Add EXT_color_buffer_half_float extension support in GPU commandbuffer service.

gpu/command_buffer/service/feature_info.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/feature_info.h"
 
 #include <set>
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 413 matching lines @@
     }
   }
 
   if (enable_texture_float) {
     texture_format_validators_[GL_ALPHA].AddValue(GL_FLOAT);
     texture_format_validators_[GL_RGB].AddValue(GL_FLOAT);
     texture_format_validators_[GL_RGBA].AddValue(GL_FLOAT);
     texture_format_validators_[GL_LUMINANCE].AddValue(GL_FLOAT);
     texture_format_validators_[GL_LUMINANCE_ALPHA].AddValue(GL_FLOAT);
     validators_.pixel_type.AddValue(GL_FLOAT);
-    validators_.read_pixel_type.AddValue(GL_FLOAT);
     AddExtensionString("GL_OES_texture_float");
     if (enable_texture_float_linear) {
       AddExtensionString("GL_OES_texture_float_linear");
     }
   }
 
   if (enable_texture_half_float) {
     texture_format_validators_[GL_ALPHA].AddValue(GL_HALF_FLOAT_OES);
     texture_format_validators_[GL_RGB].AddValue(GL_HALF_FLOAT_OES);
     texture_format_validators_[GL_RGBA].AddValue(GL_HALF_FLOAT_OES);
     texture_format_validators_[GL_LUMINANCE].AddValue(GL_HALF_FLOAT_OES);
     texture_format_validators_[GL_LUMINANCE_ALPHA].AddValue(GL_HALF_FLOAT_OES);
     validators_.pixel_type.AddValue(GL_HALF_FLOAT_OES);
-    validators_.read_pixel_type.AddValue(GL_HALF_FLOAT_OES);
     AddExtensionString("GL_OES_texture_half_float");
     if (enable_texture_half_float_linear) {
       AddExtensionString("GL_OES_texture_half_float_linear");
     }
   }
 
+  bool enable_color_buffer_half_float = false;
+  if (extensions.Contains("GL_ARB_color_buffer_float")
+    || extensions.Contains("GL_EXT_color_buffer_half_float")) {
+    if (enable_texture_half_float)
+      enable_color_buffer_half_float = true;
+  }
+  if (enable_color_buffer_half_float) {
+    validators_.render_buffer_format.AddValue(GL_RGBA16F_EXT);
+    validators_.render_buffer_format.AddValue(GL_RGB16F_EXT);
+    validators_.frame_buffer_parameter.AddValue(
+      GL_FRAMEBUFFER_ATTACHMENT_COMPONENT_TYPE_EXT);
+    validators_.read_pixel_type.AddValue(GL_HALF_FLOAT_OES);
+    validators_.read_pixel_type.AddValue(GL_FLOAT);

[Ken Russell (switch to Gerrit), 2013/07/10 02:14:24]

There's a general problem with this patch and the associated ANGLE one that it
combines EXT_color_buffer_half_float with rendering to and reading back from
FP32 targets. These must be split up. Another problem is that
http://www.khronos.org/registry/webgl/extensions/WEBGL_color_buffer_float/ is a
WebGL extension, but there's no underlying extension defined against OpenGL ES
2.0. EXT_color_buffer_float is defined against ES 3.0, so when ANGLE supports ES
3.0, it can just start supporting EXT_color_buffer_float.

I think the necessary path forward is:

 - Define an ANGLE_color_buffer_float extension (perhaps just in the ANGLE
repository; I don't see an advantage to pushing this up to Khronos at this
point, given that ES 3.0 is their focus)
 - Implement that in the current ANGLE
 - Expose two extensions here, EXT_color_buffer_half_float and
ANGLE_color_buffer_float
 - Later, in WebGLRenderingContext, expose WEBGL_color_buffer_float if the
underlying ANGLE_color_buffer_float extension is supported

What do you think?

+    AddExtensionString("GL_EXT_color_buffer_half_float");
+  }
+
   // Check for multisample support
   bool ext_has_multisample =
       extensions.Contains("GL_EXT_framebuffer_multisample");
   if (!workarounds_.disable_angle_framebuffer_multisample) {
     ext_has_multisample |=
        extensions.Contains("GL_ANGLE_framebuffer_multisample");
   }
   if (!disallowed_features_.multisampling && ext_has_multisample) {
     feature_flags_.chromium_framebuffer_multisample = true;
     validators_.frame_buffer_target.AddValue(GL_READ_FRAMEBUFFER_EXT);
@@ skipping 190 matching lines @@
   if (extensions_.find(str) == std::string::npos) {
     extensions_ += (extensions_.empty() ? "" : " ") + str;
   }
 }
 
 FeatureInfo::~FeatureInfo() {
 }
 
 }  // namespace gles2
 }  // namespace gpu