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 abstract base class which consumers of Skia can subclass and pass to Skia
+ * to use custom storage allocation in place of TexImage2D.

[bsalomon, 2016/01/26 22:20:54]

Maybe say "in place of backend API texture creation function" as there will soon
be a non-GL backend.

[erikchen, 2016/01/27 21:55:14]

Done.

+ */
+class TextureStorageAllocator {

[bsalomon, 2016/01/26 22:20:54]

Should be GrTextureStorageAllocator

[erikchen, 2016/01/27 21:55:15]

Done.

+ public:
+  /*

[bsalomon, 2016/01/26 22:20:54]

nit, we use four space indents.

[erikchen, 2016/01/27 21:55:14]

Done.

+   * The required bind target for any texture with custom storage.
+   */
+  virtual unsigned textureStorageTarget() = 0;
+  /*
+   * 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
+   * WRAP_S and WRAP_T must be GL_CLAMP_TO_EDGE.
+   */
+  virtual bool allocateTextureStorage(GrBackendObject texture, unsigned width, 

[bsalomon, 2016/01/26 22:20:54]

Don't we also need to somehow tell the allocator the pixel format that we want
to use?

Also, wondering what we should do when the client is creating a compressed
texture. Should we ignore the allocator param, respect it, or fail? Or give the
allocator the option (ternary return value - success, fail, fallback to normal
allocation).

[erikchen, 2016/01/27 21:55:14]

CHROMIUM_image on Mac supports very few pixel formats, and does not support
compressed textures. I added a new method supportsPixelConfig(GrPixelConfig
config) that Skia can call to determine whether a given pixel format is
supported.

+                                      unsigned height) = 0;
+  /*
+   * Deallocate the storage for the given texture.
+   */
+  virtual void deallocateTextureStorage(GrBackendObject texture) = 0;

[bsalomon, 2016/01/26 22:20:54]

We have a method on GrContext called abandonContext(), it's called when the 3D
context behind the GrContext is no longer available (e.g. lost context on
chrome). When that happens we don't call glDeleteTextures() (or equivalent for
other resource types).

What's our contract in that case? Do we call the deallocate function? Should we
let it know that the context was lost?

[erikchen, 2016/01/27 21:55:15]

The consumer of Skia will be responsible for destroying all extant textures.
I've updated the documentation.

+
+ protected:
+  ~TextureStorageAllocator() {}

[bsalomon, 2016/01/26 22:20:54]

Who deletes the allocator, Skia? Should this be virtual?

[erikchen, 2016/01/27 21:55:14]

Skia does not delete the allocator, but this should still be virtual.

+};
+
 /**
  * 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,
     kBottomLeft_GrSurfaceOrigin,
 };
 
 /**
  * Describes a surface to be created.
  */
 struct GrSurfaceDesc {
     GrSurfaceDesc()
     : fFlags(kNone_GrSurfaceFlags)
     , fOrigin(kDefault_GrSurfaceOrigin)
     , fWidth(0)
     , fHeight(0)
     , fConfig(kUnknown_GrPixelConfig)
-    , fSampleCnt(0) {
+    , fSampleCnt(0)
+    , fTextureStorageAllocator(nullptr) {
     }
 
     GrSurfaceFlags         fFlags;  //!< bitfield of TextureFlags
     GrSurfaceOrigin        fOrigin; //!< origin of the texture
     int                    fWidth;  //!< Width of the texture
     int                    fHeight; //!< Height of the texture
 
     /**
      * Format of source data of the texture. Not guaranteed to be the same as
      * internal format used by 3D API.
      */
     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
+     * surfaces derived from the original surface will have the same value for
+     * fTextureStorageAllocator.
+     */
+    TextureStorageAllocator*      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