Cache OpenGL textures and other objects in CompositingIOSurfaceMac copy/transform code.

content/browser/renderer_host/compositing_iosurface_transformer_mac.h

 // Copyright (c) 2013 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_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_TRANSFORMER_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_TRANSFORMER_MAC_H_
 
 #include <OpenGL/gl.h>
 
 #include "base/basictypes.h"
 #include "content/browser/renderer_host/compositing_iosurface_shader_programs_mac.h"
+#include "ui/gfx/size.h"
 
 namespace gfx {
 class Rect;
-class Size;
 }  // namespace gfx
 
 namespace content {
 
 // Provides useful image filtering operations that are implemented efficiently
 // using OpenGL shader programs.
 //
 // Note: All methods assume to be called within an active OpenGL context.
 class CompositingIOSurfaceTransformer {
  public:
   // Construct a transformer that always uses the given parameters for texture
   // bindings.  |texture_target| is one of the valid enums to use with
   // glBindTexture().
   // |src_texture_needs_y_flip| is true when the |src_texture| argument to any
   // of the methods below uses upside-down Y coordinates.
   // |shader_program_cache| is not owned by this instance.
   CompositingIOSurfaceTransformer(
       GLenum texture_target, bool src_texture_needs_y_flip,
       CompositingIOSurfaceShaderPrograms* shader_program_cache);
 
   ~CompositingIOSurfaceTransformer();
 
+  // Delete any references to currently-cached OpenGL objects.  This must be
+  // called within the OpenGL context just before destruction.
+  void ReleaseCachedGLObjects();
+
   // Resize using bilinear interpolation.  Returns false on error.  Otherwise,
-  // the |texture| argument will point to the result and the caller is
-  // responsible for calling glDeleteTexture(*texture).
+  // the |texture| argument will point to the result.  Ownership of the returned
+  // |texture| remains with CompositingIOSurfaceTransformer (i.e., the caller
+  // must not delete this texture).  The |texture| remains valid until the next
+  // call to ResizeBilinear() or ReleaseCachedGLObjects().
   //
   // If the src and dst sizes are identical, this becomes a simple copy into a
   // new texture.
   //
   // Note: This implementation is faulty in that minifications by more than 2X
   // will undergo aliasing.
   bool ResizeBilinear(GLuint src_texture, const gfx::Rect& src_subrect,
                       const gfx::Size& dst_size, GLuint* texture);
 
   // Color format conversion from RGB to planar YV12 (also known as YUV420).
   //
   // YV12 is effectively a twelve bit per pixel format consisting of a full-
   // size y (luminance) plane and half-width, half-height u and v (blue and
-  // red chrominance) planes.  This method will allocate three off-screen
-  // textures, one for each plane, and return them via the output arguments
-  // |texture_y|, |texture_u|, and |texture_v|.  While the textures are in
-  // GL_RGBA format, they should be interpreted as the appropriate single-byte,
-  // planar format after reading the pixel data.  The output arguments
-  // |packed_y_size| and |packed_uv_size| follow from these special semantics:
-  // They represent the size of their corresponding texture, if it was to be
-  // treated like RGBA pixel data.  That means their widths are in terms of
-  // "quads," where one quad contains 4 Y (or U or V) pixels.
+  // red chrominance) planes.  This method will return three off-screen
+  // textures, one for each plane, via the output arguments |texture_y|,
+  // |texture_u|, and |texture_v|.  While the textures are in GL_RGBA format,
+  // they should be interpreted as the appropriate single-byte, planar format
+  // after reading the pixel data.  The output arguments |packed_y_size| and
+  // |packed_uv_size| follow from these special semantics: They represent the
+  // size of their corresponding texture, if it was to be treated like RGBA
+  // pixel data.  That means their widths are in terms of "quads," where one
+  // quad contains 4 Y (or U or V) pixels.
+  //
+  // Ownership of the returned textures remains with
+  // CompositingIOSurfaceTransformer (i.e., the caller must not delete the
+  // textures).  The textures remain valid until the next call to
+  // TransformRGBToYV12() or ReleaseCachedGLObjects().
   //
   // If |src_subrect|'s size does not match |dst_size|, the source will be
   // bilinearly interpolated during conversion.
   //
   // Returns true if successful, and the caller is responsible for deleting the
   // output textures.
   bool TransformRGBToYV12(
       GLuint src_texture, const gfx::Rect& src_subrect,
       const gfx::Size& dst_size,
       GLuint* texture_y, GLuint* texture_u, GLuint* texture_v,
       gfx::Size* packed_y_size, gfx::Size* packed_uv_size);
 
  private:
+  enum CachedTexture {
+    RGBA_OUTPUT = 0,
+    Y_PLANE_OUTPUT,
+    UUVV_INTERMEDIATE,
+    U_PLANE_OUTPUT,
+    V_PLANE_OUTPUT,
+    NUM_CACHED_TEXTURES
+  };
+
+  // If necessary, generate the texture and/or resize it to the given |size|.
+  void PrepareTexture(CachedTexture which, const gfx::Size& size);

[ncarter (slow), 2013/04/15 23:38:19]

Should this return the texture name?

[miu, 2013/04/16 03:51:22]

If the method was public, I'd probably do that and rename it to something like
GetCachedTexture().  As an internal helper, it doesn't really matter.

+
+  // If necessary, generate a framebuffer object to be used as an intermediate
+  // destination for drawing.
+  void PrepareFramebuffer();
+
   // Target to bind all input and output textures to (which defines the type of
   // textures being created and read).  Generally, this is
   // GL_TEXTURE_RECTANGLE_ARB.
   const GLenum texture_target_;
   const bool src_texture_needs_y_flip_;
   CompositingIOSurfaceShaderPrograms* const shader_program_cache_;
 
+  // Cached OpenGL objects.
+  GLuint textures_[NUM_CACHED_TEXTURES];
+  gfx::Size texture_sizes_[NUM_CACHED_TEXTURES];
+  GLuint frame_buffer_;
+
   // Auto-detected and set once in the constructor.
   bool system_supports_multiple_draw_buffers_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositingIOSurfaceTransformer);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_TRANSFORMER_MAC_H_