impl default for canvas cache

Author: robjtede

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

@@ -13,7 +13,7 @@ use std::{cell::RefCell, marker::PhantomData, sync::Arc};
 ///
 /// [`Layer`]: ../trait.Layer.html
 /// [`Cache`]: struct.Cache.html
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct Cache<T: Drawable> {
     input: PhantomData<T>,
     state: RefCell<State>,
@@ -27,6 +27,12 @@ enum State {
     },
 }
 
+impl Default for State {
+    fn default() -> Self {
+        State::Empty
+    }
+}
+
 impl<T> Cache<T>
 where
     T: Drawable + std::fmt::Debug,
@@ -37,7 +43,7 @@ where
     pub fn new() -> Self {
         Cache {
             input: PhantomData,
-            state: RefCell::new(State::Empty),
+            state: RefCell::new(State::default()),
         }
     }