Quelle gfxTextRun.cpp Sprache: C

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=4 et sw=2 tw=80: */
/* 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 "gfxTextRun.h"

#include "gfx2DGlue.h"
#include "gfxContext.h"
#include "gfxFontConstants.h"
#include "gfxFontMissingGlyphs.h"
#include "gfxGlyphExtents.h"
#include "gfxHarfBuzzShaper.h"
#include "gfxPlatformFontList.h"
#include "gfxScriptItemizer.h"
#include "gfxUserFontSet.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Logging.h"  // for gfxCriticalError
#include "mozilla/gfx/PathHelpers.h"
#include "mozilla/intl/Locale.h"
#include "mozilla/intl/String.h"
#include "mozilla/intl/UnicodeProperties.h"
#include "mozilla/Likely.h"
#include "mozilla/MruCache.h"
#include "mozilla/ServoStyleSet.h"
#include "mozilla/Sprintf.h"
#include "mozilla/StaticPresData.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
#include "nsStyleConsts.h"
#include "nsStyleUtil.h"
#include "nsUnicodeProperties.h"
#include "SharedFontList-impl.h"
#include "TextDrawTarget.h"

#ifdef XP_WIN
#  include "gfxWindowsPlatform.h"
#endif

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

static const char16_t kEllipsisChar[] = {0x2026, 0x0};
static const char16_t kASCIIPeriodsChar[] = {'.', '.', '.', 0x0};

#ifdef DEBUG_roc
#  define DEBUG_TEXT_RUN_STORAGE_METRICS
#endif

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

void gfxTextRun::GlyphRunIterator::NextRun() {
  if (mReverse) {
    if (mGlyphRun == mTextRun->mGlyphRuns.begin()) {
      mGlyphRun = nullptr;
      return;
    }
    --mGlyphRun;
  } else {
    MOZ_DIAGNOSTIC_ASSERT(mGlyphRun != mTextRun->mGlyphRuns.end());
    ++mGlyphRun;
    if (mGlyphRun == mTextRun->mGlyphRuns.end()) {
      mGlyphRun = nullptr;
      return;
    }
  }
  if (mGlyphRun->mCharacterOffset >= mEndOffset) {
    mGlyphRun = nullptr;
    return;
  }
  uint32_t glyphRunEndOffset = mGlyphRun == mTextRun->mGlyphRuns.end() - 1
                                   ? mTextRun->GetLength()
                                   : (mGlyphRun + 1)->mCharacterOffset;
  if (glyphRunEndOffset < mStartOffset) {
    mGlyphRun = nullptr;
    return;
  }
  mStringEnd = std::min(mEndOffset, glyphRunEndOffset);
  mStringStart = std::max(mStartOffset, mGlyphRun->mCharacterOffset);
}

#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
static void AccountStorageForTextRun(gfxTextRun* aTextRun, int32_t aSign) {
  // Ignores detailed glyphs... we don't know when those have been constructed
  // Also ignores gfxSkipChars dynamic storage (which won't be anything
  // for preformatted text)
  // Also ignores GlyphRun array, again because it hasn't been constructed
  // by the time this gets called. If there's only one glyphrun that's stored
  // directly in the textrun anyway so no additional overhead.
  uint32_t length = aTextRun->GetLength();
  int32_t bytes = length * sizeof(gfxTextRun::CompressedGlyph);
  bytes += sizeof(gfxTextRun);
  gTextRunStorage += bytes * aSign;
  gTextRunStorageHighWaterMark =
      std::max(gTextRunStorageHighWaterMark, gTextRunStorage);
}
#endif

bool gfxTextRun::NeedsGlyphExtents() const {
  if (GetFlags() & gfx::ShapedTextFlags::TEXT_NEED_BOUNDING_BOX) {
    return true;
  }
  for (const auto& run : mGlyphRuns) {
    if (run.mFont->GetFontEntry()->IsUserFont()) {
      return true;
    }
  }
  return false;
}

// Helper for textRun creation to preallocate storage for glyph records;
// this function returns a pointer to the newly-allocated glyph storage.
// Returns nullptr if allocation fails.
void* gfxTextRun::AllocateStorageForTextRun(size_t aSize, uint32_t aLength) {
  // Allocate the storage we need, returning nullptr on failure rather than
  // throwing an exception (because web content can create huge runs).
  void* storage = malloc(aSize + aLength * sizeof(CompressedGlyph));
  if (!storage) {
    NS_WARNING("failed to allocate storage for text run!");
    return nullptr;
  }

  // Initialize the glyph storage (beyond aSize) to zero
  memset(reinterpret_cast<char*>(storage) + aSize, 0,
         aLength * sizeof(CompressedGlyph));

  return storage;
}

already_AddRefed<gfxTextRun> gfxTextRun::Create(
    const gfxTextRunFactory::Parameters* aParams, uint32_t aLength,
    gfxFontGroup* aFontGroup, gfx::ShapedTextFlags aFlags,
    nsTextFrameUtils::Flags aFlags2) {
  void* storage = AllocateStorageForTextRun(sizeof(gfxTextRun), aLength);
  if (!storage) {
    return nullptr;
  }

  RefPtr<gfxTextRun> result =
      new (storage) gfxTextRun(aParams, aLength, aFontGroup, aFlags, aFlags2);
  return result.forget();
}

gfxTextRun::gfxTextRun(const gfxTextRunFactory::Parameters* aParams,
                       uint32_t aLength, gfxFontGroup* aFontGroup,
                       gfx::ShapedTextFlags aFlags,
                       nsTextFrameUtils::Flags aFlags2)
    : gfxShapedText(aLength, aFlags, aParams->mAppUnitsPerDevUnit),
      mUserData(aParams->mUserData),
      mFontGroup(aFontGroup),
      mFlags2(aFlags2),
      mReleasedFontGroup(false),
      mReleasedFontGroupSkippedDrawing(false),
      mShapingState(eShapingState_Normal) {
  NS_ASSERTION(mAppUnitsPerDevUnit > 0, "Invalid app unit scale");
  NS_ADDREF(mFontGroup);

#ifndef RELEASE_OR_BETA
  gfxTextPerfMetrics* tp = aFontGroup->GetTextPerfMetrics();
  if (tp) {
    tp->current.textrunConst++;
  }
#endif

  mCharacterGlyphs = reinterpret_cast<CompressedGlyph*>(this + 1);

  if (aParams->mSkipChars) {
    mSkipChars.TakeFrom(aParams->mSkipChars);
  }

#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
  AccountStorageForTextRun(this, 1);
#endif

  mDontSkipDrawing =
      !!(aFlags2 & nsTextFrameUtils::Flags::DontSkipDrawingForPendingUserFonts);
}

gfxTextRun::~gfxTextRun() {
#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
  AccountStorageForTextRun(this, -1);
#endif
#ifdef DEBUG
  // Make it easy to detect a dead text run
  mFlags = ~gfx::ShapedTextFlags();
  mFlags2 = ~nsTextFrameUtils::Flags();
#endif

  // The cached ellipsis textrun (if any) in a fontgroup will have already
  // been told to release its reference to the group, so we mustn't do that
  // again here.
  if (!mReleasedFontGroup) {
#ifndef RELEASE_OR_BETA
    gfxTextPerfMetrics* tp = mFontGroup->GetTextPerfMetrics();
    if (tp) {
      tp->current.textrunDestr++;
    }
#endif
    NS_RELEASE(mFontGroup);
  }
}

void gfxTextRun::ReleaseFontGroup() {
  NS_ASSERTION(!mReleasedFontGroup, "doubly released!");

  // After dropping our reference to the font group, we'll no longer be able
  // to get up-to-date results for ShouldSkipDrawing().  Store the current
  // value in mReleasedFontGroupSkippedDrawing.
  //
  // (It doesn't actually matter that we can't get up-to-date results for
  // ShouldSkipDrawing(), since the only text runs that we call
  // ReleaseFontGroup() for are ellipsis text runs, and we ask the font
  // group for a new ellipsis text run each time we want to draw one,
  // and ensure that the cached one is cleared in ClearCachedData() when
  // font loading status changes.)
  mReleasedFontGroupSkippedDrawing = mFontGroup->ShouldSkipDrawing();

  NS_RELEASE(mFontGroup);
  mReleasedFontGroup = true;
}

bool gfxTextRun::SetPotentialLineBreaks(Range aRange,
                                        const uint8_t* aBreakBefore) {
  NS_ASSERTION(aRange.end <= GetLength(), "Overflow");

  uint32_t changed = 0;
  CompressedGlyph* cg = mCharacterGlyphs + aRange.start;
  const CompressedGlyph* const end = cg + aRange.Length();
  while (cg < end) {
    uint8_t canBreak = *aBreakBefore++;
    if (canBreak && !cg->IsClusterStart()) {
      // XXX If we replace the line-breaker with one based more closely
      // on UAX#14 (e.g. using ICU), this may not be needed any more.
      // Avoid possible breaks inside a cluster, EXCEPT when the previous
      // character was a space (compare UAX#14 rules LB9, LB10).
      if (cg == mCharacterGlyphs || !(cg - 1)->CharIsSpace()) {
        canBreak = CompressedGlyph::FLAG_BREAK_TYPE_NONE;
      }
    }
    // If a break is allowed here, set the break flag, but don't clear a
    // possible pre-existing emergency-break flag already in the run.
    if (canBreak) {
      changed |= cg->SetCanBreakBefore(canBreak);
    }
    ++cg;
  }
  return changed != 0;
}

gfxTextRun::LigatureData gfxTextRun::ComputeLigatureData(
    Range aPartRange, const PropertyProvider* aProvider) const {
  NS_ASSERTION(aPartRange.start < aPartRange.end,
               "Computing ligature data for empty range");
  NS_ASSERTION(aPartRange.end <= GetLength(), "Character length overflow");

  LigatureData result;
  const CompressedGlyph* charGlyphs = mCharacterGlyphs;

  uint32_t i;
  for (i = aPartRange.start; !charGlyphs[i].IsLigatureGroupStart(); --i) {
    NS_ASSERTION(i > 0, "Ligature at the start of the run??");
  }
  result.mRange.start = i;
  for (i = aPartRange.start + 1;
       i < GetLength() && !charGlyphs[i].IsLigatureGroupStart(); ++i) {
  }
  result.mRange.end = i;

  int32_t ligatureWidth = GetAdvanceForGlyphs(result.mRange);
  // Count the number of started clusters we have seen
  uint32_t totalClusterCount = 0;
  uint32_t partClusterIndex = 0;
  uint32_t partClusterCount = 0;
  for (i = result.mRange.start; i < result.mRange.end; ++i) {
    // Treat the first character of the ligature as the start of a
    // cluster for our purposes of allocating ligature width to its
    // characters.
    if (i == result.mRange.start || charGlyphs[i].IsClusterStart()) {
      ++totalClusterCount;
      if (i < aPartRange.start) {
        ++partClusterIndex;
      } else if (i < aPartRange.end) {
        ++partClusterCount;
      }
    }
  }
  NS_ASSERTION(totalClusterCount > 0, "Ligature involving no clusters??");
  result.mPartAdvance = partClusterIndex * (ligatureWidth / totalClusterCount);
  result.mPartWidth = partClusterCount * (ligatureWidth / totalClusterCount);

  // Any rounding errors are apportioned to the final part of the ligature,
  // so that measuring all parts of a ligature and summing them is equal to
  // the ligature width.
  if (aPartRange.end == result.mRange.end) {
    gfxFloat allParts = totalClusterCount * (ligatureWidth / totalClusterCount);
    result.mPartWidth += ligatureWidth - allParts;
  }

  if (partClusterCount == 0) {
    // nothing to draw
    result.mClipBeforePart = result.mClipAfterPart = true;
  } else {
    // Determine whether we should clip before or after this part when
    // drawing its slice of the ligature.
    // We need to clip before the part if any cluster is drawn before
    // this part.
    result.mClipBeforePart = partClusterIndex > 0;
    // We need to clip after the part if any cluster is drawn after
    // this part.
    result.mClipAfterPart =
        partClusterIndex + partClusterCount < totalClusterCount;
  }

  if (aProvider && (mFlags & gfx::ShapedTextFlags::TEXT_ENABLE_SPACING)) {
    gfxFont::Spacing spacing;
    if (aPartRange.start == result.mRange.start) {
      aProvider->GetSpacing(Range(aPartRange.start, aPartRange.start + 1),
                            &spacing);
      result.mPartWidth += spacing.mBefore;
    }
    if (aPartRange.end == result.mRange.end) {
      aProvider->GetSpacing(Range(aPartRange.end - 1, aPartRange.end),
                            &spacing);
      result.mPartWidth += spacing.mAfter;
    }
  }

  return result;
}

gfxFloat gfxTextRun::ComputePartialLigatureWidth(
    Range aPartRange, const PropertyProvider* aProvider) const {
  if (aPartRange.start >= aPartRange.end) return 0;
  LigatureData data = ComputeLigatureData(aPartRange, aProvider);
  return data.mPartWidth;
}

int32_t gfxTextRun::GetAdvanceForGlyphs(Range aRange) const {
  int32_t advance = 0;
  for (auto i = aRange.start; i < aRange.end; ++i) {
    advance += GetAdvanceForGlyph(i);
  }
  return advance;
}

static void GetAdjustedSpacing(
    const gfxTextRun* aTextRun, gfxTextRun::Range aRange,
    const gfxTextRun::PropertyProvider& aProvider,
    gfxTextRun::PropertyProvider::Spacing* aSpacing) {
  if (aRange.start >= aRange.end) {
    return;
  }

  aProvider.GetSpacing(aRange, aSpacing);

#ifdef DEBUG
  // Check to see if we have spacing inside ligatures

  const gfxTextRun::CompressedGlyph* charGlyphs =
      aTextRun->GetCharacterGlyphs();
  uint32_t i;

  for (i = aRange.start; i < aRange.end; ++i) {
    if (!charGlyphs[i].IsLigatureGroupStart()) {
      NS_ASSERTION(i == aRange.start || aSpacing[i - aRange.start].mBefore == 0,
                   "Before-spacing inside a ligature!");
      NS_ASSERTION(
          i - 1 <= aRange.start || aSpacing[i - 1 - aRange.start].mAfter == 0,
          "After-spacing inside a ligature!");
    }
  }
#endif
}

bool gfxTextRun::GetAdjustedSpacingArray(
    Range aRange, const PropertyProvider* aProvider, Range aSpacingRange,
    nsTArray<PropertyProvider::Spacing>* aSpacing) const {
  if (!aProvider || !(mFlags & gfx::ShapedTextFlags::TEXT_ENABLE_SPACING)) {
    return false;
  }
  if (!aSpacing->AppendElements(aRange.Length(), fallible)) {
    return false;
  }
  auto spacingOffset = aSpacingRange.start - aRange.start;
  memset(aSpacing->Elements(), 0, sizeof(gfxFont::Spacing) * spacingOffset);
  GetAdjustedSpacing(this, aSpacingRange, *aProvider,
                     aSpacing->Elements() + spacingOffset);
  memset(aSpacing->Elements() + spacingOffset + aSpacingRange.Length(), 0,
         sizeof(gfxFont::Spacing) * (aRange.end - aSpacingRange.end));
  return true;
}

bool gfxTextRun::ShrinkToLigatureBoundaries(Range* aRange) const {
  if (aRange->start >= aRange->end) {
    return false;
  }

  const CompressedGlyph* charGlyphs = mCharacterGlyphs;
  bool adjusted = false;
  while (aRange->start < aRange->end &&
         !charGlyphs[aRange->start].IsLigatureGroupStart()) {
    ++aRange->start;
    adjusted = true;
  }
  if (aRange->end < GetLength()) {
    while (aRange->end > aRange->start &&
           !charGlyphs[aRange->end].IsLigatureGroupStart()) {
      --aRange->end;
      adjusted = true;
    }
  }
  return adjusted;
}

void gfxTextRun::DrawGlyphs(gfxFont* aFont, Range aRange, gfx::Point* aPt,
                            const PropertyProvider* aProvider,
                            Range aSpacingRange, TextRunDrawParams& aParams,
                            gfx::ShapedTextFlags aOrientation) const {
  AutoTArray<PropertyProvider::Spacing, 200> spacingBuffer;
  bool haveSpacing =
      GetAdjustedSpacingArray(aRange, aProvider, aSpacingRange, &spacingBuffer);
  aParams.spacing = haveSpacing ? spacingBuffer.Elements() : nullptr;
  aFont->Draw(this, aRange.start, aRange.end, aPt, aParams, aOrientation);
}

static void ClipPartialLigature(const gfxTextRun* aTextRun, gfxFloat* aStart,
                                gfxFloat* aEnd, gfxFloat aOrigin,
                                gfxTextRun::LigatureData* aLigature) {
  if (aLigature->mClipBeforePart) {
    if (aTextRun->IsRightToLeft()) {
      *aEnd = std::min(*aEnd, aOrigin);
    } else {
      *aStart = std::max(*aStart, aOrigin);
    }
  }
  if (aLigature->mClipAfterPart) {
    gfxFloat endEdge =
        aOrigin + aTextRun->GetDirection() * aLigature->mPartWidth;
    if (aTextRun->IsRightToLeft()) {
      *aStart = std::max(*aStart, endEdge);
    } else {
      *aEnd = std::min(*aEnd, endEdge);
    }
  }
}

void gfxTextRun::DrawPartialLigature(gfxFont* aFont, Range aRange,
                                     gfx::Point* aPt,
                                     const PropertyProvider* aProvider,
                                     TextRunDrawParams& aParams,
                                     gfx::ShapedTextFlags aOrientation) const {
  if (aRange.start >= aRange.end) {
    return;
  }

  // Draw partial ligature. We hack this by clipping the ligature.
  LigatureData data = ComputeLigatureData(aRange, aProvider);
  gfxRect clipExtents = aParams.context->GetClipExtents();
  gfxFloat start, end;
  if (aParams.isVerticalRun) {
    start = clipExtents.Y() * mAppUnitsPerDevUnit;
    end = clipExtents.YMost() * mAppUnitsPerDevUnit;
    ClipPartialLigature(this, &start, &end, aPt->y, &data);
  } else {
    start = clipExtents.X() * mAppUnitsPerDevUnit;
    end = clipExtents.XMost() * mAppUnitsPerDevUnit;
    ClipPartialLigature(this, &start, &end, aPt->x, &data);
  }

  gfxClipAutoSaveRestore autoSaveClip(aParams.context);
  {
    // use division here to ensure that when the rect is aligned on multiples
    // of mAppUnitsPerDevUnit, we clip to true device unit boundaries.
    // Also, make sure we snap the rectangle to device pixels.
    Rect clipRect =
        aParams.isVerticalRun
            ? Rect(clipExtents.X(), start / mAppUnitsPerDevUnit,
                   clipExtents.Width(), (end - start) / mAppUnitsPerDevUnit)
            : Rect(start / mAppUnitsPerDevUnit, clipExtents.Y(),
                   (end - start) / mAppUnitsPerDevUnit, clipExtents.Height());
    MaybeSnapToDevicePixels(clipRect, *aParams.dt, true);

    autoSaveClip.Clip(clipRect);
  }

  gfx::Point pt;
  if (aParams.isVerticalRun) {
    pt = Point(aPt->x, aPt->y - aParams.direction * data.mPartAdvance);
  } else {
    pt = Point(aPt->x - aParams.direction * data.mPartAdvance, aPt->y);
  }

  DrawGlyphs(aFont, data.mRange, &pt, aProvider, aRange, aParams, aOrientation);

  if (aParams.isVerticalRun) {
    aPt->y += aParams.direction * data.mPartWidth;
  } else {
    aPt->x += aParams.direction * data.mPartWidth;
  }
}

// Returns true if the font has synthetic bolding enabled,
// or is a color font (COLR/SVG/sbix/CBDT), false otherwise. This is used to
// check whether the text run needs to be explicitly composited in order to
// support opacity.
static bool HasSyntheticBoldOrColor(gfxFont* aFont) {
  if (aFont->ApplySyntheticBold()) {
    return true;
  }
  gfxFontEntry* fe = aFont->GetFontEntry();
  if (fe->TryGetSVGData(aFont) || fe->TryGetColorGlyphs()) {
    return true;
  }
#if defined(XP_MACOSX)  // sbix fonts only supported via Core Text
  if (fe->HasFontTable(TRUETYPE_TAG('s', 'b', 'i', 'x'))) {
    return true;
  }
#endif
  return false;
}

// helper class for double-buffering drawing with non-opaque color
struct MOZ_STACK_CLASS BufferAlphaColor {
  explicit BufferAlphaColor(gfxContext* aContext) : mContext(aContext) {}

  ~BufferAlphaColor() = default;

  void PushSolidColor(const gfxRect& aBounds, const DeviceColor& aAlphaColor,
                      uint32_t appsPerDevUnit) {
    mContext->Save();
    mContext->SnappedClip(gfxRect(
        aBounds.X() / appsPerDevUnit, aBounds.Y() / appsPerDevUnit,
        aBounds.Width() / appsPerDevUnit, aBounds.Height() / appsPerDevUnit));
    mContext->SetDeviceColor(
        DeviceColor(aAlphaColor.r, aAlphaColor.g, aAlphaColor.b));
    mContext->PushGroupForBlendBack(gfxContentType::COLOR_ALPHA, aAlphaColor.a);
  }

  void PopAlpha() {
    // pop the text, using the color alpha as the opacity
    mContext->PopGroupAndBlend();
    mContext->Restore();
  }

  gfxContext* mContext;
};

void gfxTextRun::Draw(const Range aRange, const gfx::Point aPt,
                      const DrawParams& aParams) const {
  NS_ASSERTION(aRange.end <= GetLength(), "Substring out of range");
  NS_ASSERTION(aParams.drawMode == DrawMode::GLYPH_PATH ||
                   !(aParams.drawMode & DrawMode::GLYPH_PATH),
               "GLYPH_PATH cannot be used with GLYPH_FILL, GLYPH_STROKE or "
               "GLYPH_STROKE_UNDERNEATH");
  NS_ASSERTION(aParams.drawMode == DrawMode::GLYPH_PATH || !aParams.callbacks,
               "callback must not be specified unless using GLYPH_PATH");

  bool skipDrawing =
      !mDontSkipDrawing && (mFontGroup ? mFontGroup->ShouldSkipDrawing()
                                       : mReleasedFontGroupSkippedDrawing);
  auto* textDrawer = aParams.context->GetTextDrawer();
  if (aParams.drawMode & DrawMode::GLYPH_FILL) {
    DeviceColor currentColor;
    if (aParams.context->GetDeviceColor(currentColor) && currentColor.a == 0 &&
        !textDrawer) {
      skipDrawing = true;
    }
  }

  gfxFloat direction = GetDirection();

  if (skipDrawing) {
    // We don't need to draw anything;
    // but if the caller wants advance width, we need to compute it here
    if (aParams.advanceWidth) {
      gfxTextRun::Metrics metrics =
          MeasureText(aRange, gfxFont::LOOSE_INK_EXTENTS,
                      aParams.context->GetDrawTarget(), aParams.provider);
      *aParams.advanceWidth = metrics.mAdvanceWidth * direction;
    }

    // return without drawing
    return;
  }

  // synthetic bolding draws glyphs twice ==> colors with opacity won't draw
  // correctly unless first drawn without alpha
  BufferAlphaColor syntheticBoldBuffer(aParams.context);
  DeviceColor currentColor;
  bool mayNeedBuffering =
      aParams.drawMode & DrawMode::GLYPH_FILL &&
      aParams.context->HasNonOpaqueNonTransparentColor(currentColor) &&
      !textDrawer;

  // If we need to double-buffer, we'll need to measure the text first to
  // get the bounds of the area of interest. Ideally we'd do that just for
  // the specific glyph run(s) that need buffering, but because of bug
  // 1612610 we currently use the extent of the entire range even when
  // just buffering a subrange. So we'll measure the full range once and
  // keep the metrics on hand for any subsequent subranges.
  gfxTextRun::Metrics metrics;
  bool gotMetrics = false;

  // Set up parameters that will be constant across all glyph runs we need
  // to draw, regardless of the font used.
  TextRunDrawParams params(aParams.paletteCache);
  params.context = aParams.context;
  params.devPerApp = 1.0 / double(GetAppUnitsPerDevUnit());
  params.isVerticalRun = IsVertical();
  params.isRTL = IsRightToLeft();
  params.direction = direction;
  params.strokeOpts = aParams.strokeOpts;
  params.textStrokeColor = aParams.textStrokeColor;
  params.fontPalette = aParams.fontPalette;
  params.textStrokePattern = aParams.textStrokePattern;
  params.drawOpts = aParams.drawOpts;
  params.drawMode = aParams.drawMode;
  params.hasTextShadow = aParams.hasTextShadow;
  params.callbacks = aParams.callbacks;
  params.runContextPaint = aParams.contextPaint;
  params.paintSVGGlyphs =
      !aParams.callbacks || aParams.callbacks->mShouldPaintSVGGlyphs;
  params.dt = aParams.context->GetDrawTarget();
  params.textDrawer = textDrawer;
  if (textDrawer) {
    params.clipRect = textDrawer->GeckoClipRect();
  }
  params.allowGDI = aParams.allowGDI;

  gfxFloat advance = 0.0;
  gfx::Point pt = aPt;

  for (GlyphRunIterator iter(this, aRange); !iter.AtEnd(); iter.NextRun()) {
    gfxFont* font = iter.GlyphRun()->mFont;
    Range runRange(iter.StringStart(), iter.StringEnd());

    bool needToRestore = false;
    if (mayNeedBuffering && HasSyntheticBoldOrColor(font)) {
      needToRestore = true;
      if (!gotMetrics) {
        // Measure text; use the bounding box to determine the area we need
        // to buffer. We measure the entire range, rather than just the glyph
        // run that we're actually handling, because of bug 1612610: if the
        // bounding box passed to PushSolidColor does not intersect the
        // drawTarget's current clip, the skia backend fails to clip properly.
        // This means we may use a larger buffer than actually needed, but is
        // otherwise harmless.
        metrics = MeasureText(aRange, gfxFont::LOOSE_INK_EXTENTS, params.dt,
                              aParams.provider);
        if (IsRightToLeft()) {
          metrics.mBoundingBox.MoveBy(
              gfxPoint(aPt.x - metrics.mAdvanceWidth, aPt.y));
        } else {
          metrics.mBoundingBox.MoveBy(gfxPoint(aPt.x, aPt.y));
        }
        gotMetrics = true;
      }
      syntheticBoldBuffer.PushSolidColor(metrics.mBoundingBox, currentColor,
                                         GetAppUnitsPerDevUnit());
    }

    Range ligatureRange(runRange);
    bool adjusted = ShrinkToLigatureBoundaries(&ligatureRange);

    bool drawPartial =
        adjusted &&
        ((aParams.drawMode & (DrawMode::GLYPH_FILL | DrawMode::GLYPH_STROKE)) ||
         (aParams.drawMode == DrawMode::GLYPH_PATH && aParams.callbacks));
    gfx::Point origPt = pt;

    if (drawPartial) {
      DrawPartialLigature(font, Range(runRange.start, ligatureRange.start), &pt,
                          aParams.provider, params,
                          iter.GlyphRun()->mOrientation);
    }

    DrawGlyphs(font, ligatureRange, &pt, aParams.provider, ligatureRange,
               params, iter.GlyphRun()->mOrientation);

    if (drawPartial) {
      DrawPartialLigature(font, Range(ligatureRange.end, runRange.end), &pt,
                          aParams.provider, params,
                          iter.GlyphRun()->mOrientation);
    }

    if (params.isVerticalRun) {
      advance += (pt.y - origPt.y) * params.direction;
    } else {
      advance += (pt.x - origPt.x) * params.direction;
    }

    // composite result when synthetic bolding used
    if (needToRestore) {
      syntheticBoldBuffer.PopAlpha();
    }
  }

  if (aParams.advanceWidth) {
    *aParams.advanceWidth = advance;
  }
}

// This method is mostly parallel to Draw().
void gfxTextRun::DrawEmphasisMarks(
    gfxContext* aContext, gfxTextRun* aMark, gfxFloat aMarkAdvance,
    gfx::Point aPt, Range aRange, const PropertyProvider* aProvider,
    mozilla::gfx::PaletteCache& aPaletteCache) const {
  MOZ_ASSERT(aRange.end <= GetLength());

  EmphasisMarkDrawParams params(aContext, aPaletteCache);
  params.mark = aMark;
  params.advance = aMarkAdvance;
  params.direction = GetDirection();
  params.isVertical = IsVertical();

  float& inlineCoord = params.isVertical ? aPt.y.value : aPt.x.value;
  float direction = params.direction;

  for (GlyphRunIterator iter(this, aRange); !iter.AtEnd(); iter.NextRun()) {
    gfxFont* font = iter.GlyphRun()->mFont;
    uint32_t start = iter.StringStart();
    uint32_t end = iter.StringEnd();
    Range ligatureRange(start, end);
    bool adjusted = ShrinkToLigatureBoundaries(&ligatureRange);

    if (adjusted) {
      inlineCoord +=
          direction * ComputePartialLigatureWidth(
                          Range(start, ligatureRange.start), aProvider);
    }

    AutoTArray<PropertyProvider::Spacing, 200> spacingBuffer;
    bool haveSpacing = GetAdjustedSpacingArray(ligatureRange, aProvider,
                                               ligatureRange, &spacingBuffer);
    params.spacing = haveSpacing ? spacingBuffer.Elements() : nullptr;
    font->DrawEmphasisMarks(this, &aPt, ligatureRange.start,
                            ligatureRange.Length(), params);

    if (adjusted) {
      inlineCoord += direction * ComputePartialLigatureWidth(
                                     Range(ligatureRange.end, end), aProvider);
    }
  }
}

void gfxTextRun::AccumulateMetricsForRun(
    gfxFont* aFont, Range aRange, gfxFont::BoundingBoxType aBoundingBoxType,
    DrawTarget* aRefDrawTarget, const PropertyProvider* aProvider,
    Range aSpacingRange, gfx::ShapedTextFlags aOrientation,
    Metrics* aMetrics) const {
  AutoTArray<PropertyProvider::Spacing, 200> spacingBuffer;
  bool haveSpacing =
      GetAdjustedSpacingArray(aRange, aProvider, aSpacingRange, &spacingBuffer);
  Metrics metrics = aFont->Measure(
      this, aRange.start, aRange.end, aBoundingBoxType, aRefDrawTarget,
      haveSpacing ? spacingBuffer.Elements() : nullptr, aOrientation);
  aMetrics->CombineWith(metrics, IsRightToLeft());
}

void gfxTextRun::AccumulatePartialLigatureMetrics(
    gfxFont* aFont, Range aRange, gfxFont::BoundingBoxType aBoundingBoxType,
    DrawTarget* aRefDrawTarget, const PropertyProvider* aProvider,
    gfx::ShapedTextFlags aOrientation, Metrics* aMetrics) const {
  if (aRange.start >= aRange.end) return;

  // Measure partial ligature. We hack this by clipping the metrics in the
  // same way we clip the drawing.
  LigatureData data = ComputeLigatureData(aRange, aProvider);

  // First measure the complete ligature
  Metrics metrics;
  AccumulateMetricsForRun(aFont, data.mRange, aBoundingBoxType, aRefDrawTarget,
                          aProvider, aRange, aOrientation, &metrics);

  // Clip the bounding box to the ligature part
  gfxFloat bboxLeft = metrics.mBoundingBox.X();
  gfxFloat bboxRight = metrics.mBoundingBox.XMost();
  // Where we are going to start "drawing" relative to our left baseline origin
  gfxFloat origin =
      IsRightToLeft() ? metrics.mAdvanceWidth - data.mPartAdvance : 0;
  ClipPartialLigature(this, &bboxLeft, &bboxRight, origin, &data);
  metrics.mBoundingBox.SetBoxX(bboxLeft, bboxRight);

  // mBoundingBox is now relative to the left baseline origin for the entire
  // ligature. Shift it left.
  metrics.mBoundingBox.MoveByX(
      -(IsRightToLeft()
            ? metrics.mAdvanceWidth - (data.mPartAdvance + data.mPartWidth)
            : data.mPartAdvance));
  metrics.mAdvanceWidth = data.mPartWidth;

  aMetrics->CombineWith(metrics, IsRightToLeft());
}

gfxTextRun::Metrics gfxTextRun::MeasureText(
    Range aRange, gfxFont::BoundingBoxType aBoundingBoxType,
    DrawTarget* aRefDrawTarget, const PropertyProvider* aProvider) const {
  NS_ASSERTION(aRange.end <= GetLength(), "Substring out of range");

  Metrics accumulatedMetrics;
  for (GlyphRunIterator iter(this, aRange); !iter.AtEnd(); iter.NextRun()) {
    gfxFont* font = iter.GlyphRun()->mFont;
    uint32_t start = iter.StringStart();
    uint32_t end = iter.StringEnd();
    Range ligatureRange(start, end);
    bool adjusted = ShrinkToLigatureBoundaries(&ligatureRange);

    if (adjusted) {
      AccumulatePartialLigatureMetrics(font, Range(start, ligatureRange.start),
                                       aBoundingBoxType, aRefDrawTarget,
                                       aProvider, iter.GlyphRun()->mOrientation,
                                       &accumulatedMetrics);
    }

    // XXX This sucks. We have to get glyph extents just so we can detect
    // glyphs outside the font box, even when aBoundingBoxType is LOOSE,
    // even though in almost all cases we could get correct results just
    // by getting some ascent/descent from the font and using our stored
    // advance widths.
    AccumulateMetricsForRun(font, ligatureRange, aBoundingBoxType,
                            aRefDrawTarget, aProvider, ligatureRange,
                            iter.GlyphRun()->mOrientation, &accumulatedMetrics);

    if (adjusted) {
      AccumulatePartialLigatureMetrics(
          font, Range(ligatureRange.end, end), aBoundingBoxType, aRefDrawTarget,
          aProvider, iter.GlyphRun()->mOrientation, &accumulatedMetrics);
    }
  }

  return accumulatedMetrics;
}

void gfxTextRun::GetLineHeightMetrics(Range aRange, gfxFloat& aAscent,
                                      gfxFloat& aDescent) const {
  Metrics accumulatedMetrics;
  for (GlyphRunIterator iter(this, aRange); !iter.AtEnd(); iter.NextRun()) {
    gfxFont* font = iter.GlyphRun()->mFont;
    auto metrics =
        font->Measure(this, 0, 0, gfxFont::LOOSE_INK_EXTENTS, nullptr, nullptr,
                      iter.GlyphRun()->mOrientation);
    accumulatedMetrics.CombineWith(metrics, false);
  }
  aAscent = accumulatedMetrics.mAscent;
  aDescent = accumulatedMetrics.mDescent;
}

#define MEASUREMENT_BUFFER_SIZE 100

void gfxTextRun::ClassifyAutoHyphenations(uint32_t aStart, Range aRange,
                                          nsTArray<HyphenType>& aHyphenBuffer,
                                          HyphenationState* aWordState) {
  MOZ_ASSERT(
      aRange.end - aStart <= aHyphenBuffer.Length() && aRange.start >= aStart,
      "Range out of bounds");
  MOZ_ASSERT(aWordState->mostRecentBoundary >= aStart,
             "Unexpected aMostRecentWordBoundary!!");

  uint32_t start =
      std::min<uint32_t>(aRange.start, aWordState->mostRecentBoundary);

  for (uint32_t i = start; i < aRange.end; ++i) {
    if (aHyphenBuffer[i - aStart] == HyphenType::Explicit &&
        !aWordState->hasExplicitHyphen) {
      aWordState->hasExplicitHyphen = true;
    }
    if (!aWordState->hasManualHyphen &&
        (aHyphenBuffer[i - aStart] == HyphenType::Soft ||
         aHyphenBuffer[i - aStart] == HyphenType::Explicit)) {
      aWordState->hasManualHyphen = true;
      // This is the first manual hyphen in the current word. We can only
      // know if the current word has a manual hyphen until now. So, we need
      // to run a sub loop to update the auto hyphens between the start of
      // the current word and this manual hyphen.
      if (aWordState->hasAutoHyphen) {
        for (uint32_t j = aWordState->mostRecentBoundary; j < i; j++) {
          if (aHyphenBuffer[j - aStart] ==
              HyphenType::AutoWithoutManualInSameWord) {
            aHyphenBuffer[j - aStart] = HyphenType::AutoWithManualInSameWord;
          }
        }
      }
    }
    if (aHyphenBuffer[i - aStart] == HyphenType::AutoWithoutManualInSameWord) {
      if (!aWordState->hasAutoHyphen) {
        aWordState->hasAutoHyphen = true;
      }
      if (aWordState->hasManualHyphen) {
        aHyphenBuffer[i - aStart] = HyphenType::AutoWithManualInSameWord;
      }
    }

    // If we're at the word boundary, clear/reset couple states.
    if (mCharacterGlyphs[i].CharIsSpace() || mCharacterGlyphs[i].CharIsTab() ||
        mCharacterGlyphs[i].CharIsNewline() ||
        // Since we will not have a boundary in the end of the string, let's
        // call the end of the string a special case for word boundary.
        i == GetLength() - 1) {
      // We can only get to know whether we should raise/clear an explicit
      // manual hyphen until we get to the end of a word, because this depends
      // on whether there exists at least one auto hyphen in the same word.
      if (!aWordState->hasAutoHyphen && aWordState->hasExplicitHyphen) {
        for (uint32_t j = aWordState->mostRecentBoundary; j <= i; j++) {
          if (aHyphenBuffer[j - aStart] == HyphenType::Explicit) {
            aHyphenBuffer[j - aStart] = HyphenType::None;
          }
        }
      }
      aWordState->mostRecentBoundary = i;
      aWordState->hasManualHyphen = false;
      aWordState->hasAutoHyphen = false;
      aWordState->hasExplicitHyphen = false;
    }
  }
}

uint32_t gfxTextRun::BreakAndMeasureText(
    uint32_t aStart, uint32_t aMaxLength, bool aLineBreakBefore,
    gfxFloat aWidth, const PropertyProvider& aProvider,
    SuppressBreak aSuppressBreak, gfxFont::BoundingBoxType aBoundingBoxType,
    DrawTarget* aRefDrawTarget, bool aCanWordWrap, bool aCanWhitespaceWrap,
    bool aIsBreakSpaces,
    // output params:
    TrimmableWS* aOutTrimmableWhitespace, Metrics& aOutMetrics,
    bool& aOutUsedHyphenation, uint32_t& aOutLastBreak,
    gfxBreakPriority& aBreakPriority) {
  aMaxLength = std::min(aMaxLength, GetLength() - aStart);

  NS_ASSERTION(aStart + aMaxLength <= GetLength(), "Substring out of range");

  Range bufferRange(
      aStart, aStart + std::min<uint32_t>(aMaxLength, MEASUREMENT_BUFFER_SIZE));
  PropertyProvider::Spacing spacingBuffer[MEASUREMENT_BUFFER_SIZE];
  bool haveSpacing = !!(mFlags & gfx::ShapedTextFlags::TEXT_ENABLE_SPACING);
  if (haveSpacing) {
    GetAdjustedSpacing(this, bufferRange, aProvider, spacingBuffer);
  }
  AutoTArray<HyphenType, 4096> hyphenBuffer;
  HyphenationState wordState;
  wordState.mostRecentBoundary = aStart;
  bool haveHyphenation =
      (aProvider.GetHyphensOption() == StyleHyphens::Auto ||
       (aProvider.GetHyphensOption() == StyleHyphens::Manual &&
        !!(mFlags & gfx::ShapedTextFlags::TEXT_ENABLE_HYPHEN_BREAKS)));
  if (haveHyphenation) {
    if (hyphenBuffer.AppendElements(bufferRange.Length(), fallible)) {
      aProvider.GetHyphenationBreaks(bufferRange, hyphenBuffer.Elements());
      if (aProvider.GetHyphensOption() == StyleHyphens::Auto) {
        ClassifyAutoHyphenations(aStart, bufferRange, hyphenBuffer, &wordState);
      }
    } else {
      haveHyphenation = false;
    }
  }

  gfxFloat width = 0;
  gfxFloat advance = 0;
  // The number of space characters that can be trimmed or hang at a soft-wrap
  uint32_t trimmableChars = 0;
  // The amount of space removed by ignoring trimmableChars
  gfxFloat trimmableAdvance = 0;
  int32_t lastBreak = -1;
  int32_t lastBreakTrimmableChars = -1;
  gfxFloat lastBreakTrimmableAdvance = -1;
  // Cache the last candidate break
  int32_t lastCandidateBreak = -1;
  int32_t lastCandidateBreakTrimmableChars = -1;
  gfxFloat lastCandidateBreakTrimmableAdvance = -1;
  bool lastCandidateBreakUsedHyphenation = false;
  gfxBreakPriority lastCandidateBreakPriority = gfxBreakPriority::eNoBreak;
  bool aborted = false;
  uint32_t end = aStart + aMaxLength;
  bool lastBreakUsedHyphenation = false;
  Range ligatureRange(aStart, end);
  ShrinkToLigatureBoundaries(&ligatureRange);

  // We may need to move `i` backwards in the following loop, and re-scan
  // part of the textrun; we'll use `rescanLimit` so we can tell when that
  // is happening: if `i < rescanLimit` then we're rescanning.
  uint32_t rescanLimit = aStart;
  for (uint32_t i = aStart; i < end; ++i) {
    if (i >= bufferRange.end) {
      // Fetch more spacing and hyphenation data
      uint32_t oldHyphenBufferLength = hyphenBuffer.Length();
      bufferRange.start = i;
      bufferRange.end =
          std::min(aStart + aMaxLength, i + MEASUREMENT_BUFFER_SIZE);
      // For spacing, we always overwrite the old data with the newly
      // fetched one. However, for hyphenation, hyphenation data sometimes
      // depends on the context in every word (if "hyphens: auto" is set).
      // To ensure we get enough information between neighboring buffers,
      // we grow the hyphenBuffer instead of overwrite it.
      // NOTE that this means bufferRange does not correspond to the
      // entire hyphenBuffer, but only to the most recently added portion.
      // Therefore, we need to add the old length to hyphenBuffer.Elements()
      // when getting more data.
      if (haveSpacing) {
        GetAdjustedSpacing(this, bufferRange, aProvider, spacingBuffer);
      }
      if (haveHyphenation) {
        if (hyphenBuffer.AppendElements(bufferRange.Length(), fallible)) {
          aProvider.GetHyphenationBreaks(
              bufferRange, hyphenBuffer.Elements() + oldHyphenBufferLength);
          if (aProvider.GetHyphensOption() == StyleHyphens::Auto) {
            uint32_t prevMostRecentWordBoundary = wordState.mostRecentBoundary;
            ClassifyAutoHyphenations(aStart, bufferRange, hyphenBuffer,
                                     &wordState);
            // If the buffer boundary is in the middle of a word,
            // we need to go back to the start of the current word.
            // So, we can correct the wrong candidates that we set
            // in the previous runs of the loop.
            if (prevMostRecentWordBoundary < oldHyphenBufferLength) {
              rescanLimit = i;
              i = prevMostRecentWordBoundary - 1;
              continue;
            }
          }
        } else {
          haveHyphenation = false;
        }
      }
    }

    // There can't be a word-wrap break opportunity at the beginning of the
    // line: if the width is too small for even one character to fit, it
    // could be the first and last break opportunity on the line, and that
    // would trigger an infinite loop.
    if (aSuppressBreak != eSuppressAllBreaks &&
        (aSuppressBreak != eSuppressInitialBreak || i > aStart)) {
      bool atNaturalBreak = mCharacterGlyphs[i].CanBreakBefore() ==
                            CompressedGlyph::FLAG_BREAK_TYPE_NORMAL;
      // atHyphenationBreak indicates we're at a "soft" hyphen, where an extra
      // hyphen glyph will need to be painted. It is NOT set for breaks at an
      // explicit hyphen present in the text.
      //
      // NOTE(emilio): If you change this condition you also need to change
      // nsTextFrame::AddInlineMinISizeForFlow to match.
      bool atHyphenationBreak = !atNaturalBreak && haveHyphenation &&
                                (!aLineBreakBefore || i > aStart) &&
                                IsOptionalHyphenBreak(hyphenBuffer[i - aStart]);
      bool atAutoHyphenWithManualHyphenInSameWord =
          atHyphenationBreak &&
          hyphenBuffer[i - aStart] == HyphenType::AutoWithManualInSameWord;
      bool atBreak = atNaturalBreak || atHyphenationBreak;
      bool wordWrapping =
          (aCanWordWrap ||
           (aCanWhitespaceWrap &&
            mCharacterGlyphs[i].CanBreakBefore() ==
                CompressedGlyph::FLAG_BREAK_TYPE_EMERGENCY_WRAP)) &&
          mCharacterGlyphs[i].IsClusterStart() &&
          aBreakPriority <= gfxBreakPriority::eWordWrapBreak;

      bool whitespaceWrapping = false;
      if (i > aStart) {
        // The spec says the breaking opportunity is *after* whitespace.
        auto const& g = mCharacterGlyphs[i - 1];
        whitespaceWrapping =
            aIsBreakSpaces &&
            (g.CharIsSpace() || g.CharIsTab() || g.CharIsNewline());
      }

      if (atBreak || wordWrapping || whitespaceWrapping) {
        gfxFloat hyphenatedAdvance = advance;
        if (atHyphenationBreak) {
          hyphenatedAdvance += aProvider.GetHyphenWidth();
        }

        if (lastBreak < 0 ||
            width + hyphenatedAdvance - trimmableAdvance <= aWidth) {
          // We can break here.
          lastBreak = i;
          lastBreakTrimmableChars = trimmableChars;
          lastBreakTrimmableAdvance = trimmableAdvance;
          lastBreakUsedHyphenation = atHyphenationBreak;
          aBreakPriority = (atBreak || whitespaceWrapping)
                               ? gfxBreakPriority::eNormalBreak
                               : gfxBreakPriority::eWordWrapBreak;
        }

        width += advance;
        advance = 0;
        if (width - trimmableAdvance > aWidth) {
          // No more text fits. Abort
          aborted = true;
          break;
        }
        // There are various kinds of break opportunities:
        // 1. word wrap break,
        // 2. natural break,
        // 3. manual hyphenation break,
        // 4. auto hyphenation break without any manual hyphenation
        //    in the same word,
        // 5. auto hyphenation break with another manual hyphenation
        //    in the same word.
        // Allow all of them except the last one to be a candidate.
        // So, we can ensure that we don't use an automatic
        // hyphenation opportunity within a word that contains another
        // manual hyphenation, unless it is the only choice.
        if (wordWrapping || !atAutoHyphenWithManualHyphenInSameWord) {
          lastCandidateBreak = lastBreak;
          lastCandidateBreakTrimmableChars = lastBreakTrimmableChars;
          lastCandidateBreakTrimmableAdvance = lastBreakTrimmableAdvance;
          lastCandidateBreakUsedHyphenation = lastBreakUsedHyphenation;
          lastCandidateBreakPriority = aBreakPriority;
        }
      }
    }

    // If we're re-scanning part of a word (to re-process potential
    // hyphenation types) then we don't want to accumulate widths again
    // for the characters that were already added to `advance`.
    if (i < rescanLimit) {
      continue;
    }

    gfxFloat charAdvance;
    if (i >= ligatureRange.start && i < ligatureRange.end) {
      charAdvance = GetAdvanceForGlyphs(Range(i, i + 1));
      if (haveSpacing) {
        PropertyProvider::Spacing* space =
            &spacingBuffer[i - bufferRange.start];
        charAdvance += space->mBefore + space->mAfter;
      }
    } else {
      charAdvance = ComputePartialLigatureWidth(Range(i, i + 1), &aProvider);
    }

    advance += charAdvance;
    if (aOutTrimmableWhitespace) {
      if (mCharacterGlyphs[i].CharIsSpace()) {
        ++trimmableChars;
        trimmableAdvance += charAdvance;
      } else {
        trimmableAdvance = 0;
        trimmableChars = 0;
      }
    }
  }

  if (!aborted) {
    width += advance;
  }

  // There are three possibilities:
  // 1) all the text fit (width <= aWidth)
  // 2) some of the text fit up to a break opportunity (width > aWidth &&
  //    lastBreak >= 0)
  // 3) none of the text fits before a break opportunity (width > aWidth &&
  //    lastBreak < 0)
  uint32_t charsFit;
  aOutUsedHyphenation = false;
  if (width - trimmableAdvance <= aWidth) {
    charsFit = aMaxLength;
  } else if (lastBreak >= 0) {
    if (lastCandidateBreak >= 0 && lastCandidateBreak != lastBreak) {
      lastBreak = lastCandidateBreak;
      lastBreakTrimmableChars = lastCandidateBreakTrimmableChars;
      lastBreakTrimmableAdvance = lastCandidateBreakTrimmableAdvance;
      lastBreakUsedHyphenation = lastCandidateBreakUsedHyphenation;
      aBreakPriority = lastCandidateBreakPriority;
    }
    charsFit = lastBreak - aStart;
    trimmableChars = lastBreakTrimmableChars;
    trimmableAdvance = lastBreakTrimmableAdvance;
    aOutUsedHyphenation = lastBreakUsedHyphenation;
  } else {
    charsFit = aMaxLength;
  }

  // Get the overall metrics of the range that fit (including any potentially
  // trimmable or hanging whitespace).
  aOutMetrics = MeasureText(Range(aStart, aStart + charsFit), aBoundingBoxType,
                            aRefDrawTarget, &aProvider);

  if (aOutTrimmableWhitespace) {
    aOutTrimmableWhitespace->mAdvance = trimmableAdvance;
    aOutTrimmableWhitespace->mCount = trimmableChars;
  }

  if (charsFit == aMaxLength) {
    if (lastBreak < 0) {
      aOutLastBreak = UINT32_MAX;
    } else {
      aOutLastBreak = lastBreak - aStart;
    }
  }

  return charsFit;
}

gfxFloat gfxTextRun::GetAdvanceWidth(
    Range aRange, const PropertyProvider* aProvider,
    PropertyProvider::Spacing* aSpacing) const {
  NS_ASSERTION(aRange.end <= GetLength(), "Substring out of range");

  Range ligatureRange = aRange;
  bool adjusted = ShrinkToLigatureBoundaries(&ligatureRange);

  gfxFloat result =
      adjusted ? ComputePartialLigatureWidth(
                     Range(aRange.start, ligatureRange.start), aProvider) +
                     ComputePartialLigatureWidth(
                         Range(ligatureRange.end, aRange.end), aProvider)
               : 0.0;

  if (aSpacing) {
    aSpacing->mBefore = aSpacing->mAfter = 0;
  }

  // Account for all remaining spacing here. This is more efficient than
  // processing it along with the glyphs.
  if (aProvider && (mFlags & gfx::ShapedTextFlags::TEXT_ENABLE_SPACING)) {
    uint32_t i;
    AutoTArray<PropertyProvider::Spacing, 200> spacingBuffer;
    if (spacingBuffer.AppendElements(aRange.Length(), fallible)) {
      GetAdjustedSpacing(this, ligatureRange, *aProvider,
                         spacingBuffer.Elements());
      for (i = 0; i < ligatureRange.Length(); ++i) {
        PropertyProvider::Spacing* space = &spacingBuffer[i];
        result += space->mBefore + space->mAfter;
      }
      if (aSpacing) {
        aSpacing->mBefore = spacingBuffer[0].mBefore;
        aSpacing->mAfter = spacingBuffer.LastElement().mAfter;
      }
    }
  }

  return result + GetAdvanceForGlyphs(ligatureRange);
}

gfxFloat gfxTextRun::GetMinAdvanceWidth(Range aRange) {
  MOZ_ASSERT(aRange.end <= GetLength(), "Substring out of range");

  Range ligatureRange = aRange;
  bool adjusted = ShrinkToLigatureBoundaries(&ligatureRange);

  gfxFloat result =
      adjusted
          ? std::max(ComputePartialLigatureWidth(
                         Range(aRange.start, ligatureRange.start), nullptr),
                     ComputePartialLigatureWidth(
                         Range(ligatureRange.end, aRange.end), nullptr))
          : 0.0;

  // Compute min advance width by assuming each grapheme cluster takes its own
  // line.
  gfxFloat clusterAdvance = 0;
  for (uint32_t i = ligatureRange.start; i < ligatureRange.end; ++i) {
    if (mCharacterGlyphs[i].CharIsSpace()) {
      // Skip space char to prevent its advance width contributing to the
      // result. That is, don't consider a space can be in its own line.
      continue;
    }
    clusterAdvance += GetAdvanceForGlyph(i);
    if (i + 1 == ligatureRange.end || IsClusterStart(i + 1)) {
      result = std::max(result, clusterAdvance);
      clusterAdvance = 0;
    }
  }

  return result;
}

bool gfxTextRun::SetLineBreaks(Range aRange, bool aLineBreakBefore,
                               bool aLineBreakAfter,
                               gfxFloat* aAdvanceWidthDelta) {
  // Do nothing because our shaping does not currently take linebreaks into
  // account. There is no change in advance width.
  if (aAdvanceWidthDelta) {
    *aAdvanceWidthDelta = 0;
  }
  return false;
}

const gfxTextRun::GlyphRun* gfxTextRun::FindFirstGlyphRunContaining(
    uint32_t aOffset) const {
  MOZ_ASSERT(aOffset <= GetLength(), "Bad offset looking for glyphrun");
  MOZ_ASSERT(GetLength() == 0 || !mGlyphRuns.IsEmpty(),
             "non-empty text but no glyph runs present!");
  if (mGlyphRuns.Length() <= 1) {
    return mGlyphRuns.begin();
  }
  if (aOffset == GetLength()) {
    return mGlyphRuns.end() - 1;
  }
  const auto* start = mGlyphRuns.begin();
  const auto* limit = mGlyphRuns.end();
  while (limit - start > 1) {
    const auto* mid = start + (limit - start) / 2;
    if (mid->mCharacterOffset <= aOffset) {
      start = mid;
    } else {
      limit = mid;
    }
  }
  MOZ_ASSERT(start->mCharacterOffset <= aOffset,
             "Hmm, something went wrong, aOffset should have been found");
  return start;
}

void gfxTextRun::AddGlyphRun(gfxFont* aFont, FontMatchType aMatchType,
                             uint32_t aUTF16Offset, bool aForceNewRun,
                             gfx::ShapedTextFlags aOrientation, bool aIsCJK) {
  MOZ_ASSERT(aFont, "adding glyph run for null font!");
  MOZ_ASSERT(aOrientation != gfx::ShapedTextFlags::TEXT_ORIENT_VERTICAL_MIXED,
             "mixed orientation should have been resolved");
  if (!aFont) {
    return;
  }

  if (mGlyphRuns.IsEmpty()) {
    mGlyphRuns.AppendElement(
        GlyphRun{aFont, aUTF16Offset, aOrientation, aMatchType, aIsCJK});
    return;
  }

  uint32_t numGlyphRuns = mGlyphRuns.Length();
  if (!aForceNewRun) {
    GlyphRun* lastGlyphRun = &mGlyphRuns.LastElement();

    MOZ_ASSERT(lastGlyphRun->mCharacterOffset <= aUTF16Offset,
               "Glyph runs out of order (and run not forced)");

    // Don't append a run if the font is already the one we want
    if (lastGlyphRun->Matches(aFont, aOrientation, aIsCJK, aMatchType)) {
      return;
    }

    // If the offset has not changed, avoid leaving a zero-length run
    // by overwriting the last entry instead of appending...
    if (lastGlyphRun->mCharacterOffset == aUTF16Offset) {
      // ...except that if the run before the last entry had the same
      // font as the new one wants, merge with it instead of creating
      // adjacent runs with the same font
      if (numGlyphRuns > 1 && mGlyphRuns[numGlyphRuns - 2].Matches(
                                  aFont, aOrientation, aIsCJK, aMatchType)) {
        mGlyphRuns.TruncateLength(numGlyphRuns - 1);
        return;
      }

      lastGlyphRun->SetProperties(aFont, aOrientation, aIsCJK, aMatchType);
      return;
    }
  }

  MOZ_ASSERT(
      aForceNewRun || numGlyphRuns > 0 || aUTF16Offset == 0,
      "First run doesn't cover the first character (and run not forced)?");

  mGlyphRuns.AppendElement(
      GlyphRun{aFont, aUTF16Offset, aOrientation, aMatchType, aIsCJK});
}

void gfxTextRun::SanitizeGlyphRuns() {
  if (mGlyphRuns.Length() < 2) {
    return;
  }

  auto& runs = mGlyphRuns.Array();

  // The runs are almost certain to be already sorted, so it's worth avoiding
  // the Sort() call if possible.
  bool isSorted = true;
  uint32_t prevOffset = 0;
  for (const auto& r : runs) {
    if (r.mCharacterOffset < prevOffset) {
      isSorted = false;
      break;
    }
    prevOffset = r.mCharacterOffset;
  }
  if (!isSorted) {
    runs.Sort(GlyphRunOffsetComparator());
  }

  // Coalesce adjacent glyph runs that have the same properties, and eliminate
  // any empty runs.
  GlyphRun* prevRun = nullptr;
  const CompressedGlyph* charGlyphs = mCharacterGlyphs;

  runs.RemoveElementsBy([&](GlyphRun& aRun) -> bool {
    // First run is always retained.
    if (!prevRun) {
      prevRun = &aRun;
      return false;
    }

    // Merge any run whose properties match its predecessor.
    if (prevRun->Matches(aRun.mFont, aRun.mOrientation, aRun.mIsCJK,
                         aRun.mMatchType)) {
      return true;
    }

    if (prevRun->mCharacterOffset >= aRun.mCharacterOffset) {
      // Preceding run is empty (or has become so due to the adjusting for
      // ligature boundaries), so we will overwrite it with this one, which
      // will then be discarded.
      *prevRun = aRun;
      return true;
    }

    // If any glyph run starts with ligature-continuation characters, we need to
    // advance it to the first "real" character to avoid drawing partial
    // ligature glyphs from wrong font (seen with U+FEFF in reftest 474417-1, as
    // Core Text eliminates the glyph, which makes it appear as if a ligature
    // has been formed)
    while (charGlyphs[aRun.mCharacterOffset].IsLigatureContinuation() &&
           aRun.mCharacterOffset < GetLength()) {
      aRun.mCharacterOffset++;
    }

    // We're keeping another run, so update prevRun pointer to refer to it (in
    // its new position).
    ++prevRun;
    return false;
  });

  MOZ_ASSERT(prevRun == &runs.LastElement(), "lost track of prevRun!");

  // Drop any trailing empty run.
  if (runs.Length() > 1 && prevRun->mCharacterOffset == GetLength()) {
    runs.RemoveLastElement();
  }

  MOZ_ASSERT(!runs.IsEmpty());
  if (runs.Length() == 1) {
    mGlyphRuns.ConvertToElement();
  }
}

void gfxTextRun::CopyGlyphDataFrom(gfxShapedWord* aShapedWord,
                                   uint32_t aOffset) {
  uint32_t wordLen = aShapedWord->GetLength();
  MOZ_ASSERT(aOffset + wordLen <= GetLength(), "word overruns end of textrun");

  CompressedGlyph* charGlyphs = GetCharacterGlyphs();
  const CompressedGlyph* wordGlyphs = aShapedWord->GetCharacterGlyphs();
  if (aShapedWord->HasDetailedGlyphs()) {
    for (uint32_t i = 0; i < wordLen; ++i, ++aOffset) {
      const CompressedGlyph& g = wordGlyphs[i];
      if (!g.IsSimpleGlyph()) {
        const DetailedGlyph* details =
            g.GetGlyphCount() > 0 ? aShapedWord->GetDetailedGlyphs(i) : nullptr;
        SetDetailedGlyphs(aOffset, g.GetGlyphCount(), details);
      }
      charGlyphs[aOffset] = g;
    }
  } else {
    memcpy(charGlyphs + aOffset, wordGlyphs, wordLen * sizeof(CompressedGlyph));
  }
}

void gfxTextRun::CopyGlyphDataFrom(gfxTextRun* aSource, Range aRange,
                                   uint32_t aDest) {
  MOZ_ASSERT(aRange.end <= aSource->GetLength(),
             "Source substring out of range");
  MOZ_ASSERT(aDest + aRange.Length() <= GetLength(),
             "Destination substring out of range");

  if (aSource->mDontSkipDrawing) {
    mDontSkipDrawing = true;
  }

  // Copy base glyph data, and DetailedGlyph data where present
  const CompressedGlyph* srcGlyphs = aSource->mCharacterGlyphs + aRange.start;
  CompressedGlyph* dstGlyphs = mCharacterGlyphs + aDest;
  for (uint32_t i = 0; i < aRange.Length(); ++i) {
    CompressedGlyph g = srcGlyphs[i];
    g.SetCanBreakBefore(!g.IsClusterStart()
                            ? CompressedGlyph::FLAG_BREAK_TYPE_NONE
                            : dstGlyphs[i].CanBreakBefore());
    if (!g.IsSimpleGlyph()) {
      uint32_t count = g.GetGlyphCount();
      if (count > 0) {
        // DetailedGlyphs allocation is infallible, so this should never be
        // null unless the source textrun is somehow broken.
        DetailedGlyph* src = aSource->GetDetailedGlyphs(i + aRange.start);
        MOZ_ASSERT(src, "missing DetailedGlyphs?");
        if (src) {
          DetailedGlyph* dst = AllocateDetailedGlyphs(i + aDest, count);
          ::memcpy(dst, src, count * sizeof(DetailedGlyph));
        } else {
          g.SetMissing();
        }
      }
    }
    dstGlyphs[i] = g;
  }

  // Copy glyph runs
#ifdef DEBUG
  GlyphRun* prevRun = nullptr;
#endif
  for (GlyphRunIterator iter(aSource, aRange); !iter.AtEnd(); iter.NextRun()) {
    gfxFont* font = iter.GlyphRun()->mFont;
    MOZ_ASSERT(!prevRun || !prevRun->Matches(iter.GlyphRun()->mFont,
                                             iter.GlyphRun()->mOrientation,
                                             iter.GlyphRun()->mIsCJK,
                                             FontMatchType::Kind::kUnspecified),
               "Glyphruns not coalesced?");
#ifdef DEBUG
    prevRun = const_cast<GlyphRun*>(iter.GlyphRun());
    uint32_t end = iter.StringEnd();
#endif
    uint32_t start = iter.StringStart();

    // These used to be NS_ASSERTION()s, but WARNING is more appropriate.
    // Although it's unusual (and not desirable), it's possible for us to assign
    // different fonts to a base character and a following diacritic.
    // Example on OSX 10.5/10.6 with default fonts installed:
    //     data:text/html,<p style="font-family:helvetica, arial, sans-serif;">
    //                    &%23x043E;&%23x0486;&%23x20;&%23x043E;&%23x0486;
    // This means the rendering of the cluster will probably not be very good,
    // but it's the best we can do for now if the specified font only covered
    // the initial base character and not its applied marks.
    NS_WARNING_ASSERTION(aSource->IsClusterStart(start),
                         "Started font run in the middle of a cluster");
    NS_WARNING_ASSERTION(
        end == aSource->GetLength() || aSource->IsClusterStart(end),
        "Ended font run in the middle of a cluster");

    AddGlyphRun(font, iter.GlyphRun()->mMatchType, start - aRange.start + aDest,
                false, iter.GlyphRun()->mOrientation, iter.GlyphRun()->mIsCJK);
  }
}

void gfxTextRun::ClearGlyphsAndCharacters() {
  ResetGlyphRuns();
  memset(reinterpret_cast<char*>(mCharacterGlyphs), 0,
         mLength * sizeof(CompressedGlyph));
  mDetailedGlyphs = nullptr;
}

void gfxTextRun::SetSpaceGlyph(gfxFont* aFont, DrawTarget* aDrawTarget,
                               uint32_t aCharIndex,
                               gfx::ShapedTextFlags aOrientation) {
  if (SetSpaceGlyphIfSimple(aFont, aCharIndex, ' ', aOrientation)) {
    return;
  }

  gfx::ShapedTextFlags flags =
      gfx::ShapedTextFlags::TEXT_IS_8BIT | aOrientation;
  bool vertical =
      !!(GetFlags() & gfx::ShapedTextFlags::TEXT_ORIENT_VERTICAL_UPRIGHT);
  gfxFontShaper::RoundingFlags roundingFlags =
      aFont->GetRoundOffsetsToPixels(aDrawTarget);
  aFont->ProcessSingleSpaceShapedWord(
      aDrawTarget, vertical, mAppUnitsPerDevUnit, flags, roundingFlags,
      [&](gfxShapedWord* aShapedWord) {
        const GlyphRun* prevRun = TrailingGlyphRun();
        bool isCJK = prevRun && prevRun->mFont == aFont &&
                             prevRun->mOrientation == aOrientation
                         ? prevRun->mIsCJK
                         : false;
        AddGlyphRun(aFont, FontMatchType::Kind::kUnspecified, aCharIndex, false,
                    aOrientation, isCJK);
        CopyGlyphDataFrom(aShapedWord, aCharIndex);
        GetCharacterGlyphs()[aCharIndex].SetIsSpace();
      });
}

bool gfxTextRun::SetSpaceGlyphIfSimple(gfxFont* aFont, uint32_t aCharIndex,
                                       char16_t aSpaceChar,
                                       gfx::ShapedTextFlags aOrientation) {
  uint32_t spaceGlyph = aFont->GetSpaceGlyph();
  if (!spaceGlyph || !CompressedGlyph::IsSimpleGlyphID(spaceGlyph)) {
    return false;
  }

  gfxFont::Orientation fontOrientation =
      (aOrientation & gfx::ShapedTextFlags::TEXT_ORIENT_VERTICAL_UPRIGHT)
          ? nsFontMetrics::eVertical
          : nsFontMetrics::eHorizontal;
  uint32_t spaceWidthAppUnits = NS_lroundf(
      aFont->GetMetrics(fontOrientation).spaceWidth * mAppUnitsPerDevUnit);
  if (!CompressedGlyph::IsSimpleAdvance(spaceWidthAppUnits)) {
    return false;
  }

  const GlyphRun* prevRun = TrailingGlyphRun();
  bool isCJK = prevRun && prevRun->mFont == aFont &&
                       prevRun->mOrientation == aOrientation
                   ? prevRun->mIsCJK
                   : false;
  AddGlyphRun(aFont, FontMatchType::Kind::kUnspecified, aCharIndex, false,
              aOrientation, isCJK);
  CompressedGlyph g =
      CompressedGlyph::MakeSimpleGlyph(spaceWidthAppUnits, spaceGlyph);
  if (aSpaceChar == ' ') {
    g.SetIsSpace();
  }
  GetCharacterGlyphs()[aCharIndex] = g;
  return true;
}

void gfxTextRun::FetchGlyphExtents(DrawTarget* aRefDrawTarget) const {
  bool needsGlyphExtents = NeedsGlyphExtents();
  if (!needsGlyphExtents && !mDetailedGlyphs) {
    return;
  }

  uint32_t runCount;
  const GlyphRun* glyphRuns = GetGlyphRuns(&runCount);
  CompressedGlyph* charGlyphs = mCharacterGlyphs;
  for (uint32_t i = 0; i < runCount; ++i) {
    const GlyphRun& run = glyphRuns[i];
    gfxFont* font = run.mFont;
    if (MOZ_UNLIKELY(font->GetStyle()->AdjustedSizeMustBeZero())) {
      continue;
    }

    uint32_t start = run.mCharacterOffset;
    uint32_t end =
        i + 1 < runCount ? glyphRuns[i + 1].mCharacterOffset : GetLength();
    gfxGlyphExtents* extents =
        font->GetOrCreateGlyphExtents(mAppUnitsPerDevUnit);

    AutoReadLock lock(extents->mLock);
    for (uint32_t j = start; j < end; ++j) {
      const gfxTextRun::CompressedGlyph* glyphData = &charGlyphs[j];
      if (glyphData->IsSimpleGlyph()) {
        // If we're in speed mode, don't set up glyph extents here; we'll
        // just return "optimistic" glyph bounds later
        if (needsGlyphExtents) {
          uint32_t glyphIndex = glyphData->GetSimpleGlyph();
          if (!extents->IsGlyphKnownLocked(glyphIndex)) {
#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
            ++gGlyphExtentsSetupEagerSimple;
#endif
            extents->mLock.ReadUnlock();
            font->SetupGlyphExtents(aRefDrawTarget, glyphIndex, false, extents);
            extents->mLock.ReadLock();
          }
        }
      } else if (!glyphData->IsMissing()) {
        uint32_t glyphCount = glyphData->GetGlyphCount();
        if (glyphCount == 0) {
          continue;
        }
        const gfxTextRun::DetailedGlyph* details = GetDetailedGlyphs(j);
        if (!details) {
          continue;
        }
        for (uint32_t k = 0; k < glyphCount; ++k, ++details) {
          uint32_t glyphIndex = details->mGlyphID;
          if (!extents->IsGlyphKnownWithTightExtentsLocked(glyphIndex)) {
#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
            ++gGlyphExtentsSetupEagerTight;
#endif
            extents->mLock.ReadUnlock();
            font->SetupGlyphExtents(aRefDrawTarget, glyphIndex, true, extents);
            extents->mLock.ReadLock();
          }
        }
      }
    }
  }
}

size_t gfxTextRun::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) {
  size_t total = mGlyphRuns.ShallowSizeOfExcludingThis(aMallocSizeOf);

  if (mDetailedGlyphs) {
    total += mDetailedGlyphs->SizeOfIncludingThis(aMallocSizeOf);
  }

  return total;
}

size_t gfxTextRun::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) {
  return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
}

#ifdef DEBUG_FRAME_DUMP
void gfxTextRun::Dump(FILE* out) {
#  define APPEND_FLAG(string_, enum_, field_, flag_)                    \
    if (field_ & enum_::flag_) {                                        \
      string_.AppendPrintf(remaining != field_ ? " %s" : "%s", #flag_); \
      remaining &= ~enum_::flag_;                                       \
    }
#  define APPEND_FLAGS(string_, enum_, field_, flags_)              \
    {                                                               \
      auto remaining = field_;                                      \
      MOZ_FOR_EACH(APPEND_FLAG, (string_, enum_, field_, ), flags_) \
      if (int(remaining)) {                                         \
        string_.AppendPrintf(" %s(0x%0x)", #enum_, int(remaining)); \
      }                                                             \
    }

  nsCString flagsString;
  ShapedTextFlags orient = mFlags & ShapedTextFlags::TEXT_ORIENT_MASK;
  ShapedTextFlags otherFlags = mFlags & ~ShapedTextFlags::TEXT_ORIENT_MASK;
  APPEND_FLAGS(flagsString, ShapedTextFlags, otherFlags,
               (TEXT_IS_RTL, TEXT_ENABLE_SPACING, TEXT_IS_8BIT,
                TEXT_ENABLE_HYPHEN_BREAKS, TEXT_NEED_BOUNDING_BOX,
                TEXT_DISABLE_OPTIONAL_LIGATURES, TEXT_OPTIMIZE_SPEED,
                TEXT_HIDE_CONTROL_CHARACTERS, TEXT_TRAILING_ARABICCHAR,
                TEXT_INCOMING_ARABICCHAR, TEXT_USE_MATH_SCRIPT))

  if (orient != ShapedTextFlags::TEXT_ORIENT_HORIZONTAL &&
      !flagsString.IsEmpty()) {
    flagsString += ' ';
  }

  switch (orient) {
    case ShapedTextFlags::TEXT_ORIENT_HORIZONTAL:
      break;
    case ShapedTextFlags::TEXT_ORIENT_VERTICAL_UPRIGHT:
--> --------------------

--> maximum size reached

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

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