() const {
  // Precomputed value of tan(kDefaultAngle), the default italic/oblique slant;
  // avoids calling tan() at runtime except for custom oblique values.
  static const float kTanDefaultAngle =
      tan(FontSlantStyle::DEFAULT_OBLIQUE_DEGREES * (M_PI / 180.0));

  float angle = AngleForSyntheticOblique();
  if (angle == 0.0f) {
    return 0.0f;
  } else if (angle == FontSlantStyle::DEFAULT_OBLIQUE_DEGREES) {
    return kTanDefaultAngle;
  } else {
    return tan(angle * (M_PI / 180.0));
  }
}

void gfxFont::RunMetrics::CombineWith(const RunMetrics& aOther,
                                      bool aOtherIsOnLeft) {
  mAscent = std::max(mAscent, aOther.mAscent);
  mDescent = std::max(mDescent, aOther.mDescent);
  if (aOtherIsOnLeft) {
    mBoundingBox = (mBoundingBox + gfxPoint(aOther.mAdvanceWidth, 0))
                       .Union(aOther.mBoundingBox);
  } else {
    mBoundingBox =
        mBoundingBox.Union(aOther.mBoundingBox + gfxPoint(mAdvanceWidth, 0));
  }
  mAdvanceWidth += aOther.mAdvanceWidth;
}

gfxFont::gfxFont(const RefPtr<UnscaledFont>& aUnscaledFont,
                 gfxFontEntry* aFontEntry, const gfxFontStyle* aFontStyle,
                 AntialiasOption anAAOption)
    : mFontEntry(aFontEntry),
      mLock("gfxFont lock"),
      mUnscaledFont(aUnscaledFont),
      mStyle(*aFontStyle),
      mAdjustedSize(-1.0),       // negative to indicate "not yet initialized"
      mFUnitsConvFactor(-1.0f),  // negative to indicate "not yet initialized"
      mAntialiasOption(anAAOption),
      mIsValid(true),
      mApplySyntheticBold(false),
      mKerningEnabled(false),
      mMathInitialized(false) {
#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
  ++gFontCount;
#endif

  if (MOZ_UNLIKELY(StaticPrefs::gfx_text_disable_aa_AtStartup())) {
    mAntialiasOption = kAntialiasNone;
  }

  // Turn off AA for Ahem for testing purposes when requested.
  if (MOZ_UNLIKELY(StaticPrefs::gfx_font_rendering_ahem_antialias_none() &&
                   mFontEntry->FamilyName().EqualsLiteral("Ahem"))) {
    mAntialiasOption = kAntialiasNone;
  }

  mKerningSet = HasFeatureSet(HB_TAG('k', 'e', 'r', 'n'), mKerningEnabled);

  // Ensure the gfxFontEntry's unitsPerEm and extents fields are initialized,
  // so that GetFontExtents can use them without risk of races.
  Unused << mFontEntry->UnitsPerEm();
}

gfxFont::~gfxFont() {
  mFontEntry->NotifyFontDestroyed(this);

  // Delete objects owned through atomic pointers. (Some of these may be null,
  // but that's OK.)
  delete mVerticalMetrics.exchange(nullptr);
  delete mHarfBuzzShaper.exchange(nullptr);
  delete mGraphiteShaper.exchange(nullptr);
  delete mMathTable.exchange(nullptr);
  delete mNonAAFont.exchange(nullptr);

  if (auto* scaledFont = mAzureScaledFont.exchange(nullptr)) {
    scaledFont->Release();
  }

  if (mGlyphChangeObservers) {
    for (const auto& key : *mGlyphChangeObservers) {
      key->ForgetFont();
    }
  }
}

// Work out whether cairo will snap inter-glyph spacing to pixels.
//
// Layout does not align text to pixel boundaries, so, with font drawing
// backends that snap glyph positions to pixels, it is important that
// inter-glyph spacing within words is always an integer number of pixels.
// This ensures that the drawing backend snaps all of the word's glyphs in the
// same direction and so inter-glyph spacing remains the same.
//
gfxFont::RoundingFlags gfxFont::GetRoundOffsetsToPixels(
    DrawTarget* aDrawTarget) {
  // Could do something fancy here for ScaleFactors of
  // AxisAlignedTransforms, but we leave things simple.
  // Not much point rounding if a matrix will mess things up anyway.
  // Also check if the font already knows hint metrics is off...
  if (aDrawTarget->GetTransform().HasNonTranslation() || !ShouldHintMetrics()) {
    return RoundingFlags(0);
  }

  cairo_t* cr = static_cast<cairo_t*>(
      aDrawTarget->GetNativeSurface(NativeSurfaceType::CAIRO_CONTEXT));
  if (cr) {
    cairo_surface_t* target = cairo_get_target(cr);

    // Check whether the cairo surface's font options hint metrics.
    cairo_font_options_t* fontOptions = cairo_font_options_create();
    cairo_surface_get_font_options(target, fontOptions);
    cairo_hint_metrics_t hintMetrics =
        cairo_font_options_get_hint_metrics(fontOptions);
    cairo_font_options_destroy(fontOptions);

    switch (hintMetrics) {
      case CAIRO_HINT_METRICS_OFF:
        return RoundingFlags(0);
      case CAIRO_HINT_METRICS_ON:
        return RoundingFlags::kRoundX | RoundingFlags::kRoundY;
      default:
        break;
    }
  }

  if (ShouldRoundXOffset(cr)) {
    return RoundingFlags::kRoundX | RoundingFlags::kRoundY;
  } else {
    return RoundingFlags::kRoundY;
  }
}

gfxHarfBuzzShaper* gfxFont::GetHarfBuzzShaper() {
  if (!mHarfBuzzShaper) {
    auto* shaper = new gfxHarfBuzzShaper(this);
    shaper->Initialize();
    if (!mHarfBuzzShaper.compareExchange(nullptr, shaper)) {
      delete shaper;
    }
  }
  gfxHarfBuzzShaper* shaper = mHarfBuzzShaper;
  return shaper->IsInitialized() ? shaper : nullptr;
}

gfxFloat gfxFont::GetGlyphAdvance(uint16_t aGID, bool aVertical) {
  if (!aVertical && ProvidesGlyphWidths()) {
    return GetGlyphWidth(aGID) / 65536.0;
  }
  if (mFUnitsConvFactor < 0.0f) {
    // Metrics haven't been initialized; lock while we do that.
    AutoWriteLock lock(mLock);
    if (mFUnitsConvFactor < 0.0f) {
      GetMetrics(nsFontMetrics::eHorizontal);
    }
  }
  NS_ASSERTION(mFUnitsConvFactor >= 0.0f,
               "missing font unit conversion factor");
  if (gfxHarfBuzzShaper* shaper = GetHarfBuzzShaper()) {
    if (aVertical) {
      // Note that GetGlyphVAdvance may return -1 to indicate it was unable
      // to retrieve vertical metrics; in that case we fall back to the
      // aveCharWidth value as a default advance.
      int32_t advance = shaper->GetGlyphVAdvance(aGID);
      if (advance < 0) {
        return GetMetrics(nsFontMetrics::eVertical).aveCharWidth;
      }
      return advance / 65536.0;
    }
    return shaper->GetGlyphHAdvance(aGID) / 65536.0;
  }
  return 0.0;
}

gfxFloat gfxFont::GetCharAdvance(uint32_t aUnicode, bool aVertical) {
  uint32_t gid = 0;
  if (ProvidesGetGlyph()) {
    gid = GetGlyph(aUnicode, 0);
  } else {
    if (gfxHarfBuzzShaper* shaper = GetHarfBuzzShaper()) {
      gid = shaper->GetNominalGlyph(aUnicode);
    }
  }
  if (!gid) {
    return -1.0;
  }
  return GetGlyphAdvance(gid, aVertical);
}

static void CollectLookupsByFeature(hb_face_t* aFace, hb_tag_t aTableTag,
                                    uint32_t aFeatureIndex,
                                    hb_set_t* aLookups) {
  uint32_t lookups[32];
  uint32_t i, len, offset;

  offset = 0;
  do {
    len = std::size(lookups);
    hb_ot_layout_feature_get_lookups(aFace, aTableTag, aFeatureIndex, offset,
                                     &len, lookups);
    for (i = 0; i < len; i++) {
      hb_set_add(aLookups, lookups[i]);
    }
    offset += len;
  } while (len == std::size(lookups));
}

static void CollectLookupsByLanguage(
    hb_face_t* aFace, hb_tag_t aTableTag,
    const nsTHashSet<uint32_t>& aSpecificFeatures, hb_set_t* aOtherLookups,
    hb_set_t* aSpecificFeatureLookups, uint32_t aScriptIndex,
    uint32_t aLangIndex) {
  uint32_t reqFeatureIndex;
  if (hb_ot_layout_language_get_required_feature_index(
          aFace, aTableTag, aScriptIndex, aLangIndex, &reqFeatureIndex)) {
    CollectLookupsByFeature(aFace, aTableTag, reqFeatureIndex, aOtherLookups);
  }

  uint32_t featureIndexes[32];
  uint32_t i, len, offset;

  offset = 0;
  do {
    len = std::size(featureIndexes);
    hb_ot_layout_language_get_feature_indexes(aFace, aTableTag, aScriptIndex,
                                              aLangIndex, offset, &len,
                                              featureIndexes);

    for (i = 0; i < len; i++) {
      uint32_t featureIndex = featureIndexes[i];

      // get the feature tag
      hb_tag_t featureTag;
      uint32_t tagLen = 1;
      hb_ot_layout_language_get_feature_tags(aFace, aTableTag, aScriptIndex,
                                             aLangIndex, offset + i, &tagLen,
                                             &featureTag);

      // collect lookups
      hb_set_t* lookups = aSpecificFeatures.Contains(featureTag)
                              ? aSpecificFeatureLookups
                              : aOtherLookups;
      CollectLookupsByFeature(aFace, aTableTag, featureIndex, lookups);
    }
    offset += len;
  } while (len == std::size(featureIndexes));
}

static bool HasLookupRuleWithGlyphByScript(
    hb_face_t* aFace, hb_tag_t aTableTag, hb_tag_t aScriptTag,
    uint32_t aScriptIndex, uint16_t aGlyph,
    const nsTHashSet<uint32_t>& aDefaultFeatures,
    bool& aHasDefaultFeatureWithGlyph) {
  uint32_t numLangs, lang;
  hb_set_t* defaultFeatureLookups = hb_set_create();
  hb_set_t* nonDefaultFeatureLookups = hb_set_create();

  // default lang
  CollectLookupsByLanguage(aFace, aTableTag, aDefaultFeatures,
                           nonDefaultFeatureLookups, defaultFeatureLookups,
                           aScriptIndex, HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX);

  // iterate over langs
  numLangs = hb_ot_layout_script_get_language_tags(
      aFace, aTableTag, aScriptIndex, 0, nullptr, nullptr);
  for (lang = 0; lang < numLangs; lang++) {
    CollectLookupsByLanguage(aFace, aTableTag, aDefaultFeatures,
                             nonDefaultFeatureLookups, defaultFeatureLookups,
                             aScriptIndex, lang);
  }

  // look for the glyph among default feature lookups
  aHasDefaultFeatureWithGlyph = false;
  hb_set_t* glyphs = hb_set_create();
  hb_codepoint_t index = -1;
  while (hb_set_next(defaultFeatureLookups, &index)) {
    hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index, glyphs, glyphs,
                                       glyphs, nullptr);
    if (hb_set_has(glyphs, aGlyph)) {
      aHasDefaultFeatureWithGlyph = true;
      break;
    }
  }

  // look for the glyph among non-default feature lookups
  // if no default feature lookups contained spaces
  bool hasNonDefaultFeatureWithGlyph = false;
  if (!aHasDefaultFeatureWithGlyph) {
    hb_set_clear(glyphs);
    index = -1;
    while (hb_set_next(nonDefaultFeatureLookups, &index)) {
      hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index, glyphs,
                                         glyphs, glyphs, nullptr);
      if (hb_set_has(glyphs, aGlyph)) {
        hasNonDefaultFeatureWithGlyph = true;
        break;
      }
    }
  }

  hb_set_destroy(glyphs);
  hb_set_destroy(defaultFeatureLookups);
  hb_set_destroy(nonDefaultFeatureLookups);

  return aHasDefaultFeatureWithGlyph || hasNonDefaultFeatureWithGlyph;
}

static void HasLookupRuleWithGlyph(hb_face_t* aFace, hb_tag_t aTableTag,
                                   bool& aHasGlyph, hb_tag_t aSpecificFeature,
                                   bool& aHasGlyphSpecific, uint16_t aGlyph) {
  // iterate over the scripts in the font
  uint32_t numScripts, numLangs, script, lang;
  hb_set_t* otherLookups = hb_set_create();
  hb_set_t* specificFeatureLookups = hb_set_create();
  nsTHashSet<uint32_t> specificFeature(1);

  specificFeature.Insert(aSpecificFeature);

  numScripts =
      hb_ot_layout_table_get_script_tags(aFace, aTableTag, 0, nullptr, nullptr);

  for (script = 0; script < numScripts; script++) {
    // default lang
    CollectLookupsByLanguage(aFace, aTableTag, specificFeature, otherLookups,
                             specificFeatureLookups, script,
                             HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX);

    // iterate over langs
    numLangs = hb_ot_layout_script_get_language_tags(
        aFace, HB_OT_TAG_GPOS, script, 0, nullptr, nullptr);
    for (lang = 0; lang < numLangs; lang++) {
      CollectLookupsByLanguage(aFace, aTableTag, specificFeature, otherLookups,
                               specificFeatureLookups, script, lang);
    }
  }

  // look for the glyph among non-specific feature lookups
  hb_set_t* glyphs = hb_set_create();
  hb_codepoint_t index = -1;
  while (hb_set_next(otherLookups, &index)) {
    hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index, glyphs, glyphs,
                                       glyphs, nullptr);
    if (hb_set_has(glyphs, aGlyph)) {
      aHasGlyph = true;
      break;
    }
  }

  // look for the glyph among specific feature lookups
  hb_set_clear(glyphs);
  index = -1;
  while (hb_set_next(specificFeatureLookups, &index)) {
    hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index, glyphs, glyphs,
                                       glyphs, nullptr);
    if (hb_set_has(glyphs, aGlyph)) {
      aHasGlyphSpecific = true;
      break;
    }
  }

  hb_set_destroy(glyphs);
  hb_set_destroy(specificFeatureLookups);
  hb_set_destroy(otherLookups);
}

Atomic<nsTHashMap<nsUint32HashKey, intl::Script>*> gfxFont::sScriptTagToCode;
Atomic<nsTHashSet<uint32_t>*> gfxFont::sDefaultFeatures;

static inline bool HasSubstitution(uint32_t* aBitVector, intl::Script aScript) {
  return (aBitVector[static_cast<uint32_t>(aScript) >> 5] &
          (1 << (static_cast<uint32_t>(aScript) & 0x1f))) != 0;
}

// union of all default substitution features across scripts
static const hb_tag_t defaultFeatures[] = {
    HB_TAG('a', 'b', 'v', 'f'), HB_TAG('a', 'b', 'v', 's'),
    HB_TAG('a', 'k', 'h', 'n'), HB_TAG('b', 'l', 'w', 'f'),
    HB_TAG('b', 'l', 'w', 's'), HB_TAG('c', 'a', 'l', 't'),
    HB_TAG('c', 'c', 'm', 'p'), HB_TAG('c', 'f', 'a', 'r'),
    HB_TAG('c', 'j', 'c', 't'), HB_TAG('c', 'l', 'i', 'g'),
    HB_TAG('f', 'i', 'n', '2'), HB_TAG('f', 'i', 'n', '3'),
    HB_TAG('f', 'i', 'n', 'a'), HB_TAG('h', 'a', 'l', 'f'),
    HB_TAG('h', 'a', 'l', 'n'), HB_TAG('i', 'n', 'i', 't'),
    HB_TAG('i', 's', 'o', 'l'), HB_TAG('l', 'i', 'g', 'a'),
    HB_TAG('l', 'j', 'm', 'o'), HB_TAG('l', 'o', 'c', 'l'),
    HB_TAG('l', 't', 'r', 'a'), HB_TAG('l', 't', 'r', 'm'),
    HB_TAG('m', 'e', 'd', '2'), HB_TAG('m', 'e', 'd', 'i'),
    HB_TAG('m', 's', 'e', 't'), HB_TAG('n', 'u', 'k', 't'),
    HB_TAG('p', 'r', 'e', 'f'), HB_TAG('p', 'r', 'e', 's'),
    HB_TAG('p', 's', 't', 'f'), HB_TAG('p', 's', 't', 's'),
    HB_TAG('r', 'c', 'l', 't'), HB_TAG('r', 'l', 'i', 'g'),
    HB_TAG('r', 'k', 'r', 'f'), HB_TAG('r', 'p', 'h', 'f'),
    HB_TAG('r', 't', 'l', 'a'), HB_TAG('r', 't', 'l', 'm'),
    HB_TAG('t', 'j', 'm', 'o'), HB_TAG('v', 'a', 't', 'u'),
    HB_TAG('v', 'e', 'r', 't'), HB_TAG('v', 'j', 'm', 'o')};

void gfxFont::CheckForFeaturesInvolvingSpace() const {
  gfxFontEntry::SpaceFeatures flags = gfxFontEntry::SpaceFeatures::None;

  auto setFlags =
      MakeScopeExit([&]() { mFontEntry->mHasSpaceFeatures = flags; });

  bool log = LOG_FONTINIT_ENABLED();
  TimeStamp start;
  if (MOZ_UNLIKELY(log)) {
    start = TimeStamp::Now();
  }

  uint32_t spaceGlyph = GetSpaceGlyph();
  if (!spaceGlyph) {
    return;
  }

  auto face(GetFontEntry()->GetHBFace());

  // GSUB lookups - examine per script
  if (hb_ot_layout_has_substitution(face)) {
    // Get the script ==> code hashtable, creating it on first use.
    nsTHashMap<nsUint32HashKey, Script>* tagToCode = sScriptTagToCode;
    if (!tagToCode) {
      tagToCode = new nsTHashMap<nsUint32HashKey, Script>(
          size_t(Script::NUM_SCRIPT_CODES));
      tagToCode->InsertOrUpdate(HB_TAG('D', 'F', 'L', 'T'), Script::COMMON);
      // Ensure that we don't try to look at script codes beyond what the
      // current version of ICU (at runtime -- in case of system ICU)
      // knows about.
      Script scriptCount = Script(
          std::min<int>(intl::UnicodeProperties::GetMaxNumberOfScripts() + 1,
                        int(Script::NUM_SCRIPT_CODES)));
      for (Script s = Script::ARABIC; s < scriptCount;
           s = Script(static_cast<int>(s) + 1)) {
        hb_script_t script = hb_script_t(GetScriptTagForCode(s));
        unsigned int scriptCount = 4;
        hb_tag_t scriptTags[4];
        hb_ot_tags_from_script_and_language(script, HB_LANGUAGE_INVALID,
                                            &scriptCount, scriptTags, nullptr,
                                            nullptr);
        for (unsigned int i = 0; i < scriptCount; i++) {
          tagToCode->InsertOrUpdate(scriptTags[i], s);
        }
      }
      if (!sScriptTagToCode.compareExchange(nullptr, tagToCode)) {
        // We lost a race! Discard our new table and use the winner.
        delete tagToCode;
        tagToCode = sScriptTagToCode;
      }
    }

    // Set up the default-features hashset on first use.
    if (!sDefaultFeatures) {
      uint32_t numDefaultFeatures = std::size(defaultFeatures);
      auto* set = new nsTHashSet<uint32_t>(numDefaultFeatures);
      for (uint32_t i = 0; i < numDefaultFeatures; i++) {
        set->Insert(defaultFeatures[i]);
      }
      if (!sDefaultFeatures.compareExchange(nullptr, set)) {
        delete set;
      }
    }

    // iterate over the scripts in the font
    hb_tag_t scriptTags[8];

    uint32_t len, offset = 0;
    do {
      len = std::size(scriptTags);
      hb_ot_layout_table_get_script_tags(face, HB_OT_TAG_GSUB, offset, &len,
                                         scriptTags);
      for (uint32_t i = 0; i < len; i++) {
        bool isDefaultFeature = false;
        Script s;
        if (!HasLookupRuleWithGlyphByScript(
                face, HB_OT_TAG_GSUB, scriptTags[i], offset + i, spaceGlyph,
                *sDefaultFeatures, isDefaultFeature) ||
            !tagToCode->Get(scriptTags[i], &s)) {
          continue;
        }
        flags = flags | gfxFontEntry::SpaceFeatures::HasFeatures;
        uint32_t index = static_cast<uint32_t>(s) >> 5;
        uint32_t bit = static_cast<uint32_t>(s) & 0x1f;
        if (isDefaultFeature) {
          mFontEntry->mDefaultSubSpaceFeatures[index] |= (1 << bit);
        } else {
          mFontEntry->mNonDefaultSubSpaceFeatures[index] |= (1 << bit);
        }
      }
      offset += len;
    } while (len == std::size(scriptTags));
  }

  // spaces in default features of default script?
  // ==> can't use word cache, skip GPOS analysis
  bool canUseWordCache = true;
  if (HasSubstitution(mFontEntry->mDefaultSubSpaceFeatures, Script::COMMON)) {
    canUseWordCache = false;
  }

  // GPOS lookups - distinguish kerning from non-kerning features
  if (canUseWordCache && hb_ot_layout_has_positioning(face)) {
    bool hasKerning = false, hasNonKerning = false;
    HasLookupRuleWithGlyph(face, HB_OT_TAG_GPOS, hasNonKerning,
                           HB_TAG('k', 'e', 'r', 'n'), hasKerning, spaceGlyph);
    if (hasKerning) {
      flags |= gfxFontEntry::SpaceFeatures::HasFeatures |
               gfxFontEntry::SpaceFeatures::Kerning;
    }
    if (hasNonKerning) {
      flags |= gfxFontEntry::SpaceFeatures::HasFeatures |
               gfxFontEntry::SpaceFeatures::NonKerning;
    }
  }

  if (MOZ_UNLIKELY(log)) {
    TimeDuration elapsed = TimeStamp::Now() - start;
    LOG_FONTINIT((
        "(fontinit-spacelookups) font: %s - "
        "subst default: %8.8x %8.8x %8.8x %8.8x "
        "subst non-default: %8.8x %8.8x %8.8x %8.8x "
        "kerning: %s non-kerning: %s time: %6.3f\n",
        mFontEntry->Name().get(), mFontEntry->mDefaultSubSpaceFeatures[3],
        mFontEntry->mDefaultSubSpaceFeatures[2],
        mFontEntry->mDefaultSubSpaceFeatures[1],
        mFontEntry->mDefaultSubSpaceFeatures[0],
        mFontEntry->mNonDefaultSubSpaceFeatures[3],
        mFontEntry->mNonDefaultSubSpaceFeatures[2],
        mFontEntry->mNonDefaultSubSpaceFeatures[1],
        mFontEntry->mNonDefaultSubSpaceFeatures[0],
        (mFontEntry->mHasSpaceFeatures & gfxFontEntry::SpaceFeatures::Kerning
             ? "true"
             : "false"),
        (mFontEntry->mHasSpaceFeatures & gfxFontEntry::SpaceFeatures::NonKerning
             ? "true"
             : "false"),
        elapsed.ToMilliseconds()));
  }
}

bool gfxFont::HasSubstitutionRulesWithSpaceLookups(Script aRunScript) const {
  NS_ASSERTION(GetFontEntry()->mHasSpaceFeatures !=
                   gfxFontEntry::SpaceFeatures::Uninitialized,
               "need to initialize space lookup flags");
  NS_ASSERTION(aRunScript < Script::NUM_SCRIPT_CODES, "weird script code");
  if (aRunScript == Script::INVALID || aRunScript >= Script::NUM_SCRIPT_CODES) {
    return false;
  }

  // default features have space lookups ==> true
  if (HasSubstitution(mFontEntry->mDefaultSubSpaceFeatures, Script::COMMON) ||
      HasSubstitution(mFontEntry->mDefaultSubSpaceFeatures, aRunScript)) {
    return true;
  }

  // non-default features have space lookups and some type of
  // font feature, in font or style is specified ==> true
  if ((HasSubstitution(mFontEntry->mNonDefaultSubSpaceFeatures,
                       Script::COMMON) ||
       HasSubstitution(mFontEntry->mNonDefaultSubSpaceFeatures, aRunScript)) &&
      (!mStyle.featureSettings.IsEmpty() ||
       !mFontEntry->mFeatureSettings.IsEmpty())) {
    return true;
  }

  return false;
}

tainted_boolean_hint gfxFont::SpaceMayParticipateInShaping(
    Script aRunScript) const {
  // avoid checking fonts known not to include default space-dependent features
  if (MOZ_UNLIKELY(mFontEntry->mSkipDefaultFeatureSpaceCheck)) {
    if (!mKerningSet && mStyle.featureSettings.IsEmpty() &&
        mFontEntry->mFeatureSettings.IsEmpty()) {
      return false;
    }
  }

  if (FontCanSupportGraphite()) {
    if (gfxPlatform::GetPlatform()->UseGraphiteShaping()) {
      return mFontEntry->HasGraphiteSpaceContextuals();
    }
  }

  // We record the presence of space-dependent features in the font entry
  // so that subsequent instantiations for the same font face won't
  // require us to re-check the tables; however, the actual check is done
  // by gfxFont because not all font entry subclasses know how to create
  // a harfbuzz face for introspection.
  gfxFontEntry::SpaceFeatures flags = mFontEntry->mHasSpaceFeatures;
  if (flags == gfxFontEntry::SpaceFeatures::Uninitialized) {
    CheckForFeaturesInvolvingSpace();
    flags = mFontEntry->mHasSpaceFeatures;
  }

  if (!(flags & gfxFontEntry::SpaceFeatures::HasFeatures)) {
    return false;
  }

  // if font has substitution rules or non-kerning positioning rules
  // that involve spaces, bypass
  if (HasSubstitutionRulesWithSpaceLookups(aRunScript) ||
      (flags & gfxFontEntry::SpaceFeatures::NonKerning)) {
    return true;
  }

  // if kerning explicitly enabled/disabled via font-feature-settings or
  // font-kerning and kerning rules use spaces, only bypass when enabled
  if (mKerningSet && (flags & gfxFontEntry::SpaceFeatures::Kerning)) {
    return mKerningEnabled;
  }

  return false;
}

bool gfxFont::SupportsFeature(Script aScript, uint32_t aFeatureTag) {
  if (mGraphiteShaper && gfxPlatform::GetPlatform()->UseGraphiteShaping()) {
    return GetFontEntry()->SupportsGraphiteFeature(aFeatureTag);
  }
  return GetFontEntry()->SupportsOpenTypeFeature(aScript, aFeatureTag);
}

bool gfxFont::SupportsVariantCaps(Script aScript, uint32_t aVariantCaps,
                                  bool& aFallbackToSmallCaps,
                                  bool& aSyntheticLowerToSmallCaps,
                                  bool& aSyntheticUpperToSmallCaps) {
  bool ok = true;  // cases without fallback are fine
  aFallbackToSmallCaps = false;
  aSyntheticLowerToSmallCaps = false;
  aSyntheticUpperToSmallCaps = false;
  switch (aVariantCaps) {
    case NS_FONT_VARIANT_CAPS_SMALLCAPS:
      ok = SupportsFeature(aScript, HB_TAG('s', 'm', 'c', 'p'));
      if (!ok) {
        aSyntheticLowerToSmallCaps = true;
      }
      break;
    case NS_FONT_VARIANT_CAPS_ALLSMALL:
      ok = SupportsFeature(aScript, HB_TAG('s', 'm', 'c', 'p')) &&
           SupportsFeature(aScript, HB_TAG('c', '2', 's', 'c'));
      if (!ok) {
        aSyntheticLowerToSmallCaps = true;
        aSyntheticUpperToSmallCaps = true;
      }
      break;
    case NS_FONT_VARIANT_CAPS_PETITECAPS:
      ok = SupportsFeature(aScript, HB_TAG('p', 'c', 'a', 'p'));
      if (!ok) {
        ok = SupportsFeature(aScript, HB_TAG('s', 'm', 'c', 'p'));
        aFallbackToSmallCaps = ok;
      }
      if (!ok) {
        aSyntheticLowerToSmallCaps = true;
      }
      break;
    case NS_FONT_VARIANT_CAPS_ALLPETITE:
      ok = SupportsFeature(aScript, HB_TAG('p', 'c', 'a', 'p')) &&
           SupportsFeature(aScript, HB_TAG('c', '2', 'p', 'c'));
      if (!ok) {
        ok = SupportsFeature(aScript, HB_TAG('s', 'm', 'c', 'p')) &&
             SupportsFeature(aScript, HB_TAG('c', '2', 's', 'c'));
        aFallbackToSmallCaps = ok;
      }
      if (!ok) {
        aSyntheticLowerToSmallCaps = true;
        aSyntheticUpperToSmallCaps = true;
      }
      break;
    default:
      break;
  }

  NS_ASSERTION(
      !(ok && (aSyntheticLowerToSmallCaps || aSyntheticUpperToSmallCaps)),
      "shouldn't use synthetic features if we found real ones");

  NS_ASSERTION(!(!ok && aFallbackToSmallCaps),
               "if we found a usable fallback, that counts as ok");

  return ok;
}

bool gfxFont::SupportsSubSuperscript(uint32_t aSubSuperscript,
                                     const uint8_t* aString, uint32_t aLength,
                                     Script aRunScript) {
  NS_ConvertASCIItoUTF16 unicodeString(reinterpret_cast<const char*>(aString),
                                       aLength);
  return SupportsSubSuperscript(aSubSuperscript, unicodeString.get(), aLength,
                                aRunScript);
}

bool gfxFont::SupportsSubSuperscript(uint32_t aSubSuperscript,
                                     const char16_t* aString, uint32_t aLength,
                                     Script aRunScript) {
  NS_ASSERTION(aSubSuperscript == NS_FONT_VARIANT_POSITION_SUPER ||
                   aSubSuperscript == NS_FONT_VARIANT_POSITION_SUB,
               "unknown value of font-variant-position");

  uint32_t feature = aSubSuperscript == NS_FONT_VARIANT_POSITION_SUPER
                         ? HB_TAG('s', 'u', 'p', 's')
                         : HB_TAG('s', 'u', 'b', 's');

  if (!SupportsFeature(aRunScript, feature)) {
    return false;
  }

  // xxx - for graphite, don't really know how to sniff lookups so bail
  if (mGraphiteShaper && gfxPlatform::GetPlatform()->UseGraphiteShaping()) {
    return true;
  }

  gfxHarfBuzzShaper* shaper = GetHarfBuzzShaper();
  if (!shaper) {
    return false;
  }

  // get the hbset containing input glyphs for the feature
  const hb_set_t* inputGlyphs =
      mFontEntry->InputsForOpenTypeFeature(aRunScript, feature);

  // create an hbset containing default glyphs for the script run
  hb_set_t* defaultGlyphsInRun = hb_set_create();

  // for each character, get the glyph id
  for (uint32_t i = 0; i < aLength; i++) {
    uint32_t ch = aString[i];

    if (i + 1 < aLength && NS_IS_SURROGATE_PAIR(ch, aString[i + 1])) {
      i++;
      ch = SURROGATE_TO_UCS4(ch, aString[i]);
    }

    hb_codepoint_t gid = shaper->GetNominalGlyph(ch);
    hb_set_add(defaultGlyphsInRun, gid);
  }

  // intersect with input glyphs, if size is not the same ==> fallback
  uint32_t origSize = hb_set_get_population(defaultGlyphsInRun);
  hb_set_intersect(defaultGlyphsInRun, inputGlyphs);
  uint32_t intersectionSize = hb_set_get_population(defaultGlyphsInRun);
  hb_set_destroy(defaultGlyphsInRun);

  return origSize == intersectionSize;
}

bool gfxFont::FeatureWillHandleChar(Script aRunScript, uint32_t aFeature,
                                    uint32_t aUnicode) {
  if (!SupportsFeature(aRunScript, aFeature)) {
    return false;
  }

  // xxx - for graphite, don't really know how to sniff lookups so bail
  if (mGraphiteShaper && gfxPlatform::GetPlatform()->UseGraphiteShaping()) {
    return true;
  }

  if (gfxHarfBuzzShaper* shaper = GetHarfBuzzShaper()) {
    // get the hbset containing input glyphs for the feature
    const hb_set_t* inputGlyphs =
        mFontEntry->InputsForOpenTypeFeature(aRunScript, aFeature);

    hb_codepoint_t gid = shaper->GetNominalGlyph(aUnicode);
    return hb_set_has(inputGlyphs, gid);
  }

  return false;
}

bool gfxFont::HasFeatureSet(uint32_t aFeature, bool& aFeatureOn) {
  aFeatureOn = false;

  if (mStyle.featureSettings.IsEmpty() &&
      GetFontEntry()->mFeatureSettings.IsEmpty()) {
    return false;
  }

  // add feature values from font
  bool featureSet = false;
  uint32_t i, count;

  nsTArray<gfxFontFeature>& fontFeatures = GetFontEntry()->mFeatureSettings;
  count = fontFeatures.Length();
  for (i = 0; i < count; i++) {
    const gfxFontFeature& feature = fontFeatures.ElementAt(i);
    if (feature.mTag == aFeature) {
      featureSet = true;
      aFeatureOn = (feature.mValue != 0);
    }
  }

  // add feature values from style rules
  nsTArray<gfxFontFeature>& styleFeatures = mStyle.featureSettings;
  count = styleFeatures.Length();
  for (i = 0; i < count; i++) {
    const gfxFontFeature& feature = styleFeatures.ElementAt(i);
    if (feature.mTag == aFeature) {
      featureSet = true;
      aFeatureOn = (feature.mValue != 0);
    }
  }

  return featureSet;
}

already_AddRefed<mozilla::gfx::ScaledFont> gfxFont::GetScaledFont(
    mozilla::gfx::DrawTarget* aDrawTarget) {
  mozilla::gfx::PaletteCache dummy;
  TextRunDrawParams params(dummy);
  return GetScaledFont(params);
}

void gfxFont::InitializeScaledFont(
    const RefPtr<mozilla::gfx::ScaledFont>& aScaledFont) {
  if (!aScaledFont) {
    return;
  }

  float angle = AngleForSyntheticOblique();
  if (angle != 0.0f) {
    aScaledFont->SetSyntheticObliqueAngle(angle);
  }
}

/**
* A helper function in case we need to do any rounding or other
* processing here.
*/
#define ToDeviceUnits(aAppUnits, aDevUnitsPerAppUnit) \
  (double(aAppUnits) * double(aDevUnitsPerAppUnit))

static AntialiasMode Get2DAAMode(gfxFont::AntialiasOption aAAOption) {
  switch (aAAOption) {
    case gfxFont::kAntialiasSubpixel:
      return AntialiasMode::SUBPIXEL;
    case gfxFont::kAntialiasGrayscale:
      return AntialiasMode::GRAY;
    case gfxFont::kAntialiasNone:
      return AntialiasMode::NONE;
    default:
      return AntialiasMode::DEFAULT;
  }
}

class GlyphBufferAzure {
#define AUTO_BUFFER_SIZE (2048 / sizeof(Glyph))

  typedef mozilla::image::imgDrawingParams imgDrawingParams;

public:
  GlyphBufferAzure(const TextRunDrawParams& aRunParams,
                   const FontDrawParams& aFontParams)
      : mRunParams(aRunParams),
        mFontParams(aFontParams),
        mBuffer(*mAutoBuffer.addr()),
        mBufSize(AUTO_BUFFER_SIZE),
        mCapacity(0),
        mNumGlyphs(0) {}

  ~GlyphBufferAzure() {
    if (mNumGlyphs > 0) {
      FlushGlyphs();
    }

    if (mBuffer != *mAutoBuffer.addr()) {
      free(mBuffer);
    }
  }

  // Ensure the buffer has enough space for aGlyphCount glyphs to be added,
  // considering the supplied strike multipler aStrikeCount.
  // This MUST be called before OutputGlyph is used to actually store glyph
  // records in the buffer. It may be called repeated to add further capacity
  // in case we don't know up-front exactly what will be needed.
  void AddCapacity(uint32_t aGlyphCount, uint32_t aStrikeCount) {
    // Calculate the new capacity and ensure it will fit within the maximum
    // allowed capacity.
    static const uint64_t kMaxCapacity = 64 * 1024;
    mCapacity = uint32_t(std::min(
        kMaxCapacity,
        uint64_t(mCapacity) + uint64_t(aGlyphCount) * uint64_t(aStrikeCount)));
    // See if the required capacity fits within the already-allocated space
    if (mCapacity <= mBufSize) {
      return;
    }
    // We need to grow the buffer: determine a new size, allocate, and
    // copy the existing data over if we didn't use realloc (which would
    // do it automatically).
    mBufSize = std::max(mCapacity, mBufSize * 2);
    if (mBuffer == *mAutoBuffer.addr()) {
      // switching from autobuffer to malloc, so we need to copy
      mBuffer = reinterpret_cast<Glyph*>(moz_xmalloc(mBufSize * sizeof(Glyph)));
      std::memcpy(mBuffer, *mAutoBuffer.addr(), mNumGlyphs * sizeof(Glyph));
    } else {
      mBuffer = reinterpret_cast<Glyph*>(
          moz_xrealloc(mBuffer, mBufSize * sizeof(Glyph)));
    }
  }

  void OutputGlyph(uint32_t aGlyphID, const gfx::Point& aPt) {
    // If the buffer is full, flush to make room for the new glyph.
    if (mNumGlyphs >= mCapacity) {
      // Check that AddCapacity has been used appropriately!
      MOZ_ASSERT(mCapacity > 0 && mNumGlyphs == mCapacity);
      Flush();
    }
    Glyph* glyph = mBuffer + mNumGlyphs++;
    glyph->mIndex = aGlyphID;
    glyph->mPosition = aPt;
  }

  void Flush() {
    if (mNumGlyphs > 0) {
      FlushGlyphs();
      mNumGlyphs = 0;
    }
  }

  const TextRunDrawParams& mRunParams;
  const FontDrawParams& mFontParams;

private:
  static DrawMode GetStrokeMode(DrawMode aMode) {
    return aMode & (DrawMode::GLYPH_STROKE | DrawMode::GLYPH_STROKE_UNDERNEATH);
  }

  // Render the buffered glyphs to the draw target.
  void FlushGlyphs() {
    gfx::GlyphBuffer buf;
    buf.mGlyphs = mBuffer;
    buf.mNumGlyphs = mNumGlyphs;

    const gfxContext::AzureState& state = mRunParams.context->CurrentState();

    // Draw stroke first if the UNDERNEATH flag is set in drawMode.
    if (mRunParams.strokeOpts &&
        GetStrokeMode(mRunParams.drawMode) ==
            (DrawMode::GLYPH_STROKE | DrawMode::GLYPH_STROKE_UNDERNEATH)) {
      DrawStroke(state, buf);
    }

    if (mRunParams.drawMode & DrawMode::GLYPH_FILL) {
      if (state.pattern || mFontParams.contextPaint) {
        Pattern* pat;

        RefPtr<gfxPattern> fillPattern;
        if (mFontParams.contextPaint) {
          imgDrawingParams imgParams;
          fillPattern = mFontParams.contextPaint->GetFillPattern(
              mRunParams.context->GetDrawTarget(),
              mRunParams.context->CurrentMatrixDouble(), imgParams);
        }
        if (!fillPattern) {
          if (state.pattern) {
--> --------------------

--> maximum size reached

--> --------------------

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