gpu: Implement GL_INTEL_framebuffer_CMAA via shaders in the GPU 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 <stddef.h>
 
 #include <set>
 #include <vector>
@@ skipping 71 matching lines @@
 
 }  // anonymous namespace.
 
 FeatureInfo::FeatureFlags::FeatureFlags()
     : chromium_framebuffer_multisample(false),
       chromium_sync_query(false),
       use_core_framebuffer_multisample(false),
       multisampled_render_to_texture(false),
       use_img_for_multisampled_render_to_texture(false),
       chromium_screen_space_antialiasing(false),
+      use_chromium_screen_space_antialiasing_via_shaders(false),
       oes_standard_derivatives(false),
       oes_egl_image_external(false),
       nv_egl_stream_consumer_external(false),
       oes_depth24(false),
       oes_compressed_etc1_rgb8_texture(false),
       packed_depth24_stencil8(false),
       npot_ok(false),
       enable_texture_float_linear(false),
       enable_texture_half_float_linear(false),
       angle_translated_shader_source(false),
@@ skipping 70 matching lines @@
       command_line->HasSwitch(switches::kEnableUnsafeES3APIs);
 
   // The shader translator is needed to translate from WebGL-conformant GLES SL
   // to normal GLES SL, enforce WebGL conformance, translate from GLES SL 1.0 to
   // target context GLSL, implement emulation of OpenGL ES features on OpenGL,
   // etc.
   // The flag here is for testing only.
   disable_shader_translator_ =
       command_line->HasSwitch(switches::kDisableGLSLTranslator);
 
+  enable_cmaa_shaders_switch_ =
+      command_line->HasSwitch(switches::kEnableCMAAShaders);
+
   unsafe_es3_apis_enabled_ = false;
 
   // Default context_type_ to a GLES2 Context.
   context_type_ = CONTEXT_TYPE_OPENGLES2;
 
   chromium_color_buffer_float_rgba_available_ = false;
   chromium_color_buffer_float_rgb_available_ = false;
   ext_color_buffer_float_available_ = false;
   oes_texture_float_linear_available_ = false;
   oes_texture_half_float_linear_available_ = false;
@@ skipping 681 matching lines @@
        extensions.Contains("GL_EXT_multisample_compatibility")) {
     AddExtensionString("GL_EXT_multisample_compatibility");
     feature_flags_.ext_multisample_compatibility = true;
     validators_.capability.AddValue(GL_MULTISAMPLE_EXT);
     validators_.capability.AddValue(GL_SAMPLE_ALPHA_TO_ONE_EXT);
   }
 
   if (extensions.Contains("GL_INTEL_framebuffer_CMAA")) {
     feature_flags_.chromium_screen_space_antialiasing = true;
     AddExtensionString("GL_CHROMIUM_screen_space_antialiasing");
+  } else if (enable_cmaa_shaders_switch_ &&
+             (gl_version_info_->IsAtLeastGLES(3, 1) ||
+              (gl_version_info_->IsAtLeastGL(3, 0) &&
+               extensions.Contains("GL_ARB_shading_language_420pack") &&
+               extensions.Contains("GL_ARB_texture_gather") &&
+               extensions.Contains("GL_ARB_explicit_uniform_location") &&
+               extensions.Contains("GL_ARB_explicit_attrib_location") &&
+               extensions.Contains("GL_ARB_shader_image_load_store")))) {
+    feature_flags_.chromium_screen_space_antialiasing = true;
+    feature_flags_.use_chromium_screen_space_antialiasing_via_shaders = true;
+    AddExtensionString("GL_CHROMIUM_screen_space_antialiasing");
   }
 
   if (extensions.Contains("GL_OES_depth24") || gl::HasDesktopGLFeatures() ||
       gl_version_info_->is_es3) {
     AddExtensionString("GL_OES_depth24");
     feature_flags_.oes_depth24 = true;
     validators_.render_buffer_format.AddValue(GL_DEPTH_COMPONENT24);
   }
 
   if (gl_version_info_->is_es3 ||
@@ skipping 501 matching lines @@
   if (pos == std::string::npos) {
     extensions_ += (extensions_.empty() ? "" : " ") + str;
   }
 }
 
 FeatureInfo::~FeatureInfo() {
 }
 
 }  // namespace gles2
 }  // namespace gpu