skia: Add support for CHROMIUM_image backed textures.

include/gpu/GrTypes.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTypes_DEFINED
 #define GrTypes_DEFINED
 
@@ skipping 391 matching lines @@
     kZeroCopy_GrSurfaceFlag         = 0x2,
     /**
      * Indicates that all allocations (color buffer, FBO completeness, etc)
      * should be verified.
      */
     kCheckAllocation_GrSurfaceFlag  = 0x4,
 };
 
 GR_MAKE_BITFIELD_OPS(GrSurfaceFlags)
 
+// opaque type for 3D API object handles
+typedef intptr_t GrBackendObject;
+
+/**
+ * An container of function pointers which consumers of Skia can fill in and
+ * pass to Skia. Skia will use these function pointers in place of its backend
+ * API texture creation function. Either all of the function pointers should be
+ * filled in, or they should all be nullptr.
+ */
+struct GrTextureStorageAllocator {
+    GrTextureStorageAllocator()
+    : fAllocateTextureStorage(nullptr)
+    , fDeallocateTextureStorage(nullptr) {
+    }
+
+    enum class Result {
+        kSucceededAndUploaded,
+        kSucceededWithoutUpload,
+        kFailed
+    };
+    typedef Result (*AllocateTextureStorageProc)(
+            void* ctx, GrBackendObject texture, unsigned width,
+            unsigned height, GrPixelConfig config, const void* srcData);
+    typedef void (*DeallocateTextureStorageProc)(void* ctx, GrBackendObject texture);
+
+    /*
+     * Generates and binds a texture to |textureStorageTarget()|. Allocates
+     * storage for the texture.
+     *
+     * The MIN and MAX filters for the created texture must be GL_LINEAR. The

[bsalomon, 2016/02/01 14:54:42]

In OpenGL, ...

[erikchen, 2016/02/01 22:58:32]

Done.

+     * WRAP_S and WRAP_T must be GL_CLAMP_TO_EDGE.
+     *
+     * If |srcData| is not nullptr, then the implementation of this function

[bsalomon, 2016/02/01 14:54:42]

I think we need an origin param as well. Also, maybe make the docs say that the
impl *may* attempt to upload. I think it's only worth implementing that if there
is a faster upload path.

[erikchen, 2016/02/01 22:58:32]

Done and done.

+     * should attempt to upload the data into the texture. On successful upload,
+     * or if |srcData| is nullptr, returns kSucceededAndUploaded.
+     */
+    AllocateTextureStorageProc fAllocateTextureStorage;
+
+    /*
+     * Deallocate the storage for the given texture.
+     *
+     * Skia does not always destroy its outstanding textures. See
+     * GrContext::abandonContext() for more details. The consumer of Skia is
+     * responsible for making sure that all textures are destroyed, even if this
+     * callback is not invoked.
+     */
+    DeallocateTextureStorageProc fDeallocateTextureStorage;
+
+    /*
+     * The context to use when invoking fAllocateTextureStorage and
+     * fDeallocateTextureStorage.
+     */
+    void* fCtx;
+};
+
 /**
  * Some textures will be stored such that the upper and left edges of the content meet at the
  * the origin (in texture coord space) and for other textures the lower and left edges meet at
  * the origin. kDefault_GrSurfaceOrigin sets textures to TopLeft, and render targets
  * to BottomLeft.
  */
 
 enum GrSurfaceOrigin {
     kDefault_GrSurfaceOrigin,         // DEPRECATED; to be removed
     kTopLeft_GrSurfaceOrigin,
@@ skipping 25 matching lines @@
     GrPixelConfig          fConfig;
 
     /**
      * The number of samples per pixel or 0 to disable full scene AA. This only
      * applies if the kRenderTarget_GrSurfaceFlag is set. The actual number
      * of samples may not exactly match the request. The request will be rounded
      * up to the next supported sample count, or down if it is larger than the
      * max supported count.
      */
     int                    fSampleCnt;
+
+    /**
+     * A custom platform-specific allocator to use in place of TexImage2D. All

[bsalomon, 2016/02/01 14:54:42]

...in place of the backend APIs usual texture creation method (e.g. TexImage2D
in OpenGL).

[erikchen, 2016/02/01 22:58:32]

Done.

+     * surfaces derived from the original surface will have the same value for

[bsalomon, 2016/02/01 14:54:42]

What exactly is meant here by surfaces derived from the original surface?

[erikchen, 2016/02/01 22:58:32]

I was referring to RenderTargets created by copy-on-write. I guess that's
probably implied, and I just removed that entire portion of the comment, because
apparently it was too confusing.

+     * fTextureStorageAllocator.
+     */
+    GrTextureStorageAllocator fTextureStorageAllocator;
 };
 
 // Legacy alias
 typedef GrSurfaceDesc GrTextureDesc;
 
 /**
  * Clips are composed from these objects.
  */
 enum GrClipType {
     kRect_ClipType,
     kPath_ClipType
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
-// opaque type for 3D API object handles
-typedef intptr_t GrBackendObject;
-
 
 /** Ownership rules for external GPU resources imported into Skia. */
 enum GrWrapOwnership {
     /** Skia will assume the client will keep the resource alive and Skia will not free it. */
     kBorrow_GrWrapOwnership,
 
     /** Skia will assume ownership of the resource and free it. */
     kAdopt_GrWrapOwnership,
 };
 
@@ skipping 133 matching lines @@
             return 4 * width * height;
     }
 }
 
 /**
  * This value translates to reseting all the context state for any backend.
  */
 static const uint32_t kAll_GrBackendState = 0xffffffff;
 
 #endif