Add initialization closure and drop on exit

examples/child_window.rs

@@ -13,26 +13,12 @@ fn main() -> Result<(), impl std::error::Error> {
     #[path = "util/fill.rs"]
     mod fill;
 
-    #[derive(Default)]
     struct Application {
-        parent_window_id: Option<WindowId>,
+        parent_window_id: WindowId,
         windows: HashMap<WindowId, Box<dyn Window>>,
     }
 
     impl ApplicationHandler for Application {
-        fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
-            let attributes = WindowAttributes::default()
-                .with_title("parent window")
-                .with_position(Position::Logical(LogicalPosition::new(0.0, 0.0)))
-                .with_surface_size(LogicalSize::new(640.0f32, 480.0f32));
-            let window = event_loop.create_window(attributes).unwrap();
-
-            println!("Parent window id: {:?})", window.id());
-            self.parent_window_id = Some(window.id());
-
-            self.windows.insert(window.id(), window);
-        }
-
         fn window_event(
             &mut self,
             event_loop: &dyn ActiveEventLoop,
@@ -56,7 +42,7 @@ fn main() -> Result<(), impl std::error::Error> {
                     event: KeyEvent { state: ElementState::Pressed, .. },
                     ..
                 } => {
-                    let parent_window = self.windows.get(&self.parent_window_id.unwrap()).unwrap();
+                    let parent_window = self.windows.get(&self.parent_window_id).unwrap();
                     let child_window = spawn_child_window(parent_window.as_ref(), event_loop);
                     let child_id = child_window.id();
                     println!("Child window created with id: {child_id:?}");
@@ -72,6 +58,20 @@ fn main() -> Result<(), impl std::error::Error> {
         }
     }
 
+    fn init(event_loop: &dyn ActiveEventLoop) -> Application {
+        let attributes = WindowAttributes::default()
+            .with_title("parent window")
+            .with_position(Position::Logical(LogicalPosition::new(0.0, 0.0)))
+            .with_surface_size(LogicalSize::new(640.0f32, 480.0f32));
+        let window = event_loop.create_window(attributes).unwrap();
+
+        println!("Parent window id: {:?})", window.id());
+
+        let parent_window_id = window.id();
+        let windows = HashMap::from([(window.id(), window)]);
+        Application { parent_window_id, windows }
+    }
+
     fn spawn_child_window(
         parent: &dyn Window,
         event_loop: &dyn ActiveEventLoop,
@@ -89,7 +89,7 @@ fn main() -> Result<(), impl std::error::Error> {
     }
 
     let event_loop = EventLoop::new().unwrap();
-    event_loop.run_app(Application::default())
+    event_loop.run(init)
 }
 
 #[cfg(not(any(x11_platform, macos_platform, windows_platform)))]

examples/control_flow.rs

@@ -43,16 +43,31 @@ fn main() -> Result<(), impl std::error::Error> {
 
     let event_loop = EventLoop::new().unwrap();
 
-    event_loop.run_app(ControlFlowDemo::default())
+    event_loop.run(ControlFlowDemo::new)
 }
 
-#[derive(Default)]
 struct ControlFlowDemo {
     mode: Mode,
     request_redraw: bool,
     wait_cancelled: bool,
     close_requested: bool,
-    window: Option<Box<dyn Window>>,
+    window: Box<dyn Window>,
+}
+
+impl ControlFlowDemo {
+    fn new(event_loop: &dyn ActiveEventLoop) -> Self {
+        let window_attributes = WindowAttributes::default().with_title(
+            "Press 1, 2, 3 to change control flow mode. Press R to toggle redraw requests.",
+        );
+        let window = event_loop.create_window(window_attributes).unwrap();
+        Self {
+            mode: Mode::default(),
+            request_redraw: false,
+            wait_cancelled: false,
+            close_requested: false,
+            window,
+        }
+    }
 }
 
 impl ApplicationHandler for ControlFlowDemo {
@@ -65,13 +80,6 @@ impl ApplicationHandler for ControlFlowDemo {
         }
     }
 
-    fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
-        let window_attributes = WindowAttributes::default().with_title(
-            "Press 1, 2, 3 to change control flow mode. Press R to toggle redraw requests.",
-        );
-        self.window = Some(event_loop.create_window(window_attributes).unwrap());
-    }
-
     fn window_event(
         &mut self,
         _event_loop: &dyn ActiveEventLoop,
@@ -112,9 +120,8 @@ impl ApplicationHandler for ControlFlowDemo {
                 _ => (),
             },
             WindowEvent::RedrawRequested => {
-                let window = self.window.as_ref().unwrap();
+                self.window.pre_present_notify();
-                window.pre_present_notify();
+                fill::fill_window(&*self.window);
-                fill::fill_window(window.as_ref());
             },
             _ => (),
         }
@@ -122,7 +129,7 @@ impl ApplicationHandler for ControlFlowDemo {
 
     fn about_to_wait(&mut self, event_loop: &dyn ActiveEventLoop) {
         if self.request_redraw && !self.wait_cancelled && !self.close_requested {
-            self.window.as_ref().unwrap().request_redraw();
+            self.window.request_redraw();
         }
 
         match self.mode {

examples/pump_events.rs

@@ -8,7 +8,7 @@ fn main() -> std::process::ExitCode {
     use std::time::Duration;
 
     use winit::application::ApplicationHandler;
-    use winit::event::WindowEvent;
+    use winit::event::{StartCause, WindowEvent};
     use winit::event_loop::{ActiveEventLoop, EventLoop};
     use winit::platform::pump_events::{EventLoopExtPumpEvents, PumpStatus};
     use winit::window::{Window, WindowAttributes, WindowId};
@@ -22,9 +22,12 @@ fn main() -> std::process::ExitCode {
     }
 
     impl ApplicationHandler for PumpDemo {
-        fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
+        fn new_events(&mut self, event_loop: &dyn ActiveEventLoop, cause: StartCause) {
-            let window_attributes = WindowAttributes::default().with_title("A fantastic window!");
+            if matches!(cause, StartCause::Init) && self.window.is_none() {
-            self.window = Some(event_loop.create_window(window_attributes).unwrap());
+                let window_attributes =
+                    WindowAttributes::default().with_title("A fantastic window!");
+                self.window = Some(event_loop.create_window(window_attributes).unwrap());
+            }
         }
 
         fn window_event(

examples/run_on_demand.rs

@@ -21,14 +21,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         window: Option<Box<dyn Window>>,
     }
 
-    impl ApplicationHandler for App {
+    impl App {
-        fn about_to_wait(&mut self, _event_loop: &dyn ActiveEventLoop) {
+        fn init_window(&mut self, event_loop: &dyn ActiveEventLoop) {
-            if let Some(window) = self.window.as_ref() {
-                window.request_redraw();
-            }
-        }
-
-        fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
             let window_attributes = WindowAttributes::default()
                 .with_title("Fantastic window number one!")
                 .with_surface_size(winit::dpi::LogicalSize::new(128.0, 128.0));
@@ -36,6 +30,14 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             self.window_id = Some(window.id());
             self.window = Some(window);
         }
+    }
+
+    impl ApplicationHandler for App {
+        fn about_to_wait(&mut self, _event_loop: &dyn ActiveEventLoop) {
+            if let Some(window) = self.window.as_ref() {
+                window.request_redraw();
+            }
+        }
 
         fn window_event(
             &mut self,
@@ -81,14 +83,20 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let mut event_loop = EventLoop::new().unwrap();
 
     let mut app = App { idx: 1, ..Default::default() };
-    event_loop.run_app_on_demand(&mut app)?;
+    event_loop.run_on_demand(|event_loop| {
+        app.init_window(event_loop);
+        &mut app
+    })?;
 
     println!("--------------------------------------------------------- Finished first loop");
     println!("--------------------------------------------------------- Waiting 5 seconds");
     std::thread::sleep(Duration::from_secs(5));
 
     app.idx += 1;
-    event_loop.run_app_on_demand(&mut app)?;
+    event_loop.run_on_demand(|event_loop| {
+        app.init_window(event_loop);
+        &mut app
+    })?;
     println!("--------------------------------------------------------- Finished second loop");
     Ok(())
 }

examples/window.rs

@@ -70,8 +70,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         });
     }
 
-    let app = Application::new(&event_loop, receiver, sender);
+    Ok(event_loop.run(|event_loop| Application::new(event_loop, receiver, sender))?)
-    Ok(event_loop.run_app(app)?)
 }
 
 /// Application state and event handling.
@@ -88,21 +87,24 @@ struct Application {
     ///
     /// With OpenGL it could be EGLDisplay.
     #[cfg(not(android_platform))]
-    context: Option<Context<DisplayHandle<'static>>>,
+    context: Context<DisplayHandle<'static>>,
 }
 
 impl Application {
-    fn new(event_loop: &EventLoop, receiver: Receiver<Action>, sender: Sender<Action>) -> Self {
+    fn new(
-        // SAFETY: we drop the context right before the event loop is stopped, thus making it safe.
+        event_loop: &dyn ActiveEventLoop,
+        receiver: Receiver<Action>,
+        sender: Sender<Action>,
+    ) -> Self {
+        // SAFETY: The context is stored in the application, which is dropped right before the event
+        // loop is stopped, thus making it safe.
         #[cfg(not(android_platform))]
-        let context = Some(
+        let context = Context::new(unsafe {
-            Context::new(unsafe {
+            std::mem::transmute::<DisplayHandle<'_>, DisplayHandle<'static>>(
-                std::mem::transmute::<DisplayHandle<'_>, DisplayHandle<'static>>(
+                event_loop.display_handle().unwrap(),
-                    event_loop.display_handle().unwrap(),
+            )
-                )
+        })
-            })
+        .unwrap();
-            .unwrap(),
-        );
 
         // You'll have to choose an icon size at your own discretion. On X11, the desired size
         // varies by WM, and on Windows, you still have to account for screen scaling. Here
@@ -120,7 +122,7 @@ impl Application {
         .into_iter()
         .collect();
 
-        Self {
+        let mut app = Self {
             receiver,
             sender,
             #[cfg(not(android_platform))]
@@ -128,7 +130,16 @@ impl Application {
             custom_cursors,
             icon,
             windows: Default::default(),
-        }
+        };
+
+        app.dump_monitors(event_loop);
+
+        // Create initial window.
+        app.create_window(event_loop, None).expect("failed to create initial window");
+
+        app.print_help();
+
+        app
     }
 
     fn create_window(
@@ -560,14 +571,12 @@ impl ApplicationHandler for Application {
         info!("Device {device_id:?} event: {event:?}");
     }
 
-    fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
+    #[cfg(not(android_platform))]
-        info!("Ready to create surfaces");
+    fn can_create_surfaces(&mut self, _event_loop: &dyn ActiveEventLoop) {
-        self.dump_monitors(event_loop);
+        for window in self.windows.values_mut() {
-
+            window.surface = Some(Surface::new(&self.context, Arc::clone(&window.window)).unwrap());
-        // Create initial window.
+            window.resize(window.window.surface_size());
-        self.create_window(event_loop, None).expect("failed to create initial window");
+        }
-
-        self.print_help();
     }
 
     fn about_to_wait(&mut self, event_loop: &dyn ActiveEventLoop) {
@@ -578,9 +587,10 @@ impl ApplicationHandler for Application {
     }
 
     #[cfg(not(android_platform))]
-    fn exiting(&mut self, _event_loop: &dyn ActiveEventLoop) {
+    fn destroy_surfaces(&mut self, _event_loop: &dyn ActiveEventLoop) {
-        // We must drop the context here.
+        for window in self.windows.values_mut() {
-        self.context = None;
+            window.surface = None;
+        }
     }
 
     #[cfg(target_os = "macos")]
@@ -607,9 +617,9 @@ struct WindowState {
     ime: bool,
     /// Render surface.
     ///
-    /// NOTE: This surface must be dropped before the `Window`.
+    /// `None` when not between `can_create_surfaces` and `destroy_surfaces`.
     #[cfg(not(android_platform))]
-    surface: Surface<DisplayHandle<'static>, Arc<dyn Window>>,
+    surface: Option<Surface<DisplayHandle<'static>, Arc<dyn Window>>>,
     /// The actual winit Window.
     window: Arc<dyn Window>,
     /// The window theme we're drawing with.
@@ -642,11 +652,6 @@ impl WindowState {
     fn new(app: &Application, window: Box<dyn Window>) -> Result<Self, Box<dyn Error>> {
         let window: Arc<dyn Window> = Arc::from(window);
 
-        // SAFETY: the surface is dropped before the `window` which provided it with handle, thus
-        // it doesn't outlive it.
-        #[cfg(not(android_platform))]
-        let surface = Surface::new(app.context.as_ref().unwrap(), Arc::clone(&window))?;
-
         let theme = window.theme().unwrap_or(Theme::Dark);
         info!("Theme: {theme:?}");
         let named_idx = 0;
@@ -656,15 +661,14 @@ impl WindowState {
         let ime = true;
         window.set_ime_allowed(ime);
 
-        let size = window.surface_size();
+        Ok(Self {
-        let mut state = Self {
             #[cfg(macos_platform)]
             option_as_alt: window.option_as_alt(),
             custom_idx: app.custom_cursors.as_ref().map(Vec::len).unwrap_or(1) - 1,
             cursor_grab: CursorGrabMode::None,
             named_idx,
             #[cfg(not(android_platform))]
-            surface,
+            surface: None,
             window,
             theme,
             ime,
@@ -675,10 +679,7 @@ impl WindowState {
             rotated: Default::default(),
             panned: Default::default(),
             zoom: Default::default(),
-        };
+        })
-
-        state.resize(size);
-        Ok(state)
     }
 
     pub fn toggle_ime(&mut self) {
@@ -852,7 +853,11 @@ impl WindowState {
                 (Some(width), Some(height)) => (width, height),
                 _ => return,
             };
-            self.surface.resize(width, height).expect("failed to resize inner buffer");
+            self.surface
+                .as_mut()
+                .unwrap()
+                .resize(width, height)
+                .expect("failed to resize inner buffer");
         }
         self.window.request_redraw();
     }
@@ -945,7 +950,7 @@ impl WindowState {
             return Ok(());
         }
 
-        let mut buffer = self.surface.buffer_mut()?;
+        let mut buffer = self.surface.as_mut().unwrap().buffer_mut()?;
 
         // Draw a different color inside the safe area
         let surface_size = self.window.surface_size();

examples/x11_embed.rs

@@ -13,39 +13,28 @@ fn main() -> Result<(), Box<dyn Error>> {
     mod fill;
 
     pub struct XEmbedDemo {
-        parent_window_id: u32,
+        window: Box<dyn Window>,
-        window: Option<Box<dyn Window>>,
     }
 
     impl ApplicationHandler for XEmbedDemo {
-        fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
-            let window_attributes = WindowAttributes::default()
-                .with_title("An embedded window!")
-                .with_surface_size(winit::dpi::LogicalSize::new(128.0, 128.0))
-                .with_embed_parent_window(self.parent_window_id);
-
-            self.window = Some(event_loop.create_window(window_attributes).unwrap());
-        }
-
         fn window_event(
             &mut self,
             event_loop: &dyn ActiveEventLoop,
             _window_id: WindowId,
             event: WindowEvent,
         ) {
-            let window = self.window.as_ref().unwrap();
             match event {
                 WindowEvent::CloseRequested => event_loop.exit(),
                 WindowEvent::RedrawRequested => {
-                    window.pre_present_notify();
+                    self.window.pre_present_notify();
-                    fill::fill_window(window.as_ref());
+                    fill::fill_window(&*self.window);
                 },
                 _ => (),
             }
         }
 
         fn about_to_wait(&mut self, _event_loop: &dyn ActiveEventLoop) {
-            self.window.as_ref().unwrap().request_redraw();
+            self.window.request_redraw();
         }
     }
 
@@ -58,7 +47,15 @@ fn main() -> Result<(), Box<dyn Error>> {
     tracing_subscriber::fmt::init();
     let event_loop = EventLoop::new()?;
 
-    Ok(event_loop.run_app(XEmbedDemo { parent_window_id, window: None })?)
+    Ok(event_loop.run(|event_loop| {
+        let window_attributes = WindowAttributes::default()
+            .with_title("An embedded window!")
+            .with_surface_size(winit::dpi::LogicalSize::new(128.0, 128.0))
+            .with_embed_parent_window(parent_window_id);
+
+        let window = event_loop.create_window(window_attributes).unwrap();
+        XEmbedDemo { window }
+    })?)
 }
 
 #[cfg(not(x11_platform))]

src/application.rs

@@ -7,6 +7,8 @@ use crate::platform::macos::ApplicationHandlerExtMacOS;
 use crate::window::WindowId;
 
 /// The handler of the application events.
+///
+/// This is [dropped][std::ops::Drop] when the event loop is being shut down.
 pub trait ApplicationHandler {
     /// Emitted when new events arrive from the OS to be processed.
     ///
@@ -101,7 +103,9 @@ pub trait ApplicationHandler {
     ///
     /// [`can_create_surfaces()`]: Self::can_create_surfaces()
     /// [`destroy_surfaces()`]: Self::destroy_surfaces()
-    fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop);
+    fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
+        let _ = event_loop;
+    }
 
     /// Called after a wake up is requested using [`EventLoopProxy::wake_up()`].
     ///
@@ -142,8 +146,6 @@ pub trait ApplicationHandler {
     ///     # ) {
     ///     # }
     ///     #
-    ///     # fn can_create_surfaces(&mut self, _event_loop: &dyn ActiveEventLoop) {}
-    ///     #
     ///     fn proxy_wake_up(&mut self, _event_loop: &dyn ActiveEventLoop) {
     ///         // Iterate current events, since wake-ups may have been merged.
     ///         //
@@ -162,8 +164,6 @@ pub trait ApplicationHandler {
     ///
     ///     let (sender, receiver) = mpsc::channel();
     ///
-    ///     let mut app = MyApp { receiver };
-    ///
     ///     // Send an event in a loop
     ///     let proxy = event_loop.create_proxy();
     ///     let background_thread = thread::spawn(move || {
@@ -182,9 +182,8 @@ pub trait ApplicationHandler {
     ///         }
     ///     });
     ///
-    ///     event_loop.run_app(&mut app)?;
+    ///     event_loop.run(|_event_loop| MyApp { receiver })?;
     ///
-    ///     drop(app);
     ///     background_thread.join().unwrap();
     ///
     ///     Ok(())
@@ -286,13 +285,13 @@ pub trait ApplicationHandler {
     /// with the [`onStop`] lifecycle event which typically results in the surface to be destroyed
     /// after the app becomes invisible.
     ///
-    /// Applications that need to run on Android should assume their [`NativeWindow`] has been
+    /// Applications that need to run on Android must be able to handle their underlying
-    /// destroyed, which indirectly invalidates any existing render surfaces that may have been
+    /// [`SurfaceView`] being destroyed, which in turn indirectly invalidates any existing
-    /// created outside of Winit (such as an `EGLSurface`, [`VkSurfaceKHR`] or [`wgpu::Surface`]).
+    /// render surfaces that may have been created outside of Winit (such as an `EGLSurface`,
+    /// [`VkSurfaceKHR`] or [`wgpu::Surface`]).
     ///
-    /// When receiving [`destroy_surfaces()`] Android applications should drop all render surfaces
+    /// This means that in this method, you must drop all render surfaces before the event callback
-    /// before the event callback completes, which may be re-created when the application next
+    /// completes, and only re-create them in or after [`can_create_surfaces()`] is next recieved.
-    /// receives [`can_create_surfaces()`].
     ///
     /// [`NativeWindow`]: https://developer.android.com/ndk/reference/group/a-native-window
     /// [`Surface`]: https://developer.android.com/reference/android/view/Surface
@@ -310,14 +309,6 @@ pub trait ApplicationHandler {
         let _ = event_loop;
     }
 
-    /// Emitted when the event loop is being shut down.
-    ///
-    /// This is irreversible - if this method is called, it is guaranteed that the event loop
-    /// will exit right after.
-    fn exiting(&mut self, event_loop: &dyn ActiveEventLoop) {
-        let _ = event_loop;
-    }
-
     /// Emitted when the application has received a memory warning.
     ///
     /// ## Platform-specific
@@ -413,11 +404,6 @@ impl<A: ?Sized + ApplicationHandler> ApplicationHandler for &mut A {
         (**self).destroy_surfaces(event_loop);
     }
 
-    #[inline]
-    fn exiting(&mut self, event_loop: &dyn ActiveEventLoop) {
-        (**self).exiting(event_loop);
-    }
-
     #[inline]
     fn memory_warning(&mut self, event_loop: &dyn ActiveEventLoop) {
         (**self).memory_warning(event_loop);
@@ -487,11 +473,6 @@ impl<A: ?Sized + ApplicationHandler> ApplicationHandler for Box<A> {
         (**self).destroy_surfaces(event_loop);
     }
 
-    #[inline]
-    fn exiting(&mut self, event_loop: &dyn ActiveEventLoop) {
-        (**self).exiting(event_loop);
-    }
-
     #[inline]
     fn memory_warning(&mut self, event_loop: &dyn ActiveEventLoop) {
         (**self).memory_warning(event_loop);

src/event.rs

@@ -1,39 +1,4 @@
 //! The event enums and assorted supporting types.
-//!
-//! These are sent to the closure given to [`EventLoop::run_app(...)`], where they get
-//! processed and used to modify the program state. For more details, see the root-level
-//! documentation.
-//!
-//! Some of these events represent different "parts" of a traditional event-handling loop. You could
-//! approximate the basic ordering loop of [`EventLoop::run_app(...)`] like this:
-//!
-//! ```rust,ignore
-//! let mut start_cause = StartCause::Init;
-//!
-//! while !elwt.exiting() {
-//!     app.new_events(event_loop, start_cause);
-//!
-//!     for event in (window events, user events, device events) {
-//!         // This will pick the right method on the application based on the event.
-//!         app.handle_event(event_loop, event);
-//!     }
-//!
-//!     for window_id in (redraw windows) {
-//!         app.window_event(event_loop, window_id, RedrawRequested);
-//!     }
-//!
-//!     app.about_to_wait(event_loop);
-//!     start_cause = wait_if_necessary();
-//! }
-//!
-//! app.exiting(event_loop);
-//! ```
-//!
-//! This leaves out timing details like [`ControlFlow::WaitUntil`] but hopefully
-//! describes what happens in what order.
-//!
-//! [`EventLoop::run_app(...)`]: crate::event_loop::EventLoop::run_app
-//! [`ControlFlow::WaitUntil`]: crate::event_loop::ControlFlow::WaitUntil
 use std::path::PathBuf;
 use std::sync::{Mutex, Weak};
 #[cfg(not(web_platform))]
@@ -85,11 +50,6 @@ pub(crate) enum Event {
     /// [`ApplicationHandler::suspended()`]: crate::application::ApplicationHandler::suspended()
     Suspended,
 
-    /// See [`ApplicationHandler::can_create_surfaces()`] for details.
-    ///
-    /// [`ApplicationHandler::can_create_surfaces()`]: crate::application::ApplicationHandler::can_create_surfaces()
-    CreateSurfaces,
-
     /// See [`ApplicationHandler::resumed()`] for details.
     ///
     /// [`ApplicationHandler::resumed()`]: crate::application::ApplicationHandler::resumed()
@@ -100,11 +60,6 @@ pub(crate) enum Event {
     /// [`ApplicationHandler::about_to_wait()`]: crate::application::ApplicationHandler::about_to_wait()
     AboutToWait,
 
-    /// See [`ApplicationHandler::exiting()`] for details.
-    ///
-    /// [`ApplicationHandler::exiting()`]: crate::application::ApplicationHandler::exiting()
-    LoopExiting,
-
     /// See [`ApplicationHandler::memory_warning()`] for details.
     ///
     /// [`ApplicationHandler::memory_warning()`]: crate::application::ApplicationHandler::memory_warning()
@@ -1195,7 +1150,6 @@ mod tests {
                 let wid = WindowId::from_raw(0);
                 x(NewEvents(event::StartCause::Init));
                 x(AboutToWait);
-                x(LoopExiting);
                 x(Suspended);
                 x(Resumed);
 

src/event_loop.rs

@@ -195,10 +195,48 @@ impl EventLoop {
 }
 
 impl EventLoop {
-    /// Run the application with the event loop on the calling thread.
+    /// Run the event loop on the current thread.
+    ///
+    /// You pass in a closure that returns your application state. This closure has access to the
+    /// currently running event loop, allowing you to initialize your windows and surfaces in here.
     ///
     /// See the [`set_control_flow()`] docs on how to change the event loop's behavior.
     ///
+    /// ## Event loop flow
+    ///
+    /// This function internally handles the different parts of a traditional event-handling loop.
+    /// You could imagine this method being implemented like this:
+    ///
+    /// ```rust,ignore
+    /// // Initialize.
+    /// let mut app = init_closure(event_loop);
+    /// let mut start_cause = StartCause::Init;
+    ///
+    /// // Run loop.
+    /// while !elwt.exiting() {
+    ///     // Wake up.
+    ///     app.new_events(event_loop, start_cause);
+    ///
+    ///     // Handle events by the user.
+    ///     for (device_id, event) in incoming_device_events {
+    ///         app.device_event(event_loop, device_id, event);
+    ///     }
+    ///     for (window_id, event) in incoming_window_events {
+    ///         app.window_event(event_loop, window_id, event);
+    ///     }
+    ///
+    ///     // Done handling events, wait until we're woken up again.
+    ///     app.about_to_wait(event_loop);
+    ///     start_cause = wait_if_necessary();
+    /// }
+    ///
+    /// // Finished running, drop application state.
+    /// drop(app);
+    /// ```
+    ///
+    /// This is of course a very coarse-grained overview, and leaves out timing details like
+    /// [`ControlFlow::WaitUntil`] and life-cycle methods like [`ApplicationHandler::resumed`].
+    ///
     /// ## Platform-specific
     ///
     /// - **iOS:** Will never return to the caller and so values not passed to this function will
@@ -213,7 +251,7 @@ impl EventLoop {
         doc = "  [`EventLoopExtWeb::spawn_app()`][crate::platform::web::EventLoopExtWeb::spawn_app()]"
     )]
     #[cfg_attr(not(any(web_platform, docsrs)), doc = "  `EventLoopExtWeb::spawn_app()`")]
-    ///   [^1] instead of [`run_app()`] to avoid the need for the Javascript exception trick, and to
+    ///   [^1] instead of [`run()`] to avoid the need for the Javascript exception trick, and to
     ///   make   it clearer that the event loop runs asynchronously (via the browser's own,
     ///   internal, event   loop) and doesn't block the current thread of execution like it does
     ///   on other platforms.
@@ -223,11 +261,20 @@ impl EventLoop {
     /// [^1]: `spawn_app()` is only available on the Web platform.
     ///
     /// [`set_control_flow()`]: ActiveEventLoop::set_control_flow()
-    /// [`run_app()`]: Self::run_app()
+    /// [`run()`]: Self::run()
     #[inline]
     #[cfg(not(all(web_platform, target_feature = "exception-handling")))]
+    pub fn run<A: ApplicationHandler>(
+        self,
+        init_closure: impl FnOnce(&dyn ActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.event_loop.run(init_closure)
+    }
+
+    /// Run the event loop with the given application state.
+    #[deprecated = "less flexible version of `run`"]
     pub fn run_app<A: ApplicationHandler>(self, app: A) -> Result<(), EventLoopError> {
-        self.event_loop.run_app(app)
+        self.run(|_event_loop| app)
     }
 
     /// Creates an [`EventLoopProxy`] that can be used to dispatch user events
@@ -392,9 +439,7 @@ pub trait ActiveEventLoop: AsAny {
     /// Gets the current [`ControlFlow`].
     fn control_flow(&self) -> ControlFlow;
 
-    /// This exits the event loop.
+    /// This stops the event loop.
-    ///
-    /// See [`exiting`][crate::application::ApplicationHandler::exiting].
     fn exit(&self);
 
     /// Returns if the [`EventLoop`] is about to stop.

src/lib.rs

@@ -1,24 +1,14 @@
 //! Winit is a cross-platform window creation and event loop management library.
 //!
-//! # Building windows
-//!
-//! Before you can create a [`Window`], you first need to build an [`EventLoop`]. This is done with
-//! the [`EventLoop::new()`] function.
-//!
-//! ```no_run
-//! use winit::event_loop::EventLoop;
-//!
-//! # // Intentionally use `fn main` for clarity
-//! fn main() {
-//!     let event_loop = EventLoop::new().unwrap();
-//!     // ...
-//! }
-//! ```
-//!
-//! Then you create a [`Window`] with [`create_window`].
-//!
 //! # Event handling
 //!
+//! Basically all of the functionality that Winit exposes requires an [`ActiveEventLoop`], which you
+//! can get access to by running an [`EventLoop`] using [`EventLoop::new()`] and
+//! [`EventLoop::run()`].
+//!
+//! Once it's running, you can create your [`Window`]s with [`ActiveEventLoop::create_window()`] by
+//! passing in the desired [`WindowAttributes`].
+//!
 //! Once a [`Window`] has been created, it will generate different *events*. A [`Window`] object can
 //! generate [`WindowEvent`]s when certain input events occur, such as a cursor moving over the
 //! window or a key getting pressed while the window is focused. Devices can generate
@@ -26,9 +16,10 @@
 //! Some user activity, like mouse movement, can generate both a [`WindowEvent`] *and* a
 //! [`DeviceEvent`].
 //!
-//! You can retrieve events by calling [`EventLoop::run_app()`]. This function will
+//! You retrieve by implementing [`ApplicationHandler`] for a new type, which will be the state of
-//! dispatch events for every [`Window`] that was created with that particular [`EventLoop`], and
+//! your application. The methods in this trait will continuously receive events until
-//! will run until [`exit()`] is used, at which point [`exiting()`] is called.
+//! [`ActiveEventLoop::exit()`] is used, at which point your application state will be dropped, and
+//! the application shuts down.
 //!
 //! Winit no longer uses a `EventLoop::poll_events() -> impl Iterator<Event>`-based event loop
 //! model, since that can't be implemented properly on some platforms (e.g Web, iOS) and works
@@ -49,19 +40,20 @@
 //! use winit::application::ApplicationHandler;
 //! use winit::event::WindowEvent;
 //! use winit::event_loop::{ActiveEventLoop, ControlFlow, EventLoop};
-//! use winit::window::{Window, WindowId, WindowAttributes};
+//! use winit::window::{Window, WindowId};
 //!
-//! #[derive(Default)]
 //! struct App {
-//!     window: Option<Box<dyn Window>>,
+//!     window: Box<dyn Window>,
 //! }
 //!
 //! impl ApplicationHandler for App {
-//!     fn can_create_surfaces(&mut self, event_loop: &dyn ActiveEventLoop) {
+//!     fn window_event(
-//!         self.window = Some(event_loop.create_window(WindowAttributes::default()).unwrap());
+//!         &mut self,
-//!     }
+//!         event_loop: &dyn ActiveEventLoop,
-//!
+//!         id: WindowId,
-//!     fn window_event(&mut self, event_loop: &dyn ActiveEventLoop, id: WindowId, event: WindowEvent) {
+//!         event: WindowEvent,
+//!     ) {
+//!         // Called by `EventLoop::run` when a new event happens on the window.
 //!         match event {
 //!             WindowEvent::CloseRequested => {
 //!                 println!("The close button was pressed; stopping");
@@ -81,16 +73,19 @@
 //!                 // You only need to call this if you've determined that you need to redraw in
 //!                 // applications which do not always need to. Applications that redraw continuously
 //!                 // can render here instead.
-//!                 self.window.as_ref().unwrap().request_redraw();
+//!                 self.window.request_redraw();
-//!             }
+//!             },
 //!             _ => (),
 //!         }
 //!     }
 //! }
 //!
 //! # // Intentionally use `fn main` for clarity
-//! fn main() {
+//! fn main() -> Result<(), Box<dyn std::error::Error>> {
-//!     let event_loop = EventLoop::new().unwrap();
+//!     // Create a new event loop.
+//!     let event_loop = EventLoop::new()?;
+//!
+//!     // Configure settings before launching.
 //!
 //!     // ControlFlow::Poll continuously runs the event loop, even if the OS hasn't
 //!     // dispatched any events. This is ideal for games and similar applications.
@@ -101,8 +96,21 @@
 //!     // input, and uses significantly less power/CPU time than ControlFlow::Poll.
 //!     event_loop.set_control_flow(ControlFlow::Wait);
 //!
-//!     let mut app = App::default();
+//!     // Launch and begin running our event loop.
-//!     event_loop.run_app(&mut app);
+//!     event_loop.run(|event_loop| {
+//!         // The event loop has launched, and we can initialize our UI state in this closure.
+//!
+//!         // Create a simple window with default attributes.
+//!         let window = event_loop
+//!             .create_window(Window::default_attributes())
+//!             .expect("failed creating window");
+//!
+//!         // Give our newly created application state to Winit, which will, when necessary, call
+//!         // the `ApplicationHandler` methods configured above.
+//!         App { window }
+//!     })?;
+//!
+//!     Ok(())
 //! }
 //! ```
 //!
@@ -250,20 +258,21 @@
 //! |32-bit ARM Android                  |`arm-linux-androideabi`             |Android        |
 //! |64-bit SPARC Linux with glibc       |`sparc64-unknown-linux-gnu`         |X11, Wayland   |
 //!
+//! [`ActiveEventLoop`]: event_loop::ActiveEventLoop
 //! [`EventLoop`]: event_loop::EventLoop
 //! [`EventLoop::new()`]: event_loop::EventLoop::new
-//! [`EventLoop::run_app()`]: event_loop::EventLoop::run_app
+//! [`EventLoop::run()`]: event_loop::EventLoop::run
-//! [`exit()`]: event_loop::ActiveEventLoop::exit
+//! [`ActiveEventLoop::exit()`]: event_loop::ActiveEventLoop::exit
 //! [`Window`]: window::Window
 //! [`WindowId`]: window::WindowId
 //! [`WindowAttributes`]: window::WindowAttributes
 //! [window_new]: window::Window::new
-//! [`create_window`]: event_loop::ActiveEventLoop::create_window
+//! [`ActiveEventLoop::create_window()`]: event_loop::ActiveEventLoop::create_window
 //! [`Window::id()`]: window::Window::id
 //! [`WindowEvent`]: event::WindowEvent
 //! [`DeviceEvent`]: event::DeviceEvent
+//! [`ApplicationHandler`]: application::ApplicationHandler
 //! [`Event::UserEvent`]: event::Event::UserEvent
-//! [`exiting()`]: crate::application::ApplicationHandler::exiting
 //! [`raw_window_handle`]: ./window/struct.Window.html#method.raw_window_handle
 //! [`raw_display_handle`]: ./window/struct.Window.html#method.raw_display_handle
 //! [^1]: `EventLoopExtPumpEvents::pump_app_events()` is only available on Windows, macOS, Android, X11 and Wayland.

src/platform/macos.rs

@@ -65,7 +65,7 @@
 //!     let app = NSApplication::sharedApplication(mtm);
 //!     app.setDelegate(Some(ProtocolObject::from_ref(&*delegate)));
 //!
-//!     // event_loop.run_app(&mut my_app);
+//!     // event_loop.run(|event_loop| { ... })?;
 //!     Ok(())
 //! }
 //! ```

src/platform/run_on_demand.rs

@@ -1,16 +1,14 @@
 use crate::application::ApplicationHandler;
 use crate::error::EventLoopError;
-use crate::event_loop::EventLoop;
+use crate::event_loop::{ActiveEventLoop, EventLoop};
 #[cfg(doc)]
-use crate::{
+use crate::{platform::pump_events::EventLoopExtPumpEvents, window::Window};
-    event_loop::ActiveEventLoop, platform::pump_events::EventLoopExtPumpEvents, window::Window,
-};
 
 /// Additional methods on [`EventLoop`] to return control flow to the caller.
 pub trait EventLoopExtRunOnDemand {
     /// Run the application with the event loop on the calling thread.
     ///
-    /// Unlike [`EventLoop::run_app`], this function accepts non-`'static` (i.e. non-`move`)
+    /// Unlike [`EventLoop::run`], this function accepts non-`'static` (i.e. non-`move`)
     /// closures and it is possible to return control back to the caller without
     /// consuming the `EventLoop` (by using [`exit()`]) and
     /// so the event loop can be re-run after it has exit.
@@ -23,7 +21,7 @@ pub trait EventLoopExtRunOnDemand {
     /// to while maintaining the full state of your application. (If you need something like this
     /// you can look at the [`EventLoopExtPumpEvents::pump_app_events()`] API)
     ///
-    /// Each time `run_app_on_demand` is called the startup sequence of `init`, followed by
+    /// Each time `run_on_demand` is called the startup sequence of `init`, followed by
     /// `resume` is being preserved.
     ///
     /// See the [`set_control_flow()`] docs on how to change the event loop's behavior.
@@ -40,7 +38,7 @@ pub trait EventLoopExtRunOnDemand {
     ///   [^1] more than once instead).
     /// - No [`Window`] state can be carried between separate runs of the event loop.
     ///
-    /// You are strongly encouraged to use [`EventLoop::run_app()`] for portability, unless you
+    /// You are strongly encouraged to use [`EventLoop::run()`] for portability, unless you
     /// specifically need the ability to re-run a single event loop more than once
     ///
     /// # Supported Platforms
@@ -60,12 +58,18 @@ pub trait EventLoopExtRunOnDemand {
     ///
     /// [`exit()`]: ActiveEventLoop::exit()
     /// [`set_control_flow()`]: ActiveEventLoop::set_control_flow()
-    fn run_app_on_demand<A: ApplicationHandler>(&mut self, app: A) -> Result<(), EventLoopError>;
+    fn run_on_demand<A: ApplicationHandler>(
+        &mut self,
+        init_closure: impl FnOnce(&dyn ActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError>;
 }
 
 impl EventLoopExtRunOnDemand for EventLoop {
-    fn run_app_on_demand<A: ApplicationHandler>(&mut self, app: A) -> Result<(), EventLoopError> {
+    fn run_on_demand<A: ApplicationHandler>(
-        self.event_loop.run_app_on_demand(app)
+        &mut self,
+        init_closure: impl FnOnce(&dyn ActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.event_loop.run_on_demand(init_closure)
     }
 }
 

src/platform/web.rs

@@ -190,10 +190,10 @@ pub trait EventLoopExtWeb {
     /// Initializes the winit event loop.
     ///
     /// Unlike
-    #[cfg_attr(all(web_platform, target_feature = "exception-handling"), doc = "`run_app()`")]
+    #[cfg_attr(all(web_platform, target_feature = "exception-handling"), doc = "`run()`")]
     #[cfg_attr(
         not(all(web_platform, target_feature = "exception-handling")),
-        doc = "[`run_app()`]"
+        doc = "[`run()`]"
     )]
     /// [^1], this returns immediately, and doesn't throw an exception in order to
     /// satisfy its [`!`] return type.
@@ -206,9 +206,9 @@ pub trait EventLoopExtWeb {
     ///
     #[cfg_attr(
         not(all(web_platform, target_feature = "exception-handling")),
-        doc = "[`run_app()`]: EventLoop::run_app()"
+        doc = "[`run()`]: EventLoop::run()"
     )]
-    /// [^1]: `run_app()` is _not_ available on Wasm when the target supports `exception-handling`.
+    /// [^1]: `run()` is _not_ available on Wasm when the target supports `exception-handling`.
     fn spawn_app<A: ApplicationHandler + 'static>(self, app: A);
 
     /// Sets the strategy for [`ControlFlow::Poll`].

src/platform_impl/android/mod.rs

@@ -496,15 +496,21 @@ impl EventLoop {
         input_status
     }
 
-    pub fn run_app<A: ApplicationHandler>(mut self, app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
-        self.run_app_on_demand(app)
+        mut self,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.run_on_demand(init_closure)
     }
 
-    pub fn run_app_on_demand<A: ApplicationHandler>(
+    pub fn run_on_demand<A: ApplicationHandler>(
         &mut self,
-        mut app: A,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
     ) -> Result<(), EventLoopError> {
         self.window_target.clear_exit();
+
+        let mut app = init_closure(&self.window_target);
+
         loop {
             match self.pump_app_events(None, &mut app) {
                 PumpStatus::Exit(0) => {
@@ -546,8 +552,6 @@ impl EventLoop {
         if self.exiting() {
             self.loop_running = false;
 
-            app.exiting(&self.window_target);
-
             PumpStatus::Exit(0)
         } else {
             PumpStatus::Continue

src/platform_impl/apple/appkit/app_state.rs

@@ -9,12 +9,12 @@ use objc2_app_kit::{NSApplication, NSApplicationActivationPolicy, NSRunningAppli
 use objc2_foundation::{MainThreadMarker, NSNotification};
 
 use super::super::event_handler::EventHandler;
-use super::event_loop::{stop_app_immediately, ActiveEventLoop, EventLoopProxy, PanicInfo};
+use super::event_loop::{stop_app_immediately, EventLoopProxy, PanicInfo};
 use super::menu;
 use super::observer::{EventLoopWaker, RunLoop};
 use crate::application::ApplicationHandler;
 use crate::event::{StartCause, WindowEvent};
-use crate::event_loop::ControlFlow;
+use crate::event_loop::{ActiveEventLoop, ControlFlow};
 use crate::window::WindowId;
 
 #[derive(Debug)]
@@ -163,17 +163,25 @@ impl AppState {
     pub fn will_terminate(self: &Rc<Self>, _notification: &NSNotification) {
         trace_scope!("NSApplicationWillTerminateNotification");
         // TODO: Notify every window that it will be destroyed, like done in iOS?
+        self.with_handler(|app, event_loop| {
+            app.exiting(event_loop);
+        });
         self.internal_exit();
     }
 
     /// Place the event handler in the application state for the duration
     /// of the given closure.
-    pub fn set_event_handler<R>(
+    pub fn set_init_closure<A: ApplicationHandler, R>(
         &self,
-        handler: &mut dyn ApplicationHandler,
+        init_closure: impl FnOnce(&dyn ActiveEventLoop) -> A,
         closure: impl FnOnce() -> R,
     ) -> R {
-        self.event_handler.set(handler, closure)
+        let init_closure = Box::new(
+            |active_event_loop: &'_ dyn ActiveEventLoop| -> Box<dyn ApplicationHandler + '_> {
+                Box::new(init_closure(active_event_loop))
+            },
+        );
+        self.event_handler.set(init_closure, closure)
     }
 
     pub fn event_loop_proxy(&self) -> &Arc<EventLoopProxy> {
@@ -208,10 +216,6 @@ impl AppState {
     /// NOTE: that if the `NSApplication` has been launched then that state is preserved,
     /// and we won't need to re-launch the app if subsequent EventLoops are run.
     pub fn internal_exit(self: &Rc<Self>) {
-        self.with_handler(|app, event_loop| {
-            app.exiting(event_loop);
-        });
-
         self.set_is_running(false);
         self.set_stop_on_redraw(false);
         self.set_stop_before_wait(false);

src/platform_impl/apple/appkit/event_loop.rs

@@ -274,20 +274,23 @@ impl EventLoop {
         &self.window_target
     }
 
-    pub fn run_app<A: ApplicationHandler>(mut self, app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
-        self.run_app_on_demand(app)
+        mut self,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.run_on_demand(init_closure)
     }
 
     // NB: we don't base this on `pump_events` because for `MacOs` we can't support
     // `pump_events` elegantly (we just ask to run the loop for a "short" amount of
     // time and so a layered implementation would end up using a lot of CPU due to
     // redundant wake ups.
-    pub fn run_app_on_demand<A: ApplicationHandler>(
+    pub fn run_on_demand<A: ApplicationHandler>(
         &mut self,
-        mut app: A,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
     ) -> Result<(), EventLoopError> {
         self.app_state.clear_exit();
-        self.app_state.set_event_handler(&mut app, || {
+        self.app_state.set_init_closure(init_closure, || {
             autoreleasepool(|_| {
                 // clear / normalize pump_events state
                 self.app_state.set_wait_timeout(None);

src/platform_impl/apple/event_handler.rs

@@ -1,33 +1,55 @@
-use std::cell::RefCell;
+use std::cell::Cell;
 use std::{fmt, mem};
 
 use crate::application::ApplicationHandler;
+use crate::event_loop::ActiveEventLoop;
 
 /// A helper type for storing a reference to `ApplicationHandler`, allowing interior mutable access
 /// to it within the execution of a closure.
 #[derive(Default)]
 pub(crate) struct EventHandler {
-    /// This can be in the following states:
+    state: Cell<State>,
-    /// - Not registered by the event loop (None).
+}
-    /// - Present (Some(handler)).
+
-    /// - Currently executing the handler / in use (RefCell borrowed).
+type InitClosure<'handler> =
-    inner: RefCell<Option<&'static mut dyn ApplicationHandler>>,
+    Box<dyn FnOnce(&dyn ActiveEventLoop) -> Box<dyn ApplicationHandler + 'handler> + 'handler>;
+
+#[derive(Default)]
+enum State {
+    /// Not registered by the event loop.
+    #[default]
+    NotRegistered,
+    /// The event is registered by the event loop.
+    Registered(InitClosure<'static>),
+    /// The application has been initialized, and we're ready to handle events.
+    Ready(Box<dyn ApplicationHandler + 'static>),
+    /// Currently executing the handler.
+    CurrentlyExecuting,
+    /// The application has been terminated.
+    Terminated,
+    // TODO: Invalid state?
 }
 
 impl fmt::Debug for EventHandler {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let state = match self.inner.try_borrow().as_deref() {
+        let state = self.state.replace(State::CurrentlyExecuting);
-            Ok(Some(_)) => "<available>",
+        // NOTE: We're very careful not to panic inside the "critial" section here.
-            Ok(None) => "<not set>",
+        let string = match &state {
-            Err(_) => "<in use>",
+            State::NotRegistered => "<not registered>",
+            State::Registered(_) => "<registered>",
+            State::Ready(_) => "<ready>",
+            State::CurrentlyExecuting => "<currently executing>",
+            State::Terminated => "<terminated>",
         };
-        f.debug_struct("EventHandler").field("state", &state).finish_non_exhaustive()
+        self.state.set(state);
+
+        f.debug_struct("EventHandler").field("state", &string).finish_non_exhaustive()
     }
 }
 
 impl EventHandler {
-    pub(crate) fn new() -> Self {
+    pub(crate) const fn new() -> Self {
-        Self { inner: RefCell::new(None) }
+        Self { state: Cell::new(State::NotRegistered) }
     }
 
     /// Set the event loop handler for the duration of the given closure.
@@ -37,7 +59,7 @@ impl EventHandler {
     /// from within the closure.
     pub(crate) fn set<'handler, R>(
         &self,
-        app: &'handler mut dyn ApplicationHandler,
+        init_closure: InitClosure<'handler>,
         closure: impl FnOnce() -> R,
     ) -> R {
         // SAFETY: We extend the lifetime of the handler here so that we can
@@ -46,14 +68,9 @@ impl EventHandler {
         // This is sound, since we make sure to unset the handler again at the
         // end of this function, and as such the lifetime isn't actually
         // extended beyond `'handler`.
-        let handler = unsafe {
+        let handler = unsafe { mem::transmute::<InitClosure<'handler>, InitClosure<'static>>(app) };
-            mem::transmute::<
-                &'handler mut dyn ApplicationHandler,
-                &'static mut dyn ApplicationHandler,
-            >(app)
-        };
 
-        match self.inner.try_borrow_mut().as_deref_mut() {
+        match self.state.try_borrow_mut().as_deref_mut() {
             Ok(Some(_)) => {
                 unreachable!("tried to set handler while another was already set");
             },
@@ -69,7 +86,7 @@ impl EventHandler {
 
         impl Drop for ClearOnDrop<'_> {
             fn drop(&mut self) {
-                match self.0.inner.try_borrow_mut().as_deref_mut() {
+                match self.0.state.try_borrow_mut().as_deref_mut() {
                     Ok(data @ Some(_)) => {
                         *data = None;
                     },
@@ -101,6 +118,10 @@ impl EventHandler {
         // soundness.
     }
 
+    fn init(&self) {}
+
+    fn terminate(&self) {}
+
     #[cfg(target_os = "macos")]
     pub(crate) fn in_use(&self) -> bool {
         self.inner.try_borrow().is_err()
@@ -120,7 +141,7 @@ impl EventHandler {
                 //
                 // If the handler unwinds, the `RefMut` will ensure that the
                 // handler is no longer borrowed.
-                callback(*user_app);
+                callback(user_app);
             },
             Ok(None) => {
                 // `NSApplication`, our app state and this handler are all

src/platform_impl/linux/mod.rs

@@ -360,15 +360,18 @@ impl EventLoop {
         }
     }
 
-    pub fn run_app<A: ApplicationHandler>(self, app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
-        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run_app(app))
+        self,
+        init_closure: impl FnOnce(&dyn ActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run(init_closure))
     }
 
-    pub fn run_app_on_demand<A: ApplicationHandler>(
+    pub fn run_on_demand<A: ApplicationHandler>(
         &mut self,
-        app: A,
+        init_closure: impl FnOnce(&dyn ActiveEventLoop) -> A,
     ) -> Result<(), EventLoopError> {
-        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run_app_on_demand(app))
+        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run_on_demand(init_closure))
     }
 
     pub fn pump_app_events<A: ApplicationHandler>(

src/platform_impl/linux/wayland/event_loop/mod.rs

@@ -146,15 +146,21 @@ impl EventLoop {
         Ok(event_loop)
     }
 
-    pub fn run_app<A: ApplicationHandler>(mut self, app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
-        self.run_app_on_demand(app)
+        mut self,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.run_on_demand(init_closure)
     }
 
-    pub fn run_app_on_demand<A: ApplicationHandler>(
+    pub fn run_on_demand<A: ApplicationHandler>(
         &mut self,
-        mut app: A,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
     ) -> Result<(), EventLoopError> {
         self.active_event_loop.clear_exit();
+
+        let mut app = init_closure(&self.active_event_loop);
+
         let exit = loop {
             match self.pump_app_events(None, &mut app) {
                 PumpStatus::Exit(0) => {
@@ -198,8 +204,6 @@ impl EventLoop {
         if let Some(code) = self.exit_code() {
             self.loop_running = false;
 
-            app.exiting(&self.active_event_loop);
-
             PumpStatus::Exit(code)
         } else {
             PumpStatus::Continue

src/platform_impl/linux/x11/mod.rs

@@ -373,15 +373,21 @@ impl EventLoop {
         &self.event_processor.target
     }
 
-    pub fn run_app<A: ApplicationHandler>(mut self, app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
-        self.run_app_on_demand(app)
+        mut self,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.run_on_demand(init_closure)
     }
 
-    pub fn run_app_on_demand<A: ApplicationHandler>(
+    pub fn run_on_demand<A: ApplicationHandler>(
         &mut self,
-        mut app: A,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
     ) -> Result<(), EventLoopError> {
         self.event_processor.target.clear_exit();
+
+        let mut app = init_closure(&self.event_processor.target);
+
         let exit = loop {
             match self.pump_app_events(None, &mut app) {
                 PumpStatus::Exit(0) => {
@@ -429,8 +435,6 @@ impl EventLoop {
         if let Some(code) = self.exit_code() {
             self.loop_running = false;
 
-            app.exiting(self.window_target());
-
             PumpStatus::Exit(code)
         } else {
             PumpStatus::Continue

src/platform_impl/orbital/event_loop.rs

@@ -483,7 +483,11 @@ impl EventLoop {
         }
     }
 
-    pub fn run_app<A: ApplicationHandler>(mut self, mut app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
+        mut self,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        let mut app = init_closure(&self.window_target);
         let mut start_cause = StartCause::Init;
         loop {
             app.new_events(&self.window_target, start_cause);
@@ -654,8 +658,6 @@ impl EventLoop {
             }
         }
 
-        app.exiting(&self.window_target);
-
         Ok(())
     }
 

src/platform_impl/web/event_loop/mod.rs

@@ -96,7 +96,6 @@ fn handle_event<A: ApplicationHandler>(app: &mut A, target: &ActiveEventLoop, ev
         Event::Resumed => app.resumed(target),
         Event::CreateSurfaces => app.can_create_surfaces(target),
         Event::AboutToWait => app.about_to_wait(target),
-        Event::LoopExiting => app.exiting(target),
         Event::MemoryWarning => app.memory_warning(target),
     }
 }

src/platform_impl/web/event_loop/runner.rs

@@ -609,7 +609,7 @@ impl Shared {
         self.apply_control_flow();
         // We don't call `handle_loop_destroyed` here because we don't need to
         // perform cleanup when the Web browser is going to destroy the page.
-        self.handle_event(Event::LoopExiting);
+        todo!("drop the application handler");
     }
 
     // handle_event takes in events and either queues them or applies a callback
@@ -713,7 +713,7 @@ impl Shared {
     }
 
     fn handle_loop_destroyed(&self) {
-        self.handle_event(Event::LoopExiting);
+        todo!("drop the application handler");
         let all_canvases = std::mem::take(&mut *self.0.all_canvases.borrow_mut());
         *self.0.page_transition_event_handle.borrow_mut() = None;
         *self.0.on_mouse_move.borrow_mut() = None;

src/platform_impl/windows/event_loop.rs

@@ -220,15 +220,21 @@ impl EventLoop {
         &self.window_target
     }
 
-    pub fn run_app<A: ApplicationHandler>(mut self, app: A) -> Result<(), EventLoopError> {
+    pub fn run<A: ApplicationHandler>(
-        self.run_app_on_demand(app)
+        mut self,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
+    ) -> Result<(), EventLoopError> {
+        self.run_on_demand(init_closure)
     }
 
-    pub fn run_app_on_demand<A: ApplicationHandler>(
+    pub fn run_on_demand<A: ApplicationHandler>(
         &mut self,
-        mut app: A,
+        init_closure: impl FnOnce(&dyn RootActiveEventLoop) -> A,
     ) -> Result<(), EventLoopError> {
         self.window_target.clear_exit();
+
+        let mut app = init_closure(&self.window_target);
+
         {
             let runner = &self.window_target.runner_shared;
 
@@ -250,7 +256,6 @@ impl EventLoop {
                     Event::Resumed => app.resumed(event_loop_windows_ref),
                     Event::CreateSurfaces => app.can_create_surfaces(event_loop_windows_ref),
                     Event::AboutToWait => app.about_to_wait(event_loop_windows_ref),
-                    Event::LoopExiting => app.exiting(event_loop_windows_ref),
                     Event::MemoryWarning => app.memory_warning(event_loop_windows_ref),
                 });
             }
@@ -317,7 +322,6 @@ impl EventLoop {
                     Event::Resumed => app.resumed(event_loop_windows_ref),
                     Event::CreateSurfaces => app.can_create_surfaces(event_loop_windows_ref),
                     Event::AboutToWait => app.about_to_wait(event_loop_windows_ref),
-                    Event::LoopExiting => app.exiting(event_loop_windows_ref),
                     Event::MemoryWarning => app.memory_warning(event_loop_windows_ref),
                 });
 
@@ -348,8 +352,10 @@ impl EventLoop {
             PumpStatus::Continue
         };
 
-        // We wait until we've checked for an exit status before clearing the
+        // We wait until we've checked for an exit status before clearing the application callback,
-        // application callback, in case we need to dispatch a LoopExiting event
+        // in case any of the methods above ends up triggering an event.
+        //
+        // This drops the user's `ApplicationHandler`.
         //
         // # Safety
         // This pairs up with our call to `runner.set_event_handler` and ensures

src/platform_impl/windows/event_loop/runner.rs

@@ -248,9 +248,8 @@ impl EventLoopRunner {
         }
     }
 
-    /// Dispatch control flow events (`NewEvents`, `AboutToWait`, and
+    /// Dispatch control flow events (`new_events`, `about_to_wait`) as necessary to bring the
-    /// `LoopExiting`) as necessary to bring the internal `RunnerState` to the
+    /// internal `RunnerState` to the new runner state.
-    /// new runner state.
     ///
     /// The state transitions are defined as follows:
     ///
@@ -294,7 +293,6 @@ impl EventLoopRunner {
                 self.call_new_events(true);
                 self.call_event_handler(Event::AboutToWait);
                 self.last_events_cleared.set(Instant::now());
-                self.call_event_handler(Event::LoopExiting);
             },
             (_, Uninitialized) => panic!("cannot move state to Uninitialized"),
 
@@ -302,9 +300,7 @@ impl EventLoopRunner {
             (Idle, HandlingMainEvents) => {
                 self.call_new_events(false);
             },
-            (Idle, Destroyed) => {
+            (Idle, Destroyed) => {},
-                self.call_event_handler(Event::LoopExiting);
-            },
 
             (HandlingMainEvents, Idle) => {
                 // This is always the last event we dispatch before waiting for new events
@@ -314,7 +310,6 @@ impl EventLoopRunner {
             (HandlingMainEvents, Destroyed) => {
                 self.call_event_handler(Event::AboutToWait);
                 self.last_events_cleared.set(Instant::now());
-                self.call_event_handler(Event::LoopExiting);
             },
 
             (Destroyed, _) => panic!("cannot move state from Destroyed"),