Make window::close return and introduce Task::discard

examples/events/src/main.rs

@@ -37,7 +37,7 @@ impl Events {
             }
             Message::EventOccurred(event) => {
                 if let Event::Window(window::Event::CloseRequested) = event {
-                    window::get_latest().and_then(window::close)
+                    window::get_latest().and_then(window::close).discard()
                 } else {
                     Task::none()
                 }
@@ -47,7 +47,9 @@ impl Events {
 
                 Task::none()
             }
-            Message::Exit => window::get_latest().and_then(window::close),
+            Message::Exit => {
+                window::get_latest().and_then(window::close).discard()
+            }
         }
     }
 

examples/exit/src/main.rs

@@ -20,7 +20,9 @@ enum Message {
 impl Exit {
     fn update(&mut self, message: Message) -> Task<Message> {
         match message {
-            Message::Confirm => window::get_latest().and_then(window::close),
+            Message::Confirm => {
+                window::get_latest().and_then(window::close).discard()
+            }
             Message::Exit => {
                 self.show_confirm = true;
 

runtime/src/task.rs

@@ -159,6 +159,17 @@ impl<T> Task<T> {
         }
     }
 
+    /// Creates a new [`Task`] that discards the result of the current one.
+    ///
+    /// Useful if you only care about the side effects of a [`Task`].
+    pub fn discard<O>(self) -> Task<O>
+    where
+        T: MaybeSend + 'static,
+        O: MaybeSend + 'static,
+    {
+        self.then(|_| Task::none())
+    }
+
     /// Creates a new [`Task`] that can be aborted with the returned [`Handle`].
     pub fn abortable(self) -> (Self, Handle)
     where

runtime/src/window.rs

@@ -24,7 +24,7 @@ pub enum Action {
     Open(Id, Settings, oneshot::Sender<Id>),
 
     /// Close the window and exits the application.
-    Close(Id),
+    Close(Id, oneshot::Sender<Id>),
 
     /// Gets the [`Id`] of the oldest window.
     GetOldest(oneshot::Sender<Option<Id>>),
@@ -230,8 +230,8 @@ pub fn open(settings: Settings) -> (Id, Task<Id>) {
 }
 
 /// Closes the window with `id`.
-pub fn close<T>(id: Id) -> Task<T> {
+pub fn close(id: Id) -> Task<Id> {
-    task::effect(crate::Action::Window(Action::Close(id)))
+    task::oneshot(|channel| crate::Action::Window(Action::Close(id, channel)))
 }
 
 /// Gets the window [`Id`] of the oldest window.

winit/src/program.rs

@@ -1209,9 +1209,11 @@ fn run_action<P, C>(
 
                 *is_window_opening = true;
             }
-            window::Action::Close(id) => {
+            window::Action::Close(id, channel) => {
                 let _ = window_manager.remove(id);
                 let _ = ui_caches.remove(&id);
+
+                let _ = channel.send(id);
             }
             window::Action::GetOldest(channel) => {
                 let id =