GL backend: add a workaround for bad default current vertex attributes

src/libANGLE/renderer/gl/RendererGL.cpp

@@ -137,6 +137,17 @@ RendererGL::RendererGL(const FunctionsGL *functions, const egl::AttributeMap &at
     {
         mSkipDrawCalls = true;
     }
+
+    if (mWorkarounds.initializeCurrentVertexAttributes)
+    {
+        GLint maxVertexAttribs = 0;
+        mFunctions->getIntegerv(GL_MAX_VERTEX_ATTRIBS, &maxVertexAttribs);
+
+        for (GLint i = 0; i < maxVertexAttribs; ++i)
+        {
+            mFunctions->vertexAttrib4f(i, 0.0f, 0.0f, 0.0f, 1.0f);
+        }
+    }
 }
 
 RendererGL::~RendererGL()

src/libANGLE/renderer/gl/WorkaroundsGL.h

@@ -67,6 +67,9 @@ struct WorkaroundsGL
 
     // In the case of unpacking from a pixel unpack buffer, unpack overlapping rows row by row.
     bool unpackOverlappingRowsSeparatelyUnpackBuffer;
+
+    // During initialization, assign the current vertex attributes to the spec-mandated defaults.
+    bool initializeCurrentVertexAttributes;
 };
 }
 

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -896,6 +896,8 @@ void GenerateWorkarounds(const FunctionsGL *functions, WorkaroundsGL *workaround
     workarounds->alwaysCallUseProgramAfterLink = true;
 
     workarounds->unpackOverlappingRowsSeparatelyUnpackBuffer = vendor == VENDOR_ID_NVIDIA;
+
+    workarounds->initializeCurrentVertexAttributes = vendor == VENDOR_ID_NVIDIA;
 }
 
 }