Implement client side PBOs for glReadPixel

gpu/command_buffer/client/gles2_implementation_unittest.cc

 // Copyright (c) 2012 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.
 
 // Tests for GLES2Implementation.
 
 #include "gpu/command_buffer/client/gles2_implementation.h"
 
 #include <GLES2/gl2ext.h>
 #include <GLES2/gl2extchromium.h>
@@ skipping 1402 matching lines @@
   expected.set_token.Init(GetNextToken());
   scoped_array<int8> buffer(new int8[kWidth * kHeight * kBytesPerPixel]);
 
   EXPECT_CALL(*command_buffer(), OnFlush())
       .Times(1)
       .RetiresOnSaturation();
 
   gl_->ReadPixels(0, 0, kWidth, kHeight, kFormat, kType, buffer.get());
 }
 
+TEST_F(GLES2ImplementationTest, ReadPixelsWithPBO) {
+  struct Cmds {
+    cmds::ReadPixels read;
+    cmd::SetToken set_token;
+  };
+  const GLint kBytesPerPixel = 4;
+  const GLint kWidth = 2;
+  const GLint kHeight = 2;
+  const GLenum kFormat = 0;
+  const GLenum kType = 0;
+
+  ExpectedMemoryInfo mem1 =
+      GetExpectedMemory(kWidth * kHeight * kBytesPerPixel);
+  ExpectedMemoryInfo result1 =
+      GetExpectedResultMemory(sizeof(cmds::ReadPixels::Result));
+
+  Cmds expected;
+  expected.read.Init(
+      0, 0, kWidth, kHeight, kFormat, kType,
+      mem1.id, mem1.offset, result1.id, result1.offset);
+  expected.set_token.Init(GetNextToken());
+  scoped_array<int8> buffer(new int8[kWidth * kHeight * kBytesPerPixel]);
+
+  GLuint b;
+  gl_->GenBuffers(1, &b);
+  gl_->BindBuffer(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM, b);
+  gl_->BufferData(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
+                  kWidth * kHeight * kBytesPerPixel,
+                  NULL,
+                  0 /* GL_STREAM_READ */ );
+  gl_->ReadPixels(0, 0, kWidth, kHeight, kFormat, kType, 0);
+  EXPECT_TRUE(gl_->MapBufferCHROMIUM(
+      GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
+      GL_READ_ONLY));
+  gl_->UnmapBufferCHROMIUM(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM);
+  gl_->BindBuffer(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM, 0);
+  gl_->DeleteBuffers(1, &b);

[greggman, 2013/03/20 00:42:17]

Ideally you want to check that gl_->ReadPixels inserts the commands you expect
it to insert if there's a PBO.

so, you need 

   EXPECT_EQ(0, memcmp(&expected, commands_, sizeof(expected)))

You don't need the unmap, bind, delete (lines 1457-1459)

Up above you don't need ExpectedMemoryInfo mem1 or result1. Those are figuring
out what memory would be allocated by ReadPixels. Instead you'd expect
BufferData to allocate shared memory.

sigh....I don't see an easy way to figure out what that will be though.

If we can't figure out an easy way to do that you can write integration tests in
gl_tests. See src/gpu/command_buffer/tests

+}
+
 TEST_F(GLES2ImplementationTest, FreeUnusedSharedMemory) {
   struct Cmds {
     cmds::BufferSubData buf;
     cmd::SetToken set_token;
   };
   const GLenum kTarget = GL_ELEMENT_ARRAY_BUFFER;
   const GLintptr kOffset = 15;
   const GLsizeiptr kSize = 16;
 
   ExpectedMemoryInfo mem1 = GetExpectedMemory(kSize);
@@ skipping 1369 matching lines @@
   ClearCommands();
   gl_->Enable(GL_BLEND);
   EXPECT_TRUE(NoCommandsWritten());
 }
 
 
 #include "gpu/command_buffer/client/gles2_implementation_unittest_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu
-