Add promise images for deferred instantiation of wrapped gpu textures

This will allow a client to make an SkImage that "wraps" a gpu texture,
however the client does need to supply the actual gpu texture at Image
creation time. Instead it is retrieve at flush time via a callback.

Bug: skia:
Change-Id: I6267a55ab7102101a7bd80a6f547b6a870d2df08
Reviewed-on: https://skia-review.googlesource.com/109021
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/image/SkImage_Gpu.h b/src/image/SkImage_Gpu.h
index 9cc28c317a..24a8c78869 100644
--- a/src/image/SkImage_Gpu.h
+++ b/src/image/SkImage_Gpu.h
@@ -60,6 +60,59 @@ public:
     sk_sp<SkImage> onMakeColorSpace(sk_sp<SkColorSpace>, SkColorType,
                                     SkTransferFunctionBehavior) const override;
 
+    typedef ReleaseContext TextureContext;
+    typedef void (*TextureFulfillProc)(TextureContext textureContext, GrBackendTexture* outTexture);
+
+    /**
+        Create a new SkImage that is very similar to an SkImage created by MakeFromTexture. The main
+        difference is that the client doesn't have the backend texture on the gpu yet but they know
+        all the properties of the texture. So instead of passing in a GrBackendTexture the client
+        supplies a GrBackendFormat, width, height, and GrMipMapped state.
+
+        When we actually send the draw calls to the GPU, we will call the textureFulfillProc and
+        the client will return a GrBackendTexture to us. The properties of the GrBackendTexture must
+        match those set during the SkImage creation, and it must have a valid backend gpu texture.
+        The gpu texture supplied by the client must stay valid until we call the textureReleaseProc.
+
+        When we are done with the texture returned by the textureFulfillProc we will call the
+        textureReleaseProc passing in the textureContext. This is a signal to the client that they
+        are free to delete the underlying gpu texture. If future draws also use the same promise
+        image we will call the textureFulfillProc again if we've already called the
+        textureReleaseProc. We will always call textureFulfillProc and textureReleaseProc in pairs.
+        In other words we will never call textureFulfillProc or textureReleaseProc multiple times
+        for the same textureContext before calling the other.
+
+        @param context             Gpu context
+        @param backendFormat       format of promised gpu texture
+        @param width               width of promised gpu texture
+        @param height              height of promised gpu texture
+        @param mipMapped           mip mapped state of promised gpu texture
+        @param origin              one of: kBottomLeft_GrSurfaceOrigin, kTopLeft_GrSurfaceOrigin
+        @param colorType           one of: kUnknown_SkColorType, kAlpha_8_SkColorType,
+                                   kRGB_565_SkColorType, kARGB_4444_SkColorType,
+                                   kRGBA_8888_SkColorType, kBGRA_8888_SkColorType,
+                                   kGray_8_SkColorType, kRGBA_F16_SkColorType
+        @param alphaType           one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType,
+                                   kPremul_SkAlphaType, kUnpremul_SkAlphaType
+        @param colorSpace          range of colors; may be nullptr
+        @param textureFulfillProc  function called to get actual gpu texture
+        @param textureReleaseProc  function called when texture can be released
+        @param textureContext      state passed to textureFulfillProc and textureReleaseProc
+        @return                    created SkImage, or nullptr
+     */
+    static sk_sp<SkImage> MakePromiseTexture(GrContext* context,
+                                             const GrBackendFormat& backendFormat,
+                                             int width,
+                                             int height,
+                                             GrMipMapped mipMapped,
+                                             GrSurfaceOrigin origin,
+                                             SkColorType colorType,
+                                             SkAlphaType alphaType,
+                                             sk_sp<SkColorSpace> colorSpace,
+                                             TextureFulfillProc textureFulfillProc,
+                                             TextureReleaseProc textureReleaseProc,
+                                             TextureContext textureContext);
+
     bool onIsValid(GrContext*) const override;
 
 private: