perf counter for render

sampler/src/has_sampler.rs

@@ -20,3 +20,13 @@ pub trait HasSampler {
         ))
     }
 }
+
+#[macro_export] macro_rules! has_sampler {
+    (|$self:ident:$Struct:ty| { sampler = $e0:expr; index = $e1:expr; }) => {
+        impl HasSampler for $Struct {
+            fn sampler (&$self) -> &Option<Sampler> { &$e0 }
+            fn sampler_mut (&mut $self) -> &mut Option<Sampler> { &mut $e0 }
+            fn sample_index (&$self) -> usize { $e1 }
+        }
+    }
+}