GL: Emulate primitive restart when PRIMITIVE_RESTART_FIXED_INDEX is unavailable.

include/platform/FeaturesGL.h

@@ -355,6 +355,12 @@ struct FeaturesGL : FeatureSetBase
         "Mac incorrectly executes both sides of && and || expressions when they should "
         "short-circuit.",
         &members, "http://anglebug.com/482"};
+
+    Feature emulatePrimitiveRestartFixedIndex = {
+        "emulate_primitive_restart_fixed_index", FeatureCategory::OpenGLWorkarounds,
+        "When GL_PRIMITIVE_RESTART_FIXED_INDEX is not available, emulate it with "
+        "GL_PRIMITIVE_RESTART and glPrimitiveRestartIndex.",
+        &members, "http://anglebug.com/3997"};
 };
 
 inline FeaturesGL::FeaturesGL()  = default;

src/libANGLE/renderer/gl/ContextGL.cpp

@@ -262,6 +262,15 @@ ANGLE_INLINE angle::Result ContextGL::setDrawElementsState(const gl::Context *co
         *outIndices = indices;
     }
 
+    const angle::FeaturesGL &features = getFeaturesGL();
+    if (glState.isPrimitiveRestartEnabled() && features.emulatePrimitiveRestartFixedIndex.enabled)
+    {
+        StateManagerGL *stateManager = getStateManager();
+
+        GLuint primitiveRestartIndex = nativegl::GetPrimitiveRestartIndexForIndexType(type);
+        stateManager->setPrimitiveRestartIndex(primitiveRestartIndex);
+    }
+
 #if defined(ANGLE_STATE_VALIDATION_ENABLED)
     const VertexArrayGL *vaoGL = GetImplAs<VertexArrayGL>(vao);
     vaoGL->validateState();

src/libANGLE/renderer/gl/StateManagerGL.cpp

@@ -138,6 +138,7 @@ StateManagerGL::StateManagerGL(const FunctionsGL *functions,
       mRasterizerDiscardEnabled(false),
       mLineWidth(1.0f),
       mPrimitiveRestartEnabled(false),
+      mPrimitiveRestartIndex(0),
       mClearColor(0.0f, 0.0f, 0.0f, 0.0f),
       mClearDepth(1.0f),
       mClearStencil(0),
@@ -1438,19 +1439,35 @@ void StateManagerGL::setPrimitiveRestartEnabled(bool enabled)
     {
         mPrimitiveRestartEnabled = enabled;
 
+        GLenum cap = mFeatures.emulatePrimitiveRestartFixedIndex.enabled
+                         ? GL_PRIMITIVE_RESTART
+                         : GL_PRIMITIVE_RESTART_FIXED_INDEX;
+
         if (mPrimitiveRestartEnabled)
         {
-            mFunctions->enable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
+            mFunctions->enable(cap);
         }
         else
         {
-            mFunctions->disable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
+            mFunctions->disable(cap);
         }
 
         mLocalDirtyBits.set(gl::State::DIRTY_BIT_PRIMITIVE_RESTART_ENABLED);
     }
 }
 
+void StateManagerGL::setPrimitiveRestartIndex(GLuint index)
+{
+    if (mPrimitiveRestartIndex != index)
+    {
+        mPrimitiveRestartIndex = index;
+
+        mFunctions->primitiveRestartIndex(index);
+
+        // No dirty bit for this state, it is not exposed to the frontend.
+    }
+}
+
 void StateManagerGL::setClearDepth(float clearDepth)
 {
     if (mClearDepth != clearDepth)

src/libANGLE/renderer/gl/StateManagerGL.h

@@ -122,6 +122,7 @@ class StateManagerGL final : angle::NonCopyable
     void setLineWidth(float width);
 
     void setPrimitiveRestartEnabled(bool enabled);
+    void setPrimitiveRestartIndex(GLuint index);
 
     void setClearColor(const gl::ColorF &clearColor);
     void setClearDepth(float clearDepth);
@@ -328,6 +329,7 @@ class StateManagerGL final : angle::NonCopyable
     float mLineWidth;
 
     bool mPrimitiveRestartEnabled;
+    GLuint mPrimitiveRestartIndex;
 
     gl::ColorF mClearColor;
     float mClearDepth;

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -1575,7 +1575,9 @@ void InitializeFeatures(const FunctionsGL *functions, angle::FeaturesGL *feature
 
     ANGLE_FEATURE_CONDITION(features, rgbDXT1TexturesSampleZeroAlpha, IsApple());
 
-    ANGLE_FEATURE_CONDITION(features, unfoldShortCircuits, IsApple());
+    ANGLE_FEATURE_CONDITION(
+        features, emulatePrimitiveRestartFixedIndex,
+        !functions->isAtLeastGL(gl::Version(4, 3)) && !functions->isAtLeastGLES(gl::Version(3, 0)));
 }
 
 void InitializeFrontendFeatures(const FunctionsGL *functions, angle::FrontendFeatures *features)
@@ -1743,6 +1745,22 @@ std::string GetBufferBindingString(gl::BufferBinding bufferBinding)
     return os.str();
 }
 
+GLuint GetPrimitiveRestartIndexForIndexType(gl::DrawElementsType type)
+{
+    switch (type)
+    {
+        case gl::DrawElementsType::UnsignedByte:
+            return std::numeric_limits<GLubyte>::max();
+        case gl::DrawElementsType::UnsignedShort:
+            return std::numeric_limits<GLushort>::max();
+        case gl::DrawElementsType::UnsignedInt:
+            return std::numeric_limits<GLuint>::max();
+        default:
+            UNREACHABLE();
+            return 0;
+    }
+}
+
 }  // namespace nativegl
 
 const FunctionsGL *GetFunctionsGL(const gl::Context *context)

src/libANGLE/renderer/gl/renderergl_utils.h

@@ -108,6 +108,7 @@ bool UseTexImage3D(gl::TextureType textureType);
 GLenum GetTextureBindingQuery(gl::TextureType textureType);
 GLenum GetBufferBindingQuery(gl::BufferBinding bufferBinding);
 std::string GetBufferBindingString(gl::BufferBinding bufferBinding);
+GLuint GetPrimitiveRestartIndexForIndexType(gl::DrawElementsType type);
 }  // namespace nativegl
 
 bool CanMapBufferForRead(const FunctionsGL *functions);