Implement texel buffers

src/gpu/gl/GrGLBuffer.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLBuffer_DEFINED
 #define GrGLBuffer_DEFINED
 
 #include "GrBuffer.h"
 #include "gl/GrGLTypes.h"
 
 class GrGLGpu;
 class GrGLCaps;
 
 class GrGLBuffer : public GrBuffer {
 public:
     static GrGLBuffer* Create(GrGLGpu*, size_t size, GrBufferType intendedType, GrAccessPattern,
                               const void* data = nullptr);
 
     ~GrGLBuffer() {
         // either release or abandon should have been called by the owner of this object.
         SkASSERT(0 == fBufferID);
     }
 
     GrGLuint bufferID() const { return fBufferID; }
     size_t baseOffset() const { return reinterpret_cast<size_t>(fCPUData); }
 
+    /**
+     * Returns the actual size of the underlying GL buffer object. In certain cases we may make this
+     * smaller than the size reported by GrBuffer.
+     */
+    size_t glSizeInBytes() const { return fGLSizeInBytes; }
+
+    void setHasAttachedToTexture() { fHasAttachedToTexture = true; }

[bsalomon, 2016/04/11 16:51:38]

Maybe (set)isAttachedToTexture? More clear that is is now not just has been at
some point.

[Chris Dalton, 2016/04/11 19:48:19]

Actually the intention of this bool is to know if it has *ever* been attached to
a
texture. Then upon deletion, it only tries to detach it from any possible buffer
textures if it has been attached at some point in the past.

We could instead be more elaborate and complex, and maintain a count of how many
buffer
textures it is attached to. Do you prefer one way or the other? I don't have a
preference myself.

[bsalomon, 2016/04/11 20:37:11]

Got it. I'm ok with it as is.

+    bool hasAttachedToTexture() const { return fHasAttachedToTexture; }
+
 protected:
     GrGLBuffer(GrGLGpu*, size_t size, GrBufferType intendedType, GrAccessPattern, bool cpuBacked,
                const void* data);
 
     void onAbandon() override;
     void onRelease() override;
     void setMemoryBacking(SkTraceMemoryDump* traceMemoryDump,
                           const SkString& dumpName) const override;
 
 private:
     GrGLGpu* glGpu() const;
     const GrGLCaps& glCaps() const;
 
     void onMap() override;
     void onUnmap() override;
     bool onUpdateData(const void* src, size_t srcSizeInBytes) override;
 
 #ifdef SK_DEBUG
     void validate() const;
 #endif
 
     void*          fCPUData;
     GrBufferType   fIntendedType;
     GrGLuint       fBufferID;
     size_t         fSizeInBytes;
     GrGLenum       fUsage;
-    size_t         fGLSizeInBytes;     // In certain cases we make the size of the GL buffer object
-                                       // smaller or larger than the size in fDesc.
+    size_t         fGLSizeInBytes;
+    bool           fHasAttachedToTexture;
 
     typedef GrBuffer INHERITED;
 };
 
 #endif