Implement GLHelperReadbackSupport for GLHelper usage.

content/common/gpu/client/gl_helper_readback_support.h

+// Copyright (c) 2014 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_READBACK_SUPPORT_H_
+#define CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_
+
+#include "content/common/gpu/client/gl_helper.h"
+
+namespace content {
+
+class CONTENT_EXPORT GLHelperReadbackSupport {
+ public:
+  GLHelperReadbackSupport(gpu::gles2::GLES2Interface* gl, GLHelper* helper);
+
+  ~GLHelperReadbackSupport();
+
+  // Checks whether the readback (Color read format and type) is supported
+  // for the requested texture format  by the hardware or not.
+  // For ex: some hardwares have rgb565 readback
+  // support when binded with the frame buffer for others it may fail.
+  // Here we pass the internal textureformat as skia config.
+  bool IsReadbackConfigSupported(SkBitmap::Config texture_format);
+
+ private:
+  enum FormatSupport { FORMAT_NOT_SUPPORTED = 0, FORMAT_SUPPORTED, };
+
+  // This populates the format_support_table with the list of supported
+  // formats.
+  void InitializeReadbackSupport();
+
+  // This api is called  once per format and it is done in the
+  // InitializeReadbackSupport. We should not use this any where
+  // except the InitializeReadbackSupport.Calling this at other places
+  // can distrub the state of normal gl operations.
+  void CheckForReadbackSupport(SkBitmap::Config texture_format);
+
+  // Helper functions for checking the supported texture formats.
+  // Avoid using this API in between texture operations, as this does some
+  // teture opertions (bind, attach) internally.
+  bool SupportsFormat(GLint format, GLint type);
+
+  FormatSupport format_support_table_[SkBitmap::kConfigCount];
+
+  gpu::gles2::GLES2Interface* gl_;
+
+  GLHelper* helper_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_