MutableTextureState.h

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/*

 * Copyright 2022 Google LLC.

 * Use of this source code is governed by a BSD-style license that can be

 * found in the LICENSE file.

*/

#ifndef skgpu_MutableTextureState_DEFINED

#define skgpu_MutableTextureState_DEFINED

#include "include/core/SkRefCnt.h"

#include "include/core/SkTypes.h"

#include "include/private/base/SkAnySubclass.h"

#include <cstddef>

namespace skgpu {

enum class BackendApi : unsigned int;

class MutableTextureStateData;

/**

 * Since Skia and clients can both modify gpu textures and their connected state, Skia needs a way

 * for clients to inform us if they have modifiend any of this state. In order to not need setters

 * for every single API and state, we use this class to be a generic wrapper around all the mutable

 * state. This class is used for calls that inform Skia of these texture/image state changes by the

 * client as well as for requesting state changes to be done by Skia. The backend specific state

 * that is wrapped by this class are located in files like:

 *   - include/gpu/vk/VulkanMutableTextureState.h

*/

class SK_API MutableTextureState : public SkRefCnt {

public:

    MutableTextureState();

    ~MutableTextureState() override;

    MutableTextureState(const MutableTextureState& that);

    MutableTextureState& operator=(const MutableTextureState& that);

    void set(const MutableTextureState& that);

    BackendApi backend() const { return fBackend; }

    // Returns true if the backend mutable state has been initialized.

    bool isValid() const { return fIsValid; }

private:

    friend class MutableTextureStateData;

    friend class MutableTextureStatePriv;

    // Size determined by looking at the MutableTextureStateData subclasses, then

    // guessing-and-checking. Compiler will complain if this is too small - in that case,

    // just increase the number.

    inline constexpr static size_t kMaxSubclassSize = 16;

    using AnyStateData = SkAnySubclass<MutableTextureStateData, kMaxSubclassSize>;

    template <typename StateData>

    MutableTextureState(BackendApi api, const StateData& data) : fBackend(api), fIsValid(true) {

        fStateData.emplace<StateData>(data);

    AnyStateData fStateData;

    BackendApi fBackend;

    bool fIsValid;

};

} // namespace skgpu

#endif // skgpu_MutableTextureState_DEFINED