gecko-dev/gfx/config/gfxVars.h

/* -*- Mode: C++; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set sts=2 ts=8 sw=2 tw=99 et: */
/* 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_config_gfxVars_h
#define mozilla_gfx_config_gfxVars_h

#include <stdint.h>
#include "mozilla/Assertions.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/gfx/GraphicsMessages.h"
#include "mozilla/gfx/Point.h"
#include "mozilla/gfx/Types.h"
#include "nsTArray.h"
#include "nsXULAppAPI.h"

namespace mozilla {
namespace gfx {

class gfxVarReceiver;

// Generator for graphics vars.
#define GFX_VARS_LIST(_)                                                \
  /* C++ Name,                  Data Type,        Default Value */      \
  _(BrowserTabsRemoteAutostart, bool,             false)                \
  _(ContentBackend,             BackendType,      BackendType::NONE)    \
  _(TileSize,                   IntSize,          IntSize(-1, -1))      \
  _(UseXRender,                 bool,             false)                \
  _(OffscreenFormat,            gfxImageFormat,   mozilla::gfx::SurfaceFormat::X8R8G8B8_UINT32) \
  _(RequiresAcceleratedGLContextForCompositorOGL, bool, false)          \
  _(CanUseHardwareVideoDecoding, bool,            false)                \

  /* Add new entries above this line. */

// Some graphics settings are computed on the UI process and must be
// communicated to content and GPU processes. gfxVars helps facilitate
// this. Its function is similar to gfxPrefs, except rather than hold
// user preferences, it holds dynamically computed values.
//
// Each variable in GFX_VARS_LIST exposes the following static methods:
//
//    const DataType& CxxName();
//    void SetCxxName(const DataType& aValue);
//
// Note that the setter may only be called in the UI process; a gfxVar must be
// a variable that is determined in the UI process and pushed to child
// processes.
class gfxVars final
{
public:
  static void Initialize();
  static void Shutdown();

  static void ApplyUpdate(const GfxVarUpdate& aUpdate);
  static void AddReceiver(gfxVarReceiver* aReceiver);
  static void RemoveReceiver(gfxVarReceiver* aReceiver);

  // Return a list of updates for all variables with non-default values.
  static nsTArray<GfxVarUpdate> FetchNonDefaultVars();

public:
  // Each variable must expose Set and Get methods for IPDL.
  class VarBase
  {
  public:
    VarBase();
    virtual void SetValue(const GfxVarValue& aValue) = 0;
    virtual void GetValue(GfxVarValue* aOutValue) = 0;
    virtual bool HasDefaultValue() const = 0;
    size_t Index() const {
      return mIndex;
    }
  private:
    size_t mIndex;
  };

private:
  static StaticAutoPtr<gfxVars> sInstance;
  static StaticAutoPtr<nsTArray<VarBase*>> sVarList;

  template <typename T, T Default()>
  class VarImpl final : public VarBase
  {
  public:
    VarImpl()
     : mValue(Default())
    {}
    void SetValue(const GfxVarValue& aValue) override {
      aValue.get(&mValue);
    }
    void GetValue(GfxVarValue* aOutValue) override {
      *aOutValue = GfxVarValue(mValue);
    }
    bool HasDefaultValue() const override {
      return mValue == Default();
    }
    const T& Get() const {
      return mValue;
    }
    // Return true if the value changed, false otherwise.
    bool Set(const T& aValue) {
      MOZ_ASSERT(XRE_IsParentProcess());
      if (mValue == aValue) {
        return false;
      }
      mValue = aValue;
      return true;
    }
  private:
    T mValue;
  };

#define GFX_VAR_DECL(CxxName, DataType, DefaultValue)           \
private:                                                        \
  static DataType Get##CxxName##Default() {                     \
    return DefaultValue;                                        \
  }                                                             \
  VarImpl<DataType, Get##CxxName##Default> mVar##CxxName;       \
public:                                                         \
  static const DataType& CxxName() {                            \
    return sInstance->mVar##CxxName.Get();                      \
  }                                                             \
  static void Set##CxxName(const DataType& aValue) {            \
    if (sInstance->mVar##CxxName.Set(aValue)) {                 \
      sInstance->NotifyReceivers(&sInstance->mVar##CxxName);    \
    }                                                           \
  }

  GFX_VARS_LIST(GFX_VAR_DECL)
#undef GFX_VAR_DECL

private:
  gfxVars();

  void NotifyReceivers(VarBase* aVar);

private:
  nsTArray<gfxVarReceiver*> mReceivers;
};

#undef GFX_VARS_LIST

} // namespace gfx
} // namespace mozilla

#endif // mozilla_gfx_config_gfxVars_h