command_buffer: Implement EXT_blend_func_extended

gpu/command_buffer/service/feature_info.cc

Index: gpu/command_buffer/service/feature_info.cc
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index 282690eff665164330c6f5b92e0e00aa152dcb88..2650ffb7001702ee0d7bf6544b5b22e2caeb5476 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -170,7 +170,8 @@ FeatureInfo::FeatureFlags::FeatureFlags()
       chromium_image_ycbcr_422(false),
       enable_subscribe_uniform(false),
       emulate_primitive_restart_fixed_index(false),
-      ext_render_buffer_format_bgra8888(false) {}
+      ext_render_buffer_format_bgra8888(false),
+      ext_blend_func_extended(false) {}
 
 FeatureInfo::Workarounds::Workarounds() :
 #define GPU_OP(type, name) name(false),
@@ -1066,6 +1067,29 @@ void FeatureInfo::InitializeFeatures() {
   }
   UMA_HISTOGRAM_BOOLEAN("GPU.TextureRG", feature_flags_.ext_texture_rg);
 
+  if (gl_version_info_->IsAtLeastGL(3, 3) ||
+      (gl_version_info_->IsAtLeastGL(3, 2) &&
+       extensions.Contains("GL_ARB_blend_func_extended")) ||
+      (gl_version_info_->is_es &&
+       extensions.Contains("GL_EXT_blend_func_extended"))) {
+    feature_flags_.ext_blend_func_extended = true;
+    AddExtensionString("GL_EXT_blend_func_extended");
+
+    // NOTE: SRC_ALPHA_SATURATE is valid for ES2 src blend factor.
+    // SRC_ALPHA_SATURATE is valid for ES3 src and dst blend factor.
+    validators_.dst_blend_factor.AddValue(GL_SRC_ALPHA_SATURATE_EXT);

[Mark Kilgard, 2015/08/28 19:53:24]

good, this is actually explicitly documented in the EXT_blend_func_extended
extension and makes blend functionality more consistent with ES 3.x and big
OpenGL

In practical terms, nobody is going to care that SRC_ALPHA_SATURATE is allowed
on a dest function, but it makes everything more othogonal, particularly the
source and destination error checks are identical

+
+    validators_.src_blend_factor.AddValue(GL_SRC1_ALPHA_EXT);
+    validators_.dst_blend_factor.AddValue(GL_SRC1_ALPHA_EXT);
+    validators_.src_blend_factor.AddValue(GL_SRC1_COLOR_EXT);
+    validators_.dst_blend_factor.AddValue(GL_SRC1_COLOR_EXT);
+    validators_.src_blend_factor.AddValue(GL_ONE_MINUS_SRC1_COLOR_EXT);
+    validators_.dst_blend_factor.AddValue(GL_ONE_MINUS_SRC1_COLOR_EXT);
+    validators_.src_blend_factor.AddValue(GL_ONE_MINUS_SRC1_ALPHA_EXT);
+    validators_.dst_blend_factor.AddValue(GL_ONE_MINUS_SRC1_ALPHA_EXT);
+    validators_.g_l_state.AddValue(GL_MAX_DUAL_SOURCE_DRAW_BUFFERS_EXT);
+  }
+
 #if !defined(OS_MACOSX)
   if (workarounds_.ignore_egl_sync_failures) {
     gfx::GLFenceEGL::SetIgnoreFailures();