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

content/browser/renderer_host/compositing_iosurface_transformer_mac.h

Index: content/browser/renderer_host/compositing_iosurface_transformer_mac.h
diff --git a/content/browser/renderer_host/compositing_iosurface_transformer_mac.h b/content/browser/renderer_host/compositing_iosurface_transformer_mac.h
index d401b92d12f96e1e0c92c001b08cd2b078af25f6..48900741944157c88996db823c9c66345eb9ac38 100644
--- a/content/browser/renderer_host/compositing_iosurface_transformer_mac.h
+++ b/content/browser/renderer_host/compositing_iosurface_transformer_mac.h
@@ -9,10 +9,10 @@
 
 #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 {
@@ -35,9 +35,15 @@ class CompositingIOSurfaceTransformer {
 
   ~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.
@@ -51,15 +57,20 @@ class CompositingIOSurfaceTransformer {
   //
   // 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.
@@ -73,6 +84,22 @@ class CompositingIOSurfaceTransformer {
       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.
@@ -80,6 +107,11 @@ class CompositingIOSurfaceTransformer {
   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_;