Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1551 insertions, 0 deletions

diff --git a/gfx/thebes/gfxTextRun.h b/gfx/thebes/gfxTextRun.h
new file mode 100644
index 0000000000..e5720b21e6
--- /dev/null
+++ b/gfx/thebes/gfxTextRun.h
@@ -0,0 +1,1551 @@
+/* -*- 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/. */
+
+#ifndef GFX_TEXTRUN_H
+#define GFX_TEXTRUN_H
+
+#include <stdint.h>
+
+#include "gfxTypes.h"
+#include "gfxPoint.h"
+#include "gfxFont.h"
+#include "gfxFontConstants.h"
+#include "gfxSkipChars.h"
+#include "gfxPlatform.h"
+#include "gfxPlatformFontList.h"
+#include "gfxUserFontSet.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
+#include "nsPoint.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "nsTextFrameUtils.h"
+#include "DrawMode.h"
+#include "harfbuzz/hb.h"
+#include "nsUnicodeScriptCodes.h"
+#include "nsColor.h"
+#include "nsFrameList.h"
+#include "X11UndefineNone.h"
+
+#ifdef DEBUG_FRAME_DUMP
+#  include <stdio.h>
+#endif
+
+class gfxContext;
+class gfxFontGroup;
+class nsAtom;
+class nsLanguageAtomService;
+class gfxMissingFontRecorder;
+
+namespace mozilla {
+class PostTraversalTask;
+class SVGContextPaint;
+enum class StyleHyphens : uint8_t;
+};  // namespace mozilla
+
+/**
+ * Callback for Draw() to use when drawing text with mode
+ * DrawMode::GLYPH_PATH.
+ */
+struct gfxTextRunDrawCallbacks {
+  /**
+   * Constructs a new DrawCallbacks object.
+   *
+   * @param aShouldPaintSVGGlyphs If true, SVG glyphs will be painted.  If
+   *   false, SVG glyphs will not be painted; fallback plain glyphs are not
+   *   emitted either.
+   */
+  explicit gfxTextRunDrawCallbacks(bool aShouldPaintSVGGlyphs = false)
+      : mShouldPaintSVGGlyphs(aShouldPaintSVGGlyphs) {}
+
+  /**
+   * Called when a path has been emitted to the gfxContext when
+   * painting a text run.  This can be called any number of times,
+   * due to partial ligatures and intervening SVG glyphs.
+   */
+  virtual void NotifyGlyphPathEmitted() = 0;
+
+  bool mShouldPaintSVGGlyphs;
+};
+
+/**
+ * gfxTextRun is an abstraction for drawing and measuring substrings of a run
+ * of text. It stores runs of positioned glyph data, each run having a single
+ * gfxFont. The glyphs are associated with a string of source text, and the
+ * gfxTextRun APIs take parameters that are offsets into that source text.
+ *
+ * gfxTextRuns are mostly immutable. The only things that can change are
+ * inter-cluster spacing and line break placement. Spacing is always obtained
+ * lazily by methods that need it, it is not cached. Line breaks are stored
+ * persistently (insofar as they affect the shaping of glyphs; gfxTextRun does
+ * not actually do anything to explicitly account for line breaks). Initially
+ * there are no line breaks. The textrun can record line breaks before or after
+ * any given cluster. (Line breaks specified inside clusters are ignored.)
+ *
+ * It is important that zero-length substrings are handled correctly. This will
+ * be on the test!
+ */
+class gfxTextRun : public gfxShapedText {
+  NS_INLINE_DECL_REFCOUNTING(gfxTextRun);
+
+ protected:
+  // Override operator delete to properly free the object that was
+  // allocated via malloc.
+  void operator delete(void* p) { free(p); }
+
+  virtual ~gfxTextRun();
+
+ public:
+  typedef gfxFont::RunMetrics Metrics;
+  typedef mozilla::gfx::DrawTarget DrawTarget;
+
+  // Public textrun API for general use
+
+  bool IsClusterStart(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].IsClusterStart();
+  }
+  bool IsLigatureGroupStart(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].IsLigatureGroupStart();
+  }
+  bool CanBreakLineBefore(uint32_t aPos) const {
+    return CanBreakBefore(aPos) == CompressedGlyph::FLAG_BREAK_TYPE_NORMAL;
+  }
+  bool CanHyphenateBefore(uint32_t aPos) const {
+    return CanBreakBefore(aPos) == CompressedGlyph::FLAG_BREAK_TYPE_HYPHEN;
+  }
+
+  // Returns a gfxShapedText::CompressedGlyph::FLAG_BREAK_TYPE_* value
+  // as defined in gfxFont.h (may be NONE, NORMAL or HYPHEN).
+  uint8_t CanBreakBefore(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].CanBreakBefore();
+  }
+
+  bool CharIsSpace(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].CharIsSpace();
+  }
+  bool CharIsTab(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].CharIsTab();
+  }
+  bool CharIsNewline(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].CharIsNewline();
+  }
+  bool CharMayHaveEmphasisMark(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].CharMayHaveEmphasisMark();
+  }
+  bool CharIsFormattingControl(uint32_t aPos) const {
+    MOZ_ASSERT(aPos < GetLength());
+    return mCharacterGlyphs[aPos].CharIsFormattingControl();
+  }
+
+  // All offsets are in terms of the string passed into MakeTextRun.
+
+  // Describe range [start, end) of a text run. The range is
+  // restricted to grapheme cluster boundaries.
+  struct Range {
+    uint32_t start;
+    uint32_t end;
+    uint32_t Length() const { return end - start; }
+
+    Range() : start(0), end(0) {}
+    Range(uint32_t aStart, uint32_t aEnd) : start(aStart), end(aEnd) {}
+    explicit Range(const gfxTextRun* aTextRun)
+        : start(0), end(aTextRun->GetLength()) {}
+  };
+
+  // All coordinates are in layout/app units
+
+  /**
+   * Set the potential linebreaks for a substring of the textrun. These are
+   * the "allow break before" points. Initially, there are no potential
+   * linebreaks.
+   *
+   * This can change glyphs and/or geometry! Some textruns' shapes
+   * depend on potential line breaks (e.g., title-case-converting textruns).
+   * This function is virtual so that those textruns can reshape themselves.
+   *
+   * @return true if this changed the linebreaks, false if the new line
+   * breaks are the same as the old
+   */
+  virtual bool SetPotentialLineBreaks(Range aRange,
+                                      const uint8_t* aBreakBefore);
+
+  enum class HyphenType : uint8_t {
+    // Code in BreakAndMeasureText depends on the ordering of these values!
+    None,
+    Explicit,
+    Soft,
+    AutoWithManualInSameWord,
+    AutoWithoutManualInSameWord
+  };
+
+  struct HyphenationState {
+    uint32_t mostRecentBoundary = 0;
+    bool hasManualHyphen = false;
+    bool hasExplicitHyphen = false;
+    bool hasAutoHyphen = false;
+  };
+
+  /**
+   * Layout provides PropertyProvider objects. These allow detection of
+   * potential line break points and computation of spacing. We pass the data
+   * this way to allow lazy data acquisition; for example BreakAndMeasureText
+   * will want to only ask for properties of text it's actually looking at.
+   *
+   * NOTE that requested spacing may not actually be applied, if the textrun
+   * is unable to apply it in some context. Exception: spacing around a
+   * whitespace character MUST always be applied.
+   */
+  class PropertyProvider {
+   public:
+    // Detect hyphenation break opportunities in the given range; breaks
+    // not at cluster boundaries will be ignored.
+    virtual void GetHyphenationBreaks(Range aRange,
+                                      HyphenType* aBreakBefore) const = 0;
+
+    // Returns the provider's hyphenation setting, so callers can decide
+    // whether it is necessary to call GetHyphenationBreaks.
+    // Result is an StyleHyphens value.
+    virtual mozilla::StyleHyphens GetHyphensOption() const = 0;
+
+    // Returns the extra width that will be consumed by a hyphen. This should
+    // be constant for a given textrun.
+    virtual gfxFloat GetHyphenWidth() const = 0;
+
+    typedef gfxFont::Spacing Spacing;
+
+    /**
+     * Get the spacing around the indicated characters. Spacing must be zero
+     * inside clusters. In other words, if character i is not
+     * CLUSTER_START, then character i-1 must have zero after-spacing and
+     * character i must have zero before-spacing.
+     */
+    virtual void GetSpacing(Range aRange, Spacing* aSpacing) const = 0;
+
+    // Returns a gfxContext that can be used to measure the hyphen glyph.
+    // Only called if the hyphen width is requested.
+    virtual already_AddRefed<DrawTarget> GetDrawTarget() const = 0;
+
+    // Return the appUnitsPerDevUnit value to be used when measuring.
+    // Only called if the hyphen width is requested.
+    virtual uint32_t GetAppUnitsPerDevUnit() const = 0;
+  };
+
+  struct MOZ_STACK_CLASS DrawParams {
+    gfxContext* context;
+    DrawMode drawMode = DrawMode::GLYPH_FILL;
+    nscolor textStrokeColor = 0;
+    gfxPattern* textStrokePattern = nullptr;
+    const mozilla::gfx::StrokeOptions* strokeOpts = nullptr;
+    const mozilla::gfx::DrawOptions* drawOpts = nullptr;
+    PropertyProvider* provider = nullptr;
+    // If non-null, the advance width of the substring is set.
+    gfxFloat* advanceWidth = nullptr;
+    mozilla::SVGContextPaint* contextPaint = nullptr;
+    gfxTextRunDrawCallbacks* callbacks = nullptr;
+    explicit DrawParams(gfxContext* aContext) : context(aContext) {}
+  };
+
+  /**
+   * Draws a substring. Uses only GetSpacing from aBreakProvider.
+   * The provided point is the baseline origin on the left of the string
+   * for LTR, on the right of the string for RTL.
+   *
+   * Drawing should respect advance widths in the sense that for LTR runs,
+   *   Draw(Range(start, middle), pt, ...) followed by
+   *   Draw(Range(middle, end), gfxPoint(pt.x + advance, pt.y), ...)
+   * should have the same effect as
+   *   Draw(Range(start, end), pt, ...)
+   *
+   * For RTL runs the rule is:
+   *   Draw(Range(middle, end), pt, ...) followed by
+   *   Draw(Range(start, middle), gfxPoint(pt.x + advance, pt.y), ...)
+   * should have the same effect as
+   *   Draw(Range(start, end), pt, ...)
+   *
+   * Glyphs should be drawn in logical content order, which can be significant
+   * if they overlap (perhaps due to negative spacing).
+   */
+  void Draw(const Range aRange, const mozilla::gfx::Point aPt,
+            const DrawParams& aParams) const;
+
+  /**
+   * Draws the emphasis marks for this text run. Uses only GetSpacing
+   * from aProvider. The provided point is the baseline origin of the
+   * line of emphasis marks.
+   */
+  void DrawEmphasisMarks(gfxContext* aContext, gfxTextRun* aMark,
+                         gfxFloat aMarkAdvance, mozilla::gfx::Point aPt,
+                         Range aRange, PropertyProvider* aProvider) const;
+
+  /**
+   * Computes the ReflowMetrics for a substring.
+   * Uses GetSpacing from aBreakProvider.
+   * @param aBoundingBoxType which kind of bounding box (loose/tight)
+   */
+  Metrics MeasureText(Range aRange, gfxFont::BoundingBoxType aBoundingBoxType,
+                      DrawTarget* aDrawTargetForTightBoundingBox,
+                      PropertyProvider* aProvider) const;
+
+  Metrics MeasureText(gfxFont::BoundingBoxType aBoundingBoxType,
+                      DrawTarget* aDrawTargetForTightBoundingBox,
+                      PropertyProvider* aProvider = nullptr) const {
+    return MeasureText(Range(this), aBoundingBoxType,
+                       aDrawTargetForTightBoundingBox, aProvider);
+  }
+
+  /**
+   * Computes just the advance width for a substring.
+   * Uses GetSpacing from aBreakProvider.
+   * If aSpacing is not null, the spacing attached before and after
+   * the substring would be returned in it. NOTE: the spacing is
+   * included in the advance width.
+   */
+  gfxFloat GetAdvanceWidth(Range aRange, PropertyProvider* aProvider,
+                           PropertyProvider::Spacing* aSpacing = nullptr) const;
+
+  gfxFloat GetAdvanceWidth() const {
+    return GetAdvanceWidth(Range(this), nullptr);
+  }
+
+  /**
+   * Computes the minimum advance width for a substring assuming line
+   * breaking is allowed everywhere.
+   */
+  gfxFloat GetMinAdvanceWidth(Range aRange);
+
+  /**
+   * Clear all stored line breaks for the given range (both before and after),
+   * and then set the line-break state before aRange.start to aBreakBefore and
+   * after the last cluster to aBreakAfter.
+   *
+   * We require that before and after line breaks be consistent. For clusters
+   * i and i+1, we require that if there is a break after cluster i, a break
+   * will be specified before cluster i+1. This may be temporarily violated
+   * (e.g. after reflowing line L and before reflowing line L+1); to handle
+   * these temporary violations, we say that there is a break betwen i and i+1
+   * if a break is specified after i OR a break is specified before i+1.
+   *
+   * This can change textrun geometry! The existence of a linebreak can affect
+   * the advance width of the cluster before the break (when kerning) or the
+   * geometry of one cluster before the break or any number of clusters
+   * after the break. (The one-cluster-before-the-break limit is somewhat
+   * arbitrary; if some scripts require breaking it, then we need to
+   * alter nsTextFrame::TrimTrailingWhitespace, perhaps drastically becase
+   * it could affect the layout of frames before it...)
+   *
+   * We return true if glyphs or geometry changed, false otherwise. This
+   * function is virtual so that gfxTextRun subclasses can reshape
+   * properly.
+   *
+   * @param aAdvanceWidthDelta if non-null, returns the change in advance
+   * width of the given range.
+   */
+  virtual bool SetLineBreaks(Range aRange, bool aLineBreakBefore,
+                             bool aLineBreakAfter,
+                             gfxFloat* aAdvanceWidthDelta);
+
+  enum SuppressBreak {
+    eNoSuppressBreak,
+    // Measure the range of text as if there is no break before it.
+    eSuppressInitialBreak,
+    // Measure the range of text as if it contains no break
+    eSuppressAllBreaks
+  };
+
+  void ClassifyAutoHyphenations(uint32_t aStart, Range aRange,
+                                nsTArray<HyphenType>& aHyphenBuffer,
+                                HyphenationState* aWordState);
+
+  /**
+   * Finds the longest substring that will fit into the given width.
+   * Uses GetHyphenationBreaks and GetSpacing from aProvider.
+   * Guarantees the following:
+   * -- 0 <= result <= aMaxLength
+   * -- result is the maximal value of N such that either
+   *       N < aMaxLength && line break at N &&
+   *       GetAdvanceWidth(Range(aStart, N), aProvider) <= aWidth
+   *   OR  N < aMaxLength && hyphen break at N &&
+   *       GetAdvanceWidth(Range(aStart, N), aProvider) +
+   *       GetHyphenWidth() <= aWidth
+   *   OR  N == aMaxLength &&
+   *       GetAdvanceWidth(Range(aStart, N), aProvider) <= aWidth
+   * where GetAdvanceWidth assumes the effect of
+   * SetLineBreaks(Range(aStart, N),
+   *               aLineBreakBefore, N < aMaxLength, aProvider)
+   * -- if no such N exists, then result is the smallest N such that
+   *       N < aMaxLength && line break at N
+   *   OR  N < aMaxLength && hyphen break at N
+   *   OR  N == aMaxLength
+   *
+   * The call has the effect of
+   * SetLineBreaks(Range(aStart, result), aLineBreakBefore,
+   *               result < aMaxLength, aProvider)
+   * and the returned metrics and the invariants above reflect this.
+   *
+   * @param aMaxLength this can be UINT32_MAX, in which case the length used
+   * is up to the end of the string
+   * @param aLineBreakBefore set to true if and only if there is an actual
+   * line break at the start of this string.
+   * @param aSuppressBreak what break should be suppressed.
+   * @param aTrimWhitespace if non-null, then we allow a trailing run of
+   * spaces to be trimmed; the width of the space(s) will not be included in
+   * the measured string width for comparison with the limit aWidth, and
+   * trimmed spaces will not be included in returned metrics. The width
+   * of the trimmed spaces will be returned in aTrimWhitespace.
+   * Trimmed spaces are still counted in the "characters fit" result.
+   * @param aHangWhitespace true if we allow whitespace to overflow the
+   * container at a soft-wrap
+   * @param aMetrics if non-null, we fill this in for the returned substring.
+   * If a hyphenation break was used, the hyphen is NOT included in the returned
+   * metrics.
+   * @param aBoundingBoxType whether to make the bounding box in aMetrics tight
+   * @param aDrawTargetForTightBoundingbox a reference DrawTarget to get the
+   * tight bounding box, if requested
+   * @param aUsedHyphenation if non-null, records if we selected a hyphenation
+   * break
+   * @param aLastBreak if non-null and result is aMaxLength, we set this to
+   * the maximal N such that
+   *       N < aMaxLength && line break at N &&
+   *       GetAdvanceWidth(Range(aStart, N), aProvider) <= aWidth
+   *   OR  N < aMaxLength && hyphen break at N &&
+   *       GetAdvanceWidth(Range(aStart, N), aProvider) +
+   *         GetHyphenWidth() <= aWidth
+   * or UINT32_MAX if no such N exists, where GetAdvanceWidth assumes
+   * the effect of
+   * SetLineBreaks(Range(aStart, N), aLineBreakBefore,
+   *               N < aMaxLength, aProvider)
+   *
+   * @param aCanWordWrap true if we can break between any two grapheme
+   * clusters. This is set by overflow-wrap|word-wrap: break-word
+   *
+   * @param aBreakPriority in/out the priority of the break opportunity
+   * saved in the line. If we are prioritizing break opportunities, we will
+   * not set a break with a lower priority. @see gfxBreakPriority.
+   *
+   * Note that negative advance widths are possible especially if negative
+   * spacing is provided.
+   */
+  uint32_t BreakAndMeasureText(uint32_t aStart, uint32_t aMaxLength,
+                               bool aLineBreakBefore, gfxFloat aWidth,
+                               PropertyProvider* aProvider,
+                               SuppressBreak aSuppressBreak,
+                               gfxFloat* aTrimWhitespace, bool aHangWhitespace,
+                               Metrics* aMetrics,
+                               gfxFont::BoundingBoxType aBoundingBoxType,
+                               DrawTarget* aDrawTargetForTightBoundingBox,
+                               bool* aUsedHyphenation, uint32_t* aLastBreak,
+                               bool aCanWordWrap, bool aCanWhitespaceWrap,
+                               gfxBreakPriority* aBreakPriority);
+
+  // Utility getters
+
+  void* GetUserData() const { return mUserData; }
+  void SetUserData(void* aUserData) { mUserData = aUserData; }
+
+  void SetFlagBits(nsTextFrameUtils::Flags aFlags) { mFlags2 |= aFlags; }
+  void ClearFlagBits(nsTextFrameUtils::Flags aFlags) { mFlags2 &= ~aFlags; }
+  const gfxSkipChars& GetSkipChars() const { return mSkipChars; }
+  gfxFontGroup* GetFontGroup() const { return mFontGroup; }
+
+  // Call this, don't call "new gfxTextRun" directly. This does custom
+  // allocation and initialization
+  static already_AddRefed<gfxTextRun> Create(
+      const gfxTextRunFactory::Parameters* aParams, uint32_t aLength,
+      gfxFontGroup* aFontGroup, mozilla::gfx::ShapedTextFlags aFlags,
+      nsTextFrameUtils::Flags aFlags2);
+
+  // The text is divided into GlyphRuns as necessary. (In the vast majority
+  // of cases, a gfxTextRun contains just a single GlyphRun.)
+  struct GlyphRun {
+    RefPtr<gfxFont> mFont;      // never null in a valid GlyphRun
+    uint32_t mCharacterOffset;  // into original UTF16 string
+    mozilla::gfx::ShapedTextFlags
+        mOrientation;  // gfxTextRunFactory::TEXT_ORIENT_* value
+    FontMatchType mMatchType;
+    bool mIsCJK;  // Whether the text was a CJK script run (used to decide if
+                  // text-decoration-skip-ink should not be applied)
+
+    // Set up the properties (but NOT offset) of the GlyphRun.
+    void SetProperties(gfxFont* aFont,
+                       mozilla::gfx::ShapedTextFlags aOrientation, bool aIsCJK,
+                       FontMatchType aMatchType) {
+      mFont = aFont;
+      mOrientation = aOrientation;
+      mIsCJK = aIsCJK;
+      mMatchType = aMatchType;
+    }
+
+    // Return whether the GlyphRun matches the given properties;
+    // the given FontMatchType will be added to the run if not present.
+    bool Matches(gfxFont* aFont, mozilla::gfx::ShapedTextFlags aOrientation,
+                 bool aIsCJK, FontMatchType aMatchType) {
+      if (mFont == aFont && mOrientation == aOrientation && mIsCJK == aIsCJK) {
+        mMatchType.kind |= aMatchType.kind;
+        if (mMatchType.generic == mozilla::StyleGenericFontFamily::None) {
+          mMatchType.generic = aMatchType.generic;
+        }
+        return true;
+      }
+      return false;
+    }
+  };
+
+  // Script run codes that we will mark as CJK to suppress skip-ink behavior.
+  static inline bool IsCJKScript(Script aScript) {
+    switch (aScript) {
+      case Script::BOPOMOFO:
+      case Script::HAN:
+      case Script::HANGUL:
+      case Script::HIRAGANA:
+      case Script::KATAKANA:
+      case Script::KATAKANA_OR_HIRAGANA:
+      case Script::SIMPLIFIED_HAN:
+      case Script::TRADITIONAL_HAN:
+      case Script::JAPANESE:
+      case Script::KOREAN:
+      case Script::HAN_WITH_BOPOMOFO:
+      case Script::JAMO:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  class MOZ_STACK_CLASS GlyphRunIterator {
+   public:
+    GlyphRunIterator(const gfxTextRun* aTextRun, Range aRange,
+                     bool aReverse = false)
+        : mTextRun(aTextRun),
+          mDirection(aReverse ? -1 : 1),
+          mStartOffset(aRange.start),
+          mEndOffset(aRange.end) {
+      mNextIndex = mTextRun->FindFirstGlyphRunContaining(
+          aReverse ? aRange.end - 1 : aRange.start);
+    }
+    bool NextRun();
+    const GlyphRun* GetGlyphRun() const { return mGlyphRun; }
+    uint32_t GetStringStart() const { return mStringStart; }
+    uint32_t GetStringEnd() const { return mStringEnd; }
+
+   private:
+    const gfxTextRun* mTextRun;
+    MOZ_INIT_OUTSIDE_CTOR const GlyphRun* mGlyphRun;
+    MOZ_INIT_OUTSIDE_CTOR uint32_t mStringStart;
+    MOZ_INIT_OUTSIDE_CTOR uint32_t mStringEnd;
+    const int32_t mDirection;
+    int32_t mNextIndex;
+    uint32_t mStartOffset;
+    uint32_t mEndOffset;
+  };
+
+  class GlyphRunOffsetComparator {
+   public:
+    bool Equals(const GlyphRun& a, const GlyphRun& b) const {
+      return a.mCharacterOffset == b.mCharacterOffset;
+    }
+
+    bool LessThan(const GlyphRun& a, const GlyphRun& b) const {
+      return a.mCharacterOffset < b.mCharacterOffset;
+    }
+  };
+
+  friend class GlyphRunIterator;
+  friend class FontSelector;
+
+  // API for setting up the textrun glyphs. Should only be called by
+  // things that construct textruns.
+  /**
+   * We've found a run of text that should use a particular font. Call this
+   * only during initialization when font substitution has been computed.
+   * Call it before setting up the glyphs for the characters in this run;
+   * SetMissingGlyph requires that the correct glyphrun be installed.
+   *
+   * If aForceNewRun, a new glyph run will be added, even if the
+   * previously added run uses the same font.  If glyph runs are
+   * added out of strictly increasing aStartCharIndex order (via
+   * force), then SortGlyphRuns must be called after all glyph runs
+   * are added before any further operations are performed with this
+   * TextRun.
+   */
+  void AddGlyphRun(gfxFont* aFont, FontMatchType aMatchType,
+                   uint32_t aUTF16Offset, bool aForceNewRun,
+                   mozilla::gfx::ShapedTextFlags aOrientation, bool aIsCJK);
+  void ResetGlyphRuns() {
+    if (mHasGlyphRunArray) {
+      MOZ_ASSERT(mGlyphRunArray.Length() > 1);
+      // Discard all but the first GlyphRun...
+      mGlyphRunArray.TruncateLength(1);
+      // ...and then convert to the single-run representation.
+      ConvertFromGlyphRunArray();
+    }
+    // Clear out the one remaining GlyphRun.
+    mSingleGlyphRun.mFont = nullptr;
+  }
+  void SortGlyphRuns();
+  void SanitizeGlyphRuns();
+
+  const CompressedGlyph* GetCharacterGlyphs() const final {
+    MOZ_ASSERT(mCharacterGlyphs, "failed to initialize mCharacterGlyphs");
+    return mCharacterGlyphs;
+  }
+  CompressedGlyph* GetCharacterGlyphs() final {
+    MOZ_ASSERT(mCharacterGlyphs, "failed to initialize mCharacterGlyphs");
+    return mCharacterGlyphs;
+  }
+
+  // clean out results from shaping in progress, used for fallback scenarios
+  void ClearGlyphsAndCharacters();
+
+  void SetSpaceGlyph(gfxFont* aFont, DrawTarget* aDrawTarget,
+                     uint32_t aCharIndex,
+                     mozilla::gfx::ShapedTextFlags aOrientation);
+
+  // Set the glyph data for the given character index to the font's
+  // space glyph, IF this can be done as a "simple" glyph record
+  // (not requiring a DetailedGlyph entry). This avoids the need to call
+  // the font shaper and go through the shaped-word cache for most spaces.
+  //
+  // The parameter aSpaceChar is the original character code for which
+  // this space glyph is being used; if this is U+0020, we need to record
+  // that it could be trimmed at a run edge, whereas other kinds of space
+  // (currently just U+00A0) would not be trimmable/breakable.
+  //
+  // Returns true if it was able to set simple glyph data for the space;
+  // if it returns false, the caller needs to fall back to some other
+  // means to create the necessary (detailed) glyph data.
+  bool SetSpaceGlyphIfSimple(gfxFont* aFont, uint32_t aCharIndex,
+                             char16_t aSpaceChar,
+                             mozilla::gfx::ShapedTextFlags aOrientation);
+
+  // Record the positions of specific characters that layout may need to
+  // detect in the textrun, even though it doesn't have an explicit copy
+  // of the original text. These are recorded using flag bits in the
+  // CompressedGlyph record; if necessary, we convert "simple" glyph records
+  // to "complex" ones as the Tab and Newline flags are not present in
+  // simple CompressedGlyph records.
+  void SetIsTab(uint32_t aIndex) { EnsureComplexGlyph(aIndex).SetIsTab(); }
+  void SetIsNewline(uint32_t aIndex) {
+    EnsureComplexGlyph(aIndex).SetIsNewline();
+  }
+  void SetNoEmphasisMark(uint32_t aIndex) {
+    EnsureComplexGlyph(aIndex).SetNoEmphasisMark();
+  }
+  void SetIsFormattingControl(uint32_t aIndex) {
+    EnsureComplexGlyph(aIndex).SetIsFormattingControl();
+  }
+
+  /**
+   * Prefetch all the glyph extents needed to ensure that Measure calls
+   * on this textrun not requesting tight boundingBoxes will succeed. Note
+   * that some glyph extents might not be fetched due to OOM or other
+   * errors.
+   */
+  void FetchGlyphExtents(DrawTarget* aRefDrawTarget);
+
+  const GlyphRun* GetGlyphRuns(uint32_t* aNumGlyphRuns) const {
+    if (mHasGlyphRunArray) {
+      *aNumGlyphRuns = mGlyphRunArray.Length();
+      return mGlyphRunArray.Elements();
+    } else {
+      *aNumGlyphRuns = mSingleGlyphRun.mFont ? 1 : 0;
+      return &mSingleGlyphRun;
+    }
+  }
+
+  const GlyphRun* TrailingGlyphRun() const {
+    uint32_t count;
+    const GlyphRun* runs = GetGlyphRuns(&count);
+    return count ? runs + count - 1 : nullptr;
+  }
+
+  // Returns the index of the GlyphRun containing the given offset.
+  // Returns mGlyphRuns.Length() when aOffset is mCharacterCount.
+  uint32_t FindFirstGlyphRunContaining(uint32_t aOffset) const;
+
+  // Copy glyph data from a ShapedWord into this textrun.
+  void CopyGlyphDataFrom(gfxShapedWord* aSource, uint32_t aStart);
+
+  // Copy glyph data for a range of characters from aSource to this
+  // textrun.
+  void CopyGlyphDataFrom(gfxTextRun* aSource, Range aRange, uint32_t aDest);
+
+  // Tell the textrun to release its reference to its creating gfxFontGroup
+  // immediately, rather than on destruction. This is used for textruns
+  // that are actually owned by a gfxFontGroup, so that they don't keep it
+  // permanently alive due to a circular reference. (The caller of this is
+  // taking responsibility for ensuring the textrun will not outlive its
+  // mFontGroup.)
+  void ReleaseFontGroup();
+
+  struct LigatureData {
+    // textrun range of the containing ligature
+    Range mRange;
+    // appunits advance to the start of the ligature part within the ligature;
+    // never includes any spacing
+    gfxFloat mPartAdvance;
+    // appunits width of the ligature part; includes before-spacing
+    // when the part is at the start of the ligature, and after-spacing
+    // when the part is as the end of the ligature
+    gfxFloat mPartWidth;
+
+    bool mClipBeforePart;
+    bool mClipAfterPart;
+  };
+
+  // return storage used by this run, for memory reporter;
+  // nsTransformedTextRun needs to override this as it holds additional data
+  virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
+      MOZ_MUST_OVERRIDE;
+  virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)
+      MOZ_MUST_OVERRIDE;
+
+  nsTextFrameUtils::Flags GetFlags2() const { return mFlags2; }
+
+  // Get the size, if it hasn't already been gotten, marking as it goes.
+  size_t MaybeSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) {
+    if (mFlags2 & nsTextFrameUtils::Flags::RunSizeAccounted) {
+      return 0;
+    }
+    mFlags2 |= nsTextFrameUtils::Flags::RunSizeAccounted;
+    return SizeOfIncludingThis(aMallocSizeOf);
+  }
+  void ResetSizeOfAccountingFlags() {
+    mFlags2 &= ~nsTextFrameUtils::Flags::RunSizeAccounted;
+  }
+
+  // shaping state - for some font features, fallback is required that
+  // affects the entire run. for example, fallback for one script/font
+  // portion of a textrun requires fallback to be applied to the entire run
+
+  enum ShapingState : uint8_t {
+    eShapingState_Normal,               // default state
+    eShapingState_ShapingWithFeature,   // have shaped with feature
+    eShapingState_ShapingWithFallback,  // have shaped with fallback
+    eShapingState_Aborted,              // abort initial iteration
+    eShapingState_ForceFallbackFeature  // redo with fallback forced on
+  };
+
+  ShapingState GetShapingState() const { return mShapingState; }
+  void SetShapingState(ShapingState aShapingState) {
+    mShapingState = aShapingState;
+  }
+
+  int32_t GetAdvanceForGlyph(uint32_t aIndex) const {
+    const CompressedGlyph& glyphData = mCharacterGlyphs[aIndex];
+    if (glyphData.IsSimpleGlyph()) {
+      return glyphData.GetSimpleAdvance();
+    }
+    uint32_t glyphCount = glyphData.GetGlyphCount();
+    if (!glyphCount) {
+      return 0;
+    }
+    const DetailedGlyph* details = GetDetailedGlyphs(aIndex);
+    int32_t advance = 0;
+    for (uint32_t j = 0; j < glyphCount; ++j, ++details) {
+      advance += details->mAdvance;
+    }
+    return advance;
+  }
+
+#ifdef DEBUG_FRAME_DUMP
+  void Dump(FILE* aOutput = stderr);
+#endif
+
+ protected:
+  /**
+   * Create a textrun, and set its mCharacterGlyphs to point immediately
+   * after the base object; this is ONLY used in conjunction with placement
+   * new, after allocating a block large enough for the glyph records to
+   * follow the base textrun object.
+   */
+  gfxTextRun(const gfxTextRunFactory::Parameters* aParams, uint32_t aLength,
+             gfxFontGroup* aFontGroup, mozilla::gfx::ShapedTextFlags aFlags,
+             nsTextFrameUtils::Flags aFlags2);
+
+  /**
+   * Helper for the Create() factory method to allocate the required
+   * glyph storage for a textrun object with the basic size aSize,
+   * plus room for aLength glyph records.
+   */
+  static void* AllocateStorageForTextRun(size_t aSize, uint32_t aLength);
+
+  // Pointer to the array of CompressedGlyph records; must be initialized
+  // when the object is constructed.
+  CompressedGlyph* mCharacterGlyphs;
+
+ private:
+  // **** general helpers ****
+
+  // Get the total advance for a range of glyphs.
+  int32_t GetAdvanceForGlyphs(Range aRange) const;
+
+  // Spacing for characters outside the range aSpacingStart/aSpacingEnd
+  // is assumed to be zero; such characters are not passed to aProvider.
+  // This is useful to protect aProvider from being passed character indices
+  // it is not currently able to handle.
+  bool GetAdjustedSpacingArray(
+      Range aRange, PropertyProvider* aProvider, Range aSpacingRange,
+      nsTArray<PropertyProvider::Spacing>* aSpacing) const;
+
+  CompressedGlyph& EnsureComplexGlyph(uint32_t aIndex) {
+    gfxShapedText::EnsureComplexGlyph(aIndex, mCharacterGlyphs[aIndex]);
+    return mCharacterGlyphs[aIndex];
+  }
+
+  //  **** ligature helpers ****
+  // (Platforms do the actual ligaturization, but we need to do a bunch of stuff
+  // to handle requests that begin or end inside a ligature)
+
+  // if aProvider is null then mBeforeSpacing and mAfterSpacing are set to zero
+  LigatureData ComputeLigatureData(Range aPartRange,
+                                   PropertyProvider* aProvider) const;
+  gfxFloat ComputePartialLigatureWidth(Range aPartRange,
+                                       PropertyProvider* aProvider) const;
+  void DrawPartialLigature(gfxFont* aFont, Range aRange,
+                           mozilla::gfx::Point* aPt,
+                           PropertyProvider* aProvider,
+                           TextRunDrawParams& aParams,
+                           mozilla::gfx::ShapedTextFlags aOrientation) const;
+  // Advance aRange.start to the start of the nearest ligature, back
+  // up aRange.end to the nearest ligature end; may result in
+  // aRange->start == aRange->end.
+  void ShrinkToLigatureBoundaries(Range* aRange) const;
+  // result in appunits
+  gfxFloat GetPartialLigatureWidth(Range aRange,
+                                   PropertyProvider* aProvider) const;
+  void AccumulatePartialLigatureMetrics(
+      gfxFont* aFont, Range aRange, gfxFont::BoundingBoxType aBoundingBoxType,
+      DrawTarget* aRefDrawTarget, PropertyProvider* aProvider,
+      mozilla::gfx::ShapedTextFlags aOrientation, Metrics* aMetrics) const;
+
+  // **** measurement helper ****
+  void AccumulateMetricsForRun(gfxFont* aFont, Range aRange,
+                               gfxFont::BoundingBoxType aBoundingBoxType,
+                               DrawTarget* aRefDrawTarget,
+                               PropertyProvider* aProvider, Range aSpacingRange,
+                               mozilla::gfx::ShapedTextFlags aOrientation,
+                               Metrics* aMetrics) const;
+
+  // **** drawing helper ****
+  void DrawGlyphs(gfxFont* aFont, Range aRange, mozilla::gfx::Point* aPt,
+                  PropertyProvider* aProvider, Range aSpacingRange,
+                  TextRunDrawParams& aParams,
+                  mozilla::gfx::ShapedTextFlags aOrientation) const;
+
+  // The textrun holds either a single GlyphRun -or- an array;
+  // the flag mHasGlyphRunArray tells us which is present.
+  union {
+    GlyphRun mSingleGlyphRun;
+    nsTArray<GlyphRun> mGlyphRunArray;
+  };
+
+  void ConvertToGlyphRunArray() {
+    MOZ_ASSERT(!mHasGlyphRunArray && mSingleGlyphRun.mFont);
+    GlyphRun tmp = std::move(mSingleGlyphRun);
+    mSingleGlyphRun.~GlyphRun();
+    new (&mGlyphRunArray) nsTArray<GlyphRun>(2);
+    mGlyphRunArray.AppendElement(std::move(tmp));
+    mHasGlyphRunArray = true;
+  }
+
+  void ConvertFromGlyphRunArray() {
+    MOZ_ASSERT(mHasGlyphRunArray && mGlyphRunArray.Length() == 1);
+    GlyphRun tmp = std::move(mGlyphRunArray[0]);
+    mGlyphRunArray.~nsTArray<GlyphRun>();
+    new (&mSingleGlyphRun) GlyphRun(std::move(tmp));
+    mHasGlyphRunArray = false;
+  }
+
+  void* mUserData;
+
+  // mFontGroup is usually a strong reference, but refcounting is managed
+  // manually because it may be explicitly released by ReleaseFontGroup()
+  // in the case where the font group actually owns the textrun.
+  gfxFontGroup* MOZ_OWNING_REF mFontGroup;
+
+  gfxSkipChars mSkipChars;
+
+  nsTextFrameUtils::Flags
+      mFlags2;  // additional flags (see also gfxShapedText::mFlags)
+
+  bool mDontSkipDrawing;  // true if the text run must not skip drawing, even if
+                          // waiting for a user font download, e.g. because we
+                          // are using it to draw canvas text
+  bool mReleasedFontGroup;                // we already called NS_RELEASE on
+                                          // mFontGroup, so don't do it again
+  bool mReleasedFontGroupSkippedDrawing;  // whether our old mFontGroup value
+                                          // was set to skip drawing
+  bool mHasGlyphRunArray;                 // whether we're using an array or
+                                          // just storing a single glyphrun
+
+  // shaping state for handling variant fallback features
+  // such as subscript/superscript variant glyphs
+  ShapingState mShapingState;
+};
+
+enum class FallbackTypes : uint8_t {
+  // Font fallback used a font configured in Preferences
+  FallbackToPrefsFont = 1 << 0,
+  // Font fallback used a font with FontVisibility::Base
+  FallbackToBaseFont = 1 << 1,
+  // Font fallback used a font with FontVisibility::LangPack
+  FallbackToLangPackFont = 1 << 2,
+  // Font fallback used a font with FontVisibility::User
+  FallbackToUserFont = 1 << 3,
+  // Rendered missing-glyph because no font available for the character
+  MissingFont = 1 << 4,
+  // Rendered missing-glyph but a LangPack font could have been used
+  MissingFontLangPack = 1 << 5,
+  // Rendered missing-glyph but a User font could have been used
+  MissingFontUser = 1 << 6,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(FallbackTypes)
+
+struct FontMatchingStats {
+  // Set of names that have been looked up (whether successfully or not).
+  nsTHashtable<nsCStringHashKey> mFamilyNames;
+  // Number of font-family names resolved at each level of visibility.
+  uint32_t mBaseFonts = 0;
+  uint32_t mLangPackFonts = 0;
+  uint32_t mUserFonts = 0;
+  uint32_t mWebFonts = 0;
+  FallbackTypes mFallbacks = FallbackTypes(0);
+};
+
+class gfxFontGroup final : public gfxTextRunFactory {
+ public:
+  typedef mozilla::unicode::Script Script;
+  typedef gfxShapedText::CompressedGlyph CompressedGlyph;
+
+  static void
+  Shutdown();  // platform must call this to release the languageAtomService
+
+  gfxFontGroup(const mozilla::FontFamilyList& aFontFamilyList,
+               const gfxFontStyle* aStyle, nsAtom* aLanguage,
+               bool aExplicitLanguage, gfxTextPerfMetrics* aTextPerf,
+               FontMatchingStats* aFontMatchingStats,
+               gfxUserFontSet* aUserFontSet, gfxFloat aDevToCssSize);
+
+  virtual ~gfxFontGroup();
+
+  gfxFontGroup(const gfxFontGroup& aOther) = delete;
+
+  // Returns first valid font in the fontlist or default font.
+  // Initiates userfont loads if userfont not loaded.
+  // aGeneric: if non-null, returns the CSS generic type that was mapped to
+  //           this font
+  gfxFont* GetFirstValidFont(
+      uint32_t aCh = 0x20, mozilla::StyleGenericFontFamily* aGeneric = nullptr);
+
+  // Returns the first font in the font-group that has an OpenType MATH table,
+  // or null if no such font is available. The GetMathConstant methods may be
+  // called on the returned font.
+  gfxFont* GetFirstMathFont();
+
+  const gfxFontStyle* GetStyle() const { return &mStyle; }
+
+  /**
+   * The listed characters should be treated as invisible and zero-width
+   * when creating textruns.
+   */
+  static bool IsInvalidChar(uint8_t ch);
+  static bool IsInvalidChar(char16_t ch);
+
+  /**
+   * Make a textrun for a given string.
+   * If aText is not persistent (aFlags & TEXT_IS_PERSISTENT), the
+   * textrun will copy it.
+   * This calls FetchGlyphExtents on the textrun.
+   */
+  already_AddRefed<gfxTextRun> MakeTextRun(const char16_t* aString,
+                                           uint32_t aLength,
+                                           const Parameters* aParams,
+                                           mozilla::gfx::ShapedTextFlags aFlags,
+                                           nsTextFrameUtils::Flags aFlags2,
+                                           gfxMissingFontRecorder* aMFR);
+  /**
+   * Make a textrun for a given string.
+   * If aText is not persistent (aFlags & TEXT_IS_PERSISTENT), the
+   * textrun will copy it.
+   * This calls FetchGlyphExtents on the textrun.
+   */
+  already_AddRefed<gfxTextRun> MakeTextRun(const uint8_t* aString,
+                                           uint32_t aLength,
+                                           const Parameters* aParams,
+                                           mozilla::gfx::ShapedTextFlags aFlags,
+                                           nsTextFrameUtils::Flags aFlags2,
+                                           gfxMissingFontRecorder* aMFR);
+
+  /**
+   * Textrun creation helper for clients that don't want to pass
+   * a full Parameters record.
+   */
+  template <typename T>
+  already_AddRefed<gfxTextRun> MakeTextRun(const T* aString, uint32_t aLength,
+                                           DrawTarget* aRefDrawTarget,
+                                           int32_t aAppUnitsPerDevUnit,
+                                           mozilla::gfx::ShapedTextFlags aFlags,
+                                           nsTextFrameUtils::Flags aFlags2,
+                                           gfxMissingFontRecorder* aMFR) {
+    gfxTextRunFactory::Parameters params = {
+        aRefDrawTarget, nullptr, nullptr, nullptr, 0, aAppUnitsPerDevUnit};
+    return MakeTextRun(aString, aLength, &params, aFlags, aFlags2, aMFR);
+  }
+
+  // Get the (possibly-cached) width of the hyphen character.
+  gfxFloat GetHyphenWidth(const gfxTextRun::PropertyProvider* aProvider);
+
+  /**
+   * Make a text run representing a single hyphen character.
+   * This will use U+2010 HYPHEN if available in the first font,
+   * otherwise fall back to U+002D HYPHEN-MINUS.
+   * The caller is responsible for deleting the returned text run
+   * when no longer required.
+   */
+  already_AddRefed<gfxTextRun> MakeHyphenTextRun(DrawTarget* aDrawTarget,
+                                                 uint32_t aAppUnitsPerDevUnit);
+
+  /**
+   * Check whether a given font (specified by its gfxFontEntry)
+   * is already in the fontgroup's list of actual fonts
+   */
+  bool HasFont(const gfxFontEntry* aFontEntry);
+
+  // This returns the preferred underline for this font group.
+  // Some CJK fonts have wrong underline offset in its metrics.
+  // If this group has such "bad" font, each platform's gfxFontGroup
+  // initialized mUnderlineOffset. The value should be lower value of
+  // first font's metrics and the bad font's metrics. Otherwise, this
+  // returns from first font's metrics.
+  enum { UNDERLINE_OFFSET_NOT_SET = INT16_MAX };
+  gfxFloat GetUnderlineOffset();
+
+  gfxFont* FindFontForChar(uint32_t ch, uint32_t prevCh, uint32_t aNextCh,
+                           Script aRunScript, gfxFont* aPrevMatchedFont,
+                           FontMatchType* aMatchType);
+
+  gfxUserFontSet* GetUserFontSet();
+
+  // With downloadable fonts, the composition of the font group can change as
+  // fonts are downloaded for each change in state of the user font set, the
+  // generation value is bumped to avoid picking up previously created text runs
+  // in the text run word cache.  For font groups based on stylesheets with no
+  // @font-face rule, this always returns 0.
+  uint64_t GetGeneration();
+
+  // generation of the latest fontset rebuild, 0 when no fontset present
+  uint64_t GetRebuildGeneration();
+
+  // used when logging text performance
+  gfxTextPerfMetrics* GetTextPerfMetrics() { return mTextPerf; }
+
+  // This will call UpdateUserFonts() if the user font set is changed.
+  void SetUserFontSet(gfxUserFontSet* aUserFontSet);
+
+  void ClearCachedData() {
+    mUnderlineOffset = UNDERLINE_OFFSET_NOT_SET;
+    mSkipDrawing = false;
+    mHyphenWidth = -1;
+    mCachedEllipsisTextRun = nullptr;
+  }
+
+  // If there is a user font set, check to see whether the font list or any
+  // caches need updating.
+  void UpdateUserFonts();
+
+  // search for a specific userfont in the list of fonts
+  bool ContainsUserFont(const gfxUserFontEntry* aUserFont);
+
+  bool ShouldSkipDrawing() const { return mSkipDrawing; }
+
+  class LazyReferenceDrawTargetGetter {
+   public:
+    virtual already_AddRefed<DrawTarget> GetRefDrawTarget() = 0;
+  };
+  // The gfxFontGroup keeps ownership of this textrun.
+  // It is only guaranteed to exist until the next call to GetEllipsisTextRun
+  // (which might use a different appUnitsPerDev value or flags) for the font
+  // group, or until UpdateUserFonts is called, or the fontgroup is destroyed.
+  // Get it/use it/forget it :) - don't keep a reference that might go stale.
+  gfxTextRun* GetEllipsisTextRun(
+      int32_t aAppUnitsPerDevPixel, mozilla::gfx::ShapedTextFlags aFlags,
+      LazyReferenceDrawTargetGetter& aRefDrawTargetGetter);
+
+  void CheckForUpdatedPlatformList() {
+    auto* pfl = gfxPlatformFontList::PlatformFontList();
+    if (mFontListGeneration != pfl->GetGeneration()) {
+      // Forget cached fonts that may no longer be valid.
+      mLastPrefFamily = FontFamily();
+      mLastPrefFont = nullptr;
+      mFonts.Clear();
+      BuildFontList();
+    }
+  }
+
+  nsAtom* Language() const { return mLanguage.get(); }
+
+ protected:
+  friend class mozilla::PostTraversalTask;
+
+  struct TextRange {
+    TextRange(uint32_t aStart, uint32_t aEnd, gfxFont* aFont,
+              FontMatchType aMatchType,
+              mozilla::gfx::ShapedTextFlags aOrientation)
+        : start(aStart),
+          end(aEnd),
+          font(aFont),
+          matchType(aMatchType),
+          orientation(aOrientation) {}
+    uint32_t Length() const { return end - start; }
+    uint32_t start, end;
+    RefPtr<gfxFont> font;
+    FontMatchType matchType;
+    mozilla::gfx::ShapedTextFlags orientation;
+  };
+
+  // search through pref fonts for a character, return nullptr if no matching
+  // pref font
+  gfxFont* WhichPrefFontSupportsChar(uint32_t aCh, uint32_t aNextCh,
+                                     eFontPresentation aPresentation);
+
+  gfxFont* WhichSystemFontSupportsChar(uint32_t aCh, uint32_t aNextCh,
+                                       Script aRunScript,
+                                       eFontPresentation aPresentation);
+
+  template <typename T>
+  void ComputeRanges(nsTArray<TextRange>& aRanges, const T* aString,
+                     uint32_t aLength, Script aRunScript,
+                     mozilla::gfx::ShapedTextFlags aOrientation);
+
+  class FamilyFace {
+   public:
+    FamilyFace()
+        : mOwnedFamily(nullptr),
+          mFontEntry(nullptr),
+          mGeneric(mozilla::StyleGenericFontFamily::None),
+          mFontCreated(false),
+          mLoading(false),
+          mInvalid(false),
+          mCheckForFallbackFaces(false),
+          mIsSharedFamily(false),
+          mHasFontEntry(false) {}
+
+    FamilyFace(gfxFontFamily* aFamily, gfxFont* aFont,
+               mozilla::StyleGenericFontFamily aGeneric)
+        : mOwnedFamily(aFamily),
+          mGeneric(aGeneric),
+          mFontCreated(true),
+          mLoading(false),
+          mInvalid(false),
+          mCheckForFallbackFaces(false),
+          mIsSharedFamily(false),
+          mHasFontEntry(false) {
+      NS_ASSERTION(aFont, "font pointer must not be null");
+      NS_ASSERTION(!aFamily || aFamily->ContainsFace(aFont->GetFontEntry()),
+                   "font is not a member of the given family");
+      NS_IF_ADDREF(aFamily);
+      mFont = aFont;
+      NS_ADDREF(aFont);
+    }
+
+    FamilyFace(gfxFontFamily* aFamily, gfxFontEntry* aFontEntry,
+               mozilla::StyleGenericFontFamily aGeneric)
+        : mOwnedFamily(aFamily),
+          mGeneric(aGeneric),
+          mFontCreated(false),
+          mLoading(false),
+          mInvalid(false),
+          mCheckForFallbackFaces(false),
+          mIsSharedFamily(false),
+          mHasFontEntry(true) {
+      NS_ASSERTION(aFontEntry, "font entry pointer must not be null");
+      NS_ASSERTION(!aFamily || aFamily->ContainsFace(aFontEntry),
+                   "font is not a member of the given family");
+      NS_IF_ADDREF(aFamily);
+      mFontEntry = aFontEntry;
+      NS_ADDREF(aFontEntry);
+    }
+
+    FamilyFace(mozilla::fontlist::Family* aFamily, gfxFontEntry* aFontEntry,
+               mozilla::StyleGenericFontFamily aGeneric)
+        : mSharedFamily(aFamily),
+          mGeneric(aGeneric),
+          mFontCreated(false),
+          mLoading(false),
+          mInvalid(false),
+          mCheckForFallbackFaces(false),
+          mIsSharedFamily(true),
+          mHasFontEntry(true) {
+      MOZ_ASSERT(aFamily && aFontEntry && aFontEntry->mShmemFace);
+      mFontEntry = aFontEntry;
+      NS_ADDREF(aFontEntry);
+    }
+
+    FamilyFace(const FamilyFace& aOtherFamilyFace)
+        : mGeneric(aOtherFamilyFace.mGeneric),
+          mFontCreated(aOtherFamilyFace.mFontCreated),
+          mLoading(aOtherFamilyFace.mLoading),
+          mInvalid(aOtherFamilyFace.mInvalid),
+          mCheckForFallbackFaces(aOtherFamilyFace.mCheckForFallbackFaces),
+          mIsSharedFamily(aOtherFamilyFace.mIsSharedFamily),
+          mHasFontEntry(aOtherFamilyFace.mHasFontEntry) {
+      if (mIsSharedFamily) {
+        mSharedFamily = aOtherFamilyFace.mSharedFamily;
+        if (mFontCreated) {
+          mFont = aOtherFamilyFace.mFont;
+          NS_ADDREF(mFont);
+        } else if (mHasFontEntry) {
+          mFontEntry = aOtherFamilyFace.mFontEntry;
+          NS_ADDREF(mFontEntry);
+        } else {
+          mSharedFace = aOtherFamilyFace.mSharedFace;
+        }
+      } else {
+        mOwnedFamily = aOtherFamilyFace.mOwnedFamily;
+        NS_IF_ADDREF(mOwnedFamily);
+        if (mFontCreated) {
+          mFont = aOtherFamilyFace.mFont;
+          NS_ADDREF(mFont);
+        } else {
+          mFontEntry = aOtherFamilyFace.mFontEntry;
+          NS_IF_ADDREF(mFontEntry);
+        }
+      }
+    }
+
+    ~FamilyFace() {
+      if (mFontCreated) {
+        NS_RELEASE(mFont);
+      }
+      if (!mIsSharedFamily) {
+        NS_IF_RELEASE(mOwnedFamily);
+      }
+      if (mHasFontEntry) {
+        NS_RELEASE(mFontEntry);
+      }
+    }
+
+    FamilyFace& operator=(const FamilyFace& aOther) {
+      if (mFontCreated) {
+        NS_RELEASE(mFont);
+      }
+      if (!mIsSharedFamily) {
+        NS_IF_RELEASE(mOwnedFamily);
+      }
+      if (mHasFontEntry) {
+        NS_RELEASE(mFontEntry);
+      }
+
+      mGeneric = aOther.mGeneric;
+      mFontCreated = aOther.mFontCreated;
+      mLoading = aOther.mLoading;
+      mInvalid = aOther.mInvalid;
+      mIsSharedFamily = aOther.mIsSharedFamily;
+      mHasFontEntry = aOther.mHasFontEntry;
+
+      if (mIsSharedFamily) {
+        mSharedFamily = aOther.mSharedFamily;
+        if (mFontCreated) {
+          mFont = aOther.mFont;
+          NS_ADDREF(mFont);
+        } else if (mHasFontEntry) {
+          mFontEntry = aOther.mFontEntry;
+          NS_ADDREF(mFontEntry);
+        } else {
+          mSharedFace = aOther.mSharedFace;
+        }
+      } else {
+        mOwnedFamily = aOther.mOwnedFamily;
+        NS_IF_ADDREF(mOwnedFamily);
+        if (mFontCreated) {
+          mFont = aOther.mFont;
+          NS_ADDREF(mFont);
+        } else {
+          mFontEntry = aOther.mFontEntry;
+          NS_IF_ADDREF(mFontEntry);
+        }
+      }
+
+      return *this;
+    }
+
+    gfxFontFamily* OwnedFamily() const {
+      MOZ_ASSERT(!mIsSharedFamily);
+      return mOwnedFamily;
+    }
+    mozilla::fontlist::Family* SharedFamily() const {
+      MOZ_ASSERT(mIsSharedFamily);
+      return mSharedFamily;
+    }
+    gfxFont* Font() const { return mFontCreated ? mFont : nullptr; }
+
+    gfxFontEntry* FontEntry() const {
+      if (mFontCreated) {
+        return mFont->GetFontEntry();
+      }
+      if (mHasFontEntry) {
+        return mFontEntry;
+      }
+      if (mIsSharedFamily) {
+        return gfxPlatformFontList::PlatformFontList()->GetOrCreateFontEntry(
+            mSharedFace, SharedFamily());
+      }
+      return nullptr;
+    }
+
+    mozilla::StyleGenericFontFamily Generic() const { return mGeneric; }
+
+    bool IsSharedFamily() const { return mIsSharedFamily; }
+    bool IsUserFontContainer() const {
+      gfxFontEntry* fe = FontEntry();
+      return fe && fe->mIsUserFontContainer;
+    }
+    bool IsLoading() const { return mLoading; }
+    bool IsInvalid() const { return mInvalid; }
+    void CheckState(bool& aSkipDrawing);
+    void SetLoading(bool aIsLoading) { mLoading = aIsLoading; }
+    void SetInvalid() { mInvalid = true; }
+    bool CheckForFallbackFaces() const { return mCheckForFallbackFaces; }
+    void SetCheckForFallbackFaces() { mCheckForFallbackFaces = true; }
+
+    // Return true if we're currently loading (or waiting for) a resource that
+    // may support the given character.
+    bool IsLoadingFor(uint32_t aCh) {
+      if (!IsLoading()) {
+        return false;
+      }
+      MOZ_ASSERT(IsUserFontContainer());
+      auto* ufe = static_cast<gfxUserFontEntry*>(FontEntry());
+      return ufe && ufe->CharacterInUnicodeRange(aCh);
+    }
+
+    void SetFont(gfxFont* aFont) {
+      NS_ASSERTION(aFont, "font pointer must not be null");
+      NS_ADDREF(aFont);
+      if (mFontCreated) {
+        NS_RELEASE(mFont);
+      } else if (mHasFontEntry) {
+        NS_RELEASE(mFontEntry);
+        mHasFontEntry = false;
+      }
+      mFont = aFont;
+      mFontCreated = true;
+      mLoading = false;
+    }
+
+    bool EqualsUserFont(const gfxUserFontEntry* aUserFont) const;
+
+   private:
+    union {
+      gfxFontFamily* MOZ_OWNING_REF mOwnedFamily;
+      mozilla::fontlist::Family* MOZ_NON_OWNING_REF mSharedFamily;
+    };
+    // either a font or a font entry exists
+    union {
+      // Whichever of these fields is actually present will be a strong
+      // reference, with refcounting handled manually.
+      gfxFont* MOZ_OWNING_REF mFont;
+      gfxFontEntry* MOZ_OWNING_REF mFontEntry;
+      mozilla::fontlist::Face* MOZ_NON_OWNING_REF mSharedFace;
+    };
+    mozilla::StyleGenericFontFamily mGeneric;
+    bool mFontCreated : 1;
+    bool mLoading : 1;
+    bool mInvalid : 1;
+    bool mCheckForFallbackFaces : 1;
+    bool mIsSharedFamily : 1;
+    bool mHasFontEntry : 1;
+  };
+
+  // List of font families, either named or generic.
+  // Generic names map to system pref fonts based on language.
+  mozilla::FontFamilyList mFamilyList;
+
+  // Fontlist containing a font entry for each family found. gfxFont objects
+  // are created as needed and userfont loads are initiated when needed.
+  // Code should be careful about addressing this array directly.
+  nsTArray<FamilyFace> mFonts;
+
+  RefPtr<gfxFont> mDefaultFont;
+  gfxFontStyle mStyle;
+
+  RefPtr<nsAtom> mLanguage;
+
+  gfxFloat mUnderlineOffset;
+  gfxFloat mHyphenWidth;
+  gfxFloat mDevToCssSize;
+
+  RefPtr<gfxUserFontSet> mUserFontSet;
+  uint64_t mCurrGeneration;  // track the current user font set generation,
+                             // rebuild font list if needed
+
+  gfxTextPerfMetrics* mTextPerf;
+
+  FontMatchingStats* mFontMatchingStats;
+
+  // Cache a textrun representing an ellipsis (useful for CSS text-overflow)
+  // at a specific appUnitsPerDevPixel size and orientation
+  RefPtr<gfxTextRun> mCachedEllipsisTextRun;
+
+  // cache the most recent pref font to avoid general pref font lookup
+  FontFamily mLastPrefFamily;
+  RefPtr<gfxFont> mLastPrefFont;
+  eFontPrefLang mLastPrefLang;  // lang group for last pref font
+  eFontPrefLang mPageLang;
+  bool mLastPrefFirstFont;  // is this the first font in the list of pref fonts
+                            // for this lang group?
+
+  bool mSkipDrawing;  // hide text while waiting for a font
+                      // download to complete (or fallback
+                      // timer to fire)
+
+  bool mExplicitLanguage;  // Does mLanguage come from an explicit attribute?
+
+  uint32_t mFontListGeneration = 0;  // platform font list generation for this
+                                     // fontgroup
+
+  /**
+   * Textrun creation short-cuts for special cases where we don't need to
+   * call a font shaper to generate glyphs.
+   */
+  already_AddRefed<gfxTextRun> MakeEmptyTextRun(
+      const Parameters* aParams, mozilla::gfx::ShapedTextFlags aFlags,
+      nsTextFrameUtils::Flags aFlags2);
+
+  already_AddRefed<gfxTextRun> MakeSpaceTextRun(
+      const Parameters* aParams, mozilla::gfx::ShapedTextFlags aFlags,
+      nsTextFrameUtils::Flags aFlags2);
+
+  template <typename T>
+  already_AddRefed<gfxTextRun> MakeBlankTextRun(
+      const T* aString, uint32_t aLength, const Parameters* aParams,
+      mozilla::gfx::ShapedTextFlags aFlags, nsTextFrameUtils::Flags aFlags2);
+
+  // Initialize the list of fonts
+  void BuildFontList();
+
+  // Get the font at index i within the fontlist, for character aCh (in case
+  // of fonts with multiple resources and unicode-range partitioning).
+  // Will initiate userfont load if not already loaded.
+  // May return null if userfont not loaded or if font invalid.
+  // If *aLoading is true, a relevant resource is already being loaded so no
+  // new download will be initiated; if a download is started, *aLoading will
+  // be set to true on return.
+  gfxFont* GetFontAt(int32_t i, uint32_t aCh, bool* aLoading);
+
+  // Simplified version of GetFontAt() for use where we just need a font for
+  // metrics, math layout tables, etc.
+  gfxFont* GetFontAt(int32_t i, uint32_t aCh = 0x20) {
+    bool loading = false;
+    return GetFontAt(i, aCh, &loading);
+  }
+
+  // will always return a font or force a shutdown
+  gfxFont* GetDefaultFont();
+
+  // Init this font group's font metrics. If there no bad fonts, you don't need
+  // to call this. But if there are one or more bad fonts which have bad
+  // underline offset, you should call this with the *first* bad font.
+  void InitMetricsForBadFont(gfxFont* aBadFont);
+
+  // Set up the textrun glyphs for an entire text run:
+  // find script runs, and then call InitScriptRun for each
+  template <typename T>
+  void InitTextRun(DrawTarget* aDrawTarget, gfxTextRun* aTextRun,
+                   const T* aString, uint32_t aLength,
+                   gfxMissingFontRecorder* aMFR);
+
+  // InitTextRun helper to handle a single script run, by finding font ranges
+  // and calling each font's InitTextRun() as appropriate
+  template <typename T>
+  void InitScriptRun(DrawTarget* aDrawTarget, gfxTextRun* aTextRun,
+                     const T* aString, uint32_t aScriptRunStart,
+                     uint32_t aScriptRunEnd, Script aRunScript,
+                     gfxMissingFontRecorder* aMFR);
+
+  // Helper for font-matching:
+  // search all faces in a family for a fallback in cases where it's unclear
+  // whether the family might have a font for a given character
+  gfxFont* FindFallbackFaceForChar(const FamilyFace& aFamily, uint32_t aCh,
+                                   uint32_t aNextCh,
+                                   eFontPresentation aPresentation);
+
+  gfxFont* FindFallbackFaceForChar(mozilla::fontlist::Family* aFamily,
+                                   uint32_t aCh, uint32_t aNextCh,
+                                   eFontPresentation aPresentation);
+
+  gfxFont* FindFallbackFaceForChar(gfxFontFamily* aFamily, uint32_t aCh,
+                                   uint32_t aNextCh,
+                                   eFontPresentation aPresentation);
+
+  // helper methods for looking up fonts
+
+  // lookup and add a font with a given name (i.e. *not* a generic!)
+  void AddPlatformFont(const nsACString& aName, bool aQuotedName,
+                       nsTArray<FamilyAndGeneric>& aFamilyList);
+
+  // do style selection and add entries to list
+  void AddFamilyToFontList(gfxFontFamily* aFamily,
+                           mozilla::StyleGenericFontFamily aGeneric);
+  void AddFamilyToFontList(mozilla::fontlist::Family* aFamily,
+                           mozilla::StyleGenericFontFamily aGeneric);
+};
+
+// A "missing font recorder" is to be used during text-run creation to keep
+// a record of any scripts encountered for which font coverage was lacking;
+// when Flush() is called, it sends a notification that front-end code can use
+// to download fonts on demand (or whatever else it wants to do).
+
+#define GFX_MISSING_FONTS_NOTIFY_PREF "gfx.missing_fonts.notify"
+
+class gfxMissingFontRecorder {
+ public:
+  gfxMissingFontRecorder() {
+    MOZ_COUNT_CTOR(gfxMissingFontRecorder);
+    memset(&mMissingFonts, 0, sizeof(mMissingFonts));
+  }
+
+  ~gfxMissingFontRecorder() {
+#ifdef DEBUG
+    for (uint32_t i = 0; i < kNumScriptBitsWords; i++) {
+      NS_ASSERTION(mMissingFonts[i] == 0,
+                   "failed to flush the missing-font recorder");
+    }
+#endif
+    MOZ_COUNT_DTOR(gfxMissingFontRecorder);
+  }
+
+  // record this script code in our mMissingFonts bitset
+  void RecordScript(mozilla::unicode::Script aScriptCode) {
+    mMissingFonts[static_cast<uint32_t>(aScriptCode) >> 5] |=
+        (1 << (static_cast<uint32_t>(aScriptCode) & 0x1f));
+  }
+
+  // send a notification of any missing-scripts that have been
+  // recorded, and clear the mMissingFonts set for re-use
+  void Flush();
+
+  // forget any missing-scripts that have been recorded up to now;
+  // called before discarding a recorder we no longer care about
+  void Clear() { memset(&mMissingFonts, 0, sizeof(mMissingFonts)); }
+
+ private:
+  // Number of 32-bit words needed for the missing-script flags
+  static const uint32_t kNumScriptBitsWords =
+      ((static_cast<int>(mozilla::unicode::Script::NUM_SCRIPT_CODES) + 31) /
+       32);
+  uint32_t mMissingFonts[kNumScriptBitsWords];
+};
+
+#endif