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* Copyright 2017 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef GrBackendTextureImageGenerator_DEFINED
#define GrBackendTextureImageGenerator_DEFINED
#include "SkImageGenerator.h"
#include "GrBackendSurface.h"
#include "SkMutex.h"
class GrSemaphore;
* This ImageGenerator is used to wrap a texture in one GrContext and can then be used as a source
* in another GrContext. It holds onto a semaphore which the producing GrContext will signal and the
* consuming GrContext will wait on before using the texture. Only one GrContext can ever be used
* as a consumer (this is mostly because Vulkan can't allow multiple things to wait on the same
* semaphore).
* In practice, this capability is used by clients to create backend-specific texture resources in
* one thread (with, say, GrContext-A) and then ship them over to another GrContext (say,
* GrContext-B) which will then use the texture as a source for draws. GrContext-A uses the
* semaphore to notify GrContext-B when the shared texture is ready to use.
class GrBackendTextureImageGenerator : public SkImageGenerator {
static std::unique_ptr<SkImageGenerator> Make(sk_sp<GrTexture>, GrSurfaceOrigin,
sk_sp<GrSemaphore>, SkColorType,
SkAlphaType, sk_sp<SkColorSpace>);
~GrBackendTextureImageGenerator() override;
// NOTE: We would like to validate that the owning context hasn't been abandoned, but we can't
// do that safely (we might be on another thread). So assume everything is fine.
bool onIsValid(GrContext*) const override { return true; }
TexGenType onCanGenerateTexture() const override { return TexGenType::kCheap; }
sk_sp<GrTextureProxy> onGenerateTexture(GrContext*, const SkImageInfo&, const SkIPoint&,
bool willNeedMipMaps) override;
GrBackendTextureImageGenerator(const SkImageInfo& info, GrTexture*, GrSurfaceOrigin,
uint32_t owningContextID, sk_sp<GrSemaphore>,
const GrBackendTexture&);
static void ReleaseRefHelper_TextureReleaseProc(void* ctx);
class RefHelper : public SkNVRefCnt<RefHelper> {
RefHelper(GrTexture* texture, uint32_t owningContextID)
: fOriginalTexture(texture)
, fOwningContextID(owningContextID)
, fBorrowedTexture(nullptr)
, fBorrowingContextReleaseProc(nullptr)
, fBorrowingContextID(SK_InvalidGenID) {}
GrTexture* fOriginalTexture;
uint32_t fOwningContextID;
// There is never a ref associated with this pointer. We rely on our atomic bookkeeping
// with the context ID to know when this pointer is valid and safe to use. This lets us
// avoid releasing a ref from another thread, or get into races during context shutdown.
GrTexture* fBorrowedTexture;
// For the same reason as the fBorrowedTexture, there is no ref associated with this
// pointer. The fBorrowingContextReleaseProc is used to make sure all uses of the wrapped
// texture are finished on the borrowing context before we open this back up to other
// contexts. In general a ref to this release proc is owned by all proxies and gpu uses of
// the backend texture.
GrReleaseProcHelper* fBorrowingContextReleaseProc;
uint32_t fBorrowingContextID;
RefHelper* fRefHelper;
// This Mutex is used to guard the borrowing of the texture to one GrContext at a time as well
// as the creation of the fBorrowingContextReleaseProc. The latter happening if two threads with
// the same consuming GrContext try to generate a texture at the same time.
SkMutex fBorrowingMutex;
sk_sp<GrSemaphore> fSemaphore;
GrBackendTexture fBackendTexture;
GrPixelConfig fConfig;
GrSurfaceOrigin fSurfaceOrigin;
typedef SkImageGenerator INHERITED;
#endif // GrBackendTextureImageGenerator_DEFINED