super hacky opaque black clear bug workaround

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 2119 matching lines @@
     if (offscreen_target_frame_buffer_.get()) {
       return offscreen_buffer_should_have_alpha_;
     }
     return (back_buffer_color_format_ == GL_RGBA ||
             back_buffer_color_format_ == GL_RGBA8);
   }
 
   // If the back buffer has a non-emulated alpha channel, the clear color should
   // be 0. Otherwise, the clear color should be 1.
   GLfloat BackBufferAlphaClearColor() const {
-    return offscreen_buffer_should_have_alpha_ ? 0.f : 1.f;
+    return offscreen_buffer_should_have_alpha_ ? 0.f : 1.001f;
   }
 
   // Set remaining commands to process to 0 to force DoCommands to return
   // and allow context preemption and GPU watchdog checks in CommandExecutor().
   void ExitCommandProcessingEarly() { commands_to_process_ = 0; }
 
   void ProcessPendingReadPixels(bool did_finish);
   void FinishReadPixels(GLsizei width,
                         GLsizei height,
                         GLsizei format,
@@ skipping 455 matching lines @@
       decoder_->should_use_native_gmb_for_backbuffer_ &&
       !decoder_->offscreen_buffer_should_have_alpha_ &&
       decoder_->ChromiumImageNeedsRGBEmulation() &&
       decoder_->workarounds()
           .disable_multisampling_color_mask_usage;
   if (alpha_channel_needs_clear) {
     glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT,
                          decoder_->offscreen_target_frame_buffer_->id());
     decoder_->state_.SetDeviceColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_TRUE);
     decoder->state_.SetDeviceCapabilityState(GL_SCISSOR_TEST, false);
-    glClearColor(0, 0, 0, 1);
+    glClearColor(0, 0, 0, 1.001);
     glClear(GL_COLOR_BUFFER_BIT);
     decoder_->RestoreClearState();
   }
 
   glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT,
                        decoder_->offscreen_target_frame_buffer_->id());
   GLuint targetid;
   if (internal) {
     if (!decoder_->offscreen_resolved_frame_buffer_.get()) {
       decoder_->offscreen_resolved_frame_buffer_.reset(
@@ skipping 953 matching lines @@
   // because the system already clears the buffer before each draw. Proper
   // fix might be setting the scissor clip properly before initialize. See
   // crbug.com/259023 for details.
   call_gl_clear = surface_->GetHandle();
 #endif
   if (call_gl_clear) {
     // On configs where we report no alpha, if the underlying surface has
     // alpha, clear the surface alpha to 1.0 to be correct on ReadPixels/etc.
     bool clear_alpha = back_buffer_color_format_ == GL_RGB && alpha_bits > 0;
     if (clear_alpha) {
-      glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+      glClearColor(0.0f, 0.0f, 0.0f, 1.001f);
     }
 
     // Clear the backbuffer.
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
 
     // Restore alpha clear value if we changed it.
     if (clear_alpha) {
       glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
     }
   }
@@ skipping 4109 matching lines @@
   }
 
   framebuffer_manager()->MarkAttachmentsAsCleared(
       framebuffer, renderbuffer_manager(), texture_manager());
 }
 
 void GLES2DecoderImpl::RestoreClearState() {
   framebuffer_state_.clear_state_dirty = true;
   glClearColor(
       state_.color_clear_red, state_.color_clear_green, state_.color_clear_blue,
-      state_.color_clear_alpha);
+      state_.color_clear_alpha + 0.001);
   glClearStencil(state_.stencil_clear);
   glClearDepth(state_.depth_clear);
   state_.SetDeviceCapabilityState(GL_SCISSOR_TEST,
                                   state_.enable_flags.scissor_test);
   gfx::Vector2d scissor_offset = GetBoundFramebufferDrawOffset();
   glScissor(state_.scissor_x + scissor_offset.x(),
             state_.scissor_y + scissor_offset.y(), state_.scissor_width,
             state_.scissor_height);
 }
 
@@ skipping 914 matching lines @@
   glBindFramebufferEXT(GL_FRAMEBUFFER, validation_fbo_multisample_);
   glFramebufferRenderbufferEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
       GL_RENDERBUFFER, 0);
 
   // Restore cached state.
   if (scissor_enabled)
     state_.SetDeviceCapabilityState(GL_SCISSOR_TEST, true);
 
   state_.SetDeviceColorMask(
       color_mask[0], color_mask[1], color_mask[2], color_mask[3]);
-  glClearColor(clear_color[0], clear_color[1], clear_color[2], clear_color[3]);
+  glClearColor(clear_color[0], clear_color[1], clear_color[2], clear_color[3] + 0.001);
   glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER, draw_framebuffer);
   glBindFramebufferEXT(GL_READ_FRAMEBUFFER, read_framebuffer);
 
   // Return true if the pixel matched the desired key color.
   return (pixel[0] == 0xFF &&
       pixel[1] == 0x00 &&
       pixel[2] == 0xFF);
 }
 
 void GLES2DecoderImpl::DoRenderbufferStorage(
@@ skipping 10994 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