Introduce black_box and chain in widget::operation

runtime/src/lib.rs

@@ -59,7 +59,7 @@ pub enum Action<T> {
     },
 
     /// Run a widget operation.
-    Widget(Box<dyn widget::Operation<()>>),
+    Widget(Box<dyn widget::Operation>),
 
     /// Run a clipboard action.
     Clipboard(clipboard::Action),
@@ -79,7 +79,7 @@ pub enum Action<T> {
 
 impl<T> Action<T> {
     /// Creates a new [`Action::Widget`] with the given [`widget::Operation`].
-    pub fn widget(operation: impl widget::Operation<()> + 'static) -> Self {
+    pub fn widget(operation: impl widget::Operation + 'static) -> Self {
         Self::Widget(Box::new(operation))
     }
 

runtime/src/multi_window/state.rs

@@ -205,7 +205,7 @@ where
     pub fn operate(
         &mut self,
         renderer: &mut P::Renderer,
-        operations: impl Iterator<Item = Box<dyn Operation<()>>>,
+        operations: impl Iterator<Item = Box<dyn Operation>>,
         bounds: Size,
         debug: &mut Debug,
     ) {

runtime/src/overlay/nested.rs

@@ -131,13 +131,13 @@ where
         &mut self,
         layout: Layout<'_>,
         renderer: &Renderer,
-        operation: &mut dyn widget::Operation<()>,
+        operation: &mut dyn widget::Operation,
     ) {
         fn recurse<Message, Theme, Renderer>(
             element: &mut overlay::Element<'_, Message, Theme, Renderer>,
             layout: Layout<'_>,
             renderer: &Renderer,
-            operation: &mut dyn widget::Operation<()>,
+            operation: &mut dyn widget::Operation,
         ) where
             Renderer: renderer::Renderer,
         {

runtime/src/program/state.rs

@@ -178,7 +178,7 @@ where
     pub fn operate(
         &mut self,
         renderer: &mut P::Renderer,
-        operations: impl Iterator<Item = Box<dyn Operation<()>>>,
+        operations: impl Iterator<Item = Box<dyn Operation>>,
         bounds: Size,
         debug: &mut Debug,
     ) {

runtime/src/user_interface.rs

@@ -566,7 +566,7 @@ where
     pub fn operate(
         &mut self,
         renderer: &Renderer,
-        operation: &mut dyn widget::Operation<()>,
+        operation: &mut dyn widget::Operation,
     ) {
         self.root.as_widget().operate(
             &mut self.state,