Add GL_EXT_color_buffer_half_float support

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 1ca1169fac907915b19c160fbd3b69cbcde36924..e08f96397c65b23a3bc9d7a6130b29771c592a8f 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -233,7 +233,22 @@ void FeatureInfo::EnableEXTColorBufferFloat() {
       GL_RGBA32F);
   validators_.texture_sized_color_renderable_internal_format.AddValue(
       GL_R11F_G11F_B10F);
-  feature_flags_.enable_color_buffer_float = true;
+}
+
+void FeatureInfo::EnableEXTColorBufferHalfFloat() {
+  if (!feature_flags_.enable_color_buffer_half_float)
+    return;
+  AddExtensionString("GL_EXT_color_buffer_half_float");
+  validators_.render_buffer_format.AddValue(GL_R16F);
+  validators_.render_buffer_format.AddValue(GL_RG16F);
+  validators_.render_buffer_format.AddValue(GL_RGB16F);
+  validators_.render_buffer_format.AddValue(GL_RGBA16F);
+  validators_.texture_sized_color_renderable_internal_format.AddValue(GL_R16F);
+  validators_.texture_sized_color_renderable_internal_format.AddValue(GL_RG16F);
+  validators_.texture_sized_color_renderable_internal_format.AddValue(
+      GL_RGB16F);
+  validators_.texture_sized_color_renderable_internal_format.AddValue(
+      GL_RGBA16F);
 }
 
 void FeatureInfo::EnableCHROMIUMColorBufferFloatRGBA() {
@@ -735,11 +750,12 @@ void FeatureInfo::InitializeFeatures() {
 
   bool may_enable_chromium_color_buffer_float = false;
 
-  // This extension allows a variety of floating point formats to be
+  // These extensions allow a variety of floating point formats to be
   // rendered to via framebuffer objects.
-  if (extensions.Contains("GL_EXT_color_buffer_float")) {
+  if (extensions.Contains("GL_EXT_color_buffer_float"))
     enable_ext_color_buffer_float = true;
-  }
+  if (extensions.Contains("GL_EXT_color_buffer_half_float"))
+    feature_flags_.enable_color_buffer_half_float = true;
 
   if (extensions.Contains("GL_ARB_texture_float") ||
       gl_version_info_->is_desktop_core_profile) {
@@ -835,34 +851,41 @@ void FeatureInfo::InitializeFeatures() {
     // range of formats supported by EXT_color_buffer_float
     if (status_rgba == GL_FRAMEBUFFER_COMPLETE && enable_es3) {
       bool full_float_support = true;
-
-      glTexImage2D(GL_TEXTURE_2D, 0, GL_R16F, width, width, 0, GL_RED,
-          GL_FLOAT, NULL);
-      full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
-          GL_FRAMEBUFFER_COMPLETE;
-      glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, width, width, 0, GL_RG,
-          GL_FLOAT, NULL);
-      full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
-          GL_FRAMEBUFFER_COMPLETE;
-      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, width, width, 0, GL_RGBA,
-          GL_FLOAT, NULL);
-      full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
-          GL_FRAMEBUFFER_COMPLETE;
-      glTexImage2D(GL_TEXTURE_2D, 0, GL_R32F, width, width, 0, GL_RED,
-          GL_FLOAT, NULL);
-      full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
-          GL_FRAMEBUFFER_COMPLETE;
-      glTexImage2D(GL_TEXTURE_2D, 0, GL_RG32F, width, width, 0, GL_RG,
-          GL_FLOAT, NULL);
-      full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
-          GL_FRAMEBUFFER_COMPLETE;
-      glTexImage2D(GL_TEXTURE_2D, 0, GL_R11F_G11F_B10F, width, width, 0, GL_RGB,
-          GL_FLOAT, NULL);
-      full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
-          GL_FRAMEBUFFER_COMPLETE;
-
+      GLenum internal_formats[] = {
+          GL_R16F, GL_RG16F, GL_RGBA16F, GL_R32F, GL_RG32F, GL_R11F_G11F_B10F,
+      };
+      GLenum formats[] = {
+          GL_RED, GL_RG, GL_RGBA, GL_RED, GL_RG, GL_RGB,
+      };
+      DCHECK_EQ(arraysize(internal_formats), arraysize(formats));
+      for (size_t i = 0; i < arraysize(formats); ++i) {
+        glTexImage2D(GL_TEXTURE_2D, 0, internal_formats[i], width, width, 0,
+                     formats[i], GL_FLOAT, NULL);
+        full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
+                              GL_FRAMEBUFFER_COMPLETE;
+      }
       enable_ext_color_buffer_float = full_float_support;
     }
+    // Likewise for EXT_color_buffer_half_float on ES2 contexts.
+    if (context_type_ == CONTEXT_TYPE_OPENGLES2 &&

[Zhenyao Mo, 2017/02/23 00:36:57]

or WebGL1

Since you are working on it for internal ES2, it's only a little extra bits to
get it right for WebGL1

[ccameron, 2017/02/23 02:11:57]

Done.

+        !feature_flags_.enable_color_buffer_half_float) {
+      bool full_half_float_support = true;
+      GLenum internal_formats[] = {
+          GL_R16F, GL_RG16F, GL_RGB16F, GL_RGBA16F,
+      };
+      GLenum formats[] = {
+          GL_RED, GL_RG, GL_RGB, GL_RGBA,
+      };
+      DCHECK_EQ(arraysize(internal_formats), arraysize(formats));
+      for (size_t i = 0; i < arraysize(formats); ++i) {
+        glTexImage2D(GL_TEXTURE_2D, 0, internal_formats[i], width, width, 0,
+                     formats[i], GL_FLOAT, NULL);
+        full_half_float_support &=
+            glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
+            GL_FRAMEBUFFER_COMPLETE;
+      }
+      feature_flags_.enable_color_buffer_half_float = full_half_float_support;
+    }
 
     glDeleteFramebuffersEXT(1, &fb_id);
     glDeleteTextures(1, &tex_id);
@@ -891,6 +914,9 @@ void FeatureInfo::InitializeFeatures() {
       EnableEXTColorBufferFloat();
   }
 
+  // Enable GL_EXT_color_buffer_half_float if we have found the capability.
+  EnableEXTColorBufferHalfFloat();

[Zhenyao Mo, 2017/02/23 00:36:57]

You can't enable this by default on WebGL contexts.  Look at
ContextGroup::Initialize(), where you should set disallowed_features_ and only
enable it conditionally like other texture extensions.

[ccameron, 2017/02/23 02:11:57]

Disallowed for WebGL 2.

+
   // Check for multisample support
   if (!workarounds_.disable_chromium_framebuffer_multisample) {
     bool ext_has_multisample =