Complete disable_gl_rgb_format workaround for Mali-400 GPU

gpu/command_buffer/service/gles2_cmd_decoder.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/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 1833 matching lines @@
     if (ShouldDeferReads())
       return error::kDeferCommandUntilLater;
     if (!offscreen_target_frame_buffer_.get() &&
         !framebuffer_state_.bound_read_framebuffer.get() &&
         !surface_->SetBackbufferAllocation(true))
       return error::kLostContext;
     return error::kNoError;
   }
 
   bool BackBufferHasAlpha() const {
+    if (state_.emulating_rgb_with_rgba)
+      return false;
     if (back_buffer_draw_buffer_ == GL_NONE)
       return false;
     if (offscreen_target_frame_buffer_.get()) {
       return (offscreen_target_color_format_ == GL_RGBA ||
               offscreen_target_color_format_ == GL_RGBA8);
     }
     return (back_buffer_color_format_ == GL_RGBA ||
             back_buffer_color_format_ == GL_RGBA8);
   }
 
@@ skipping 882 matching lines @@
           context_->HasExtension("GL_OES_rgb8_rgba8");
       // The only available default render buffer formats in GLES2 have very
       // little precision.  Don't enable multisampling unless 8-bit render
       // buffer formats are available--instead fall back to 8-bit textures.
       if (rgb8_supported && offscreen_target_samples_ > 1) {
         offscreen_target_color_format_ = attrib_parser.alpha_size > 0 ?
             GL_RGBA8 : GL_RGB8;
       } else {
         offscreen_target_samples_ = 1;
         offscreen_target_color_format_ =
-            attrib_parser.alpha_size > 0 || workarounds().disable_gl_rgb_format
-                ? GL_RGBA
-                : GL_RGB;
+            (attrib_parser.alpha_size > 0) ? GL_RGBA : GL_RGB;
+        if (offscreen_target_color_format_ == GL_RGB &&
+            workarounds().disable_gl_rgb_format) {
+          offscreen_target_color_format_ = GL_RGBA;
+          state_.emulating_rgb_with_rgba = true;
+        }
       }
 
       // ANGLE only supports packed depth/stencil formats, so use it if it is
       // available.
       const bool depth24_stencil8_supported =
           feature_info_->feature_flags().packed_depth24_stencil8;
       VLOG(1) << "GL_OES_packed_depth_stencil "
               << (depth24_stencil8_supported ? "" : "not ") << "supported.";
       if ((attrib_parser.depth_size > 0 || attrib_parser.stencil_size > 0) &&
           depth24_stencil8_supported) {
         offscreen_target_depth_format_ = GL_DEPTH24_STENCIL8;
         offscreen_target_stencil_format_ = 0;
       } else {
         // It may be the case that this depth/stencil combination is not
         // supported, but this will be checked later by CheckFramebufferStatus.
         offscreen_target_depth_format_ = attrib_parser.depth_size > 0 ?
             GL_DEPTH_COMPONENT16 : 0;
         offscreen_target_stencil_format_ = attrib_parser.stencil_size > 0 ?
             GL_STENCIL_INDEX8 : 0;
       }
     } else {
       offscreen_target_color_format_ =
-          attrib_parser.alpha_size > 0 || workarounds().disable_gl_rgb_format
-              ? GL_RGBA
-              : GL_RGB;
+          (attrib_parser.alpha_size > 0) ? GL_RGBA : GL_RGB;
+      if (offscreen_target_color_format_ == GL_RGB &&
+          workarounds().disable_gl_rgb_format) {
+        offscreen_target_color_format_ = GL_RGBA;
+        state_.emulating_rgb_with_rgba = true;
+      }
 
       // If depth is requested at all, use the packed depth stencil format if
       // it's available, as some desktop GL drivers don't support any non-packed
       // formats for depth attachments.
       const bool depth24_stencil8_supported =
           feature_info_->feature_flags().packed_depth24_stencil8;
       VLOG(1) << "GL_EXT_packed_depth_stencil "
               << (depth24_stencil8_supported ? "" : "not ") << "supported.";
 
       if ((attrib_parser.depth_size > 0 || attrib_parser.stencil_size > 0) &&
@@ skipping 3344 matching lines @@
     //   is complete on the READ attachment will be complete as a DRAW
     //   attachment.
     glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, 0);
     glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, framebuffer->service_id());
   }
   GLbitfield clear_bits = 0;
   if (framebuffer->HasUnclearedColorAttachments()) {
     // We should always use alpha == 0 here, because 1) some draw buffers may
     // have alpha and some may not; 2) we won't have the same situation as the
     // back buffer where alpha channel exists but is not requested.
-    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+    float clear_alpha = 0.0f;
+    if (workarounds().disable_gl_rgb_format &&
+        (GLES2Util::GetChannelsForFormat(
+             framebuffer->GetColorAttachment0Format()) &
+         0x0008) == 0) {
+      clear_alpha = 1.0f;
+    }
+    glClearColor(0.0f, 0.0f, 0.0f, clear_alpha);
+
     state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
     clear_bits |= GL_COLOR_BUFFER_BIT;
     if (feature_info_->feature_flags().ext_draw_buffers ||
         feature_info_->IsES3Enabled()) {
       framebuffer->PrepareDrawBuffersForClear();
     }
   }
 
   if (framebuffer->HasUnclearedAttachment(GL_STENCIL_ATTACHMENT) ||
       framebuffer->HasUnclearedAttachment(GL_DEPTH_STENCIL_ATTACHMENT)) {
@@ skipping 9495 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu