Implement client side PBOs for glReadPixel

gpu/command_buffer/client/gles2_implementation.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.
 
 // A class to emulate GLES2 over command buffers.
 
 #include "../client/gles2_implementation.h"
 
 #include <algorithm>
 #include <map>
@@ skipping 2085 matching lines @@
   int8* dest = reinterpret_cast<int8*>(pixels);
   uint32 temp_size;
   uint32 unpadded_row_size;
   uint32 padded_row_size;
   if (!GLES2Util::ComputeImageDataSizes(
       width, 2, format, type, pack_alignment_, &temp_size, &unpadded_row_size,
       &padded_row_size)) {
     SetGLError(GL_INVALID_VALUE, "glReadPixels", "size too large.");
     return;
   }
+
+  if (bound_pixel_unpack_transfer_buffer_id_) {

[greggman, 2013/03/19 20:54:11]

As pointed out else where, "unpack" is for providing data to GL, "pack" is for
reading data.

[hubbe, 2013/03/19 22:42:42]

Done.

+    GLuint offset = ToGLuint(pixels);
+    BufferTracker::Buffer* buffer = GetBoundPixelUnpackTransferBufferIfValid(
+        "glReadPixels", offset, temp_size);
+    if (buffer) {
+      helper_->ReadPixels(xoffset, yoffset, width, height, format, type,
+                          buffer->shm_id(), buffer->shm_offset(),
+                          0, 0);
+      buffer->set_transfer_ready_token(helper_->InsertToken());
+    }
+    return;

[apatrick_chromium, 2013/03/19 18:34:48]

Should this not generate INVALID_OPERATION?

[hubbe, 2013/03/19 22:42:42]

Done. (And in other similar places)

+  }
+
+  if (!pixels) {
+    SetGLError(GL_INVALID_VALUE, "glReadPixels", "pixels = NULL");
+    return;
+  }
+
   // Transfer by rows.
   // The max rows we can transfer.
   while (height) {
     GLsizei desired_size = padded_row_size * height - 1 + unpadded_row_size;
     ScopedTransferBufferPtr buffer(desired_size, helper_, transfer_buffer_);
     if (!buffer.valid()) {
       return;
     }
     GLint num_rows = ComputeNumRowsThatFitInBuffer(
         padded_row_size, unpadded_row_size, buffer.size());
@@ skipping 1181 matching lines @@
 
 void* GLES2Implementation::MapBufferCHROMIUM(GLuint target, GLenum access) {
   GPU_CLIENT_SINGLE_THREAD_CHECK();
   GPU_CLIENT_LOG("[" << GetLogPrefix() << "] glMapBufferCHROMIUM("
       << target << ", " << GLES2Util::GetStringEnum(access) << ")");
   if (target != GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM) {
     SetGLError(
         GL_INVALID_ENUM, "glMapBufferCHROMIUM", "invalid target");
     return NULL;
   }
-  if (access != GL_WRITE_ONLY) {
+  if (access != GL_WRITE_ONLY && access != GL_READ_ONLY) {
     SetGLError(GL_INVALID_ENUM, "glMapBufferCHROMIUM", "bad access mode");
     return NULL;
   }
   BufferTracker::Buffer* buffer = buffer_tracker_->GetBuffer(
         bound_pixel_unpack_transfer_buffer_id_);
   if (!buffer) {
     SetGLError(GL_INVALID_OPERATION, "glMapBufferCHROMIUM", "invalid buffer");
     return NULL;
   }
   if (buffer->mapped()) {
     SetGLError(GL_INVALID_OPERATION, "glMapBufferCHROMIUM", "already mapped");
     return NULL;
   }
+  if (buffer->transfer_ready_token()) {

[greggman, 2013/03/19 20:54:11]

It seems like if you're going to add this check you should add it for all
operations on a buffer, not just readPixels. In other words, TexImage2D when
using a PBO should set a token and block in map if it's busy.

[hubbe, 2013/03/19 22:42:42]

I can do it either way.
I think I prefer implementing the blocking semantics as certain kinds of patters
get a lot easier this way.

+    helper_->WaitForToken(buffer->transfer_ready_token());
+    buffer->set_transfer_ready_token(0);
+  }
   buffer->set_mapped(true);
 
   GPU_DCHECK(buffer->address());
   GPU_CLIENT_LOG("  returned " << buffer->address());
   CheckGLError();
   return buffer->address();
 }
 
 GLboolean GLES2Implementation::UnmapBufferCHROMIUM(GLuint target) {
   GPU_CLIENT_SINGLE_THREAD_CHECK();
@@ skipping 122 matching lines @@
   return helper_->InsertSyncPointCHROMIUM();
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "../client/gles2_implementation_impl_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu