Workaround for Intel 6xxx clear to 0/1 bug

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index baa2852131694f5e10ee3f33f89c325cd318370c..c0922abd1456f60a607a1595acb3e18f7fc9fcaa 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -1461,6 +1461,10 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
 
   // Wrapper for glClear*()
   error::Error DoClear(GLbitfield mask);
+  void DoClearColor(GLclampf red,
+                    GLclampf green,
+                    GLclampf blue,
+                    GLclampf alpha);
   void DoClearBufferiv(GLenum buffer,
                        GLint drawbuffer,
                        const volatile GLint* value);
@@ -2608,7 +2612,7 @@ ScopedResolvedFramebufferBinder::ScopedResolvedFramebufferBinder(
                          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);
+    decoder_->DoClearColor(0, 0, 0, 1);
     glClear(GL_COLOR_BUFFER_BIT);
     decoder_->RestoreClearState();
   }
@@ -2860,7 +2864,7 @@ bool BackTexture::AllocateNativeGpuMemoryBuffer(const gfx::Size& size,
       ScopedFramebufferBinder binder(decoder_, fbo);
       glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, Target(),
                                 id(), 0);
-      glClearColor(0, 0, 0, decoder_->BackBufferAlphaClearColor());
+      decoder_->DoClearColor(0, 0, 0, decoder_->BackBufferAlphaClearColor());
       decoder_->state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
       decoder_->state_.SetDeviceCapabilityState(GL_SCISSOR_TEST, false);
       glClear(GL_COLOR_BUFFER_BIT);
@@ -2953,7 +2957,7 @@ bool BackRenderbuffer::AllocateStorage(const gfx::Size& size,
       ScopedFramebufferBinder binder(decoder_, fbo);
       glFramebufferRenderbufferEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                    GL_RENDERBUFFER, id_);
-      glClearColor(0, 0, 0, decoder_->BackBufferAlphaClearColor());
+      decoder_->DoClearColor(0, 0, 0, decoder_->BackBufferAlphaClearColor());
       decoder_->state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
       decoder_->state_.SetDeviceCapabilityState(GL_SCISSOR_TEST, false);
       glClear(GL_COLOR_BUFFER_BIT);
@@ -3603,7 +3607,7 @@ bool GLES2DecoderImpl::Initialize(
     // 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);
+      DoClearColor(0.0f, 0.0f, 0.0f, 1.0f);
     }
 
     // Clear the backbuffer.
@@ -3611,7 +3615,7 @@ bool GLES2DecoderImpl::Initialize(
 
     // Restore alpha clear value if we changed it.
     if (clear_alpha) {
-      glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+      DoClearColor(0.0f, 0.0f, 0.0f, 0.0f);
     }
   }
 
@@ -4360,7 +4364,7 @@ bool GLES2DecoderImpl::CheckFramebufferValid(
     if (surfaceless_)
       return false;
     if (backbuffer_needs_clear_bits_) {
-      glClearColor(0, 0, 0, BackBufferAlphaClearColor());
+      DoClearColor(0, 0, 0, BackBufferAlphaClearColor());
       state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
       glClearStencil(0);
       state_.SetDeviceStencilMaskSeparate(GL_FRONT, kDefaultStencilMask);
@@ -5108,7 +5112,7 @@ bool GLES2DecoderImpl::ResizeOffscreenFramebuffer(const gfx::Size& size) {
   // Clear the target frame buffer.
   {
     ScopedFramebufferBinder binder(this, offscreen_target_frame_buffer_->id());
-    glClearColor(0, 0, 0, BackBufferAlphaClearColor());
+    DoClearColor(0, 0, 0, BackBufferAlphaClearColor());
     state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
     glClearStencil(0);
     state_.SetDeviceStencilMaskSeparate(GL_FRONT, kDefaultStencilMask);
@@ -7379,6 +7383,21 @@ error::Error GLES2DecoderImpl::DoClear(GLbitfield mask) {
   return error::kNoError;
 }
 
+void GLES2DecoderImpl::DoClearColor(GLclampf red,
+                                    GLclampf green,
+                                    GLclampf blue,
+                                    GLclampf alpha) {
+  if (workarounds().clear_to_boundary_values_is_broken &&
+      (1 == red || 0 == red) && (1 == green || 0 == green) &&
+      (1 == blue || 0 == blue) && (1 == alpha || 0 == alpha)) {
+    if (1 == alpha)
+      alpha = 2;
+    else
+      alpha = -1;
+  }
+  glClearColor(red, green, blue, alpha);
+}
+
 void GLES2DecoderImpl::DoClearBufferiv(GLenum buffer,
                                        GLint drawbuffer,
                                        const volatile GLint* value) {
@@ -7617,7 +7636,7 @@ void GLES2DecoderImpl::ClearUnclearedAttachments(
     // 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);
+    DoClearColor(0.0f, 0.0f, 0.0f, 0.0f);
     state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
     clear_bits |= GL_COLOR_BUFFER_BIT;
 
@@ -7672,9 +7691,8 @@ void GLES2DecoderImpl::ClearUnclearedAttachments(
 
 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);
+  DoClearColor(state_.color_clear_red, state_.color_clear_green,
+               state_.color_clear_blue, state_.color_clear_alpha);
   glClearStencil(state_.stencil_clear);
   glClearDepth(state_.depth_clear);
   state_.SetDeviceCapabilityState(GL_SCISSOR_TEST,
@@ -8633,7 +8651,7 @@ bool GLES2DecoderImpl::VerifyMultisampleRenderbufferIntegrity(
 
   GLfloat clear_color[4] = {0.0f, 0.0f, 0.0f, 0.0f};
   glGetFloatv(GL_COLOR_CLEAR_VALUE, clear_color);
-  glClearColor(1.0f, 0.0f, 1.0f, 1.0f);
+  DoClearColor(1.0f, 0.0f, 1.0f, 1.0f);
 
   // Clear the buffer to the desired key color.
   glClear(GL_COLOR_BUFFER_BIT);
@@ -8662,7 +8680,7 @@ bool GLES2DecoderImpl::VerifyMultisampleRenderbufferIntegrity(
 
   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]);
+  DoClearColor(clear_color[0], clear_color[1], clear_color[2], clear_color[3]);
   glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER, draw_framebuffer);
   glBindFramebufferEXT(GL_READ_FRAMEBUFFER, read_framebuffer);
 
@@ -15565,7 +15583,7 @@ void GLES2DecoderImpl::DoSwapBuffers() {
         {
           ScopedFramebufferBinder binder(this,
                                          offscreen_saved_frame_buffer_->id());
-          glClearColor(0, 0, 0, BackBufferAlphaClearColor());
+          DoClearColor(0, 0, 0, BackBufferAlphaClearColor());
           state_.SetDeviceColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
           state_.SetDeviceCapabilityState(GL_SCISSOR_TEST, false);
           glClear(GL_COLOR_BUFFER_BIT);