Implement GLHelperReadbackSupport for GLHelper usage.

content/common/gpu/client/gl_helper.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_
 #define CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_
 
+#include <map>
+
 #include "base/atomicops.h"
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/common/content_export.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "gpu/command_buffer/common/mailbox_holder.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
 namespace gfx {
@@ skipping 252 matching lines @@
   // Resizes the texture's size to |size|.
   void ResizeTexture(GLuint texture, const gfx::Size& size);
 
   // Copies the framebuffer data given in |rect| to |texture|.
   void CopyTextureSubImage(GLuint texture, const gfx::Rect& rect);
 
   // Copies the all framebuffer data to |texture|. |size| specifies the
   // size of the framebuffer.
   void CopyTextureFullImage(GLuint texture, const gfx::Size& size);
 
-  // Check whether rgb565 readback is supported or not.
-  bool CanUseRgb565Readback();
+  // Helper functions for checking the supported texture formats.
+  bool SupportsFormat(GLint format, GLint type);

[no sievers, 2014/02/18 19:35:44]

nit: can be private

[sivag, 2014/02/19 15:49:04]

Done.

+
+  // Checks whether the readback using passed texture format
+  // is supported or not.
+  bool IsReadBackConfigSupported(const SkBitmap::Config& texture_format);

[no sievers, 2014/02/18 19:35:44]

Please describe that this does not specify whether conversion during readback is
supported. Based on the test we do, we only know that the readback *should* work
if the texture format/type exactly match the readback format/type.
Maybe it even makes more sense to pass in the GL format/type here?

[sivag, 2014/02/19 15:49:04]

The reason why i kept a SkBitmap::Config is  in CopyfromCOmpositingSurface i
wanted to do early return if the requested format is not supported.

Any way we have the SupportsFormat API which takes format/type as the input.

Do you think we have to alter the function names?

 
   // A scaler will cache all intermediate textures and programs
   // needed to scale from a specified size to a destination size.
   // If the source or destination sizes changes, you must create
   // a new scaler.
   class CONTENT_EXPORT ScalerInterface {
    public:
     ScalerInterface() {}
     virtual ~ScalerInterface() {}
 
@@ skipping 41 matching lines @@
 
   // Creates |copy_texture_to_impl_| if NULL.
   void InitCopyTextToImpl();
   // Creates |scaler_impl_| if NULL.
   void InitScalerImpl();
 
   gpu::gles2::GLES2Interface* gl_;
   gpu::ContextSupport* context_support_;
   scoped_ptr<CopyTextureToImpl> copy_texture_to_impl_;
   scoped_ptr<GLHelperScaling> scaler_impl_;
-  bool initialized_565_format_check_;
-  bool support_565_format_;
+  std::map<SkBitmap::Config, bool> config_map_;

[piman, 2014/02/18 22:23:15]

map is way overkill.
SkBitmap::Config is a finite set - just use an array?

[sivag, 2014/02/19 15:49:04]

Done.

 
   DISALLOW_COPY_AND_ASSIGN(GLHelper);
 };
 
 // Similar to a ScalerInterface, a yuv readback pipeline will
 // cache a scaler and all intermediate textures and frame buffers
 // needed to scale, crop, letterbox and read back a texture from
 // the GPU into CPU-accessible RAM. A single readback pipeline
 // can handle multiple outstanding readbacks at the same time, but
 // if the source or destination sizes change, you'll need to create
 // a new readback pipeline.
 class CONTENT_EXPORT ReadbackYUVInterface {
  public:
   ReadbackYUVInterface() {}
   virtual ~ReadbackYUVInterface() {}
 
   // Note that |target| must use YV12 format.
   virtual void ReadbackYUV(const gpu::Mailbox& mailbox,
                            uint32 sync_point,
                            const scoped_refptr<media::VideoFrame>& target,
                            const base::Callback<void(bool)>& callback) = 0;
   virtual GLHelper::ScalerInterface* scaler() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_