Implement client side PBOs for glReadPixel

gpu/command_buffer/tests/gl_readback_unittests.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.
+
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+#include <GLES2/gl2extchromium.h>
+
+#include "gpu/command_buffer/tests/gl_manager.h"
+#include "gpu/command_buffer/tests/gl_test_utils.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace gpu {
+
+class GLReadbackTest : public testing::Test {
+ protected:
+  virtual void SetUp() {
+    gl_.Initialize(GLManager::Options());
+  }
+
+  virtual void TearDown() {
+    gl_.Destroy();
+  }
+
+  GLManager gl_;
+};
+
+
+TEST_F(GLReadbackTest, ReadPixelsWithPBO) {

[apatrick_chromium, 2013/03/21 22:51:27]

Can you clear the FBO to a particular color and then check that the color that
is read back is the same? glClearColor and then glClear.

[hubbe, 2013/03/21 23:00:58]

Done.

+  const GLint kBytesPerPixel = 4;
+  const GLint kWidth = 2;
+  const GLint kHeight = 2;
+
+  GLuint b;
+  glGenBuffers(1, &b);
+  glBindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, b);
+  glBufferData(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+               kWidth * kHeight * kBytesPerPixel,
+               NULL,
+               0 /* should be  GL_STREAM_READ, but that is not defined in
+                    GLES2, and the code currently doesn't care */);
+  glReadPixels(0, 0, kWidth, kHeight, GL_RGBA, GL_UNSIGNED_BYTE, 0);
+  glFlush();

[apatrick_chromium, 2013/03/21 22:51:27]

You shouldn't need this glFlush() because glMapBufferCHROMIUM should do it.

[hubbe, 2013/03/21 23:00:58]

Done.

+  EXPECT_TRUE(glMapBufferCHROMIUM(
+      GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+      GL_READ_ONLY));
+  glUnmapBufferCHROMIUM(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM);
+  glBindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, 0);
+  glDeleteBuffers(1, &b);
+  GLTestHelper::CheckGLError("no errors", __LINE__);
+}
+
+TEST_F(GLReadbackTest, ReadPixelsWithPBOAndQuery) {
+  const GLint kBytesPerPixel = 4;
+  const GLint kWidth = 2;
+  const GLint kHeight = 2;
+
+  GLuint b, q;
+  glGenBuffers(1, &b);
+  glGenQueriesEXT(1, &q);

[apatrick_chromium, 2013/03/21 22:51:27]

The query object leaks.

[hubbe, 2013/03/21 23:00:58]

Done.

+  glBindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, b);
+  glBufferData(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+               kWidth * kHeight * kBytesPerPixel,
+               NULL,
+               0 /* should be  GL_STREAM_READ, but that is not defined in
+                    GLES2, and the code currently doesn't care */);
+  glBeginQueryEXT(GL_COMMANDS_ISSUED_CHROMIUM, q);
+  glReadPixels(0, 0, kWidth, kHeight, GL_RGBA, GL_UNSIGNED_BYTE, 0);
+  glEndQueryEXT(GL_COMMANDS_ISSUED_CHROMIUM);
+  unsigned int done = 0;
+  while (!done) {

[apatrick_chromium, 2013/03/21 22:51:27]

I think you need a glFlush before this loop.

[hubbe, 2013/03/21 23:00:58]

Done.

+    glGetQueryObjectuivEXT(q, GL_QUERY_RESULT_AVAILABLE_EXT, &done);
+  }
+
+  // TODO(hubbe): Check that glMapBufferCHROMIUM does not block here.
+  EXPECT_TRUE(glMapBufferCHROMIUM(
+      GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+      GL_READ_ONLY));
+  glUnmapBufferCHROMIUM(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM);
+  glBindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, 0);
+  glDeleteBuffers(1, &b);
+  GLTestHelper::CheckGLError("no errors", __LINE__);
+}
+
+}  // namespace gpu