Draft Program interactivity for Canvas

wgpu/src/widget/canvas/layer/cache.rs

@@ -1,5 +1,5 @@
 use crate::{
-    canvas::{Drawable, Frame, Layer},
+    canvas::{Drawable, Frame, Layer, Program},
     Primitive,
 };
 
@@ -79,6 +79,20 @@ where
     }
 }
 
+impl<T> Program for Cache<T>
+where
+    T: Drawable + std::fmt::Debug,
+{
+    type Input = T;
+
+    fn layers<'a>(
+        &'a self,
+        input: &'a Self::Input,
+    ) -> Vec<Box<dyn Layer + 'a>> {
+        vec![Box::new(self.with(input))]
+    }
+}
+
 #[derive(Debug)]
 struct Bind<'a, T: Drawable> {
     cache: &'a Cache<T>,