Implement support for rendering to 32-bit float textures on ES3

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 573cec4f8687d283e686da2ca9e9745775a8cbdc..19db779ce1688294ab5f1db72258edd8b8f44185 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -99,7 +99,8 @@ void StringToWorkarounds(
 }  // anonymous namespace.
 
 FeatureInfo::FeatureFlags::FeatureFlags()
-    : chromium_framebuffer_multisample(false),
+    : chromium_color_buffer_float(false),
+      chromium_framebuffer_multisample(false),
       use_core_framebuffer_multisample(false),
       multisampled_render_to_texture(false),
       use_img_for_multisampled_render_to_texture(false),
@@ -437,26 +438,27 @@ void FeatureInfo::InitializeFeatures() {
   bool enable_texture_half_float = false;
   bool enable_texture_half_float_linear = false;
 
-  bool have_arb_texture_float = extensions.Contains("GL_ARB_texture_float");
+  bool may_enable_chromium_color_buffer_float = false;
 
-  if (have_arb_texture_float) {
+  if (extensions.Contains("GL_ARB_texture_float")) {
     enable_texture_float = true;
     enable_texture_float_linear = true;
     enable_texture_half_float = true;
     enable_texture_half_float_linear = true;
+    may_enable_chromium_color_buffer_float = true;
   } else {
-    if (extensions.Contains("GL_OES_texture_float") || have_arb_texture_float) {
+    if (extensions.Contains("GL_OES_texture_float")) {
       enable_texture_float = true;
-      if (extensions.Contains("GL_OES_texture_float_linear") ||
-          have_arb_texture_float) {
+      if (extensions.Contains("GL_OES_texture_float_linear")) {
         enable_texture_float_linear = true;
       }
+      if (is_es3 && extensions.Contains("GL_EXT_color_buffer_float")) {
+        may_enable_chromium_color_buffer_float = true;
+      }
     }
-    if (extensions.Contains("GL_OES_texture_half_float") ||
-        have_arb_texture_float) {
+    if (extensions.Contains("GL_OES_texture_half_float")) {
       enable_texture_half_float = true;
-      if (extensions.Contains("GL_OES_texture_half_float_linear") ||
-          have_arb_texture_float) {
+      if (extensions.Contains("GL_OES_texture_half_float_linear")) {
         enable_texture_half_float_linear = true;
       }
     }
@@ -490,6 +492,56 @@ void FeatureInfo::InitializeFeatures() {
     }
   }
 
+  if (may_enable_chromium_color_buffer_float) {
+    DCHECK(GL_RGBA32F_ARB == GL_RGBA32F && GL_RGBA32F_EXT == GL_RGBA32F &&
+           GL_RGB32F_ARB == GL_RGB32F && GL_RGB32F_EXT == GL_RGB32F);

[piman, 2014/02/07 00:43:10]

nit: you can use COMPILE_ASSERT

[oetuaho-nv, 2014/02/07 09:26:58]

Done.

+    // We don't check extension support beyond ARB_texture_float on desktop GL,
+    // and spec prior to OpenGL 3.0 mandates framebuffer support only for one
+    // implementation-chosen format. Check for framebuffer completeness with
+    // formats that the extension exposes, and only enable the extension when
+    // framebuffers created with both float texture formats result in a
+    // complete framebuffer.
+    GLint fb_binding = 0;
+    GLint tex_binding = 0;
+    glGetIntegerv(GL_FRAMEBUFFER_BINDING, &fb_binding);
+    glGetIntegerv(GL_TEXTURE_BINDING_2D, &tex_binding);
+
+    GLuint tex_id = 0;
+    GLuint fb_id = 0;
+    GLsizei width = 16;
+    GLfloat* data = new GLfloat[width * width * 4];

[piman, 2014/02/07 00:43:10]

Why not passing NULL to the glTexImage2D below?

[oetuaho-nv, 2014/02/07 09:26:58]

True, NULL is fine.

+
+    glGenTextures(1, &tex_id);
+    glGenFramebuffersEXT(1, &fb_id);
+    glBindTexture(GL_TEXTURE_2D, tex_id);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, width, width, 0, GL_RGBA,
+                 GL_FLOAT, static_cast<GLvoid*>(data));
+    glBindFramebufferEXT(GL_FRAMEBUFFER, fb_id);
+    glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                              GL_TEXTURE_2D, tex_id, 0);
+    GLenum statusRGBA = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB32F, width, width, 0, GL_RGB,
+                 GL_FLOAT, static_cast<GLvoid*>(data));
+    GLenum statusRGB = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER);
+    glDeleteFramebuffersEXT(1, &fb_id);
+    glDeleteTextures(1, &tex_id);
+
+    delete[] data;
+
+    glBindFramebufferEXT(GL_FRAMEBUFFER, static_cast<GLuint>(fb_binding));
+    glBindTexture(GL_TEXTURE_2D, static_cast<GLuint>(tex_binding));
+
+    DCHECK(glGetError() == GL_NO_ERROR);
+
+    if (statusRGBA == GL_FRAMEBUFFER_COMPLETE &&
+        statusRGB == GL_FRAMEBUFFER_COMPLETE) {
+      validators_.texture_internal_format.AddValue(GL_RGBA32F);
+      validators_.texture_internal_format.AddValue(GL_RGB32F);
+      feature_flags_.chromium_color_buffer_float = true;
+      AddExtensionString("GL_CHROMIUM_color_buffer_float");
+    }
+  }
+
   // Check for multisample support
   if (!disallowed_features_.multisampling &&
       !workarounds_.disable_framebuffer_multisample) {