gpu: support immutable texture on Linux Mesa driver and GLES3.

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 <set>
 
 #include "base/command_line.h"
 #include "base/macros.h"
@@ skipping 377 matching lines @@
 
   if (extensions.Contains("GL_OES_element_index_uint") ||
       gfx::HasDesktopGLFeatures()) {
     AddExtensionString("GL_OES_element_index_uint");
     validators_.index_type.AddValue(GL_UNSIGNED_INT);
   }
 
   bool enable_texture_format_bgra8888 = false;
   bool enable_read_format_bgra = false;
   bool enable_render_buffer_bgra = false;
+  bool enable_immutable_texture_format_bgra =
+      extensions.Contains("GL_APPLE_texture_format_BGRA8888");
 
   // Check if we should allow GL_EXT_texture_format_BGRA8888
   if (extensions.Contains("GL_EXT_texture_format_BGRA8888") ||
-      extensions.Contains("GL_APPLE_texture_format_BGRA8888") ||
+      enable_immutable_texture_format_bgra ||
       extensions.Contains("GL_EXT_bgra")) {
     enable_texture_format_bgra8888 = true;
   }
 
   if (extensions.Contains("GL_EXT_bgra")) {
     enable_render_buffer_bgra = true;
   }
 
   if (extensions.Contains("GL_EXT_read_format_bgra") ||
       extensions.Contains("GL_EXT_bgra")) {
@@ skipping 272 matching lines @@
     validators_.pixel_store.AddValue(GL_PACK_REVERSE_ROW_ORDER_ANGLE);
     validators_.g_l_state.AddValue(GL_PACK_REVERSE_ROW_ORDER_ANGLE);
   }
 
   if (extensions.Contains("GL_ANGLE_texture_usage")) {
     feature_flags_.angle_texture_usage = true;
     AddExtensionString("GL_ANGLE_texture_usage");
     validators_.texture_parameter.AddValue(GL_TEXTURE_USAGE_ANGLE);
   }
 
-  if (extensions.Contains("GL_EXT_texture_storage")) {
+  // Only APPLE_texture_format_BGRA8888 extension allows BGRA8_EXT in ES3's
+  // glTexStorage2D.
+  enable_immutable_texture_format_bgra &= is_es3;

[piman, 2014/08/26 19:06:29]

nit: modifying this variable is hard to follow. How about simply testing
(enable_immutable_texture_format_bgra && is_es3) in the if below?

+  if (extensions.Contains("GL_EXT_texture_storage") ||
+      extensions.Contains("GL_ARB_texture_storage") ||

[piman, 2014/08/26 19:06:29]

So, GL_ARB_texture_storage doesn't by itself allow GL_BGRA8 to be passed, at
least in GLES. I'm not fully sure about desktop GL, where the rules on internal
formats are different than the ES rules, but GL_BGRA8 isn't anywhere in OpenGL
2.0 spec (even though it does have GL_EXT_bgra folded in).

[dshwang, 2014/08/26 19:24:04]

Linux mesa GL driver on both desktop and chromebook supports
GL_ARB_texture_storage and works very well with GL_BGRA8 by GL_EXT_bgra

If GL_ARB_texture_storage is in trouble on GLES, GL_EXT_texture_storage is
supposed to be in trouble also although there are not any GLES1/2 devices
supporting GL_EXT_texture_storage yet, because currently chromium is fine.

I'll block all ES devices unless supporting GL_APPLE_texture_format_BGRA8888

+      enable_immutable_texture_format_bgra) {
     feature_flags_.ext_texture_storage = true;
     AddExtensionString("GL_EXT_texture_storage");
     validators_.texture_parameter.AddValue(GL_TEXTURE_IMMUTABLE_FORMAT_EXT);
     if (enable_texture_format_bgra8888)
         validators_.texture_internal_format_storage.AddValue(GL_BGRA8_EXT);
     if (enable_texture_float) {
         validators_.texture_internal_format_storage.AddValue(GL_RGBA32F_EXT);
         validators_.texture_internal_format_storage.AddValue(GL_RGB32F_EXT);
         validators_.texture_internal_format_storage.AddValue(GL_ALPHA32F_EXT);
         validators_.texture_internal_format_storage.AddValue(
@@ skipping 139 matching lines @@
   if (pos == std::string::npos) {
     extensions_ += (extensions_.empty() ? "" : " ") + str;
   }
 }
 
 FeatureInfo::~FeatureInfo() {
 }
 
 }  // namespace gles2
 }  // namespace gpu