gecko-dev/gfx/2d/PatternHelpers.h

/* -*- 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_PATTERNHELPERS_H
#define _MOZILLA_GFX_PATTERNHELPERS_H

#include "mozilla/Alignment.h"
#include "mozilla/gfx/2D.h"

namespace mozilla {
namespace gfx {

/**
 * This class is used to allow general pattern creation functions to return
 * any type of pattern via an out-paramater without allocating a pattern
 * instance on the free-store (an instance of this class being created on the
 * stack before passing it in to the creation function). Without this class
 * writing pattern creation functions would be a pain since Pattern objects are
 * not reference counted, making lifetime management of instances created on
 * the free-store and returned from a creation function hazardous. Besides
 * that, in the case that ColorPattern's are expected to be common, it is
 * particularly desirable to avoid the overhead of allocating on the
 * free-store.
 */
class GeneralPattern
{
public:
  explicit GeneralPattern()
    : mPattern(nullptr)
  {}

  GeneralPattern(const GeneralPattern& aOther)
    : mPattern(nullptr)
  {}

  ~GeneralPattern() {
    if (mPattern) {
      mPattern->~Pattern();
    }
  }

  Pattern* Init(const Pattern& aPattern) {
    MOZ_ASSERT(!mPattern);
    switch (aPattern.GetType()) {
    case PatternType::COLOR:
      mPattern = new (mColorPattern.addr())
        ColorPattern(static_cast<const ColorPattern&>(aPattern));
      break;
    case PatternType::LINEAR_GRADIENT:
      mPattern = new (mLinearGradientPattern.addr())
        LinearGradientPattern(static_cast<const LinearGradientPattern&>(aPattern));
      break;
    case PatternType::RADIAL_GRADIENT:
      mPattern = new (mRadialGradientPattern.addr())
        RadialGradientPattern(static_cast<const RadialGradientPattern&>(aPattern));
      break;
    case PatternType::SURFACE:
      mPattern = new (mSurfacePattern.addr())
        SurfacePattern(static_cast<const SurfacePattern&>(aPattern));
      break;
    default:
      MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unknown pattern type");
    }
    return mPattern;
  }

  ColorPattern* InitColorPattern(const Color &aColor) {
    MOZ_ASSERT(!mPattern);
    mPattern = new (mColorPattern.addr()) ColorPattern(aColor);
    return mColorPattern.addr();
  }

  LinearGradientPattern* InitLinearGradientPattern(const Point &aBegin,
                                                   const Point &aEnd,
                                                   GradientStops *aStops,
                                                   const Matrix &aMatrix = Matrix()) {
    MOZ_ASSERT(!mPattern);
    mPattern = new (mLinearGradientPattern.addr())
      LinearGradientPattern(aBegin, aEnd, aStops, aMatrix);
    return mLinearGradientPattern.addr();
  }

  RadialGradientPattern* InitRadialGradientPattern(const Point &aCenter1,
                                                   const Point &aCenter2,
                                                   Float aRadius1,
                                                   Float aRadius2,
                                                   GradientStops *aStops,
                                                   const Matrix &aMatrix = Matrix()) {
    MOZ_ASSERT(!mPattern);
    mPattern = new (mRadialGradientPattern.addr())
      RadialGradientPattern(aCenter1, aCenter2, aRadius1, aRadius2, aStops, aMatrix);
    return mRadialGradientPattern.addr();
  }

  SurfacePattern* InitSurfacePattern(SourceSurface *aSourceSurface,
                                     ExtendMode aExtendMode,
                                     const Matrix &aMatrix = Matrix(),
                                     Filter aFilter = Filter::GOOD,
                                     const IntRect &aSamplingRect = IntRect()) {
    MOZ_ASSERT(!mPattern);
    mPattern = new (mSurfacePattern.addr())
      SurfacePattern(aSourceSurface, aExtendMode, aMatrix, aFilter, aSamplingRect);
    return mSurfacePattern.addr();
  }

  Pattern* GetPattern() {
    return mPattern;
  }

  const Pattern* GetPattern() const {
    return mPattern;
  }

  operator Pattern&() {
    if (!mPattern) {
      MOZ_CRASH("GeneralPattern not initialized");
    }
    return *mPattern;
  }

private:
  union {
    AlignedStorage2<ColorPattern> mColorPattern;
    AlignedStorage2<LinearGradientPattern> mLinearGradientPattern;
    AlignedStorage2<RadialGradientPattern> mRadialGradientPattern;
    AlignedStorage2<SurfacePattern> mSurfacePattern;
  };
  Pattern *mPattern;
};

} // namespace gfx
} // namespace mozilla

#endif //  _MOZILLA_GFX_PATTERNHELPERS_H