GL: Work around Intel driver bug when clearing to zeros or ones.

include/platform/FeaturesGL.h

@@ -306,6 +306,13 @@ struct FeaturesGL : FeatureSetBase
                                         "Reset texture base level before calling glTexImage2D to "
                                         "work around pixel comparison failure.",
                                         &members, "https://crbug.com/705865"};
+
+    // glClearColor does not always work on Intel 6xxx Mac drivers when the clear color made up of
+    // all zeros and ones.
+    Feature clearToZeroOrOneBroken = {
+        "clear_to_zero_or_one_broken", FeatureCategory::OpenGLWorkarounds,
+        "Clears when the clear color is all zeros or ones do not work.", &members,
+        "https://crbug.com/710443"};
 };
 
 inline FeaturesGL::FeaturesGL()  = default;

src/libANGLE/renderer/gl/RendererGL.cpp

@@ -198,7 +198,8 @@ RendererGL::RendererGL(std::unique_ptr<FunctionsGL> functions,
     ASSERT(mFunctions);
     nativegl_gl::InitializeFeatures(mFunctions.get(), &mFeatures);
     OverrideFeaturesWithDisplayState(&mFeatures, display->getState());
-    mStateManager = new StateManagerGL(mFunctions.get(), getNativeCaps(), getNativeExtensions());
+    mStateManager =
+        new StateManagerGL(mFunctions.get(), getNativeCaps(), getNativeExtensions(), mFeatures);
     mBlitter          = new BlitGL(mFunctions.get(), mFeatures, mStateManager);
     mMultiviewClearer = new ClearMultiviewGL(mFunctions.get(), mStateManager);
 

src/libANGLE/renderer/gl/StateManagerGL.cpp

@@ -38,8 +38,10 @@ StateManagerGL::IndexedBufferBinding::IndexedBufferBinding() : offset(0), size(0
 
 StateManagerGL::StateManagerGL(const FunctionsGL *functions,
                                const gl::Caps &rendererCaps,
-                               const gl::Extensions &extensions)
+                               const gl::Extensions &extensions,
+                               const angle::FeaturesGL &features)
     : mFunctions(functions),
+      mFeatures(features),
       mProgram(0),
       mVAO(0),
       mVertexAttribCurrentValues(rendererCaps.maxVertexAttributes),
@@ -1475,9 +1477,26 @@ void StateManagerGL::setClearDepth(float clearDepth)
 
 void StateManagerGL::setClearColor(const gl::ColorF &clearColor)
 {
-    if (mClearColor != clearColor)
+    gl::ColorF modifiedClearColor = clearColor;
+    if (mFeatures.clearToZeroOrOneBroken.enabled &&
+        (clearColor.red == 1.0f || clearColor.red == 0.0f) &&
+        (clearColor.green == 1.0f || clearColor.green == 0.0f) &&
+        (clearColor.blue == 1.0f || clearColor.blue == 0.0f) &&
+        (clearColor.alpha == 1.0f || clearColor.alpha == 0.0f))
     {
-        mClearColor = clearColor;
+        if (clearColor.alpha == 1.0f)
+        {
+            modifiedClearColor.alpha = 2.0f;
+        }
+        else
+        {
+            modifiedClearColor.alpha = -1.0f;
+        }
+    }
+
+    if (mClearColor != modifiedClearColor)
+    {
+        mClearColor = modifiedClearColor;
         mFunctions->clearColor(mClearColor.red, mClearColor.green, mClearColor.blue,
                                mClearColor.alpha);
 

src/libANGLE/renderer/gl/StateManagerGL.h

@@ -14,6 +14,7 @@
 #include "libANGLE/State.h"
 #include "libANGLE/angletypes.h"
 #include "libANGLE/renderer/gl/functionsgl_typedefs.h"
+#include "platform/FeaturesGL.h"
 
 #include <map>
 
@@ -38,7 +39,8 @@ class StateManagerGL final : angle::NonCopyable
   public:
     StateManagerGL(const FunctionsGL *functions,
                    const gl::Caps &rendererCaps,
-                   const gl::Extensions &extensions);
+                   const gl::Extensions &extensions,
+                   const angle::FeaturesGL &features);
     ~StateManagerGL();
 
     void deleteProgram(GLuint program);
@@ -198,6 +200,7 @@ class StateManagerGL final : angle::NonCopyable
         const gl::FramebufferState &drawFramebufferState) const;
 
     const FunctionsGL *mFunctions;
+    const angle::FeaturesGL &mFeatures;
 
     GLuint mProgram;
 

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -1517,6 +1517,9 @@ void InitializeFeatures(const FunctionsGL *functions, angle::FeaturesGL *feature
 
     features->resetTexImage2DBaseLevel.enabled =
         IsApple() && IsIntel(vendor) && GetMacOSVersion() >= OSVersion(10, 12, 4);
+
+    features->clearToZeroOrOneBroken.enabled =
+        IsApple() && IsIntel(vendor) && GetMacOSVersion() < OSVersion(10, 12, 6);
 }
 
 void InitializeFrontendFeatures(const FunctionsGL *functions, angle::FrontendFeatures *features)