[gpu/GLES2DecoderImpl] Force updating scissor state on Nexus 7 gen.2

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 821 matching lines @@
   // Get the size (in pixels) of the currently bound frame buffer (either FBO
   // or regular back buffer).
   gfx::Size GetBoundReadFramebufferSize();
 
   // Get the service side ID for the bound read framebuffer.
   // If it's back buffer, 0 is returned.
   GLuint GetBoundReadFramebufferServiceId();
 
   // Get the service side ID for the bound draw framebuffer.
   // If it's back buffer, 0 is returned.
-  GLuint GetBoundDrawFramebufferServiceId();
+  GLuint GetBoundDrawFramebufferServiceId() const;
 
   // Get the format/type of the currently bound frame buffer (either FBO or
   // regular back buffer).
   // If the color image is a renderbuffer, returns 0 for type.
   GLenum GetBoundReadFramebufferTextureType();
   GLenum GetBoundReadFramebufferInternalFormat();
 
   // Get the i-th draw buffer's internal format/type from the bound framebuffer.
   // If no framebuffer is bound, or no image is attached, or the DrawBuffers
   // setting for that image is GL_NONE, return 0.
@@ skipping 3597 matching lines @@
   }
   if (offscreen_target_frame_buffer_.get()) {
     return offscreen_target_frame_buffer_->id();
   }
   if (surface_.get()) {
     return surface_->GetBackingFramebufferObject();
   }
   return 0;
 }
 
-GLuint GLES2DecoderImpl::GetBoundDrawFramebufferServiceId() {
+GLuint GLES2DecoderImpl::GetBoundDrawFramebufferServiceId() const {
   Framebuffer* framebuffer = GetBoundDrawFramebuffer();
   if (framebuffer) {
     return framebuffer->service_id();
   }
   if (offscreen_target_frame_buffer_.get()) {
     return offscreen_target_frame_buffer_->id();
   }
   if (surface_.get()) {
     return surface_->GetBackingFramebufferObject();
   }
@@ skipping 1135 matching lines @@
 }
 
 // Added specifically for testing backbuffer_needs_clear_bits unittests.
 uint32_t GLES2DecoderImpl::GetAndClearBackbufferClearBitsForTest() {
   uint32_t clear_bits = backbuffer_needs_clear_bits_;
   backbuffer_needs_clear_bits_ = 0;
   return clear_bits;
 }
 
 void GLES2DecoderImpl::OnFboChanged() const {
-  if (workarounds().restore_scissor_on_fbo_change)
-    state_.fbo_binding_for_scissor_workaround_dirty = true;
+  state_.fbo_binding_for_scissor_workaround_dirty = true;
 }
 
 // Called after the FBO is checked for completeness.
 void GLES2DecoderImpl::OnUseFramebuffer() const {
-  if (state_.fbo_binding_for_scissor_workaround_dirty) {
-    state_.fbo_binding_for_scissor_workaround_dirty = false;
+  if (!state_.fbo_binding_for_scissor_workaround_dirty)
+    return;
+  state_.fbo_binding_for_scissor_workaround_dirty = false;
+
+  if (workarounds().restore_scissor_on_fbo_change) {
     // The driver forgets the correct scissor when modifying the FBO binding.
     glScissor(state_.scissor_x,
               state_.scissor_y,
               state_.scissor_width,
               state_.scissor_height);
 
     // crbug.com/222018 - Also on QualComm, the flush here avoids flicker,
     // it's unclear how this bug works.
     glFlush();
   }
+
+  if (workarounds().force_update_scissor_state_when_binding_fbo0 &&
+      !GetBoundDrawFramebufferServiceId()) {

[brianderson, 2017/01/27 08:07:56]

...Id() == 0

+    // The theory is that FBO0 keeps some internal (in HW regs maybe?) scissor
+    // test state, but the driver forgets to update it with GL_SCISSOR_TEST
+    // when FBO0 gets bound. (So it stuck with whatever state we last switched
+    // from it.)
+    // If the internal scissor test state was enabled, it does update its
+    // internal scissor rect with GL_SCISSOR_BOX though.
+    if (state_.enable_flags.cached_scissor_test) {
+      // The driver early outs if the new state matches previous state so some
+      // shake up is needed.
+      glDisable(GL_SCISSOR_TEST);
+      glEnable(GL_SCISSOR_TEST);
+    } else {
+      // Ditto.
+      glEnable(GL_SCISSOR_TEST);
+      glDisable(GL_SCISSOR_TEST);
+    }
+  }
 }
 
 void GLES2DecoderImpl::DoBindFramebuffer(GLenum target, GLuint client_id) {
   Framebuffer* framebuffer = NULL;
   GLuint service_id = 0;
   if (client_id != 0) {
     framebuffer = GetFramebuffer(client_id);
     if (!framebuffer) {
       if (!group_->bind_generates_resource()) {
         LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION,
@@ skipping 13553 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