Emulate GL_PRIMITIVE_RESTART_FIXED_INDEX: part I

Note that this is only partial implementation.

BUG=481184,480709
TEST=gpu_unittests
R=piman@chromium.org

Review URL: https://codereview.chromium.org/1106833002

Cr-Commit-Position: refs/heads/master@{#327202}

gpu/command_buffer/service/context_state.cc

@@ -285,16 +285,8 @@ ErrorState* ContextState::GetErrorState() {
 
 void ContextState::EnableDisable(GLenum pname, bool enable) const {
   if (pname == GL_PRIMITIVE_RESTART_FIXED_INDEX) {
-    // This is only available on Desktop GL 4.3+, but we emulate ES 3.0 on top
-    // of Desktop GL 4.2+.
-    const gfx::GLVersionInfo& gl_version = feature_info_->gl_version_info();
-    if (!gl_version.is_es &&
-        (gl_version.major_version < 4 ||
-         (gl_version.major_version == 4 && gl_version.minor_version < 3))) {
-      // TODO(zmo): Ignoring it may not be the best emulation.
-      NOTIMPLEMENTED();
-      return;
-    }
+    if (feature_info_->feature_flags().emulate_primitive_restart_fixed_index)
+      pname = GL_PRIMITIVE_RESTART;
   }
   if (enable) {
     glEnable(pname);

gpu/command_buffer/service/feature_info.cc

@@ -161,7 +161,8 @@ FeatureInfo::FeatureFlags::FeatureFlags()
       blend_equation_advanced(false),
       blend_equation_advanced_coherent(false),
       ext_texture_rg(false),
-      enable_subscribe_uniform(false) {
+      enable_subscribe_uniform(false),
+      emulate_primitive_restart_fixed_index(false) {
 }
 
 FeatureInfo::Workarounds::Workarounds() :
@@ -1097,6 +1098,13 @@ void FeatureInfo::InitializeFeatures() {
     gfx::GLFenceEGL::SetIgnoreFailures();
   }
 #endif
+
+  if (gl_version_info_->IsLowerThanGL(4, 3)) {
+    // crbug.com/481184.
+    // GL_PRIMITIVE_RESTART_FIXED_INDEX is only available on Desktop GL 4.3+,
+    // but we emulate ES 3.0 on top of Desktop GL 4.2+.
+    feature_flags_.emulate_primitive_restart_fixed_index = true;
+  }
 }
 
 bool FeatureInfo::IsES3Capable() const {

gpu/command_buffer/service/feature_info.h

@@ -78,6 +78,7 @@ class GPU_EXPORT FeatureInfo : public base::RefCounted<FeatureInfo> {
     bool blend_equation_advanced_coherent;
     bool ext_texture_rg;
     bool enable_subscribe_uniform;
+    bool emulate_primitive_restart_fixed_index;
   };
 
   struct Workarounds {

gpu/command_buffer/service/gles2_cmd_decoder.cc

@@ -7073,6 +7073,9 @@ error::Error GLES2DecoderImpl::DoDrawArrays(
 
 error::Error GLES2DecoderImpl::HandleDrawArrays(uint32 immediate_data_size,
                                                 const void* cmd_data) {
+  // TODO(zmo): crbug.com/481184
+  // On Desktop GL with versions lower than 4.3, we need to emulate
+  // GL_PRIMITIVE_RESTART_FIXED_INDEX using glPrimitiveRestartIndex().
   const cmds::DrawArrays& c = *static_cast<const cmds::DrawArrays*>(cmd_data);
   return DoDrawArrays("glDrawArrays",
                       false,
@@ -7216,6 +7219,9 @@ error::Error GLES2DecoderImpl::DoDrawElements(
 
 error::Error GLES2DecoderImpl::HandleDrawElements(uint32 immediate_data_size,
                                                   const void* cmd_data) {
+  // TODO(zmo): crbug.com/481184
+  // On Desktop GL with versions lower than 4.3, we need to emulate
+  // GL_PRIMITIVE_RESTART_FIXED_INDEX using glPrimitiveRestartIndex().
   const gles2::cmds::DrawElements& c =
       *static_cast<const gles2::cmds::DrawElements*>(cmd_data);
   return DoDrawElements("glDrawElements",

ui/gl/gl_version_info.h

@@ -24,6 +24,11 @@ struct GL_EXPORT GLVersionInfo {
                       (major_version == major && minor_version >= minor));
   }
 
+  bool IsLowerThanGL(unsigned major, unsigned minor) const {
+    return !is_es && (major_version < major ||
+                      (major_version == major && minor_version < minor));
+  }
+
   bool IsAtLeastGLES(unsigned major, unsigned minor) const {
     return is_es && (major_version > major ||
                      (major_version == major && minor_version >= minor));