Added a prototype for the application exit event handler.

src/application.rs

@@ -161,6 +161,9 @@ pub trait Application: Sized {
         window::Mode::Windowed
     }
 
+    /// APPLICATION EXIT EVENT
+    fn on_exit(&mut self);
+
     /// Runs the [`Application`].
     ///
     /// This method will take control of the current thread and __will NOT
@@ -221,10 +224,12 @@ where
     fn subscription(&self) -> Subscription<Self::Message> {
         self.0.subscription()
     }
-
     fn view(&mut self) -> Element<'_, Self::Message> {
         self.0.view()
     }
+    fn on_exit(&mut self) {
+        self.0.on_exit()
+    }
 }
 
 #[cfg(target_arch = "wasm32")]
@@ -251,4 +256,7 @@ where
     fn view(&mut self) -> Element<'_, Self::Message> {
         self.0.view()
     }
+    fn on_exit(&mut self) {
+        self.0.on_exit()
+    }
 }

src/sandbox.rs

@@ -127,6 +127,9 @@ pub trait Sandbox {
     {
         <Self as Application>::run(settings)
     }
+
+    /// APPLICATION EXIT EVENT
+    fn on_exit(&mut self);
 }
 
 impl<T> Application for T
@@ -157,4 +160,7 @@ where
     fn view(&mut self) -> Element<'_, T::Message> {
         T::view(self)
     }
+    fn on_exit(&mut self) {
+        T::on_exit(self)
+    }
 }

winit/src/application.rs

@@ -89,6 +89,9 @@ pub trait Application: Sized {
         Mode::Windowed
     }
 
+    /// APPLICATION EXIT EVENT
+    fn on_exit(&mut self);
+
     /// Runs the [`Application`].
     ///
     /// This method will take control of the current thread and __will NOT
@@ -296,6 +299,8 @@ pub trait Application: Sized {
 
                 window.request_redraw();
             }
+            // event::Event::LoopDestroyed => {
+            // }
             event::Event::UserEvent(message) => {
                 external_messages.push(message);
             }
@@ -346,6 +351,7 @@ pub trait Application: Sized {
                     resized = true;
                 }
                 WindowEvent::CloseRequested => {
+                    application.on_exit();
                     *control_flow = ControlFlow::Exit;
                 }
                 WindowEvent::CursorMoved { position, .. } => {