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ColorPattern

Config

DataSourceSurface

DrawEventRecorder

DrawOptions

DrawSurfaceOptions

DrawTarget

DrawTargetCapture

Factory

Glyph

GlyphBuffer

GlyphMetrics

GlyphRenderingOptions

GradientStops

LinearGradientPattern

MapType

MappedSurface

NativeFont

NativeFontResource

NativeSurface

Path

PathBuilder

PathSink

Pattern

RadialGradientPattern

ScaledFont

ScopedMap

SourceSurface

StrokeOptions

SurfacePattern

Tile

TileSet

UnscaledFont

WeakPtrTraits

Macros

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

#ifndef _MOZILLA_GFX_2D_H
#define _MOZILLA_GFX_2D_H

#include "Types.h"
#include "Point.h"
#include "Rect.h"
#include "Matrix.h"
#include "Quaternion.h"
#include "UserData.h"
#include "FontVariation.h"
#include <vector>

// GenericRefCountedBase allows us to hold on to refcounted objects of any type
// (contrary to RefCounted<T> which requires knowing the type T) and, in particular,
// without having a dependency on that type. This is used for DrawTargetSkia
// to be able to hold on to a GLContext.
#include "mozilla/GenericRefCounted.h"
#include "mozilla/MemoryReporting.h"

// This RefPtr class isn't ideal for usage in Azure, as it doesn't allow T**
// outparams using the &-operator. But it will have to do as there's no easy
// solution.
#include "mozilla/RefPtr.h"
#include "mozilla/ServoUtils.h"
#include "mozilla/WeakPtr.h"

#include "mozilla/DebugOnly.h"

#if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_GTK)
  #ifndef MOZ_ENABLE_FREETYPE
  #define MOZ_ENABLE_FREETYPE
  #endif
#endif

struct _cairo_surface;
typedef _cairo_surface cairo_surface_t;

struct _cairo_scaled_font;
typedef _cairo_scaled_font cairo_scaled_font_t;

struct _FcPattern;
typedef _FcPattern FcPattern;

struct FT_LibraryRec_;
typedef FT_LibraryRec_* FT_Library;

struct FT_FaceRec_;
typedef FT_FaceRec_* FT_Face;

struct ID3D11Texture2D;
struct ID3D11Device;
struct ID2D1Device;
struct IDWriteFactory;
struct IDWriteRenderingParams;
struct IDWriteFontFace;

class GrContext;
class SkCanvas;
struct gfxFontStyle;

struct CGContext;
typedef struct CGContext *CGContextRef;

namespace mozilla {

class Mutex;

namespace gfx {
class UnscaledFont;
}

template<>
struct WeakPtrTraits<gfx::UnscaledFont>
{
  static void AssertSafeToAccessFromNonOwningThread()
  {
    // We want to allow UnscaledFont objects that were created on the main
    // thread to be accessed from other threads if the Servo font metrics
    // mutex is locked, and for objects created on Servo style worker threads
    // to be accessed later back on the main thread.
    AssertIsMainThreadOrServoFontMetricsLocked();
  }
};

namespace gfx {

class ScaledFont;
class SourceSurface;
class DataSourceSurface;
class DrawTarget;
class DrawEventRecorder;
class FilterNode;
class LogForwarder;

struct NativeSurface {
  NativeSurfaceType mType;
  SurfaceFormat mFormat;
  gfx::IntSize mSize;
  void *mSurface;
};

struct NativeFont {
  NativeFontType mType;
  void *mFont;
};

/**
 * This structure is used to send draw options that are universal to all drawing
 * operations.
 */
struct DrawOptions {
  /// For constructor parameter description, see member data documentation.
  explicit DrawOptions(Float aAlpha = 1.0f,
                       CompositionOp aCompositionOp = CompositionOp::OP_OVER,
                       AntialiasMode aAntialiasMode = AntialiasMode::DEFAULT)
    : mAlpha(aAlpha)
    , mCompositionOp(aCompositionOp)
    , mAntialiasMode(aAntialiasMode)
  {}

  Float mAlpha;                 /**< Alpha value by which the mask generated by this
                                     operation is multiplied. */
  CompositionOp mCompositionOp; /**< The operator that indicates how the source and
                                     destination patterns are blended. */
  AntialiasMode mAntialiasMode; /**< The AntiAlias mode used for this drawing
                                     operation. */
};

/**
 * This structure is used to send stroke options that are used in stroking
 * operations.
 */
struct StrokeOptions {
  /// For constructor parameter description, see member data documentation.
  explicit StrokeOptions(Float aLineWidth = 1.0f,
                         JoinStyle aLineJoin = JoinStyle::MITER_OR_BEVEL,
                         CapStyle aLineCap = CapStyle::BUTT,
                         Float aMiterLimit = 10.0f,
                         size_t aDashLength = 0,
                         const Float* aDashPattern = 0,
                         Float aDashOffset = 0.f)
    : mLineWidth(aLineWidth)
    , mMiterLimit(aMiterLimit)
    , mDashPattern(aDashLength > 0 ? aDashPattern : 0)
    , mDashLength(aDashLength)
    , mDashOffset(aDashOffset)
    , mLineJoin(aLineJoin)
    , mLineCap(aLineCap)
  {
    MOZ_ASSERT(aDashLength == 0 || aDashPattern);
  }

  Float mLineWidth;          //!< Width of the stroke in userspace.
  Float mMiterLimit;         //!< Miter limit in units of linewidth
  const Float* mDashPattern; /**< Series of on/off userspace lengths defining dash.
                                  Owned by the caller; must live at least as long as
                                  this StrokeOptions.
                                  mDashPattern != null <=> mDashLength > 0. */
  size_t mDashLength;        //!< Number of on/off lengths in mDashPattern.
  Float mDashOffset;         /**< Userspace offset within mDashPattern at which
                                  stroking begins. */
  JoinStyle mLineJoin;       //!< Join style used for joining lines.
  CapStyle mLineCap;         //!< Cap style used for capping lines.
};

/**
 * This structure supplies additional options for calls to DrawSurface.
 */
struct DrawSurfaceOptions {
  /// For constructor parameter description, see member data documentation.
  explicit DrawSurfaceOptions(SamplingFilter aSamplingFilter = SamplingFilter::LINEAR,
                              SamplingBounds aSamplingBounds = SamplingBounds::UNBOUNDED)
    : mSamplingFilter(aSamplingFilter)
    , mSamplingBounds(aSamplingBounds)
  { }

  SamplingFilter mSamplingFilter; /**< SamplingFilter used when resampling source surface
                                       region to the destination region. */
  SamplingBounds mSamplingBounds; /**< This indicates whether the implementation is
                                       allowed to sample pixels outside the source
                                       rectangle as specified in DrawSurface on
                                       the surface. */

};

/**
 * This class is used to store gradient stops, it can only be used with a
 * matching DrawTarget. Not adhering to this condition will make a draw call
 * fail.
 */
class GradientStops : public RefCounted<GradientStops>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(GradientStops)
  virtual ~GradientStops() {}

  virtual BackendType GetBackendType() const = 0;
  virtual bool IsValid() const { return true; }

protected:
  GradientStops() {}
};

/**
 * This is the base class for 'patterns'. Patterns describe the pixels used as
 * the source for a masked composition operation that is done by the different
 * drawing commands. These objects are not backend specific, however for
 * example the gradient stops on a gradient pattern can be backend specific.
 */
class Pattern
{
public:
  virtual ~Pattern() {}

  virtual PatternType GetType() const = 0;

protected:
  Pattern() {}
};

class ColorPattern : public Pattern
{
public:
  // Explicit because consumers should generally use ToDeviceColor when
  // creating a ColorPattern.
  explicit ColorPattern(const Color &aColor)
    : mColor(aColor)
  {}

  virtual PatternType GetType() const override
  {
    return PatternType::COLOR;
  }

  Color mColor;
};

/**
 * This class is used for Linear Gradient Patterns, the gradient stops are
 * stored in a separate object and are backend dependent. This class itself
 * may be used on the stack.
 */
class LinearGradientPattern : public Pattern
{
public:
  /// For constructor parameter description, see member data documentation.
  LinearGradientPattern(const Point &aBegin,
                        const Point &aEnd,
                        GradientStops *aStops,
                        const Matrix &aMatrix = Matrix())
    : mBegin(aBegin)
    , mEnd(aEnd)
    , mStops(aStops)
    , mMatrix(aMatrix)
  {
  }

  virtual PatternType GetType() const override
  {
    return PatternType::LINEAR_GRADIENT;
  }

  Point mBegin;                 //!< Start of the linear gradient
  Point mEnd;                   /**< End of the linear gradient - NOTE: In the case
                                     of a zero length gradient it will act as the
                                     color of the last stop. */
  RefPtr<GradientStops> mStops; /**< GradientStops object for this gradient, this
                                     should match the backend type of the draw
                                     target this pattern will be used with. */
  Matrix mMatrix;               /**< A matrix that transforms the pattern into
                                     user space */
};

/**
 * This class is used for Radial Gradient Patterns, the gradient stops are
 * stored in a separate object and are backend dependent. This class itself
 * may be used on the stack.
 */
class RadialGradientPattern : public Pattern
{
public:
  /// For constructor parameter description, see member data documentation.
  RadialGradientPattern(const Point &aCenter1,
                        const Point &aCenter2,
                        Float aRadius1,
                        Float aRadius2,
                        GradientStops *aStops,
                        const Matrix &aMatrix = Matrix())
    : mCenter1(aCenter1)
    , mCenter2(aCenter2)
    , mRadius1(aRadius1)
    , mRadius2(aRadius2)
    , mStops(aStops)
    , mMatrix(aMatrix)
  {
  }

  virtual PatternType GetType() const override
  {
    return PatternType::RADIAL_GRADIENT;
  }

  Point mCenter1; //!< Center of the inner (focal) circle.
  Point mCenter2; //!< Center of the outer circle.
  Float mRadius1; //!< Radius of the inner (focal) circle.
  Float mRadius2; //!< Radius of the outer circle.
  RefPtr<GradientStops> mStops; /**< GradientStops object for this gradient, this
                                     should match the backend type of the draw target
                                     this pattern will be used with. */
  Matrix mMatrix; //!< A matrix that transforms the pattern into user space
};

/**
 * This class is used for Surface Patterns, they wrap a surface and a
 * repetition mode for the surface. This may be used on the stack.
 */
class SurfacePattern : public Pattern
{
public:
  /// For constructor parameter description, see member data documentation.
  SurfacePattern(SourceSurface *aSourceSurface, ExtendMode aExtendMode,
                 const Matrix &aMatrix = Matrix(),
                 SamplingFilter aSamplingFilter = SamplingFilter::GOOD,
                 const IntRect &aSamplingRect = IntRect())
    : mSurface(aSourceSurface)
    , mExtendMode(aExtendMode)
    , mSamplingFilter(aSamplingFilter)
    , mMatrix(aMatrix)
    , mSamplingRect(aSamplingRect)
  {}

  virtual PatternType GetType() const override
  {
    return PatternType::SURFACE;
  }

  RefPtr<SourceSurface> mSurface; //!< Surface to use for drawing
  ExtendMode mExtendMode;         /**< This determines how the image is extended
                                       outside the bounds of the image */
  SamplingFilter mSamplingFilter; //!< Resampling filter for resampling the image.
  Matrix mMatrix;                 //!< Transforms the pattern into user space

  IntRect mSamplingRect;          /**< Rect that must not be sampled outside of,
                                       or an empty rect if none has been specified. */
};

class StoredPattern;
class DrawTargetCaptureImpl;

/**
 * This is the base class for source surfaces. These objects are surfaces
 * which may be used as a source in a SurfacePattern or a DrawSurface call.
 * They cannot be drawn to directly.
 *
 * Although SourceSurface has thread-safe refcount, some SourceSurface cannot
 * be used on random threads at the same time. Only DataSourceSurface can be
 * used on random threads now. This will be fixed in the future. Eventually
 * all SourceSurface should be thread-safe.
 */
class SourceSurface : public external::AtomicRefCounted<SourceSurface>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(SourceSurface)
  virtual ~SourceSurface() {}

  virtual SurfaceType GetType() const = 0;
  virtual IntSize GetSize() const = 0;
  virtual SurfaceFormat GetFormat() const = 0;

  /** This returns false if some event has made this source surface invalid for
   * usage with current DrawTargets. For example in the case of Direct2D this
   * could return false if we have switched devices since this surface was
   * created.
   */
  virtual bool IsValid() const { return true; }

  /**
   * This function will return true if the surface type matches that of a
   * DataSourceSurface and if GetDataSurface will return the same object.
   */
  bool IsDataSourceSurface() const {
    SurfaceType type = GetType();
    return type == SurfaceType::DATA ||
           type == SurfaceType::DATA_SHARED;
  }

  /**
   * This function will get a DataSourceSurface for this surface, a
   * DataSourceSurface's data can be accessed directly.
   */
  virtual already_AddRefed<DataSourceSurface> GetDataSurface() = 0;

  /** Tries to get this SourceSurface's native surface.  This will fail if aType
   * is not the type of this SourceSurface's native surface.
   */
  virtual void *GetNativeSurface(NativeSurfaceType aType) {
    return nullptr;
  }

  void AddUserData(UserDataKey *key, void *userData, void (*destroy)(void*)) {
    mUserData.Add(key, userData, destroy);
  }
  void *GetUserData(UserDataKey *key) {
    return mUserData.Get(key);
  }
  void RemoveUserData(UserDataKey *key) {
    mUserData.RemoveAndDestroy(key);
  }

protected:
  friend class DrawTargetCaptureImpl;
  friend class StoredPattern;

  // This is for internal use, it ensures the SourceSurface's data remains
  // valid during the lifetime of the SourceSurface.
  // @todo XXX - We need something better here :(. But we may be able to get rid
  // of CreateWrappingDataSourceSurface in the future.
  virtual void GuaranteePersistance() {}

  UserData mUserData;
};

class DataSourceSurface : public SourceSurface
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(DataSourceSurface, override)
  DataSourceSurface()
    : mIsMapped(false)
  {
  }

#ifdef DEBUG
  virtual ~DataSourceSurface()
  {
    MOZ_ASSERT(!mIsMapped, "Someone forgot to call Unmap()");
  }
#endif

  struct MappedSurface {
    uint8_t *mData;
    int32_t mStride;
  };

  enum MapType {
    READ,
    WRITE,
    READ_WRITE
  };

  /**
   * This is a scoped version of Map(). Map() is called in the constructor and
   * Unmap() in the destructor. Use this for automatic unmapping of your data
   * surfaces.
   *
   * Use IsMapped() to verify whether Map() succeeded or not.
   */
  class ScopedMap {
  public:
    explicit ScopedMap(DataSourceSurface* aSurface, MapType aType)
      : mSurface(aSurface)
      , mIsMapped(aSurface->Map(aType, &mMap)) {}

    virtual ~ScopedMap()
    {
      if (mIsMapped) {
        mSurface->Unmap();
      }
    }

    uint8_t* GetData() const
    {
      MOZ_ASSERT(mIsMapped);
      return mMap.mData;
    }

    int32_t GetStride() const
    {
      MOZ_ASSERT(mIsMapped);
      return mMap.mStride;
    }

    const MappedSurface* GetMappedSurface() const
    {
      MOZ_ASSERT(mIsMapped);
      return &mMap;
    }

    bool IsMapped() const { return mIsMapped; }

  private:
    RefPtr<DataSourceSurface> mSurface;
    MappedSurface mMap;
    bool mIsMapped;
  };

  virtual SurfaceType GetType() const override { return SurfaceType::DATA; }
  /** @deprecated
   * Get the raw bitmap data of the surface.
   * Can return null if there was OOM allocating surface data.
   */
  virtual uint8_t *GetData() = 0;

  /** @deprecated
   * Stride of the surface, distance in bytes between the start of the image
   * data belonging to row y and row y+1. This may be negative.
   * Can return 0 if there was OOM allocating surface data.
   */
  virtual int32_t Stride() = 0;

  /**
   * The caller is responsible for ensuring aMappedSurface is not null.
   */
  virtual bool Map(MapType, MappedSurface *aMappedSurface)
  {
    aMappedSurface->mData = GetData();
    aMappedSurface->mStride = Stride();
    mIsMapped = !!aMappedSurface->mData;
    return mIsMapped;
  }

  virtual void Unmap()
  {
    MOZ_ASSERT(mIsMapped);
    mIsMapped = false;
  }

  /**
   * Returns a DataSourceSurface with the same data as this one, but
   * guaranteed to have surface->GetType() == SurfaceType::DATA.
   *
   * The returning surface might be null, because of OOM or gfx device reset.
   * The caller needs to do null-check before using it.
   */
  virtual already_AddRefed<DataSourceSurface> GetDataSurface() override;

  /**
   * Add the size of the underlying data buffer to the aggregate.
   */
  virtual void AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
                                      size_t& aHeapSizeOut,
                                      size_t& aNonHeapSizeOut) const
  {
  }

  /**
   * Returns whether or not the data was allocated on the heap. This should
   * be used to determine if the memory needs to be cleared to 0.
   */
  virtual bool OnHeap() const
  {
    return true;
  }

protected:
  bool mIsMapped;
};

/** This is an abstract object that accepts path segments. */
class PathSink : public RefCounted<PathSink>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PathSink)
  virtual ~PathSink() {}

  /** Move the current point in the path, any figure currently being drawn will
   * be considered closed during fill operations, however when stroking the
   * closing line segment will not be drawn.
   */
  virtual void MoveTo(const Point &aPoint) = 0;
  /** Add a linesegment to the current figure */
  virtual void LineTo(const Point &aPoint) = 0;
  /** Add a cubic bezier curve to the current figure */
  virtual void BezierTo(const Point &aCP1,
                        const Point &aCP2,
                        const Point &aCP3) = 0;
  /** Add a quadratic bezier curve to the current figure */
  virtual void QuadraticBezierTo(const Point &aCP1,
                                 const Point &aCP2) = 0;
  /** Close the current figure, this will essentially generate a line segment
   * from the current point to the starting point for the current figure
   */
  virtual void Close() = 0;
  /** Add an arc to the current figure */
  virtual void Arc(const Point &aOrigin, float aRadius, float aStartAngle,
                   float aEndAngle, bool aAntiClockwise = false) = 0;
  /** Point the current subpath is at - or where the next subpath will start
   * if there is no active subpath.
   */
  virtual Point CurrentPoint() const = 0;
};

class PathBuilder;
class FlattenedPath;

/** The path class is used to create (sets of) figures of any shape that can be
 * filled or stroked to a DrawTarget
 */
class Path : public RefCounted<Path>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(Path)
  virtual ~Path();

  virtual BackendType GetBackendType() const = 0;

  /** This returns a PathBuilder object that contains a copy of the contents of
   * this path and is still writable.
   */
  inline already_AddRefed<PathBuilder> CopyToBuilder() const {
    return CopyToBuilder(GetFillRule());
  }
  inline already_AddRefed<PathBuilder> TransformedCopyToBuilder(const Matrix &aTransform) const {
    return TransformedCopyToBuilder(aTransform, GetFillRule());
  }
  /** This returns a PathBuilder object that contains a copy of the contents of
   * this path, converted to use the specified FillRule, and still writable.
   */
  virtual already_AddRefed<PathBuilder> CopyToBuilder(FillRule aFillRule) const = 0;
  virtual already_AddRefed<PathBuilder> TransformedCopyToBuilder(const Matrix &aTransform,
                                                             FillRule aFillRule) const = 0;

  /** This function checks if a point lies within a path. It allows passing a
   * transform that will transform the path to the coordinate space in which
   * aPoint is given.
   */
  virtual bool ContainsPoint(const Point &aPoint, const Matrix &aTransform) const = 0;


  /** This function checks if a point lies within the stroke of a path using the
   * specified strokeoptions. It allows passing a transform that will transform
   * the path to the coordinate space in which aPoint is given.
   */
  virtual bool StrokeContainsPoint(const StrokeOptions &aStrokeOptions,
                                   const Point &aPoint,
                                   const Matrix &aTransform) const = 0;

  /** This functions gets the bounds of this path. These bounds are not
   * guaranteed to be tight. A transform may be specified that gives the bounds
   * after application of the transform.
   */
  virtual Rect GetBounds(const Matrix &aTransform = Matrix()) const = 0;

  /** This function gets the bounds of the stroke of this path using the
   * specified strokeoptions. These bounds are not guaranteed to be tight.
   * A transform may be specified that gives the bounds after application of
   * the transform.
   */
  virtual Rect GetStrokedBounds(const StrokeOptions &aStrokeOptions,
                                const Matrix &aTransform = Matrix()) const = 0;

  /** Take the contents of this path and stream it to another sink, this works
   * regardless of the backend that might be used for the destination sink.
   */
  virtual void StreamToSink(PathSink *aSink) const = 0;

  /** This gets the fillrule this path's builder was created with. This is not
   * mutable.
   */
  virtual FillRule GetFillRule() const = 0;

  virtual Float ComputeLength();

  virtual Point ComputePointAtLength(Float aLength,
                                     Point* aTangent = nullptr);

protected:
  Path();
  void EnsureFlattenedPath();

  RefPtr<FlattenedPath> mFlattenedPath;
};

/** The PathBuilder class allows path creation. Once finish is called on the
 * pathbuilder it may no longer be written to.
 */
class PathBuilder : public PathSink
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PathBuilder)
  /** Finish writing to the path and return a Path object that can be used for
   * drawing. Future use of the builder results in a crash!
   */
  virtual already_AddRefed<Path> Finish() = 0;

  virtual BackendType GetBackendType() const = 0;
};

struct Glyph
{
  uint32_t mIndex;
  Point mPosition;
};

static inline bool operator==(const Glyph& aOne, const Glyph& aOther) {
  return aOne.mIndex == aOther.mIndex && aOne.mPosition == aOther.mPosition;
}

/** This class functions as a glyph buffer that can be drawn to a DrawTarget.
 * @todo XXX - This should probably contain the guts of gfxTextRun in the future as
 * roc suggested. But for now it's a simple container for a glyph vector.
 */
struct GlyphBuffer
{
  const Glyph *mGlyphs; //!< A pointer to a buffer of glyphs. Managed by the caller.
  uint32_t mNumGlyphs;  //!< Number of glyphs mGlyphs points to.
};

struct GlyphMetrics
{
  // Horizontal distance from the origin to the leftmost side of the bounding
  // box of the drawn glyph. This can be negative!
  Float mXBearing;
  // Horizontal distance from the origin of this glyph to the origin of the
  // next glyph.
  Float mXAdvance;
  // Vertical distance from the origin to the topmost side of the bounding box
  // of the drawn glyph.
  Float mYBearing;
  // Vertical distance from the origin of this glyph to the origin of the next
  // glyph, this is used when drawing vertically and will typically be 0.
  Float mYAdvance;
  // Width of the glyph's black box.
  Float mWidth;
  // Height of the glyph's black box.
  Float mHeight;
};

class UnscaledFont
  : public external::AtomicRefCounted<UnscaledFont>
  , public SupportsWeakPtr<UnscaledFont>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(UnscaledFont)
  MOZ_DECLARE_WEAKREFERENCE_TYPENAME(UnscaledFont)

  virtual ~UnscaledFont();

  virtual FontType GetType() const = 0;

  static uint32_t DeletionCounter() { return sDeletionCounter; }

  typedef void (*FontFileDataOutput)(const uint8_t *aData, uint32_t aLength, uint32_t aIndex,
                                     void *aBaton);
  typedef void (*FontInstanceDataOutput)(const uint8_t* aData, uint32_t aLength, void* aBaton);
  typedef void (*FontDescriptorOutput)(const uint8_t* aData, uint32_t aLength, void* aBaton);

  virtual bool GetFontFileData(FontFileDataOutput, void *) { return false; }

  virtual bool GetFontInstanceData(FontInstanceDataOutput, void *) { return false; }

  virtual bool GetFontDescriptor(FontDescriptorOutput, void *) { return false; }

  virtual already_AddRefed<ScaledFont>
    CreateScaledFont(Float aGlyphSize,
                     const uint8_t* aInstanceData,
                     uint32_t aInstanceDataLength)
  {
    return nullptr;
  }

protected:
  UnscaledFont() {}

private:
  static uint32_t sDeletionCounter;
};

/** This class is an abstraction of a backend/platform specific font object
 * at a particular size. It is passed into text drawing calls to describe
 * the font used for the drawing call.
 */
class ScaledFont : public external::AtomicRefCounted<ScaledFont>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(ScaledFont)
  virtual ~ScaledFont() {}

  virtual FontType GetType() const = 0;
  virtual Float GetSize() const = 0;
  virtual AntialiasMode GetDefaultAAMode();

  /** This allows getting a path that describes the outline of a set of glyphs.
   * A target is passed in so that the guarantee is made the returned path
   * can be used with any DrawTarget that has the same backend as the one
   * passed in.
   */
  virtual already_AddRefed<Path> GetPathForGlyphs(const GlyphBuffer &aBuffer, const DrawTarget *aTarget) = 0;

  /** This copies the path describing the glyphs into a PathBuilder. We use this
   * API rather than a generic API to append paths because it allows easier
   * implementation in some backends, and more efficient implementation in
   * others.
   */
  virtual void CopyGlyphsToBuilder(const GlyphBuffer &aBuffer, PathBuilder *aBuilder, const Matrix *aTransformHint = nullptr) = 0;

  /* This gets the metrics of a set of glyphs for the current font face.
   */
  virtual void GetGlyphDesignMetrics(const uint16_t* aGlyphIndices, uint32_t aNumGlyphs, GlyphMetrics* aGlyphMetrics) = 0;

  typedef void (*FontInstanceDataOutput)(const uint8_t* aData, uint32_t aLength, void* aBaton);

  virtual bool GetFontInstanceData(FontInstanceDataOutput, void *) { return false; }

  virtual bool CanSerialize() { return false; }

  void AddUserData(UserDataKey *key, void *userData, void (*destroy)(void*)) {
    mUserData.Add(key, userData,