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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_
      6 #define CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_
      7 
      8 #include <vector>
      9 
     10 #include "content/common/gpu/client/gl_helper.h"
     11 
     12 namespace content {
     13 
     14 class CONTENT_EXPORT GLHelperReadbackSupport {
     15  public:
     16   enum FormatSupport { SUPPORTED, SWIZZLE, NOT_SUPPORTED };
     17 
     18   GLHelperReadbackSupport(gpu::gles2::GLES2Interface* gl);
     19 
     20   ~GLHelperReadbackSupport();
     21 
     22   // For a given color type retrieve whether readback is supported and if so
     23   // how it should be performed. The |format|, |type| and |bytes_per_pixel| are
     24   // the values that should be used with glReadPixels to facilitate the
     25   // readback. If |can_swizzle| is true then this method will return SWIZZLE if
     26   // the data needs to be swizzled before using the returned |format| otherwise
     27   // the method will return SUPPORTED to indicate that readback is permitted of
     28   // this color othewise NOT_SUPPORTED will be returned.  This method always
     29   // overwrites the out values irrespective of the return value.
     30   FormatSupport GetReadbackConfig(SkColorType color_type,
     31                                   bool can_swizzle,
     32                                   GLenum* format,
     33                                   GLenum* type,
     34                                   size_t* bytes_per_pixel);
     35   // Provides the additional readback format/type pairing for a render target
     36   // of a given format/type pairing
     37   void GetAdditionalFormat(GLenum format, GLenum type, GLenum *format_out,
     38                            GLenum *type_out);
     39  private:
     40   struct FormatCacheEntry {
     41     GLenum format;
     42     GLenum type;
     43     GLenum read_format;
     44     GLenum read_type;
     45   };
     46 
     47   // This populates the format_support_table with the list of supported
     48   // formats.
     49   void InitializeReadbackSupport();
     50 
     51   // This api is called  once per format and it is done in the
     52   // InitializeReadbackSupport. We should not use this any where
     53   // except the InitializeReadbackSupport.Calling this at other places
     54   // can distrub the state of normal gl operations.
     55   void CheckForReadbackSupport(SkColorType texture_format);
     56 
     57   // Helper functions for checking the supported texture formats.
     58   // Avoid using this API in between texture operations, as this does some
     59   // teture opertions (bind, attach) internally.
     60   bool SupportsFormat(GLenum format, GLenum type);
     61 
     62   FormatSupport format_support_table_[kLastEnum_SkColorType + 1];
     63 
     64   gpu::gles2::GLES2Interface* gl_;
     65   std::vector<struct FormatCacheEntry> format_cache_;
     66 };
     67 
     68 }  // namespace content
     69 
     70 #endif  // CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_
     71