3 files changed, 49 insertions, 1 deletions
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index e7377c82e69..7e6d16f59db 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -193,6 +193,15 @@ impl<T: JSTraceable> JSTraceable for Vec<T> {
     }
 }
 
+impl<T: JSTraceable> JSTraceable for (T, T, T, T) {
+    fn trace(&self, trc: *mut JSTracer) {
+        self.0.trace(trc);
+        self.1.trace(trc);
+        self.2.trace(trc);
+        self.3.trace(trc);
+    }
+}
+
 // XXXManishearth Check if the following three are optimized to no-ops
 // if e.trace() is a no-op (e.g it is an no_jsmanaged_fields type)
 impl<T: JSTraceable + 'static> JSTraceable for SmallVec<[T; 1]> {
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index 70b98ce06cd..4223598a985 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -83,6 +83,8 @@ pub struct WebGLRenderingContext {
     bound_buffer_array: MutNullableHeap<JS<WebGLBuffer>>,
     bound_buffer_element_array: MutNullableHeap<JS<WebGLBuffer>>,
     current_program: MutNullableHeap<JS<WebGLProgram>>,
+    #[ignore_heap_size_of = "Because it's small"]
+    current_vertex_attrib_0: Cell<(f32, f32, f32, f32)>,
 }
 
 impl WebGLRenderingContext {
@@ -111,6 +113,7 @@ impl WebGLRenderingContext {
                 bound_buffer_array: MutNullableHeap::new(None),
                 bound_buffer_element_array: MutNullableHeap::new(None),
                 current_program: MutNullableHeap::new(None),
+                current_vertex_attrib_0: Cell::new((0f32, 0f32, 0f32, 1f32)),
             }
         })
     }
@@ -175,6 +178,10 @@ impl WebGLRenderingContext {
             return self.webgl_error(InvalidValue);
         }
 
+        if indx == 0 {
+            self.current_vertex_attrib_0.set((x, y, z, w))
+        }
+
         self.ipc_renderer
             .send(CanvasMsg::WebGL(WebGLCommand::VertexAttrib(indx, x, y, z, w)))
             .unwrap();
@@ -1138,6 +1145,38 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
         })
     }
 
+    #[allow(unsafe_code)]
+    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.9
+    fn GetVertexAttrib(&self, cx: *mut JSContext, index: u32, pname: u32) -> JSVal {
+        if index == 0 && pname == constants::CURRENT_VERTEX_ATTRIB {
+            let mut result = RootedValue::new(cx, UndefinedValue());
+            let (x, y, z, w) = self.current_vertex_attrib_0.get();
+            let attrib = vec![x, y, z, w];
+            unsafe {
+                attrib.to_jsval(cx, result.handle_mut());
+            }
+            return result.ptr
+        }
+
+        let (sender, receiver) = ipc::channel().unwrap();
+        self.ipc_renderer.send(CanvasMsg::WebGL(WebGLCommand::GetVertexAttrib(index, pname, sender))).unwrap();
+
+        match handle_potential_webgl_error!(self, receiver.recv().unwrap(), WebGLParameter::Invalid) {
+            WebGLParameter::Int(val) => Int32Value(val),
+            WebGLParameter::Bool(val) => BooleanValue(val),
+            WebGLParameter::String(_) => panic!("Vertex attrib should not be string"),
+            WebGLParameter::Float(_) => panic!("Vertex attrib should not be float"),
+            WebGLParameter::FloatArray(val) => {
+                let mut result = RootedValue::new(cx, UndefinedValue());
+                unsafe {
+                    val.to_jsval(cx, result.handle_mut());
+                }
+                result.ptr
+            }
+            WebGLParameter::Invalid => NullValue(),
+        }
+    }
+
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3
     fn Hint(&self, target: u32, mode: u32) {
         if target != constants::GENERATE_MIPMAP_HINT {
diff --git a/components/script/dom/webidls/WebGLRenderingContext.webidl b/components/script/dom/webidls/WebGLRenderingContext.webidl
index f46da97fd65..f5f1629ca48 100644
--- a/components/script/dom/webidls/WebGLRenderingContext.webidl
+++ b/components/script/dom/webidls/WebGLRenderingContext.webidl
@@ -595,7 +595,7 @@ interface WebGLRenderingContextBase
 
     WebGLUniformLocation? getUniformLocation(WebGLProgram? program, DOMString name);
 
-    //any getVertexAttrib(GLuint index, GLenum pname);
+    any getVertexAttrib(GLuint index, GLenum pname);
 
     //[WebGLHandlesContextLoss] GLsizeiptr getVertexAttribOffset(GLuint index, GLenum pname);