Implement EXT_draw_buffers WebGL extention support in command buffer.

gpu/command_buffer/service/gles2_cmd_decoder.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 "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <stdio.h>
 
 #include <algorithm>
 #include <list>
@@ skipping 852 matching lines @@
 
   void DoBindTexImage2DCHROMIUM(
       GLenum target,
       GLint image_id);
   void DoReleaseTexImage2DCHROMIUM(
       GLenum target,
       GLint image_id);
 
   void DoTraceEndCHROMIUM(void);
 
+  void DoDrawBuffersEXT(GLsizei count, const GLenum* bufs);
+
   // Creates a Program for the given program.
   Program* CreateProgram(
       GLuint client_id, GLuint service_id) {
     return program_manager()->CreateProgram(client_id, service_id);
   }
 
   // Gets the program info for the given program. Returns NULL if none exists.
   Program* GetProgram(GLuint client_id) {
     return program_manager()->GetProgram(client_id);
   }
@@ skipping 1628 matching lines @@
   resources.MaxVertexAttribs = group_->max_vertex_attribs();
   resources.MaxVertexUniformVectors =
       group_->max_vertex_uniform_vectors();
   resources.MaxVaryingVectors = group_->max_varying_vectors();
   resources.MaxVertexTextureImageUnits =
       group_->max_vertex_texture_image_units();
   resources.MaxCombinedTextureImageUnits = group_->max_texture_units();
   resources.MaxTextureImageUnits = group_->max_texture_image_units();
   resources.MaxFragmentUniformVectors =
       group_->max_fragment_uniform_vectors();
-  resources.MaxDrawBuffers = 1;
+  resources.MaxDrawBuffers = group_->max_draw_buffers();
 
 #if (ANGLE_SH_VERSION >= 110)
   resources.FragmentPrecisionHigh = 1;
 #endif
 
   if (force_webgl_glsl_validation_) {
     resources.OES_standard_derivatives = derivatives_explicitly_enabled_;
   } else {
     resources.OES_standard_derivatives =
         features().oes_standard_derivatives ? 1 : 0;
     resources.ARB_texture_rectangle =
         features().arb_texture_rectangle ? 1 : 0;
     resources.OES_EGL_image_external =
         features().oes_egl_image_external ? 1 : 0;
+    resources.EXT_draw_buffers =
+        features().ext_draw_buffers ? 1 : 0;
   }
 
   ShShaderSpec shader_spec = force_webgl_glsl_validation_ ||
       force_webgl_glsl_validation_ ? SH_WEBGL_SPEC : SH_GLES2_SPEC;
   if (shader_spec == SH_WEBGL_SPEC && features().enable_shader_name_hashing)
 #if !defined(ANGLE_SH_VERSION) || ANGLE_SH_VERSION < 108
     resources.HashFunction = &CityHashForAngle;
 #else
     resources.HashFunction = &CityHash64;
 #endif
@@ skipping 324 matching lines @@
   if (framebuffer_manager()->IsComplete(framebuffer)) {
     return true;
   }
 
   GLenum completeness = framebuffer->IsPossiblyComplete();
   if (completeness != GL_FRAMEBUFFER_COMPLETE) {
     SetGLError(
         GL_INVALID_FRAMEBUFFER_OPERATION, func_name, "framebuffer incomplete");
     return false;
   }
 

[greggman, 2013/03/08 21:48:28]

It seems like you need some code here to work around that mac driver issue where
setting GL_COLOR_ATTACHMENTX to a framebuffer that doesn't have
GL_COLOR_ATTACHMENTX makes the framebuffer incomplete

Like you did for WebGL you need to call glDrawBufferEXT with GL_NONE for each
missing attachment no?

Ideally you'd only do this once so if attachments have not changed and
glDrawBufferEXT has not been called since for this framebuffer you don't need to
do it again.

[Zhenyao Mo, 2013/03/13 01:22:02]

Plan to do the workaround in a separate CL. Easy to review and track in the
future.

   // Are all the attachments cleared?
   if (renderbuffer_manager()->HaveUnclearedRenderbuffers() ||
       texture_manager()->HaveUnclearedMips()) {
     if (!framebuffer->IsCleared()) {
       // Can we clear them?
       if (framebuffer->GetStatus(texture_manager(), target) !=
           GL_FRAMEBUFFER_COMPLETE) {
         SetGLError(
             GL_INVALID_FRAMEBUFFER_OPERATION, func_name,
             "framebuffer incomplete (clear)");
@@ skipping 1124 matching lines @@
       if (params) {
         params[0] = texture_manager()->MaxSizeForTarget(GL_TEXTURE_2D);
       }
       return true;
     case GL_MAX_CUBE_MAP_TEXTURE_SIZE:
       *num_written = 1;
       if (params) {
         params[0] = texture_manager()->MaxSizeForTarget(GL_TEXTURE_CUBE_MAP);
       }
       return true;
+    case GL_MAX_COLOR_ATTACHMENTS_EXT:
+      *num_written = 1;
+      if (params) {
+        params[0] = group_->max_color_attachments();
+      }
+      return true;
+    case GL_MAX_DRAW_BUFFERS_ARB:
+      *num_written = 1;
+      if (params) {
+        params[0] = group_->max_draw_buffers();
+      }
+      return true;
+    case GL_DRAW_BUFFER0_ARB:

[greggman, 2013/03/08 21:48:28]

If we're making this forward compatible it seems like rather than this being a
case it should be under default as in

   default:
     if (pname >= GL_DRAW_BUFFER0_ARB && 
         pname < GL_DRAW_BUFFER0_ARB + max_draw_buffers) {
       ...
       return true;
     }

[Zhenyao Mo, 2013/03/13 01:22:02]

Done.

+    case GL_DRAW_BUFFER1_ARB:
+    case GL_DRAW_BUFFER2_ARB:
+    case GL_DRAW_BUFFER3_ARB:
+    case GL_DRAW_BUFFER4_ARB:
+    case GL_DRAW_BUFFER5_ARB:
+    case GL_DRAW_BUFFER6_ARB:
+    case GL_DRAW_BUFFER7_ARB:
+    case GL_DRAW_BUFFER8_ARB:
+    case GL_DRAW_BUFFER9_ARB:
+    case GL_DRAW_BUFFER10_ARB:
+    case GL_DRAW_BUFFER11_ARB:
+    case GL_DRAW_BUFFER12_ARB:
+    case GL_DRAW_BUFFER13_ARB:
+    case GL_DRAW_BUFFER14_ARB:
+    case GL_DRAW_BUFFER15_ARB:
+      *num_written = 1;
+      if (params) {
+        Framebuffer* framebuffer =
+            GetFramebufferInfoForTarget(GL_FRAMEBUFFER);
+        if (framebuffer)
+          params[0] = framebuffer->GetDrawBuffer(pname);
+        else
+          NOTREACHED();
+      }
+      return true;
     case GL_ALPHA_BITS:
       *num_written = 1;
       if (params) {
         GLint v = 0;
         glGetIntegerv(GL_ALPHA_BITS, &v);
         params[0] = BoundFramebufferHasColorAttachmentWithAlpha() ? v : 0;
       }
       return true;
     case GL_DEPTH_BITS:
       *num_written = 1;
@@ skipping 5912 matching lines @@
 void GLES2DecoderImpl::DoTraceEndCHROMIUM() {
   if (gpu_tracer_->CurrentName().empty()) {
     SetGLError(GL_INVALID_OPERATION,
                "glTraceEndCHROMIUM", "no trace begin found");
     return;
   }
   TRACE_EVENT_COPY_ASYNC_END0("gpu", gpu_tracer_->CurrentName().c_str(), this);
   gpu_tracer_->End();
 }
 
+void GLES2DecoderImpl::DoDrawBuffersEXT(
+    GLsizei count, const GLenum* bufs) {
+  Framebuffer* framebuffer = GetFramebufferInfoForTarget(GL_FRAMEBUFFER);
+  if (framebuffer) {

[greggman, 2013/03/08 21:48:28]

framebuffer will be NULL if the current target is the backbuffer IIRC. You'll
need to do some other work here for the case where it's NULL. I'm guessing you
need to check that count/bufs is correct for the backbuffer. But then you need
to actually use GL_COLOR_ATTACHMENT0, GL_NONE etc since when it's not actually
the backbuffer.

[Zhenyao Mo, 2013/03/13 01:22:02]

Done.

+    if (count > static_cast<GLsizei>(group_->max_draw_buffers())) {
+      SetGLError(GL_INVALID_VALUE,
+                 "glDrawBuffersEXT", "greater than GL_MAX_DRAW_BUFFERS_EXT");
+      return;
+    }
+    for (GLsizei i = 0; i < count; ++i) {
+      if (bufs[i] != static_cast<GLenum>(GL_COLOR_ATTACHMENT0 + i) &&
+          bufs[i] != GL_NONE) {
+        SetGLError(GL_INVALID_OPERATION,
+                   "glDrawBuffersEXT",
+                   "bufs[i] not GL_NONE or GL_COLOR_ATTACHMENTi_EXT");
+        return;
+      }
+    }
+    framebuffer->SetDrawBuffers(count, bufs);
+    glDrawBuffersARB(count, bufs);
+  } else {
+    NOTREACHED();
+  }
+}
+
 bool GLES2DecoderImpl::ValidateAsyncTransfer(
     const char* function_name,
     Texture* info,
     GLenum target,
     GLint level,
     const void * data) {
   // We only support async uploads to 2D textures for now.
   if (GL_TEXTURE_2D != target) {
     SetGLErrorInvalidEnum(function_name, target, "target");
     return false;
@@ skipping 205 matching lines @@
   return error::kNoError;
 }
 
 // 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 "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu