content/common/gpu/client/gl_helper_readback_support.h

   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_