Emit suspended on shutdown

When debug assertions are enabled, check that events are emitted in the
expected order, and if not, log an error.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "winit"
-version = "0.30.1"
+version = "0.30.0"
 authors = [
     "The winit contributors",
     "Pierre Krieger <pierre.krieger1708@gmail.com>",
@@ -112,12 +112,10 @@ objc2 = "0.5.2"
 
 [target.'cfg(target_os = "macos")'.dependencies]
 core-graphics = "0.23.1"
-block2 = "0.5.1"
 
 [target.'cfg(target_os = "macos")'.dependencies.objc2-foundation]
 version = "0.2.2"
 features = [
-    "block2",
     "dispatch",
     "NSArray",
     "NSAttributedString",

README.md

@@ -8,7 +8,7 @@
 
 ```toml
 [dependencies]
-winit = "0.30.1"
+winit = "0.30.0"
 ```
 
 ## [Documentation](https://docs.rs/winit)

examples/child_window.rs

@@ -3,50 +3,45 @@
 fn main() -> Result<(), impl std::error::Error> {
     use std::collections::HashMap;
 
+    use winit::application::ApplicationHandler;
     use winit::dpi::{LogicalPosition, LogicalSize, Position};
-    use winit::event::{ElementState, Event, KeyEvent, WindowEvent};
+    use winit::event::{ElementState, KeyEvent, WindowEvent};
     use winit::event_loop::{ActiveEventLoop, EventLoop};
     use winit::raw_window_handle::HasRawWindowHandle;
-    use winit::window::Window;
+    use winit::window::{Window, WindowId};
 
     #[path = "util/fill.rs"]
     mod fill;
 
-    fn spawn_child_window(parent: &Window, event_loop: &ActiveEventLoop) -> Window {
-        let parent = parent.raw_window_handle().unwrap();
-        let mut window_attributes = Window::default_attributes()
-            .with_title("child window")
-            .with_inner_size(LogicalSize::new(200.0f32, 200.0f32))
-            .with_position(Position::Logical(LogicalPosition::new(0.0, 0.0)))
-            .with_visible(true);
-        // `with_parent_window` is unsafe. Parent window must be a valid window.
-        window_attributes = unsafe { window_attributes.with_parent_window(Some(parent)) };
-
-        event_loop.create_window(window_attributes).unwrap()
+    #[derive(Default)]
+    struct Application {
+        parent_window_id: Option<WindowId>,
+        windows: HashMap<WindowId, Window>,
     }
 
-    let mut windows = HashMap::new();
+    impl ApplicationHandler for Application {
+        fn resumed(&mut self, event_loop: &ActiveEventLoop) {
+            let attributes = Window::default_attributes()
+                .with_title("parent window")
+                .with_position(Position::Logical(LogicalPosition::new(0.0, 0.0)))
+                .with_inner_size(LogicalSize::new(640.0f32, 480.0f32));
+            let window = event_loop.create_window(attributes).unwrap();
 
-    let event_loop: EventLoop<()> = EventLoop::new().unwrap();
-    let mut parent_window_id = None;
+            println!("Parent window id: {:?})", window.id());
+            self.parent_window_id = Some(window.id());
 
-    event_loop.run(move |event: Event<()>, event_loop| {
-        match event {
-            Event::Resumed => {
-                let attributes = Window::default_attributes()
-                    .with_title("parent window")
-                    .with_position(Position::Logical(LogicalPosition::new(0.0, 0.0)))
-                    .with_inner_size(LogicalSize::new(640.0f32, 480.0f32));
-                let window = event_loop.create_window(attributes).unwrap();
+            self.windows.insert(window.id(), window);
+        }
 
-                parent_window_id = Some(window.id());
-
-                println!("Parent window id: {parent_window_id:?})");
-                windows.insert(window.id(), window);
-            },
-            Event::WindowEvent { window_id, event } => match event {
+        fn window_event(
+            &mut self,
+            event_loop: &ActiveEventLoop,
+            window_id: winit::window::WindowId,
+            event: WindowEvent,
+        ) {
+            match event {
                 WindowEvent::CloseRequested => {
-                    windows.clear();
+                    self.windows.clear();
                     event_loop.exit();
                 },
                 WindowEvent::CursorEntered { device_id: _ } => {
@@ -61,22 +56,38 @@ fn main() -> Result<(), impl std::error::Error> {
                     event: KeyEvent { state: ElementState::Pressed, .. },
                     ..
                 } => {
-                    let parent_window = windows.get(&parent_window_id.unwrap()).unwrap();
+                    let parent_window = self.windows.get(&self.parent_window_id.unwrap()).unwrap();
                     let child_window = spawn_child_window(parent_window, event_loop);
                     let child_id = child_window.id();
                     println!("Child window created with id: {child_id:?}");
-                    windows.insert(child_id, child_window);
+                    self.windows.insert(child_id, child_window);
                 },
                 WindowEvent::RedrawRequested => {
-                    if let Some(window) = windows.get(&window_id) {
+                    if let Some(window) = self.windows.get(&window_id) {
                         fill::fill_window(window);
                     }
                 },
                 _ => (),
-            },
-            _ => (),
+            }
         }
-    })
+    }
+
+    fn spawn_child_window(parent: &Window, event_loop: &ActiveEventLoop) -> Window {
+        let parent = parent.raw_window_handle().unwrap();
+        let mut window_attributes = Window::default_attributes()
+            .with_title("child window")
+            .with_inner_size(LogicalSize::new(200.0f32, 200.0f32))
+            .with_position(Position::Logical(LogicalPosition::new(0.0, 0.0)))
+            .with_visible(true);
+        // `with_parent_window` is unsafe. Parent window must be a valid window.
+        window_attributes = unsafe { window_attributes.with_parent_window(Some(parent)) };
+
+        event_loop.create_window(window_attributes).unwrap()
+    }
+
+    let event_loop: EventLoop<()> = EventLoop::new().unwrap();
+    let mut app = Application::default();
+    event_loop.run_app(&mut app)
 }
 
 #[cfg(all(feature = "rwh_06", not(any(x11_platform, macos_platform, windows_platform))))]

examples/window.rs

@@ -17,7 +17,9 @@ use softbuffer::{Context, Surface};
 
 use winit::application::ApplicationHandler;
 use winit::dpi::{LogicalSize, PhysicalPosition, PhysicalSize};
-use winit::event::{DeviceEvent, DeviceId, Ime, MouseButton, MouseScrollDelta, WindowEvent};
+use winit::event::{
+    DeviceEvent, DeviceId, Ime, MouseButton, MouseScrollDelta, StartCause, WindowEvent,
+};
 use winit::event_loop::{ActiveEventLoop, EventLoop};
 use winit::keyboard::{Key, ModifiersState};
 use winit::window::{
@@ -303,6 +305,12 @@ impl Application {
 }
 
 impl ApplicationHandler<UserEvent> for Application {
+    fn new_events(&mut self, _event_loop: &ActiveEventLoop, start_cause: StartCause) {
+        if let StartCause::Init = start_cause {
+            info!("Started the event loop");
+        }
+    }
+
     fn user_event(&mut self, _event_loop: &ActiveEventLoop, event: UserEvent) {
         info!("User event: {event:?}");
     }
@@ -320,6 +328,7 @@ impl ApplicationHandler<UserEvent> for Application {
 
         match event {
             WindowEvent::Resized(size) => {
+                info!("Resized({size:?})");
                 window.resize(size);
             },
             WindowEvent::Focused(focused) => {

src/changelog/unreleased.md

@@ -12,6 +12,7 @@ on how to add them:
 ### Added
 
 - Add `Window::turbo()`, implemented on X11, Wayland, and Web.
+- Add traits `EventLoopExtWayland` and `EventLoopExtX11`, providing methods `is_wayland` and `is_x11` on `EventLoop`.
 - On X11, add `Window::some_rare_api`.
 - On X11, add `Window::even_more_rare_api`.
 - On Wayland, add `Window::common_api`.
@@ -39,3 +40,19 @@ The migration guide could reference other migration examples in the current
 changelog entry.
 
 ## Unreleased
+
+### Added
+
+- Reexport `raw-window-handle` versions 0.4 and 0.5 as `raw_window_handle_04` and `raw_window_handle_05`.
+- Implement `ApplicationHandler` for `&mut` references and heap allocations to something that implements `ApplicationHandler`.
+
+### Removed
+
+- Remove `EventLoop::run`.
+- Remove `EventLoopExtRunOnDemand::run_on_demand`.
+- Remove `EventLoopExtPumpEvents::pump_events`.
+
+### Fixed
+
+- On macOS, fix panic on exit when dropping windows outside the event loop.
+- On macOS, fix window dragging glitches when dragging across a monitor boundary with different scale factor.

src/changelog/v0.30.md

@@ -1,18 +1,3 @@
-## 0.30.1
-
-### Added
-
-- Reexport `raw-window-handle` versions 0.4 and 0.5 as `raw_window_handle_04` and `raw_window_handle_05`.
-- Implement `ApplicationHandler` for `&mut` references and heap allocations to something that implements `ApplicationHandler`.
-
-### Fixed
-
-- On macOS, fix panic on exit when dropping windows outside the event loop.
-- On macOS, fix window dragging glitches when dragging across a monitor boundary with different scale factor.
-- On macOS, fix the range in `Ime::Preedit`.
-- On macOS, use the system's internal mechanisms for queuing events.
-- On macOS, handle events directly instead of queuing when possible.
-
 ## 0.30.0
 
 ### Added
@@ -80,7 +65,7 @@
   `Fn`. The semantics are mostly the same, given that the capture list of the
   closure is your new `State`. Consider the following code:
 
-  ```rust,no_run
+  ```rust,no_run,ignore
   use winit::event::Event;
   use winit::event_loop::EventLoop;
   use winit::window::Window;

src/event_loop.rs

@@ -20,7 +20,6 @@ use web_time::{Duration, Instant};
 
 use crate::application::ApplicationHandler;
 use crate::error::{EventLoopError, OsError};
-use crate::event::Event;
 use crate::monitor::MonitorHandle;
 use crate::platform_impl;
 use crate::window::{CustomCursor, CustomCursorSource, Window, WindowAttributes};
@@ -152,6 +151,7 @@ impl fmt::Debug for ActiveEventLoop {
 /// Defaults to [`Wait`].
 ///
 /// [`Wait`]: Self::Wait
+/// [`Event::AboutToWait`]: crate::event::Event::AboutToWait
 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
 pub enum ControlFlow {
     /// When the current loop iteration finishes, immediately begin a new iteration regardless of
@@ -209,6 +209,110 @@ impl EventLoop<()> {
     }
 }
 
+#[cfg(debug_assertions)]
+pub(crate) fn ensure_event_order<'a, T: 'static>(
+    handler: impl ApplicationHandler<T> + 'a,
+) -> impl ApplicationHandler<T> + 'a {
+    use crate::event::{DeviceEvent, DeviceId, StartCause, WindowEvent};
+    use crate::window::WindowId;
+
+    #[derive(Default, Debug, PartialEq, Eq, Clone)]
+    enum State {
+        #[default]
+        NotRunning,
+        Suspended,
+        Running,
+        Waiting,
+    }
+
+    impl State {
+        #[track_caller]
+        fn expect(&self, expected: State) {
+            if *self != expected {
+                tracing::error!("expected state to be {expected:?}, found {self:?}");
+            }
+        }
+
+        #[track_caller]
+        fn transition(&mut self, from: State, to: State) {
+            if *self != from {
+                tracing::error!(
+                    "invalid state transition to {to:?}. Expected {from:?}, found {self:?}"
+                );
+            }
+            *self = to;
+        }
+    }
+
+    struct EnsureEventOrder<A> {
+        inner: A,
+        state: State,
+    }
+
+    impl<A: ApplicationHandler<T>, T: 'static> ApplicationHandler<T> for EnsureEventOrder<A> {
+        fn new_events(&mut self, event_loop: &ActiveEventLoop, cause: StartCause) {
+            match cause {
+                StartCause::Init => self.state.transition(State::NotRunning, State::Suspended),
+                _ => self.state.transition(State::Waiting, State::Running),
+            }
+
+            self.inner.new_events(event_loop, cause);
+        }
+
+        fn resumed(&mut self, event_loop: &ActiveEventLoop) {
+            self.state.transition(State::Suspended, State::Running);
+            self.inner.resumed(event_loop);
+        }
+
+        fn suspended(&mut self, event_loop: &ActiveEventLoop) {
+            self.state.transition(State::Running, State::Suspended);
+            self.inner.suspended(event_loop);
+        }
+
+        fn about_to_wait(&mut self, event_loop: &ActiveEventLoop) {
+            self.state.transition(State::Running, State::Waiting);
+            self.inner.about_to_wait(event_loop);
+        }
+
+        fn exiting(&mut self, event_loop: &ActiveEventLoop) {
+            self.state.transition(State::Suspended, State::NotRunning);
+            self.inner.exiting(event_loop);
+        }
+
+        fn user_event(&mut self, event_loop: &ActiveEventLoop, event: T) {
+            self.state.expect(State::Running);
+            self.inner.user_event(event_loop, event);
+        }
+
+        fn window_event(
+            &mut self,
+            event_loop: &ActiveEventLoop,
+            window_id: WindowId,
+            event: WindowEvent,
+        ) {
+            self.state.expect(State::Running);
+            self.inner.window_event(event_loop, window_id, event);
+        }
+
+        fn device_event(
+            &mut self,
+            event_loop: &ActiveEventLoop,
+            device_id: DeviceId,
+            event: DeviceEvent,
+        ) {
+            self.state.expect(State::Running);
+            self.inner.device_event(event_loop, device_id, event);
+        }
+
+        fn memory_warning(&mut self, event_loop: &ActiveEventLoop) {
+            // TODO: What states are allowed when receiving this?
+            self.inner.memory_warning(event_loop);
+        }
+    }
+
+    EnsureEventOrder { inner: handler, state: State::NotRunning }
+}
+
 impl<T> EventLoop<T> {
     /// Start building a new event loop, with the given type as the user event
     /// type.
@@ -216,21 +320,6 @@ impl<T> EventLoop<T> {
         EventLoopBuilder { platform_specific: Default::default(), _p: PhantomData }
     }
 
-    /// See [`run_app`].
-    ///
-    /// [`run_app`]: Self::run_app
-    #[inline]
-    #[deprecated = "use `EventLoop::run_app` instead"]
-    #[cfg(not(all(web_platform, target_feature = "exception-handling")))]
-    pub fn run<F>(self, event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &ActiveEventLoop),
-    {
-        let _span = tracing::debug_span!("winit::EventLoop::run").entered();
-
-        self.event_loop.run(event_handler)
-    }
-
     /// Run the application with the event loop on the calling thread.
     ///
     /// See the [`set_control_flow()`] docs on how to change the event loop's behavior.
@@ -262,7 +351,9 @@ impl<T> EventLoop<T> {
     #[inline]
     #[cfg(not(all(web_platform, target_feature = "exception-handling")))]
     pub fn run_app<A: ApplicationHandler<T>>(self, app: &mut A) -> Result<(), EventLoopError> {
-        self.event_loop.run(|event, event_loop| dispatch_event_for_app(app, event_loop, event))
+        #[cfg(debug_assertions)]
+        let app = &mut ensure_event_order(app);
+        self.event_loop.run_app(app)
     }
 
     /// Creates an [`EventLoopProxy`] that can be used to dispatch user events
@@ -449,7 +540,7 @@ impl ActiveEventLoop {
 
     /// This exits the event loop.
     ///
-    /// See [`LoopExiting`][Event::LoopExiting].
+    /// See [`LoopExiting`][crate::event::Event::LoopExiting].
     pub fn exit(&self) {
         let _span = tracing::debug_span!("winit::ActiveEventLoop::exit",).entered();
 
@@ -618,23 +709,3 @@ impl AsyncRequestSerial {
         Self { serial }
     }
 }
-
-/// Shim for various run APIs.
-#[inline(always)]
-pub(crate) fn dispatch_event_for_app<T: 'static, A: ApplicationHandler<T>>(
-    app: &mut A,
-    event_loop: &ActiveEventLoop,
-    event: Event<T>,
-) {
-    match event {
-        Event::NewEvents(cause) => app.new_events(event_loop, cause),
-        Event::WindowEvent { window_id, event } => app.window_event(event_loop, window_id, event),
-        Event::DeviceEvent { device_id, event } => app.device_event(event_loop, device_id, event),
-        Event::UserEvent(event) => app.user_event(event_loop, event),
-        Event::Suspended => app.suspended(event_loop),
-        Event::Resumed => app.resumed(event_loop),
-        Event::AboutToWait => app.about_to_wait(event_loop),
-        Event::LoopExiting => app.exiting(event_loop),
-        Event::MemoryWarning => app.memory_warning(event_loop),
-    }
-}

src/platform/android.rs

@@ -62,7 +62,7 @@
 //! If your application is currently based on `NativeActivity` via the `ndk-glue` crate and building
 //! with `cargo apk`, then the minimal changes would be:
 //! 1. Remove `ndk-glue` from your `Cargo.toml`
-//! 2. Enable the `"android-native-activity"` feature for Winit: `winit = { version = "0.30.1",
+//! 2. Enable the `"android-native-activity"` feature for Winit: `winit = { version = "0.30.0",
 //!    features = [ "android-native-activity" ] }`
 //! 3. Add an `android_main` entrypoint (as above), instead of using the '`[ndk_glue::main]` proc
 //!    macro from `ndk-macros` (optionally add a dependency on `android_logger` and initialize

src/platform/pump_events.rs

@@ -1,12 +1,13 @@
 use std::time::Duration;
 
 use crate::application::ApplicationHandler;
-use crate::event::Event;
-use crate::event_loop::{self, ActiveEventLoop, EventLoop};
+use crate::event_loop::EventLoop;
 
 /// Additional methods on [`EventLoop`] for pumping events within an external event loop
 pub trait EventLoopExtPumpEvents {
     /// A type provided by the user that can be passed through [`Event::UserEvent`].
+    ///
+    /// [`Event::UserEvent`]: crate::event::Event::UserEvent
     type UserEvent: 'static;
 
     /// Pump the `EventLoop` to check for and dispatch pending events.
@@ -107,30 +108,18 @@ pub trait EventLoopExtPumpEvents {
         &mut self,
         timeout: Option<Duration>,
         app: &mut A,
-    ) -> PumpStatus {
-        #[allow(deprecated)]
-        self.pump_events(timeout, |event, event_loop| {
-            event_loop::dispatch_event_for_app(app, event_loop, event)
-        })
-    }
-
-    /// See [`pump_app_events`].
-    ///
-    /// [`pump_app_events`]: Self::pump_app_events
-    #[deprecated = "use EventLoopExtPumpEvents::pump_app_events"]
-    fn pump_events<F>(&mut self, timeout: Option<Duration>, event_handler: F) -> PumpStatus
-    where
-        F: FnMut(Event<Self::UserEvent>, &ActiveEventLoop);
+    ) -> PumpStatus;
 }
 
 impl<T> EventLoopExtPumpEvents for EventLoop<T> {
     type UserEvent = T;
 
-    fn pump_events<F>(&mut self, timeout: Option<Duration>, event_handler: F) -> PumpStatus
-    where
-        F: FnMut(Event<Self::UserEvent>, &ActiveEventLoop),
-    {
-        self.event_loop.pump_events(timeout, event_handler)
+    fn pump_app_events<A: ApplicationHandler<Self::UserEvent>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
+        self.event_loop.pump_app_events(timeout, app)
     }
 }
 

src/platform/run_on_demand.rs

@@ -1,7 +1,6 @@
 use crate::application::ApplicationHandler;
 use crate::error::EventLoopError;
-use crate::event::Event;
-use crate::event_loop::{self, ActiveEventLoop, EventLoop};
+use crate::event_loop::{ActiveEventLoop, EventLoop};
 
 #[cfg(doc)]
 use crate::{platform::pump_events::EventLoopExtPumpEvents, window::Window};
@@ -9,15 +8,9 @@ use crate::{platform::pump_events::EventLoopExtPumpEvents, window::Window};
 /// Additional methods on [`EventLoop`] to return control flow to the caller.
 pub trait EventLoopExtRunOnDemand {
     /// A type provided by the user that can be passed through [`Event::UserEvent`].
-    type UserEvent: 'static;
-
-    /// See [`run_app_on_demand`].
     ///
-    /// [`run_app_on_demand`]: Self::run_app_on_demand
-    #[deprecated = "use EventLoopExtRunOnDemand::run_app_on_demand"]
-    fn run_on_demand<F>(&mut self, event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<Self::UserEvent>, &ActiveEventLoop);
+    /// [`Event::UserEvent`]: crate::event::Event::UserEvent
+    type UserEvent: 'static;
 
     /// Run the application with the event loop on the calling thread.
     ///
@@ -68,23 +61,18 @@ pub trait EventLoopExtRunOnDemand {
     fn run_app_on_demand<A: ApplicationHandler<Self::UserEvent>>(
         &mut self,
         app: &mut A,
-    ) -> Result<(), EventLoopError> {
-        #[allow(deprecated)]
-        self.run_on_demand(|event, event_loop| {
-            event_loop::dispatch_event_for_app(app, event_loop, event)
-        })
-    }
+    ) -> Result<(), EventLoopError>;
 }
 
 impl<T> EventLoopExtRunOnDemand for EventLoop<T> {
     type UserEvent = T;
 
-    fn run_on_demand<F>(&mut self, event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<Self::UserEvent>, &ActiveEventLoop),
-    {
+    fn run_app_on_demand<A: ApplicationHandler<Self::UserEvent>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
         self.event_loop.window_target().clear_exit();
-        self.event_loop.run_on_demand(event_handler)
+        self.event_loop.run_app_on_demand(app)
     }
 }
 

src/platform/web.rs

@@ -55,8 +55,7 @@ use web_sys::HtmlCanvasElement;
 
 use crate::application::ApplicationHandler;
 use crate::cursor::CustomCursorSource;
-use crate::event::Event;
-use crate::event_loop::{self, ActiveEventLoop, EventLoop};
+use crate::event_loop::{ActiveEventLoop, EventLoop};
 #[cfg(web_platform)]
 use crate::platform_impl::CustomCursorFuture as PlatformCustomCursorFuture;
 use crate::platform_impl::PlatformCustomCursorSource;
@@ -156,7 +155,9 @@ impl WindowAttributesExtWebSys for WindowAttributes {
 
 /// Additional methods on `EventLoop` that are specific to the web.
 pub trait EventLoopExtWebSys {
-    /// A type provided by the user that can be passed through `Event::UserEvent`.
+    /// A type provided by the user that can be passed through [`Event::UserEvent`].
+    ///
+    /// [`Event::UserEvent`]: crate::event::Event::UserEvent
     type UserEvent: 'static;
 
     /// Initializes the winit event loop.
@@ -182,30 +183,13 @@ pub trait EventLoopExtWebSys {
     )]
     /// [^1]: `run_app()` is _not_ available on WASM when the target supports `exception-handling`.
     fn spawn_app<A: ApplicationHandler<Self::UserEvent> + 'static>(self, app: A);
-
-    /// See [`spawn_app`].
-    ///
-    /// [`spawn_app`]: Self::spawn_app
-    #[deprecated = "use EventLoopExtWebSys::spawn_app"]
-    fn spawn<F>(self, event_handler: F)
-    where
-        F: 'static + FnMut(Event<Self::UserEvent>, &ActiveEventLoop);
 }
 
 impl<T> EventLoopExtWebSys for EventLoop<T> {
     type UserEvent = T;
 
-    fn spawn_app<A: ApplicationHandler<Self::UserEvent> + 'static>(self, mut app: A) {
-        self.event_loop.spawn(move |event, event_loop| {
-            event_loop::dispatch_event_for_app(&mut app, event_loop, event)
-        });
-    }
-
-    fn spawn<F>(self, event_handler: F)
-    where
-        F: 'static + FnMut(Event<Self::UserEvent>, &ActiveEventLoop),
-    {
-        self.event_loop.spawn(event_handler)
+    fn spawn_app<A: ApplicationHandler<Self::UserEvent> + 'static>(self, app: A) {
+        self.event_loop.spawn_app(app);
     }
 }
 

src/platform_impl/android/mod.rs

@@ -14,12 +14,13 @@ use android_activity::{
 };
 use tracing::{debug, trace, warn};
 
+use crate::application::ApplicationHandler;
 use crate::cursor::Cursor;
 use crate::dpi::{PhysicalPosition, PhysicalSize, Position, Size};
 use crate::error;
 use crate::error::EventLoopError;
 use crate::event::{self, Force, InnerSizeWriter, StartCause};
-use crate::event_loop::{self, ActiveEventLoop as RootAEL, ControlFlow, DeviceEvents};
+use crate::event_loop::{self, ControlFlow, DeviceEvents};
 use crate::platform::pump_events::PumpStatus;
 use crate::platform_impl::Fullscreen;
 use crate::window::{
@@ -197,27 +198,28 @@ impl<T: 'static> EventLoop<T> {
         })
     }
 
-    fn single_iteration<F>(&mut self, main_event: Option<MainEvent<'_>>, callback: &mut F)
-    where
-        F: FnMut(event::Event<T>, &RootAEL),
-    {
+    fn single_iteration<A: ApplicationHandler<T>>(
+        &mut self,
+        main_event: Option<MainEvent<'_>>,
+        app: &mut A,
+    ) {
         trace!("Mainloop iteration");
 
         let cause = self.cause;
         let mut pending_redraw = self.pending_redraw;
         let mut resized = false;
 
-        callback(event::Event::NewEvents(cause), self.window_target());
+        app.new_events(self.window_target(), cause);
 
         if let Some(event) = main_event {
             trace!("Handling main event {:?}", event);
 
             match event {
                 MainEvent::InitWindow { .. } => {
-                    callback(event::Event::Resumed, self.window_target());
+                    app.resumed(self.window_target());
                 },
                 MainEvent::TerminateWindow { .. } => {
-                    callback(event::Event::Suspended, self.window_target());
+                    app.suspended(self.window_target());
                 },
                 MainEvent::WindowResized { .. } => resized = true,
                 MainEvent::RedrawNeeded { .. } => pending_redraw = true,
@@ -226,23 +228,15 @@ impl<T: 'static> EventLoop<T> {
                 },
                 MainEvent::GainedFocus => {
                     HAS_FOCUS.store(true, Ordering::Relaxed);
-                    callback(
-                        event::Event::WindowEvent {
-                            window_id: window::WindowId(WindowId),
-                            event: event::WindowEvent::Focused(true),
-                        },
-                        self.window_target(),
-                    );
+                    let window_id = window::WindowId(WindowId);
+                    let event = event::WindowEvent::Focused(true);
+                    app.window_event(self.window_target(), window_id, event);
                 },
                 MainEvent::LostFocus => {
                     HAS_FOCUS.store(false, Ordering::Relaxed);
-                    callback(
-                        event::Event::WindowEvent {
-                            window_id: window::WindowId(WindowId),
-                            event: event::WindowEvent::Focused(false),
-                        },
-                        self.window_target(),
-                    );
+                    let window_id = window::WindowId(WindowId);
+                    let event = event::WindowEvent::Focused(false);
+                    app.window_event(self.window_target(), window_id, event);
                 },
                 MainEvent::ConfigChanged { .. } => {
                     let monitor = MonitorHandle::new(self.android_app.clone());
@@ -252,20 +246,19 @@ impl<T: 'static> EventLoop<T> {
                         let new_inner_size = Arc::new(Mutex::new(
                             MonitorHandle::new(self.android_app.clone()).size(),
                         ));
-                        let event = event::Event::WindowEvent {
-                            window_id: window::WindowId(WindowId),
-                            event: event::WindowEvent::ScaleFactorChanged {
-                                inner_size_writer: InnerSizeWriter::new(Arc::downgrade(
-                                    &new_inner_size,
-                                )),
-                                scale_factor,
-                            },
+                        let window_id = window::WindowId(WindowId);
+                        let event = event::WindowEvent::ScaleFactorChanged {
+                            inner_size_writer: InnerSizeWriter::new(Arc::downgrade(
+                                &new_inner_size,
+                            )),
+                            scale_factor,
                         };
-                        callback(event, self.window_target());
+
+                        app.window_event(self.window_target(), window_id, event);
                     }
                 },
                 MainEvent::LowMemory => {
-                    callback(event::Event::MemoryWarning, self.window_target());
+                    app.memory_warning(self.window_target());
                 },
                 MainEvent::Start => {
                     // XXX: how to forward this state to applications?
@@ -313,7 +306,7 @@ impl<T: 'static> EventLoop<T> {
         match android_app.input_events_iter() {
             Ok(mut input_iter) => loop {
                 let read_event =
-                    input_iter.next(|event| self.handle_input_event(&android_app, event, callback));
+                    input_iter.next(|event| self.handle_input_event(&android_app, event, app));
 
                 if !read_event {
                     break;
@@ -327,7 +320,7 @@ impl<T: 'static> EventLoop<T> {
         // Empty the user event buffer
         {
             while let Ok(event) = self.user_events_receiver.try_recv() {
-                callback(crate::event::Event::UserEvent(event), self.window_target());
+                app.user_event(self.window_target(), event);
             }
         }
 
@@ -340,39 +333,32 @@ impl<T: 'static> EventLoop<T> {
                 } else {
                     PhysicalSize::new(0, 0)
                 };
-                let event = event::Event::WindowEvent {
-                    window_id: window::WindowId(WindowId),
-                    event: event::WindowEvent::Resized(size),
-                };
-                callback(event, self.window_target());
+                let window_id = window::WindowId(WindowId);
+                let event = event::WindowEvent::Resized(size);
+                app.window_event(self.window_target(), window_id, event);
             }
 
             pending_redraw |= self.redraw_flag.get_and_reset();
             if pending_redraw {
                 pending_redraw = false;
-                let event = event::Event::WindowEvent {
-                    window_id: window::WindowId(WindowId),
-                    event: event::WindowEvent::RedrawRequested,
-                };
-                callback(event, self.window_target());
+                let window_id = window::WindowId(WindowId);
+                let event = event::WindowEvent::RedrawRequested;
+                app.window_event(self.window_target(), window_id, event);
             }
         }
 
         // This is always the last event we dispatch before poll again
-        callback(event::Event::AboutToWait, self.window_target());
+        app.about_to_wait(self.window_target());
 
         self.pending_redraw = pending_redraw;
     }
 
-    fn handle_input_event<F>(
+    fn handle_input_event<A: ApplicationHandler<T>>(
         &mut self,
         android_app: &AndroidApp,
         event: &InputEvent<'_>,
-        callback: &mut F,
-    ) -> InputStatus
-    where
-        F: FnMut(event::Event<T>, &RootAEL),
-    {
+        app: &mut A,
+    ) -> InputStatus {
         let mut input_status = InputStatus::Handled;
         match event {
             InputEvent::MotionEvent(motion_event) => {
@@ -410,17 +396,16 @@ impl<T: 'static> EventLoop<T> {
                             "Input event {device_id:?}, {phase:?}, loc={location:?}, \
                              pointer={pointer:?}"
                         );
-                        let event = event::Event::WindowEvent {
-                            window_id,
-                            event: event::WindowEvent::Touch(event::Touch {
-                                device_id,
-                                phase,
-                                location,
-                                id: pointer.pointer_id() as u64,
-                                force: Some(Force::Normalized(pointer.pressure() as f64)),
-                            }),
-                        };
-                        callback(event, self.window_target());
+
+                        let event = event::WindowEvent::Touch(event::Touch {
+                            device_id,
+                            phase,
+                            location,
+                            id: pointer.pointer_id() as u64,
+                            force: Some(Force::Normalized(pointer.pressure() as f64)),
+                        });
+
+                        app.window_event(self.window_target(), window_id, event);
                     }
                 }
             },
@@ -448,23 +433,22 @@ impl<T: 'static> EventLoop<T> {
                             &mut self.combining_accent,
                         );
 
-                        let event = event::Event::WindowEvent {
-                            window_id: window::WindowId(WindowId),
-                            event: event::WindowEvent::KeyboardInput {
-                                device_id: event::DeviceId(DeviceId(key.device_id())),
-                                event: event::KeyEvent {
-                                    state,
-                                    physical_key: keycodes::to_physical_key(keycode),
-                                    logical_key: keycodes::to_logical(key_char, keycode),
-                                    location: keycodes::to_location(keycode),
-                                    repeat: key.repeat_count() > 0,
-                                    text: None,
-                                    platform_specific: KeyEventExtra {},
-                                },
-                                is_synthetic: false,
+                        let window_id = window::WindowId(WindowId);
+                        let event = event::WindowEvent::KeyboardInput {
+                            device_id: event::DeviceId(DeviceId(key.device_id())),
+                            event: event::KeyEvent {
+                                state,
+                                physical_key: keycodes::to_physical_key(keycode),
+                                logical_key: keycodes::to_logical(key_char, keycode),
+                                location: keycodes::to_location(keycode),
+                                repeat: key.repeat_count() > 0,
+                                text: None,
+                                platform_specific: KeyEventExtra {},
                             },
+                            is_synthetic: false,
                         };
-                        callback(event, self.window_target());
+
+                        app.window_event(self.window_target(), window_id, event);
                     },
                 }
             },
@@ -476,19 +460,16 @@ impl<T: 'static> EventLoop<T> {
         input_status
     }
 
-    pub fn run<F>(mut self, event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(event::Event<T>, &event_loop::ActiveEventLoop),
-    {
-        self.run_on_demand(event_handler)
+    pub fn run_app<A: ApplicationHandler<T>>(mut self, app: &mut A) -> Result<(), EventLoopError> {
+        self.run_app_on_demand(app)
     }
 
-    pub fn run_on_demand<F>(&mut self, mut event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(event::Event<T>, &event_loop::ActiveEventLoop),
-    {
+    pub fn run_app_on_demand<A: ApplicationHandler<T>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
         loop {
-            match self.pump_events(None, &mut event_handler) {
+            match self.pump_app_events(None, app) {
                 PumpStatus::Exit(0) => {
                     break Ok(());
                 },
@@ -502,10 +483,11 @@ impl<T: 'static> EventLoop<T> {
         }
     }
 
-    pub fn pump_events<F>(&mut self, timeout: Option<Duration>, mut callback: F) -> PumpStatus
-    where
-        F: FnMut(event::Event<T>, &RootAEL),
-    {
+    pub fn pump_app_events<A: ApplicationHandler<T>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
         if !self.loop_running {
             self.loop_running = true;
 
@@ -516,18 +498,18 @@ impl<T: 'static> EventLoop<T> {
             self.cause = StartCause::Init;
 
             // run the initial loop iteration
-            self.single_iteration(None, &mut callback);
+            self.single_iteration(None, app);
         }
 
         // Consider the possibility that the `StartCause::Init` iteration could
         // request to Exit
         if !self.exiting() {
-            self.poll_events_with_timeout(timeout, &mut callback);
+            self.poll_events_with_timeout(timeout, app);
         }
         if self.exiting() {
             self.loop_running = false;
 
-            callback(event::Event::LoopExiting, self.window_target());
+            app.exiting(self.window_target());
 
             PumpStatus::Exit(0)
         } else {
@@ -535,10 +517,11 @@ impl<T: 'static> EventLoop<T> {
         }
     }
 
-    fn poll_events_with_timeout<F>(&mut self, mut timeout: Option<Duration>, mut callback: F)
-    where
-        F: FnMut(event::Event<T>, &RootAEL),
-    {
+    fn poll_events_with_timeout<A: ApplicationHandler<T>>(
+        &mut self,
+        mut timeout: Option<Duration>,
+        app: &mut A,
+    ) {
         let start = Instant::now();
 
         self.pending_redraw |= self.redraw_flag.get_and_reset();
@@ -559,8 +542,8 @@ impl<T: 'static> EventLoop<T> {
                 min_timeout(control_flow_timeout, timeout)
             };
 
-        let app = self.android_app.clone(); // Don't borrow self as part of poll expression
-        app.poll_events(timeout, |poll_event| {
+        let android_app = self.android_app.clone(); // Don't borrow self as part of poll expression
+        android_app.poll_events(timeout, |poll_event| {
             let mut main_event = None;
 
             match poll_event {
@@ -601,7 +584,7 @@ impl<T: 'static> EventLoop<T> {
                 },
             };
 
-            self.single_iteration(main_event, &mut callback);
+            self.single_iteration(main_event, app);
         });
     }
 

src/platform_impl/ios/app_delegate.rs

@@ -1,9 +1,11 @@
 use objc2::{declare_class, mutability, ClassType, DeclaredClass};
-use objc2_foundation::{MainThreadMarker, NSObject};
-use objc2_ui_kit::UIApplication;
+use objc2_foundation::{MainThreadMarker, NSObject, NSObjectProtocol};
+use objc2_ui_kit::{UIApplication, UIWindow};
 
-use super::app_state::{self, send_occluded_event_for_all_windows, EventWrapper};
-use crate::event::Event;
+use super::app_state::{self, EventWrapper};
+use super::window::WinitUIWindow;
+use crate::event::{Event, WindowEvent};
+use crate::window::WindowId as RootWindowId;
 
 declare_class!(
     pub struct AppDelegate;
@@ -38,17 +40,35 @@ declare_class!(
 
         #[method(applicationWillEnterForeground:)]
         fn will_enter_foreground(&self, application: &UIApplication) {
-            send_occluded_event_for_all_windows(application, false);
+            self.send_occluded_event_for_all_windows(application, false);
         }
 
         #[method(applicationDidEnterBackground:)]
         fn did_enter_background(&self, application: &UIApplication) {
-            send_occluded_event_for_all_windows(application, true);
+            self.send_occluded_event_for_all_windows(application, true);
         }
 
         #[method(applicationWillTerminate:)]
         fn will_terminate(&self, application: &UIApplication) {
-            app_state::terminated(application);
+            let mut events = Vec::new();
+            #[allow(deprecated)]
+            for window in application.windows().iter() {
+                if window.is_kind_of::<WinitUIWindow>() {
+                    // SAFETY: We just checked that the window is a `winit` window
+                    let window = unsafe {
+                        let ptr: *const UIWindow = window;
+                        let ptr: *const WinitUIWindow = ptr.cast();
+                        &*ptr
+                    };
+                    events.push(EventWrapper::StaticEvent(Event::WindowEvent {
+                        window_id: RootWindowId(window.id()),
+                        event: WindowEvent::Destroyed,
+                    }));
+                }
+            }
+            let mtm = MainThreadMarker::new().unwrap();
+            app_state::handle_nonuser_events(mtm, events);
+            app_state::terminated(mtm);
         }
 
         #[method(applicationDidReceiveMemoryWarning:)]
@@ -58,3 +78,26 @@ declare_class!(
         }
     }
 );
+
+impl AppDelegate {
+    fn send_occluded_event_for_all_windows(&self, application: &UIApplication, occluded: bool) {
+        let mut events = Vec::new();
+        #[allow(deprecated)]
+        for window in application.windows().iter() {
+            if window.is_kind_of::<WinitUIWindow>() {
+                // SAFETY: We just checked that the window is a `winit` window
+                let window = unsafe {
+                    let ptr: *const UIWindow = window;
+                    let ptr: *const WinitUIWindow = ptr.cast();
+                    &*ptr
+                };
+                events.push(EventWrapper::StaticEvent(Event::WindowEvent {
+                    window_id: RootWindowId(window.id()),
+                    event: WindowEvent::Occluded(occluded),
+                }));
+            }
+        }
+        let mtm = MainThreadMarker::new().unwrap();
+        app_state::handle_nonuser_events(mtm, events);
+    }
+}

src/platform_impl/ios/app_state.rs

@@ -20,7 +20,7 @@ use objc2_foundation::{
     CGRect, CGSize, MainThreadMarker, NSInteger, NSObjectProtocol, NSOperatingSystemVersion,
     NSProcessInfo,
 };
-use objc2_ui_kit::{UIApplication, UICoordinateSpace, UIView, UIWindow};
+use objc2_ui_kit::{UICoordinateSpace, UIView};
 
 use super::window::WinitUIWindow;
 use crate::dpi::PhysicalSize;
@@ -662,28 +662,6 @@ fn handle_user_events(mtm: MainThreadMarker) {
     }
 }
 
-pub(crate) fn send_occluded_event_for_all_windows(application: &UIApplication, occluded: bool) {
-    let mtm = MainThreadMarker::from(application);
-
-    let mut events = Vec::new();
-    #[allow(deprecated)]
-    for window in application.windows().iter() {
-        if window.is_kind_of::<WinitUIWindow>() {
-            // SAFETY: We just checked that the window is a `winit` window
-            let window = unsafe {
-                let ptr: *const UIWindow = window;
-                let ptr: *const WinitUIWindow = ptr.cast();
-                &*ptr
-            };
-            events.push(EventWrapper::StaticEvent(Event::WindowEvent {
-                window_id: RootWindowId(window.id()),
-                event: WindowEvent::Occluded(occluded),
-            }));
-        }
-    }
-    handle_nonuser_events(mtm, events);
-}
-
 pub fn handle_main_events_cleared(mtm: MainThreadMarker) {
     let mut this = AppState::get_mut(mtm);
     if !this.has_launched() || this.has_terminated() {
@@ -718,27 +696,7 @@ pub fn handle_events_cleared(mtm: MainThreadMarker) {
     AppState::get_mut(mtm).events_cleared_transition();
 }
 
-pub(crate) fn terminated(application: &UIApplication) {
-    let mtm = MainThreadMarker::from(application);
-
-    let mut events = Vec::new();
-    #[allow(deprecated)]
-    for window in application.windows().iter() {
-        if window.is_kind_of::<WinitUIWindow>() {
-            // SAFETY: We just checked that the window is a `winit` window
-            let window = unsafe {
-                let ptr: *const UIWindow = window;
-                let ptr: *const WinitUIWindow = ptr.cast();
-                &*ptr
-            };
-            events.push(EventWrapper::StaticEvent(Event::WindowEvent {
-                window_id: RootWindowId(window.id()),
-                event: WindowEvent::Destroyed,
-            }));
-        }
-    }
-    handle_nonuser_events(mtm, events);
-
+pub fn terminated(mtm: MainThreadMarker) {
     let mut this = AppState::get_mut(mtm);
     let mut handler = this.terminated_transition();
     drop(this);

src/platform_impl/ios/event_loop.rs

@@ -16,6 +16,7 @@ use objc2::{msg_send_id, ClassType};
 use objc2_foundation::{MainThreadMarker, NSString};
 use objc2_ui_kit::{UIApplication, UIApplicationMain, UIDevice, UIScreen, UIUserInterfaceIdiom};
 
+use crate::application::ApplicationHandler;
 use crate::error::EventLoopError;
 use crate::event::Event;
 use crate::event_loop::{
@@ -108,17 +109,28 @@ impl OwnedDisplayHandle {
     }
 }
 
-fn map_user_event<T: 'static>(
-    mut handler: impl FnMut(Event<T>, &RootActiveEventLoop),
+fn map_user_event<T: 'static, A: ApplicationHandler<T>>(
+    app: &mut A,
     receiver: mpsc::Receiver<T>,
-) -> impl FnMut(Event<HandlePendingUserEvents>, &RootActiveEventLoop) {
-    move |event, window_target| match event.map_nonuser_event() {
-        Ok(event) => (handler)(event, window_target),
-        Err(_) => {
+) -> impl FnMut(Event<HandlePendingUserEvents>, &RootActiveEventLoop) + '_ {
+    move |event, window_target| match event {
+        Event::NewEvents(cause) => app.new_events(window_target, cause),
+        Event::WindowEvent { window_id, event } => {
+            app.window_event(window_target, window_id, event)
+        },
+        Event::DeviceEvent { device_id, event } => {
+            app.device_event(window_target, device_id, event)
+        },
+        Event::UserEvent(_) => {
             for event in receiver.try_iter() {
-                (handler)(Event::UserEvent(event), window_target);
+                app.user_event(window_target, event);
             }
         },
+        Event::Suspended => app.suspended(window_target),
+        Event::Resumed => app.resumed(window_target),
+        Event::AboutToWait => app.about_to_wait(window_target),
+        Event::LoopExiting => app.exiting(window_target),
+        Event::MemoryWarning => app.memory_warning(window_target),
     }
 }
 
@@ -161,10 +173,7 @@ impl<T: 'static> EventLoop<T> {
         })
     }
 
-    pub fn run<F>(self, handler: F) -> !
-    where
-        F: FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    pub fn run_app<A: ApplicationHandler<T>>(self, app: &mut A) -> ! {
         let application: Option<Retained<UIApplication>> =
             unsafe { msg_send_id![UIApplication::class(), sharedApplication] };
         assert!(
@@ -174,7 +183,7 @@ impl<T: 'static> EventLoop<T> {
              `EventLoop::run_app` calls `UIApplicationMain` on iOS",
         );
 
-        let handler = map_user_event(handler, self.receiver);
+        let handler = map_user_event(app, self.receiver);
 
         let handler = unsafe {
             std::mem::transmute::<

src/platform_impl/linux/mod.rs

@@ -11,6 +11,8 @@ use std::{env, fmt};
 #[cfg(x11_platform)]
 use std::{ffi::CStr, mem::MaybeUninit, os::raw::*, sync::Mutex};
 
+use crate::application::ApplicationHandler;
+use crate::platform::pump_events::PumpStatus;
 #[cfg(x11_platform)]
 use crate::utils::Lazy;
 use smol_str::SmolStr;
@@ -19,12 +21,9 @@ use smol_str::SmolStr;
 use self::x11::{X11Error, XConnection, XError, XNotSupported};
 use crate::dpi::{PhysicalPosition, PhysicalSize, Position, Size};
 use crate::error::{EventLoopError, ExternalError, NotSupportedError, OsError as RootOsError};
-use crate::event_loop::{
-    ActiveEventLoop as RootELW, AsyncRequestSerial, ControlFlow, DeviceEvents, EventLoopClosed,
-};
+use crate::event_loop::{AsyncRequestSerial, ControlFlow, DeviceEvents, EventLoopClosed};
 use crate::icon::Icon;
 use crate::keyboard::Key;
-use crate::platform::pump_events::PumpStatus;
 #[cfg(x11_platform)]
 use crate::platform::x11::{WindowType as XWindowType, XlibErrorHook};
 use crate::window::{
@@ -799,25 +798,23 @@ impl<T: 'static> EventLoop<T> {
         x11_or_wayland!(match self; EventLoop(evlp) => evlp.create_proxy(); as EventLoopProxy)
     }
 
-    pub fn run<F>(mut self, callback: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(crate::event::Event<T>, &RootELW),
-    {
-        self.run_on_demand(callback)
+    pub fn run_app<A: ApplicationHandler<T>>(self, app: &mut A) -> Result<(), EventLoopError> {
+        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run_app(app))
     }
 
-    pub fn run_on_demand<F>(&mut self, callback: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(crate::event::Event<T>, &RootELW),
-    {
-        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run_on_demand(callback))
+    pub fn run_app_on_demand<A: ApplicationHandler<T>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
+        x11_or_wayland!(match self; EventLoop(evlp) => evlp.run_app_on_demand(app))
     }
 
-    pub fn pump_events<F>(&mut self, timeout: Option<Duration>, callback: F) -> PumpStatus
-    where
-        F: FnMut(crate::event::Event<T>, &RootELW),
-    {
-        x11_or_wayland!(match self; EventLoop(evlp) => evlp.pump_events(timeout, callback))
+    pub fn pump_app_events<A: ApplicationHandler<T>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
+        x11_or_wayland!(match self; EventLoop(evlp) => evlp.pump_app_events(timeout, app))
     }
 
     pub fn window_target(&self) -> &crate::event_loop::ActiveEventLoop {

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

@@ -14,6 +14,7 @@ use sctk::reexports::calloop::Error as CalloopError;
 use sctk::reexports::calloop_wayland_source::WaylandSource;
 use sctk::reexports::client::{globals, Connection, QueueHandle};
 
+use crate::application::ApplicationHandler;
 use crate::cursor::OnlyCursorImage;
 use crate::dpi::LogicalSize;
 use crate::error::{EventLoopError, OsError as RootOsError};
@@ -173,12 +174,16 @@ impl<T: 'static> EventLoop<T> {
         Ok(event_loop)
     }
 
-    pub fn run_on_demand<F>(&mut self, mut event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    pub fn run_app<A: ApplicationHandler<T>>(mut self, app: &mut A) -> Result<(), EventLoopError> {
+        self.run_app_on_demand(app)
+    }
+
+    pub fn run_app_on_demand<A: ApplicationHandler<T>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
         let exit = loop {
-            match self.pump_events(None, &mut event_handler) {
+            match self.pump_app_events(None, app) {
                 PumpStatus::Exit(0) => {
                     break Ok(());
                 },
@@ -200,26 +205,27 @@ impl<T: 'static> EventLoop<T> {
         exit
     }
 
-    pub fn pump_events<F>(&mut self, timeout: Option<Duration>, mut callback: F) -> PumpStatus
-    where
-        F: FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    pub fn pump_app_events<A: ApplicationHandler<T>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
         if !self.loop_running {
             self.loop_running = true;
 
             // Run the initial loop iteration.
-            self.single_iteration(&mut callback, StartCause::Init);
+            self.single_iteration(app, StartCause::Init);
         }
 
         // Consider the possibility that the `StartCause::Init` iteration could
         // request to Exit.
         if !self.exiting() {
-            self.poll_events_with_timeout(timeout, &mut callback);
+            self.poll_events_with_timeout(timeout, app);
         }
         if let Some(code) = self.exit_code() {
             self.loop_running = false;
 
-            callback(Event::LoopExiting, self.window_target());
+            app.exiting(&self.window_target);
 
             PumpStatus::Exit(code)
         } else {
@@ -227,10 +233,11 @@ impl<T: 'static> EventLoop<T> {
         }
     }
 
-    pub fn poll_events_with_timeout<F>(&mut self, mut timeout: Option<Duration>, mut callback: F)
-    where
-        F: FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    pub fn poll_events_with_timeout<A: ApplicationHandler<T>>(
+        &mut self,
+        mut timeout: Option<Duration>,
+        app: &mut A,
+    ) {
         let cause = loop {
             let start = Instant::now();
 
@@ -292,13 +299,10 @@ impl<T: 'static> EventLoop<T> {
             break cause;
         };
 
-        self.single_iteration(&mut callback, cause);
+        self.single_iteration(app, cause);
     }
 
-    fn single_iteration<F>(&mut self, callback: &mut F, cause: StartCause)
-    where
-        F: FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    fn single_iteration<A: ApplicationHandler<T>>(&mut self, app: &mut A, cause: StartCause) {
         // NOTE currently just indented to simplify the diff
 
         // We retain these grow-only scratch buffers as part of the EventLoop
@@ -309,18 +313,18 @@ impl<T: 'static> EventLoop<T> {
         let mut buffer_sink = std::mem::take(&mut self.buffer_sink);
         let mut window_ids = std::mem::take(&mut self.window_ids);
 
-        callback(Event::NewEvents(cause), &self.window_target);
+        app.new_events(&self.window_target, cause);
 
         // NB: For consistency all platforms must emit a 'resumed' event even though Wayland
         // applications don't themselves have a formal suspend/resume lifecycle.
         if cause == StartCause::Init {
-            callback(Event::Resumed, &self.window_target);
+            app.resumed(&self.window_target);
         }
 
         // Handle pending user events. We don't need back buffer, since we can't dispatch
         // user events indirectly via callback to the user.
         for user_event in self.pending_user_events.borrow_mut().drain(..) {
-            callback(Event::UserEvent(user_event), &self.window_target);
+            app.user_event(&self.window_target, user_event);
         }
 
         // Drain the pending compositor updates.
@@ -341,18 +345,13 @@ impl<T: 'static> EventLoop<T> {
                 let old_physical_size = physical_size;
 
                 let new_inner_size = Arc::new(Mutex::new(physical_size));
-                callback(
-                    Event::WindowEvent {
-                        window_id: crate::window::WindowId(window_id),
-                        event: WindowEvent::ScaleFactorChanged {
-                            scale_factor,
-                            inner_size_writer: InnerSizeWriter::new(Arc::downgrade(
-                                &new_inner_size,
-                            )),
-                        },
-                    },
-                    &self.window_target,
-                );
+                let root_window_id = crate::window::WindowId(window_id);
+                let event = WindowEvent::ScaleFactorChanged {
+                    scale_factor,
+                    inner_size_writer: InnerSizeWriter::new(Arc::downgrade(&new_inner_size)),
+                };
+
+                app.window_event(&self.window_target, root_window_id, event);
 
                 let physical_size = *new_inner_size.lock().unwrap();
                 drop(new_inner_size);
@@ -395,23 +394,14 @@ impl<T: 'static> EventLoop<T> {
                     size
                 });
 
-                callback(
-                    Event::WindowEvent {
-                        window_id: crate::window::WindowId(window_id),
-                        event: WindowEvent::Resized(physical_size),
-                    },
-                    &self.window_target,
-                );
+                let window_id = crate::window::WindowId(window_id);
+                let event = WindowEvent::Resized(physical_size);
+                app.window_event(&self.window_target, window_id, event);
             }
 
             if compositor_update.close_window {
-                callback(
-                    Event::WindowEvent {
-                        window_id: crate::window::WindowId(window_id),
-                        event: WindowEvent::CloseRequested,
-                    },
-                    &self.window_target,
-                );
+                let window_id = crate::window::WindowId(window_id);
+                app.window_event(&self.window_target, window_id, WindowEvent::CloseRequested);
             }
         }
 
@@ -420,8 +410,15 @@ impl<T: 'static> EventLoop<T> {
             buffer_sink.append(&mut state.window_events_sink.lock().unwrap());
         });
         for event in buffer_sink.drain() {
-            let event = event.map_nonuser_event().unwrap();
-            callback(event, &self.window_target);
+            match event {
+                Event::WindowEvent { window_id, event } => {
+                    app.window_event(&self.window_target, window_id, event)
+                },
+                Event::DeviceEvent { device_id, event } => {
+                    app.device_event(&self.window_target, device_id, event)
+                },
+                _ => unreachable!("event which is neither device nor window event."),
+            }
         }
 
         // Handle non-synthetic events.
@@ -429,8 +426,15 @@ impl<T: 'static> EventLoop<T> {
             buffer_sink.append(&mut state.events_sink);
         });
         for event in buffer_sink.drain() {
-            let event = event.map_nonuser_event().unwrap();
-            callback(event, &self.window_target);
+            match event {
+                Event::WindowEvent { window_id, event } => {
+                    app.window_event(&self.window_target, window_id, event)
+                },
+                Event::DeviceEvent { device_id, event } => {
+                    app.device_event(&self.window_target, device_id, event)
+                },
+                _ => unreachable!("event which is neither device nor window event."),
+            }
         }
 
         // Collect the window ids
@@ -466,10 +470,8 @@ impl<T: 'static> EventLoop<T> {
             });
 
             if let Some(event) = event {
-                callback(
-                    Event::WindowEvent { window_id: crate::window::WindowId(*window_id), event },
-                    &self.window_target,
-                );
+                let window_id = crate::window::WindowId(*window_id);
+                app.window_event(&self.window_target, window_id, event);
             }
         }
 
@@ -479,7 +481,7 @@ impl<T: 'static> EventLoop<T> {
         });
 
         // This is always the last event we dispatch before poll again
-        callback(Event::AboutToWait, &self.window_target);
+        app.about_to_wait(&self.window_target);
 
         // Update the window frames and schedule redraws.
         let mut wake_up = false;

src/platform_impl/linux/x11/mod.rs

@@ -27,6 +27,7 @@ use x11rb::protocol::xproto::{self, ConnectionExt as _};
 use x11rb::x11_utils::X11Error as LogicalError;
 use x11rb::xcb_ffi::ReplyOrIdError;
 
+use crate::application::ApplicationHandler;
 use crate::error::{EventLoopError, OsError as RootOsError};
 use crate::event::{Event, StartCause, WindowEvent};
 use crate::event_loop::{ActiveEventLoop as RootAEL, ControlFlow, DeviceEvents, EventLoopClosed};
@@ -379,12 +380,16 @@ impl<T: 'static> EventLoop<T> {
         &self.event_processor.target
     }
 
-    pub fn run_on_demand<F>(&mut self, mut event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
+    pub fn run_app<A: ApplicationHandler<T>>(mut self, app: &mut A) -> Result<(), EventLoopError> {
+        self.run_app_on_demand(app)
+    }
+
+    pub fn run_app_on_demand<A: ApplicationHandler<T>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
         let exit = loop {
-            match self.pump_events(None, &mut event_handler) {
+            match self.pump_app_events(None, app) {
                 PumpStatus::Exit(0) => {
                     break Ok(());
                 },
@@ -409,26 +414,27 @@ impl<T: 'static> EventLoop<T> {
         exit
     }
 
-    pub fn pump_events<F>(&mut self, timeout: Option<Duration>, mut callback: F) -> PumpStatus
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
+    pub fn pump_app_events<A: ApplicationHandler<T>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
         if !self.loop_running {
             self.loop_running = true;
 
             // run the initial loop iteration
-            self.single_iteration(&mut callback, StartCause::Init);
+            self.single_iteration(app, StartCause::Init);
         }
 
         // Consider the possibility that the `StartCause::Init` iteration could
         // request to Exit.
         if !self.exiting() {
-            self.poll_events_with_timeout(timeout, &mut callback);
+            self.poll_events_with_timeout(timeout, app);
         }
         if let Some(code) = self.exit_code() {
             self.loop_running = false;
 
-            callback(Event::LoopExiting, self.window_target());
+            app.exiting(self.window_target());
 
             PumpStatus::Exit(code)
         } else {
@@ -442,10 +448,11 @@ impl<T: 'static> EventLoop<T> {
             || self.redraw_receiver.has_incoming()
     }
 
-    pub fn poll_events_with_timeout<F>(&mut self, mut timeout: Option<Duration>, mut callback: F)
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
+    pub fn poll_events_with_timeout<A: ApplicationHandler<T>>(
+        &mut self,
+        mut timeout: Option<Duration>,
+        app: &mut A,
+    ) {
         let start = Instant::now();
 
         let has_pending = self.has_pending();
@@ -503,23 +510,20 @@ impl<T: 'static> EventLoop<T> {
             return;
         }
 
-        self.single_iteration(&mut callback, cause);
+        self.single_iteration(app, cause);
     }
 
-    fn single_iteration<F>(&mut self, callback: &mut F, cause: StartCause)
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
-        callback(Event::NewEvents(cause), &self.event_processor.target);
+    fn single_iteration<A: ApplicationHandler<T>>(&mut self, app: &mut A, cause: StartCause) {
+        app.new_events(&self.event_processor.target, cause);
 
         // NB: For consistency all platforms must emit a 'resumed' event even though X11
         // applications don't themselves have a formal suspend/resume lifecycle.
         if cause == StartCause::Init {
-            callback(Event::Resumed, &self.event_processor.target);
+            app.resumed(&self.event_processor.target)
         }
 
         // Process all pending events
-        self.drain_events(callback);
+        self.drain_events(app);
 
         // Empty activation tokens.
         while let Ok((window_id, serial)) = self.activation_receiver.try_recv() {
@@ -529,14 +533,12 @@ impl<T: 'static> EventLoop<T> {
 
             match token {
                 Some(Ok(token)) => {
-                    let event = Event::WindowEvent {
-                        window_id: crate::window::WindowId(window_id),
-                        event: WindowEvent::ActivationTokenDone {
-                            serial,
-                            token: crate::window::ActivationToken::_new(token),
-                        },
+                    let window_id = crate::window::WindowId(window_id);
+                    let event = WindowEvent::ActivationTokenDone {
+                        serial,
+                        token: crate::window::ActivationToken::_new(token),
                     };
-                    callback(event, &self.event_processor.target)
+                    app.window_event(&self.event_processor.target, window_id, event);
                 },
                 Some(Err(e)) => {
                     tracing::error!("Failed to get activation token: {}", e);
@@ -548,7 +550,7 @@ impl<T: 'static> EventLoop<T> {
         // Empty the user event buffer
         {
             while let Ok(event) = self.user_receiver.try_recv() {
-                callback(Event::UserEvent(event), &self.event_processor.target);
+                app.user_event(&self.event_processor.target, event);
             }
         }
 
@@ -562,28 +564,24 @@ impl<T: 'static> EventLoop<T> {
 
             for window_id in windows {
                 let window_id = crate::window::WindowId(window_id);
-                callback(
-                    Event::WindowEvent { window_id, event: WindowEvent::RedrawRequested },
+                app.window_event(
                     &self.event_processor.target,
+                    window_id,
+                    WindowEvent::RedrawRequested,
                 );
             }
         }
 
         // This is always the last event we dispatch before poll again
-        {
-            callback(Event::AboutToWait, &self.event_processor.target);
-        }
+        app.about_to_wait(&self.event_processor.target);
     }
 
-    fn drain_events<F>(&mut self, callback: &mut F)
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
+    fn drain_events<A: ApplicationHandler<T>>(&mut self, app: &mut A) {
         let mut xev = MaybeUninit::uninit();
 
         while unsafe { self.event_processor.poll_one_event(xev.as_mut_ptr()) } {
             let mut xev = unsafe { xev.assume_init() };
-            self.event_processor.process_event(&mut xev, |window_target, event| {
+            self.event_processor.process_event(&mut xev, |window_target, event: Event<T>| {
                 if let Event::WindowEvent {
                     window_id: crate::window::WindowId(wid),
                     event: WindowEvent::RedrawRequested,
@@ -592,7 +590,15 @@ impl<T: 'static> EventLoop<T> {
                     let window_target = EventProcessor::window_target(window_target);
                     window_target.redraw_sender.send(wid).unwrap();
                 } else {
-                    callback(event, window_target);
+                    match event {
+                        Event::WindowEvent { window_id, event } => {
+                            app.window_event(window_target, window_id, event)
+                        },
+                        Event::DeviceEvent { device_id, event } => {
+                            app.device_event(window_target, device_id, event)
+                        },
+                        _ => unreachable!("event which is neither device nor window event."),
+                    }
                 }
             });
         }

src/platform_impl/macos/app.rs

@@ -4,7 +4,7 @@ use objc2::{declare_class, msg_send, mutability, ClassType, DeclaredClass};
 use objc2_app_kit::{NSApplication, NSEvent, NSEventModifierFlags, NSEventType, NSResponder};
 use objc2_foundation::{MainThreadMarker, NSObject};
 
-use super::app_state::ApplicationDelegate;
+use super::app_delegate::ApplicationDelegate;
 use crate::event::{DeviceEvent, ElementState};
 
 declare_class!(
@@ -57,27 +57,25 @@ fn maybe_dispatch_device_event(delegate: &ApplicationDelegate, event: &NSEvent)
             let delta_y = unsafe { event.deltaY() } as f64;
 
             if delta_x != 0.0 {
-                delegate.maybe_queue_device_event(DeviceEvent::Motion { axis: 0, value: delta_x });
+                delegate.queue_device_event(DeviceEvent::Motion { axis: 0, value: delta_x });
             }
 
             if delta_y != 0.0 {
-                delegate.maybe_queue_device_event(DeviceEvent::Motion { axis: 1, value: delta_y })
+                delegate.queue_device_event(DeviceEvent::Motion { axis: 1, value: delta_y })
             }
 
             if delta_x != 0.0 || delta_y != 0.0 {
-                delegate.maybe_queue_device_event(DeviceEvent::MouseMotion {
-                    delta: (delta_x, delta_y),
-                });
+                delegate.queue_device_event(DeviceEvent::MouseMotion { delta: (delta_x, delta_y) });
             }
         },
         NSEventType::LeftMouseDown | NSEventType::RightMouseDown | NSEventType::OtherMouseDown => {
-            delegate.maybe_queue_device_event(DeviceEvent::Button {
+            delegate.queue_device_event(DeviceEvent::Button {
                 button: unsafe { event.buttonNumber() } as u32,
                 state: ElementState::Pressed,
             });
         },
         NSEventType::LeftMouseUp | NSEventType::RightMouseUp | NSEventType::OtherMouseUp => {
-            delegate.maybe_queue_device_event(DeviceEvent::Button {
+            delegate.queue_device_event(DeviceEvent::Button {
                 button: unsafe { event.buttonNumber() } as u32,
                 state: ElementState::Released,
             });

src/platform_impl/macos/app_delegate.rs

@@ -1,27 +1,40 @@
 use std::cell::{Cell, RefCell};
+use std::collections::VecDeque;
 use std::mem;
 use std::rc::Weak;
+use std::sync::{Arc, Mutex};
 use std::time::Instant;
 
 use objc2::rc::Retained;
+use objc2::runtime::AnyObject;
 use objc2::{declare_class, msg_send_id, mutability, ClassType, DeclaredClass};
 use objc2_app_kit::{NSApplication, NSApplicationActivationPolicy, NSApplicationDelegate};
-use objc2_foundation::{MainThreadMarker, NSNotification, NSObject, NSObjectProtocol};
+use objc2_foundation::{MainThreadMarker, NSObject, NSObjectProtocol, NSSize};
 
 use super::event_handler::EventHandler;
 use super::event_loop::{stop_app_immediately, ActiveEventLoop, PanicInfo};
 use super::observer::{EventLoopWaker, RunLoop};
+use super::window::WinitWindow;
 use super::{menu, WindowId, DEVICE_ID};
-use crate::event::{DeviceEvent, Event, StartCause, WindowEvent};
+use crate::dpi::PhysicalSize;
+use crate::event::{DeviceEvent, Event, InnerSizeWriter, StartCause, WindowEvent};
 use crate::event_loop::{ActiveEventLoop as RootActiveEventLoop, ControlFlow};
 use crate::window::WindowId as RootWindowId;
 
 #[derive(Debug)]
-pub(super) struct AppState {
-    activation_policy: NSApplicationActivationPolicy,
+struct Policy(NSApplicationActivationPolicy);
+
+impl Default for Policy {
+    fn default() -> Self {
+        Self(NSApplicationActivationPolicy::Regular)
+    }
+}
+
+#[derive(Debug, Default)]
+pub(super) struct State {
+    activation_policy: Policy,
     default_menu: bool,
     activate_ignoring_other_apps: bool,
-    run_loop: RunLoop,
     event_handler: EventHandler,
     stop_on_launch: Cell<bool>,
     stop_before_wait: Cell<bool>,
@@ -37,6 +50,7 @@ pub(super) struct AppState {
     waker: RefCell<EventLoopWaker>,
     start_time: Cell<Option<Instant>>,
     wait_timeout: Cell<Option<Instant>>,
+    pending_events: RefCell<VecDeque<QueuedEvent>>,
     pending_redraw: RefCell<Vec<WindowId>>,
     // NOTE: This is strongly referenced by our `NSWindowDelegate` and our `NSView` subclass, and
     // as such should be careful to not add fields that, in turn, strongly reference those.
@@ -53,20 +67,62 @@ declare_class!(
     }
 
     impl DeclaredClass for ApplicationDelegate {
-        type Ivars = AppState;
+        type Ivars = State;
     }
 
     unsafe impl NSObjectProtocol for ApplicationDelegate {}
 
     unsafe impl NSApplicationDelegate for ApplicationDelegate {
+        // NOTE: This will, globally, only be run once, no matter how many
+        // `EventLoop`s the user creates.
         #[method(applicationDidFinishLaunching:)]
-        fn app_did_finish_launching(&self, notification: &NSNotification) {
-            self.did_finish_launching(notification)
+        fn did_finish_launching(&self, _sender: Option<&AnyObject>) {
+            trace_scope!("applicationDidFinishLaunching:");
+            self.ivars().is_launched.set(true);
+
+            let mtm = MainThreadMarker::from(self);
+            let app = NSApplication::sharedApplication(mtm);
+            // We need to delay setting the activation policy and activating the app
+            // until `applicationDidFinishLaunching` has been called. Otherwise the
+            // menu bar is initially unresponsive on macOS 10.15.
+            app.setActivationPolicy(self.ivars().activation_policy.0);
+
+            window_activation_hack(&app);
+            #[allow(deprecated)]
+            app.activateIgnoringOtherApps(self.ivars().activate_ignoring_other_apps);
+
+            if self.ivars().default_menu {
+                // The menubar initialization should be before the `NewEvents` event, to allow
+                // overriding of the default menu even if it's created
+                menu::initialize(&app);
+            }
+
+            self.ivars().waker.borrow_mut().start();
+
+            self.set_is_running(true);
+            self.dispatch_init_events();
+
+            // If the application is being launched via `EventLoop::pump_app_events()` then we'll
+            // want to stop the app once it is launched (and return to the external loop)
+            //
+            // In this case we still want to consider Winit's `EventLoop` to be "running",
+            // so we call `start_running()` above.
+            if self.ivars().stop_on_launch.get() {
+                // NOTE: the original idea had been to only stop the underlying `RunLoop`
+                // for the app but that didn't work as expected (`-[NSApplication run]`
+                // effectively ignored the attempt to stop the RunLoop and re-started it).
+                //
+                // So we return from `pump_events` by stopping the application.
+                let app = NSApplication::sharedApplication(mtm);
+                stop_app_immediately(&app);
+            }
         }
 
         #[method(applicationWillTerminate:)]
-        fn app_will_terminate(&self, notification: &NSNotification) {
-            self.will_terminate(notification)
+        fn will_terminate(&self, _sender: Option<&AnyObject>) {
+            trace_scope!("applicationWillTerminate:");
+            // TODO: Notify every window that it will be destroyed, like done in iOS?
+            self.internal_exit();
         }
     }
 );
@@ -78,78 +134,15 @@ impl ApplicationDelegate {
         default_menu: bool,
         activate_ignoring_other_apps: bool,
     ) -> Retained<Self> {
-        let this = mtm.alloc().set_ivars(AppState {
-            activation_policy,
+        let this = mtm.alloc().set_ivars(State {
+            activation_policy: Policy(activation_policy),
             default_menu,
             activate_ignoring_other_apps,
-            run_loop: RunLoop::main(mtm),
-            event_handler: EventHandler::new(),
-            stop_on_launch: Cell::new(false),
-            stop_before_wait: Cell::new(false),
-            stop_after_wait: Cell::new(false),
-            stop_on_redraw: Cell::new(false),
-            is_launched: Cell::new(false),
-            is_running: Cell::new(false),
-            exit: Cell::new(false),
-            control_flow: Cell::new(ControlFlow::default()),
-            waker: RefCell::new(EventLoopWaker::new()),
-            start_time: Cell::new(None),
-            wait_timeout: Cell::new(None),
-            pending_redraw: RefCell::new(vec![]),
+            ..Default::default()
         });
         unsafe { msg_send_id![super(this), init] }
     }
 
-    // NOTE: This will, globally, only be run once, no matter how many
-    // `EventLoop`s the user creates.
-    fn did_finish_launching(&self, _notification: &NSNotification) {
-        trace_scope!("applicationDidFinishLaunching:");
-        self.ivars().is_launched.set(true);
-
-        let mtm = MainThreadMarker::from(self);
-        let app = NSApplication::sharedApplication(mtm);
-        // We need to delay setting the activation policy and activating the app
-        // until `applicationDidFinishLaunching` has been called. Otherwise the
-        // menu bar is initially unresponsive on macOS 10.15.
-        app.setActivationPolicy(self.ivars().activation_policy);
-
-        window_activation_hack(&app);
-        #[allow(deprecated)]
-        app.activateIgnoringOtherApps(self.ivars().activate_ignoring_other_apps);
-
-        if self.ivars().default_menu {
-            // The menubar initialization should be before the `NewEvents` event, to allow
-            // overriding of the default menu even if it's created
-            menu::initialize(&app);
-        }
-
-        self.ivars().waker.borrow_mut().start();
-
-        self.set_is_running(true);
-        self.dispatch_init_events();
-
-        // If the application is being launched via `EventLoop::pump_app_events()` then we'll
-        // want to stop the app once it is launched (and return to the external loop)
-        //
-        // In this case we still want to consider Winit's `EventLoop` to be "running",
-        // so we call `start_running()` above.
-        if self.ivars().stop_on_launch.get() {
-            // NOTE: the original idea had been to only stop the underlying `RunLoop`
-            // for the app but that didn't work as expected (`-[NSApplication run]`
-            // effectively ignored the attempt to stop the RunLoop and re-started it).
-            //
-            // So we return from `pump_events` by stopping the application.
-            let app = NSApplication::sharedApplication(mtm);
-            stop_app_immediately(&app);
-        }
-    }
-
-    fn will_terminate(&self, _notification: &NSNotification) {
-        trace_scope!("applicationWillTerminate:");
-        // TODO: Notify every window that it will be destroyed, like done in iOS?
-        self.internal_exit();
-    }
-
     pub fn get(mtm: MainThreadMarker) -> Retained<Self> {
         let app = NSApplication::sharedApplication(mtm);
         let delegate =
@@ -200,6 +193,7 @@ impl ApplicationDelegate {
     /// 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) {
+        self.handle_event(Event::Suspended);
         self.handle_event(Event::LoopExiting);
 
         self.set_is_running(false);
@@ -241,16 +235,28 @@ impl ApplicationDelegate {
         self.ivars().control_flow.get()
     }
 
-    pub fn maybe_queue_window_event(&self, window_id: WindowId, event: WindowEvent) {
-        self.maybe_queue_event(Event::WindowEvent { window_id: RootWindowId(window_id), event });
+    pub fn queue_window_event(&self, window_id: WindowId, event: WindowEvent) {
+        self.ivars()
+            .pending_events
+            .borrow_mut()
+            .push_back(QueuedEvent::WindowEvent(window_id, event));
     }
 
-    pub fn handle_window_event(&self, window_id: WindowId, event: WindowEvent) {
-        self.handle_event(Event::WindowEvent { window_id: RootWindowId(window_id), event });
+    pub fn queue_device_event(&self, event: DeviceEvent) {
+        self.ivars().pending_events.borrow_mut().push_back(QueuedEvent::DeviceEvent(event));
     }
 
-    pub fn maybe_queue_device_event(&self, event: DeviceEvent) {
-        self.maybe_queue_event(Event::DeviceEvent { device_id: DEVICE_ID, event });
+    pub fn queue_static_scale_factor_changed_event(
+        &self,
+        window: Retained<WinitWindow>,
+        suggested_size: PhysicalSize<u32>,
+        scale_factor: f64,
+    ) {
+        self.ivars().pending_events.borrow_mut().push_back(QueuedEvent::ScaleFactorChanged {
+            window,
+            suggested_size,
+            scale_factor,
+        });
     }
 
     pub fn handle_redraw(&self, window_id: WindowId) {
@@ -278,27 +284,9 @@ impl ApplicationDelegate {
         if !pending_redraw.contains(&window_id) {
             pending_redraw.push(window_id);
         }
-        self.ivars().run_loop.wakeup();
+        unsafe { RunLoop::get() }.wakeup();
     }
 
-    #[track_caller]
-    fn maybe_queue_event(&self, event: Event<HandlePendingUserEvents>) {
-        // Most programmer actions in AppKit (e.g. change window fullscreen, set focused, etc.)
-        // result in an event being queued, and applied at a later point.
-        //
-        // However, it is not documented which actions do this, and which ones are done immediately,
-        // so to make sure that we don't encounter re-entrancy issues, we first check if we're
-        // currently handling another event, and if we are, we queue the event instead.
-        if !self.ivars().event_handler.in_use() {
-            self.handle_event(event);
-        } else {
-            tracing::debug!(?event, "had to queue event since another is currently being handled");
-            let this = self.retain();
-            self.ivars().run_loop.queue_closure(move || this.handle_event(event));
-        }
-    }
-
-    #[track_caller]
     fn handle_event(&self, event: Event<HandlePendingUserEvents>) {
         self.ivars().event_handler.handle_event(event, &ActiveEventLoop::new_root(self.retain()))
     }
@@ -360,6 +348,49 @@ impl ApplicationDelegate {
 
         self.handle_event(Event::UserEvent(HandlePendingUserEvents));
 
+        let events = mem::take(&mut *self.ivars().pending_events.borrow_mut());
+        for event in events {
+            match event {
+                QueuedEvent::WindowEvent(window_id, event) => {
+                    self.handle_event(Event::WindowEvent {
+                        window_id: RootWindowId(window_id),
+                        event,
+                    });
+                },
+                QueuedEvent::DeviceEvent(event) => {
+                    self.handle_event(Event::DeviceEvent { device_id: DEVICE_ID, event });
+                },
+                QueuedEvent::ScaleFactorChanged { window, suggested_size, scale_factor } => {
+                    let new_inner_size = Arc::new(Mutex::new(suggested_size));
+                    let scale_factor_changed_event = Event::WindowEvent {
+                        window_id: RootWindowId(window.id()),
+                        event: WindowEvent::ScaleFactorChanged {
+                            scale_factor,
+                            inner_size_writer: InnerSizeWriter::new(Arc::downgrade(
+                                &new_inner_size,
+                            )),
+                        },
+                    };
+
+                    self.handle_event(scale_factor_changed_event);
+
+                    let physical_size = *new_inner_size.lock().unwrap();
+                    drop(new_inner_size);
+                    if physical_size != suggested_size {
+                        let logical_size = physical_size.to_logical(scale_factor);
+                        let size = NSSize::new(logical_size.width, logical_size.height);
+                        window.setContentSize(size);
+                    }
+
+                    let resized_event = Event::WindowEvent {
+                        window_id: RootWindowId(window.id()),
+                        event: WindowEvent::Resized(physical_size),
+                    };
+                    self.handle_event(resized_event);
+                },
+            }
+        }
+
         let redraw = mem::take(&mut *self.ivars().pending_redraw.borrow_mut());
         for window_id in redraw {
             self.handle_event(Event::WindowEvent {
@@ -390,6 +421,17 @@ impl ApplicationDelegate {
     }
 }
 
+#[derive(Debug)]
+pub(crate) enum QueuedEvent {
+    WindowEvent(WindowId, WindowEvent),
+    DeviceEvent(DeviceEvent),
+    ScaleFactorChanged {
+        window: Retained<WinitWindow>,
+        suggested_size: PhysicalSize<u32>,
+        scale_factor: f64,
+    },
+}
+
 #[derive(Debug)]
 pub(crate) struct HandlePendingUserEvents;
 

src/platform_impl/macos/event_handler.rs

@@ -1,7 +1,7 @@
 use std::cell::RefCell;
 use std::{fmt, mem};
 
-use super::app_state::HandlePendingUserEvents;
+use super::app_delegate::HandlePendingUserEvents;
 use crate::event::Event;
 use crate::event_loop::ActiveEventLoop as RootActiveEventLoop;
 
@@ -16,7 +16,7 @@ impl fmt::Debug for EventHandlerData {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub(crate) struct EventHandler {
     /// This can be in the following states:
     /// - Not registered by the event loop (None).
@@ -26,10 +26,6 @@ pub(crate) struct EventHandler {
 }
 
 impl EventHandler {
-    pub(crate) const fn new() -> Self {
-        Self { inner: RefCell::new(None) }
-    }
-
     /// Set the event loop handler for the duration of the given closure.
     ///
     /// This is similar to using the `scoped-tls` or `scoped-tls-hkt` crates

src/platform_impl/macos/event_loop.rs

@@ -21,10 +21,11 @@ use objc2_app_kit::{NSApplication, NSApplicationActivationPolicy, NSWindow};
 use objc2_foundation::{MainThreadMarker, NSObjectProtocol};
 
 use super::app::WinitApplication;
-use super::app_state::{ApplicationDelegate, HandlePendingUserEvents};
+use super::app_delegate::{ApplicationDelegate, HandlePendingUserEvents};
 use super::event::dummy_event;
 use super::monitor::{self, MonitorHandle};
 use super::observer::setup_control_flow_observers;
+use crate::application::ApplicationHandler;
 use crate::error::EventLoopError;
 use crate::event::Event;
 use crate::event_loop::{
@@ -155,17 +156,28 @@ impl ActiveEventLoop {
     }
 }
 
-fn map_user_event<T: 'static>(
-    mut handler: impl FnMut(Event<T>, &RootWindowTarget),
+fn map_user_event<T: 'static, A: ApplicationHandler<T>>(
+    app: &mut A,
     receiver: Rc<mpsc::Receiver<T>>,
-) -> impl FnMut(Event<HandlePendingUserEvents>, &RootWindowTarget) {
-    move |event, window_target| match event.map_nonuser_event() {
-        Ok(event) => (handler)(event, window_target),
-        Err(_) => {
+) -> impl FnMut(Event<HandlePendingUserEvents>, &RootWindowTarget) + '_ {
+    move |event, window_target| match event {
+        Event::NewEvents(cause) => app.new_events(window_target, cause),
+        Event::WindowEvent { window_id, event } => {
+            app.window_event(window_target, window_id, event)
+        },
+        Event::DeviceEvent { device_id, event } => {
+            app.device_event(window_target, device_id, event)
+        },
+        Event::UserEvent(_) => {
             for event in receiver.try_iter() {
-                (handler)(Event::UserEvent(event), window_target);
+                app.user_event(window_target, event);
             }
         },
+        Event::Suspended => app.suspended(window_target),
+        Event::Resumed => app.resumed(window_target),
+        Event::AboutToWait => app.about_to_wait(window_target),
+        Event::LoopExiting => app.exiting(window_target),
+        Event::MemoryWarning => app.memory_warning(window_target),
     }
 }
 
@@ -240,7 +252,7 @@ impl<T> EventLoop<T> {
         });
 
         let panic_info: Rc<PanicInfo> = Default::default();
-        setup_control_flow_observers(mtm, Rc::downgrade(&panic_info));
+        setup_control_flow_observers(Rc::downgrade(&panic_info));
 
         let (sender, receiver) = mpsc::channel();
         Ok(EventLoop {
@@ -260,22 +272,19 @@ impl<T> EventLoop<T> {
         &self.window_target
     }
 
-    pub fn run<F>(mut self, handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &RootWindowTarget),
-    {
-        self.run_on_demand(handler)
+    pub fn run_app<A: ApplicationHandler<T>>(mut self, app: &mut A) -> Result<(), EventLoopError> {
+        self.run_app_on_demand(app)
     }
 
     // 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_on_demand<F>(&mut self, handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &RootWindowTarget),
-    {
-        let handler = map_user_event(handler, self.receiver.clone());
+    pub fn run_app_on_demand<A: ApplicationHandler<T>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
+        let handler = map_user_event(app, self.receiver.clone());
 
         self.delegate.set_event_handler(handler, || {
             autoreleasepool(|_| {
@@ -310,11 +319,12 @@ impl<T> EventLoop<T> {
         Ok(())
     }
 
-    pub fn pump_events<F>(&mut self, timeout: Option<Duration>, handler: F) -> PumpStatus
-    where
-        F: FnMut(Event<T>, &RootWindowTarget),
-    {
-        let handler = map_user_event(handler, self.receiver.clone());
+    pub fn pump_app_events<A: ApplicationHandler<T>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
+        let handler = map_user_event(app, self.receiver.clone());
 
         self.delegate.set_event_handler(handler, || {
             autoreleasepool(|_| {

src/platform_impl/macos/mod.rs

@@ -2,7 +2,7 @@
 mod util;
 
 mod app;
-mod app_state;
+mod app_delegate;
 mod cursor;
 mod event;
 mod event_handler;

src/platform_impl/macos/observer.rs

@@ -1,28 +1,21 @@
-//! Utilities for working with `CFRunLoop`.
-//!
-//! See Apple's documentation on Run Loops for details:
-//! <https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Multithreading/RunLoopManagement/RunLoopManagement.html>
-use std::cell::Cell;
 use std::ffi::c_void;
 use std::panic::{AssertUnwindSafe, UnwindSafe};
 use std::ptr;
 use std::rc::Weak;
 use std::time::Instant;
 
-use block2::Block;
-use core_foundation::base::{CFIndex, CFOptionFlags, CFRelease, CFTypeRef};
+use core_foundation::base::{CFIndex, CFOptionFlags, CFRelease};
 use core_foundation::date::CFAbsoluteTimeGetCurrent;
 use core_foundation::runloop::{
-    kCFRunLoopAfterWaiting, kCFRunLoopBeforeWaiting, kCFRunLoopCommonModes, kCFRunLoopDefaultMode,
-    kCFRunLoopExit, CFRunLoopActivity, CFRunLoopAddObserver, CFRunLoopAddTimer, CFRunLoopGetMain,
+    kCFRunLoopAfterWaiting, kCFRunLoopBeforeWaiting, kCFRunLoopCommonModes, kCFRunLoopExit,
+    CFRunLoopActivity, CFRunLoopAddObserver, CFRunLoopAddTimer, CFRunLoopGetMain,
     CFRunLoopObserverCallBack, CFRunLoopObserverContext, CFRunLoopObserverCreate,
     CFRunLoopObserverRef, CFRunLoopRef, CFRunLoopTimerCreate, CFRunLoopTimerInvalidate,
     CFRunLoopTimerRef, CFRunLoopTimerSetNextFireDate, CFRunLoopWakeUp,
 };
 use objc2_foundation::MainThreadMarker;
-use tracing::error;
 
-use super::app_state::ApplicationDelegate;
+use super::app_delegate::ApplicationDelegate;
 use super::event_loop::{stop_app_on_panic, PanicInfo};
 use super::ffi;
 
@@ -91,20 +84,10 @@ extern "C" fn control_flow_end_handler(
     }
 }
 
-#[derive(Debug)]
 pub struct RunLoop(CFRunLoopRef);
 
-impl Default for RunLoop {
-    fn default() -> Self {
-        Self(ptr::null_mut())
-    }
-}
-
 impl RunLoop {
-    pub fn main(mtm: MainThreadMarker) -> Self {
-        // SAFETY: We have a MainThreadMarker here, which means we know we're on the main thread, so
-        // scheduling (and scheduling a non-`Send` block) to that thread is allowed.
-        let _ = mtm;
+    pub unsafe fn get() -> Self {
         RunLoop(unsafe { CFRunLoopGetMain() })
     }
 
@@ -131,79 +114,9 @@ impl RunLoop {
         };
         unsafe { CFRunLoopAddObserver(self.0, observer, kCFRunLoopCommonModes) };
     }
-
-    /// Submit a closure to run on the main thread as the next step in the run loop, before other
-    /// event sources are processed.
-    ///
-    /// This is used for running event handlers, as those are not allowed to run re-entrantly.
-    ///
-    /// # Implementation
-    ///
-    /// This queuing could be implemented in the following several ways with subtle differences in
-    /// timing. This list is sorted in rough order in which they are run:
-    ///
-    /// 1. Using `CFRunLoopPerformBlock` or `-[NSRunLoop performBlock:]`.
-    ///
-    /// 2. Using `-[NSObject performSelectorOnMainThread:withObject:waitUntilDone:]` or wrapping the
-    ///    event in `NSEvent` and posting that to `-[NSApplication postEvent:atStart:]` (both
-    ///    creates a custom `CFRunLoopSource`, and signals that to wake up the main event loop).
-    ///
-    ///    a. `atStart = true`.
-    ///
-    ///    b. `atStart = false`.
-    ///
-    /// 3. `dispatch_async` or `dispatch_async_f`. Note that this may appear before 2b, it does not
-    ///    respect the ordering that runloop events have.
-    ///
-    /// We choose the first one, both for ease-of-implementation, but mostly for consistency, as we
-    /// want the event to be queued in a way that preserves the order the events originally arrived
-    /// in.
-    ///
-    /// As an example, let's assume that we receive two events from the user, a mouse click which we
-    /// handled by queuing it, and a window resize which we handled immediately. If we allowed
-    /// AppKit to choose the ordering when queuing the mouse event, it might get put in the back of
-    /// the queue, and the events would appear out of order to the user of Winit. So we must instead
-    /// put the event at the very front of the queue, to be handled as soon as possible after
-    /// handling whatever event it's currently handling.
-    pub fn queue_closure(&self, closure: impl FnOnce() + 'static) {
-        extern "C" {
-            fn CFRunLoopPerformBlock(rl: CFRunLoopRef, mode: CFTypeRef, block: &Block<dyn Fn()>);
-        }
-
-        // Convert `FnOnce()` to `Block<dyn Fn()>`.
-        let closure = Cell::new(Some(closure));
-        let block = block2::RcBlock::new(move || {
-            if let Some(closure) = closure.take() {
-                closure()
-            } else {
-                error!("tried to execute queued closure on main thread twice");
-            }
-        });
-
-        // There are a few common modes (`kCFRunLoopCommonModes`) defined by Cocoa:
-        // - `NSDefaultRunLoopMode`, alias of `kCFRunLoopDefaultMode`.
-        // - `NSEventTrackingRunLoopMode`, used when mouse-dragging and live-resizing a window.
-        // - `NSModalPanelRunLoopMode`, used when running a modal inside the Winit event loop.
-        // - `NSConnectionReplyMode`: TODO.
-        //
-        // We only want to run event handlers in the default mode, as we support running a blocking
-        // modal inside a Winit event handler (see [#1779]) which outrules the modal panel mode, and
-        // resizing such panel window enters the event tracking run loop mode, so we can't directly
-        // trigger events inside that mode either.
-        //
-        // Any events that are queued while running a modal or when live-resizing will instead wait,
-        // and be delivered to the application afterwards.
-        //
-        // [#1779]: https://github.com/rust-windowing/winit/issues/1779
-        let mode = unsafe { kCFRunLoopDefaultMode as CFTypeRef };
-
-        // SAFETY: The runloop is valid, the mode is a `CFStringRef`, and the block is `'static`.
-        unsafe { CFRunLoopPerformBlock(self.0, mode, &block) }
-    }
 }
 
-pub fn setup_control_flow_observers(mtm: MainThreadMarker, panic_info: Weak<PanicInfo>) {
-    let run_loop = RunLoop::main(mtm);
+pub fn setup_control_flow_observers(panic_info: Weak<PanicInfo>) {
     unsafe {
         let mut context = CFRunLoopObserverContext {
             info: Weak::into_raw(panic_info) as *mut _,
@@ -212,6 +125,7 @@ pub fn setup_control_flow_observers(mtm: MainThreadMarker, panic_info: Weak<Pani
             release: None,
             copyDescription: None,
         };
+        let run_loop = RunLoop::get();
         run_loop.add_observer(
             kCFRunLoopAfterWaiting,
             CFIndex::min_value(),
@@ -251,8 +165,8 @@ impl Drop for EventLoopWaker {
     }
 }
 
-impl EventLoopWaker {
-    pub(crate) fn new() -> Self {
+impl Default for EventLoopWaker {
+    fn default() -> EventLoopWaker {
         extern "C" fn wakeup_main_loop(_timer: CFRunLoopTimerRef, _info: *mut c_void) {}
         unsafe {
             // Create a timer with a 0.1µs interval (1ns does not work) to mimic polling.
@@ -268,10 +182,12 @@ impl EventLoopWaker {
                 ptr::null_mut(),
             );
             CFRunLoopAddTimer(CFRunLoopGetMain(), timer, kCFRunLoopCommonModes);
-            Self { timer, start_instant: Instant::now(), next_fire_date: None }
+            EventLoopWaker { timer, start_instant: Instant::now(), next_fire_date: None }
         }
     }
+}
 
+impl EventLoopWaker {
     pub fn stop(&mut self) {
         if self.next_fire_date.is_some() {
             self.next_fire_date = None;

src/platform_impl/macos/view.rs

@@ -16,7 +16,7 @@ use objc2_foundation::{
     NSPoint, NSRange, NSRect, NSSize, NSString, NSUInteger,
 };
 
-use super::app_state::ApplicationDelegate;
+use super::app_delegate::ApplicationDelegate;
 use super::cursor::{default_cursor, invisible_cursor};
 use super::event::{
     code_to_key, code_to_location, create_key_event, event_mods, lalt_pressed, ralt_pressed,
@@ -270,20 +270,19 @@ declare_class!(
         fn set_marked_text(
             &self,
             string: &NSObject,
-            selected_range: NSRange,
+            _selected_range: NSRange,
             _replacement_range: NSRange,
         ) {
-            // TODO: Use _replacement_range, requires changing the event to report surrounding text.
             trace_scope!("setMarkedText:selectedRange:replacementRange:");
 
             // SAFETY: This method is guaranteed to get either a `NSString` or a `NSAttributedString`.
-            let (marked_text, string) = if string.is_kind_of::<NSAttributedString>() {
+            let (marked_text, preedit_string) = if string.is_kind_of::<NSAttributedString>() {
                 let string: *const NSObject = string;
                 let string: *const NSAttributedString = string.cast();
                 let string = unsafe { &*string };
                 (
                     NSMutableAttributedString::from_attributed_nsstring(string),
-                    string.string(),
+                    string.string().to_string(),
                 )
             } else {
                 let string: *const NSObject = string;
@@ -291,7 +290,7 @@ declare_class!(
                 let string = unsafe { &*string };
                 (
                     NSMutableAttributedString::from_nsstring(string),
-                    string.copy(),
+                    string.to_string(),
                 )
             };
 
@@ -311,21 +310,16 @@ declare_class!(
                 self.ivars().ime_state.set(ImeState::Ground);
             }
 
-            let cursor_range = if string.is_empty() {
-                // An empty string basically means that there's no preedit, so indicate that by
-                // sending a `None` cursor range.
+            // Empty string basically means that there's no preedit, so indicate that by sending
+            // `None` cursor range.
+            let cursor_range = if preedit_string.is_empty() {
                 None
             } else {
-                // Convert the selected range from UTF-16 indices to UTF-8 indices.
-                let sub_string_a = unsafe { string.substringToIndex(selected_range.location) };
-                let sub_string_b = unsafe { string.substringToIndex(selected_range.end()) };
-                let lowerbound_utf8 = sub_string_a.len();
-                let upperbound_utf8 = sub_string_b.len();
-                Some((lowerbound_utf8, upperbound_utf8))
+                Some((preedit_string.len(), preedit_string.len()))
             };
 
             // Send WindowEvent for updating marked text
-            self.queue_event(WindowEvent::Ime(Ime::Preedit(string.to_string(), cursor_range)));
+            self.queue_event(WindowEvent::Ime(Ime::Preedit(preedit_string, cursor_range)));
         }
 
         #[method(unmarkText)]
@@ -385,7 +379,6 @@ declare_class!(
 
         #[method(insertText:replacementRange:)]
         fn insert_text(&self, string: &NSObject, _replacement_range: NSRange) {
-            // TODO: Use _replacement_range, requires changing the event to report surrounding text.
             trace_scope!("insertText:replacementRange:");
 
             // SAFETY: This method is guaranteed to get either a `NSString` or a `NSAttributedString`.
@@ -686,7 +679,7 @@ declare_class!(
 
             self.update_modifiers(event, false);
 
-            self.ivars().app_delegate.maybe_queue_device_event(DeviceEvent::MouseWheel { delta });
+            self.queue_device_event(DeviceEvent::MouseWheel { delta });
             self.queue_event(WindowEvent::MouseWheel {
                 device_id: DEVICE_ID,
                 delta,
@@ -830,7 +823,11 @@ impl WinitView {
     }
 
     fn queue_event(&self, event: WindowEvent) {
-        self.ivars().app_delegate.maybe_queue_window_event(self.window().id(), event);
+        self.ivars().app_delegate.queue_window_event(self.window().id(), event);
+    }
+
+    fn queue_device_event(&self, event: DeviceEvent) {
+        self.ivars().app_delegate.queue_device_event(event);
     }
 
     fn scale_factor(&self) -> f64 {

src/platform_impl/macos/window_delegate.rs

@@ -1,7 +1,6 @@
 #![allow(clippy::unnecessary_cast)]
 use std::cell::{Cell, RefCell};
 use std::collections::VecDeque;
-use std::sync::{Arc, Mutex};
 
 use core_graphics::display::{CGDisplay, CGPoint};
 use monitor::VideoModeHandle;
@@ -22,16 +21,15 @@ use objc2_foundation::{
     NSPoint, NSRect, NSSize, NSString,
 };
 
-use super::app_state::ApplicationDelegate;
+use super::app_delegate::ApplicationDelegate;
 use super::cursor::cursor_from_icon;
 use super::monitor::{self, flip_window_screen_coordinates, get_display_id};
-use super::observer::RunLoop;
 use super::view::WinitView;
 use super::window::WinitWindow;
 use super::{ffi, Fullscreen, MonitorHandle, OsError, WindowId};
 use crate::dpi::{LogicalPosition, LogicalSize, PhysicalPosition, PhysicalSize, Position, Size};
 use crate::error::{ExternalError, NotSupportedError, OsError as RootOsError};
-use crate::event::{InnerSizeWriter, WindowEvent};
+use crate::event::WindowEvent;
 use crate::platform::macos::{OptionAsAlt, WindowExtMacOS};
 use crate::window::{
     Cursor, CursorGrabMode, Icon, ImePurpose, ResizeDirection, Theme, UserAttentionType,
@@ -186,17 +184,7 @@ declare_class!(
         #[method(windowDidChangeBackingProperties:)]
         fn window_did_change_backing_properties(&self, _: Option<&AnyObject>) {
             trace_scope!("windowDidChangeBackingProperties:");
-            let scale_factor = self.scale_factor();
-            if scale_factor == self.ivars().previous_scale_factor.get() {
-                return;
-            };
-            self.ivars().previous_scale_factor.set(scale_factor);
-
-            let mtm = MainThreadMarker::from(self);
-            let this = self.retain();
-            RunLoop::main(mtm).queue_closure(move || {
-                this.handle_scale_factor_changed(scale_factor);
-            });
+            self.queue_static_scale_factor_changed_event();
         }
 
         #[method(windowDidBecomeKey:)]
@@ -693,10 +681,7 @@ impl WindowDelegate {
         let delegate: Retained<WindowDelegate> = unsafe { msg_send_id![super(delegate), init] };
 
         if scale_factor != 1.0 {
-            let delegate = delegate.clone();
-            RunLoop::main(mtm).queue_closure(move || {
-                delegate.handle_scale_factor_changed(scale_factor);
-            });
+            delegate.queue_static_scale_factor_changed_event();
         }
         window.setDelegate(Some(ProtocolObject::from_ref(&*delegate)));
 
@@ -769,31 +754,24 @@ impl WindowDelegate {
     }
 
     pub(crate) fn queue_event(&self, event: WindowEvent) {
-        self.ivars().app_delegate.maybe_queue_window_event(self.window().id(), event);
+        self.ivars().app_delegate.queue_window_event(self.window().id(), event);
     }
 
-    fn handle_scale_factor_changed(&self, scale_factor: CGFloat) {
-        let app_delegate = &self.ivars().app_delegate;
-        let window = self.window();
+    fn queue_static_scale_factor_changed_event(&self) {
+        let scale_factor = self.scale_factor();
+        if scale_factor == self.ivars().previous_scale_factor.get() {
+            return;
+        };
 
-        let content_size = window.contentRectForFrameRect(window.frame()).size;
+        self.ivars().previous_scale_factor.set(scale_factor);
+        let content_size = self.window().contentRectForFrameRect(self.window().frame()).size;
         let content_size = LogicalSize::new(content_size.width, content_size.height);
 
-        let suggested_size = content_size.to_physical(scale_factor);
-        let new_inner_size = Arc::new(Mutex::new(suggested_size));
-        app_delegate.handle_window_event(window.id(), WindowEvent::ScaleFactorChanged {
+        self.ivars().app_delegate.queue_static_scale_factor_changed_event(
+            self.window().retain(),
+            content_size.to_physical(scale_factor),
             scale_factor,
-            inner_size_writer: InnerSizeWriter::new(Arc::downgrade(&new_inner_size)),
-        });
-        let physical_size = *new_inner_size.lock().unwrap();
-        drop(new_inner_size);
-
-        if physical_size != suggested_size {
-            let logical_size = physical_size.to_logical(scale_factor);
-            let size = NSSize::new(logical_size.width, logical_size.height);
-            window.setContentSize(size);
-        }
-        app_delegate.handle_window_event(window.id(), WindowEvent::Resized(physical_size));
+        );
     }
 
     fn emit_move_event(&self) {

src/platform_impl/orbital/event_loop.rs

@@ -12,6 +12,7 @@ use orbclient::{
 };
 use smol_str::SmolStr;
 
+use crate::application::ApplicationHandler;
 use crate::error::EventLoopError;
 use crate::event::{self, Ime, Modifiers, StartCause};
 use crate::event_loop::{self, ControlFlow, DeviceEvents};
@@ -322,14 +323,13 @@ impl<T: 'static> EventLoop<T> {
         })
     }
 
-    fn process_event<F>(
+    fn process_event<A: ApplicationHandler<T>>(
         window_id: WindowId,
         event_option: EventOption,
         event_state: &mut EventState,
-        mut event_handler: F,
-    ) where
-        F: FnMut(event::Event<T>),
-    {
+        window_target: &event_loop::ActiveEventLoop,
+        app: &mut A,
+    ) {
         match event_option {
             EventOption::Key(KeyEvent { character, scancode, pressed }) => {
                 // Convert scancode
@@ -371,125 +371,128 @@ impl<T: 'static> EventLoop<T> {
                     key_without_modifiers = logical_key.clone();
                 }
 
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::KeyboardInput {
-                        device_id: event::DeviceId(DeviceId),
-                        event: event::KeyEvent {
-                            logical_key,
-                            physical_key,
-                            location: KeyLocation::Standard,
-                            state: element_state(pressed),
-                            repeat: false,
-                            text,
-                            platform_specific: KeyEventExtra {
-                                key_without_modifiers,
-                                text_with_all_modifiers,
-                            },
+                let window_id = RootWindowId(window_id);
+                let event = event::WindowEvent::KeyboardInput {
+                    device_id: event::DeviceId(DeviceId),
+                    event: event::KeyEvent {
+                        logical_key,
+                        physical_key,
+                        location: KeyLocation::Standard,
+                        state: element_state(pressed),
+                        repeat: false,
+                        text,
+                        platform_specific: KeyEventExtra {
+                            key_without_modifiers,
+                            text_with_all_modifiers,
                         },
-                        is_synthetic: false,
                     },
-                });
+                    is_synthetic: false,
+                };
+
+                app.window_event(window_target, window_id, event);
 
                 // If the state of the modifiers has changed, send the event.
                 if modifiers_before != event_state.keyboard {
-                    event_handler(event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::ModifiersChanged(event_state.modifiers()),
-                    })
+                    app.window_event(
+                        window_target,
+                        window_id,
+                        event::WindowEvent::ModifiersChanged(event_state.modifiers()),
+                    );
                 }
             },
             EventOption::TextInput(TextInputEvent { character }) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::Ime(Ime::Preedit("".into(), None)),
-                });
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::Ime(Ime::Commit(character.into())),
-                });
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::Ime(Ime::Preedit("".into(), None)),
+                );
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::Ime(Ime::Commit(character.into())),
+                );
             },
             EventOption::Mouse(MouseEvent { x, y }) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::CursorMoved {
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::CursorMoved {
                         device_id: event::DeviceId(DeviceId),
                         position: (x, y).into(),
                     },
-                });
+                );
             },
             EventOption::MouseRelative(MouseRelativeEvent { dx, dy }) => {
-                event_handler(event::Event::DeviceEvent {
-                    device_id: event::DeviceId(DeviceId),
-                    event: event::DeviceEvent::MouseMotion { delta: (dx as f64, dy as f64) },
-                });
+                app.device_event(
+                    window_target,
+                    event::DeviceId(DeviceId),
+                    event::DeviceEvent::MouseMotion { delta: (dx as f64, dy as f64) },
+                );
             },
             EventOption::Button(ButtonEvent { left, middle, right }) => {
                 while let Some((button, state)) = event_state.mouse(left, middle, right) {
-                    event_handler(event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::MouseInput {
+                    app.window_event(
+                        window_target,
+                        RootWindowId(window_id),
+                        event::WindowEvent::MouseInput {
                             device_id: event::DeviceId(DeviceId),
                             state,
                             button,
                         },
-                    });
+                    );
                 }
             },
             EventOption::Scroll(ScrollEvent { x, y }) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::MouseWheel {
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::MouseWheel {
                         device_id: event::DeviceId(DeviceId),
                         delta: event::MouseScrollDelta::LineDelta(x as f32, y as f32),
                         phase: event::TouchPhase::Moved,
                     },
-                });
+                );
             },
             EventOption::Quit(QuitEvent {}) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::CloseRequested,
-                });
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::CloseRequested,
+                );
             },
             EventOption::Focus(FocusEvent { focused }) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::Focused(focused),
-                });
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::Focused(focused),
+                );
             },
             EventOption::Move(MoveEvent { x, y }) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::Moved((x, y).into()),
-                });
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::Moved((x, y).into()),
+                );
             },
             EventOption::Resize(ResizeEvent { width, height }) => {
-                event_handler(event::Event::WindowEvent {
-                    window_id: RootWindowId(window_id),
-                    event: event::WindowEvent::Resized((width, height).into()),
-                });
+                app.window_event(
+                    window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::Resized((width, height).into()),
+                );
 
                 // Acknowledge resize after event loop.
                 event_state.resize_opt = Some((width, height));
             },
             // TODO: Screen, Clipboard, Drop
             EventOption::Hover(HoverEvent { entered }) => {
-                if entered {
-                    event_handler(event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::CursorEntered {
-                            device_id: event::DeviceId(DeviceId),
-                        },
-                    });
+                let event = if entered {
+                    event::WindowEvent::CursorEntered { device_id: event::DeviceId(DeviceId) }
                 } else {
-                    event_handler(event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::CursorLeft {
-                            device_id: event::DeviceId(DeviceId),
-                        },
-                    });
-                }
+                    event::WindowEvent::CursorLeft { device_id: event::DeviceId(DeviceId) }
+                };
+
+                app.window_event(window_target, RootWindowId(window_id), event);
             },
             other => {
                 tracing::warn!("unhandled event: {:?}", other);
@@ -497,22 +500,13 @@ impl<T: 'static> EventLoop<T> {
         }
     }
 
-    pub fn run<F>(mut self, mut event_handler_inner: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(event::Event<T>, &event_loop::ActiveEventLoop),
-    {
-        let mut event_handler =
-            move |event: event::Event<T>, window_target: &event_loop::ActiveEventLoop| {
-                event_handler_inner(event, window_target);
-            };
-
+    pub fn run_app<A: ApplicationHandler<T>>(mut self, app: &mut A) -> Result<(), EventLoopError> {
         let mut start_cause = StartCause::Init;
-
         loop {
-            event_handler(event::Event::NewEvents(start_cause), &self.window_target);
+            app.new_events(&self.window_target, start_cause);
 
             if start_cause == StartCause::Init {
-                event_handler(event::Event::Resumed, &self.window_target);
+                app.resumed(&self.window_target);
             }
 
             // Handle window creates.
@@ -528,23 +522,15 @@ impl<T: 'static> EventLoop<T> {
 
                 self.windows.push((window, EventState::default()));
 
-                // Send resize event on create to indicate first size.
-                event_handler(
-                    event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::Resized((properties.w, properties.h).into()),
-                    },
-                    &self.window_target,
-                );
+                let window_id = RootWindowId(window_id);
 
-                // Send resize event on create to indicate first position.
-                event_handler(
-                    event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::Moved((properties.x, properties.y).into()),
-                    },
-                    &self.window_target,
-                );
+                // Send resize event on create to indicate first size.
+                let event = event::WindowEvent::Resized((properties.w, properties.h).into());
+                app.window_event(&self.window_target, window_id, event);
+
+                // Send moved event on create to indicate first position.
+                let event = event::WindowEvent::Moved((properties.x, properties.y).into());
+                app.window_event(&self.window_target, window_id, event);
             }
 
             // Handle window destroys.
@@ -552,14 +538,8 @@ impl<T: 'static> EventLoop<T> {
                 let mut destroys = self.window_target.p.destroys.lock().unwrap();
                 destroys.pop_front()
             } {
-                event_handler(
-                    event::Event::WindowEvent {
-                        window_id: RootWindowId(destroy_id),
-                        event: event::WindowEvent::Destroyed,
-                    },
-                    &self.window_target,
-                );
-
+                let window_id = RootWindowId(destroy_id);
+                app.window_event(&self.window_target, window_id, event::WindowEvent::Destroyed);
                 self.windows.retain(|(window, _event_state)| window.fd as u64 != destroy_id.fd);
             }
 
@@ -586,7 +566,8 @@ impl<T: 'static> EventLoop<T> {
                         window_id,
                         orbital_event.to_option(),
                         event_state,
-                        |event| event_handler(event, &self.window_target),
+                        &self.window_target,
+                        app,
                     );
                 }
 
@@ -614,7 +595,7 @@ impl<T: 'static> EventLoop<T> {
             }
 
             while let Ok(event) = self.user_events_receiver.try_recv() {
-                event_handler(event::Event::UserEvent(event), &self.window_target);
+                app.user_event(&self.window_target, event);
             }
 
             // To avoid deadlocks the redraws lock is not held during event processing.
@@ -622,16 +603,14 @@ impl<T: 'static> EventLoop<T> {
                 let mut redraws = self.window_target.p.redraws.lock().unwrap();
                 redraws.pop_front()
             } {
-                event_handler(
-                    event::Event::WindowEvent {
-                        window_id: RootWindowId(window_id),
-                        event: event::WindowEvent::RedrawRequested,
-                    },
+                app.window_event(
                     &self.window_target,
+                    RootWindowId(window_id),
+                    event::WindowEvent::RedrawRequested,
                 );
             }
 
-            event_handler(event::Event::AboutToWait, &self.window_target);
+            app.about_to_wait(&self.window_target);
 
             if self.window_target.p.exiting() {
                 break;
@@ -695,7 +674,7 @@ impl<T: 'static> EventLoop<T> {
             }
         }
 
-        event_handler(event::Event::LoopExiting, &self.window_target);
+        app.exiting(&self.window_target);
 
         Ok(())
     }

src/platform_impl/web/event_loop/mod.rs

@@ -1,6 +1,7 @@
 use std::marker::PhantomData;
 use std::sync::mpsc::{self, Receiver, Sender};
 
+use crate::application::ApplicationHandler;
 use crate::error::EventLoopError;
 use crate::event::Event;
 use crate::event_loop::ActiveEventLoop as RootActiveEventLoop;
@@ -31,25 +32,13 @@ impl<T> EventLoop<T> {
         Ok(EventLoop { elw, user_event_sender, user_event_receiver })
     }
 
-    pub fn run<F>(self, mut event_handler: F) -> !
-    where
-        F: FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    pub fn run_app<A: ApplicationHandler<T>>(self, app: &mut A) -> ! {
         let target = RootActiveEventLoop { p: self.elw.p.clone(), _marker: PhantomData };
 
         // SAFETY: Don't use `move` to make sure we leak the `event_handler` and `target`.
-        let handler: Box<dyn FnMut(Event<()>)> = Box::new(|event| {
-            let event = match event.map_nonuser_event() {
-                Ok(event) => event,
-                Err(Event::UserEvent(())) => Event::UserEvent(
-                    self.user_event_receiver
-                        .try_recv()
-                        .expect("handler woken up without user event"),
-                ),
-                Err(_) => unreachable!(),
-            };
-            event_handler(event, &target)
-        });
+        let handler: Box<dyn FnMut(Event<()>)> =
+            Box::new(|event| handle_event(app, &target, &self.user_event_receiver, event));
+
         // SAFETY: The `transmute` is necessary because `run()` requires `'static`. This is safe
         // because this function will never return and all resources not cleaned up by the point we
         // `throw` will leak, making this actually `'static`.
@@ -65,24 +54,12 @@ impl<T> EventLoop<T> {
         unreachable!();
     }
 
-    pub fn spawn<F>(self, mut event_handler: F)
-    where
-        F: 'static + FnMut(Event<T>, &RootActiveEventLoop),
-    {
+    pub fn spawn_app<A: ApplicationHandler<T> + 'static>(self, mut app: A) {
         let target = RootActiveEventLoop { p: self.elw.p.clone(), _marker: PhantomData };
 
         self.elw.p.run(
             Box::new(move |event| {
-                let event = match event.map_nonuser_event() {
-                    Ok(event) => event,
-                    Err(Event::UserEvent(())) => Event::UserEvent(
-                        self.user_event_receiver
-                            .try_recv()
-                            .expect("handler woken up without user event"),
-                    ),
-                    Err(_) => unreachable!(),
-                };
-                event_handler(event, &target)
+                handle_event(&mut app, &target, &self.user_event_receiver, event)
             }),
             true,
         );
@@ -96,3 +73,26 @@ impl<T> EventLoop<T> {
         &self.elw
     }
 }
+
+fn handle_event<T: 'static, A: ApplicationHandler<T>>(
+    app: &mut A,
+    target: &RootActiveEventLoop,
+    user_event_receiver: &Receiver<T>,
+    event: Event<()>,
+) {
+    match event {
+        Event::NewEvents(cause) => app.new_events(target, cause),
+        Event::WindowEvent { window_id, event } => app.window_event(target, window_id, event),
+        Event::DeviceEvent { device_id, event } => app.device_event(target, device_id, event),
+        Event::UserEvent(_) => {
+            let event =
+                user_event_receiver.try_recv().expect("user event signaled but not received");
+            app.user_event(target, event);
+        },
+        Event::Suspended => app.suspended(target),
+        Event::Resumed => app.resumed(target),
+        Event::AboutToWait => app.about_to_wait(target),
+        Event::LoopExiting => app.exiting(target),
+        Event::MemoryWarning => app.memory_warning(target),
+    }
+}

src/platform_impl/windows/event_loop.rs

@@ -57,6 +57,7 @@ use windows_sys::Win32::UI::WindowsAndMessaging::{
     WS_EX_NOACTIVATE, WS_EX_TOOLWINDOW, WS_EX_TRANSPARENT, WS_OVERLAPPED, WS_POPUP, WS_VISIBLE,
 };
 
+use crate::application::ApplicationHandler;
 use crate::dpi::{PhysicalPosition, PhysicalSize};
 use crate::error::EventLoopError;
 use crate::event::{
@@ -215,17 +216,14 @@ impl<T: 'static> EventLoop<T> {
         &self.window_target
     }
 
-    pub fn run<F>(mut self, event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
-        self.run_on_demand(event_handler)
+    pub fn run_app<A: ApplicationHandler<T>>(mut self, app: &mut A) -> Result<(), EventLoopError> {
+        self.run_app_on_demand(app)
     }
 
-    pub fn run_on_demand<F>(&mut self, mut event_handler: F) -> Result<(), EventLoopError>
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
+    pub fn run_app_on_demand<A: ApplicationHandler<T>>(
+        &mut self,
+        app: &mut A,
+    ) -> Result<(), EventLoopError> {
         {
             let runner = &self.window_target.p.runner_shared;
 
@@ -236,21 +234,32 @@ impl<T: 'static> EventLoop<T> {
             // returning
             unsafe {
                 runner.set_event_handler(move |event| {
-                    // the shared `EventLoopRunner` is not parameterized
-                    // `EventLoopProxy::send_event()` calls `PostMessage`
-                    // to wakeup and dispatch a placeholder `UserEvent`,
-                    // when we received the placeholder event here, the
-                    // real UserEvent(T) should already be put in the
-                    // mpsc channel and ready to be pulled
-                    let event = match event.map_nonuser_event() {
-                        Ok(non_user_event) => non_user_event,
-                        Err(_user_event_placeholder) => Event::UserEvent(
-                            user_event_receiver
+                    match event {
+                        Event::NewEvents(cause) => app.new_events(event_loop_windows_ref, cause),
+                        Event::WindowEvent { window_id, event } => {
+                            app.window_event(event_loop_windows_ref, window_id, event)
+                        },
+                        Event::DeviceEvent { device_id, event } => {
+                            app.device_event(event_loop_windows_ref, device_id, event)
+                        },
+                        // The shared `EventLoopRunner` is not parameterized
+                        // `EventLoopProxy::send_event()` calls `PostMessage`
+                        // to wakeup and dispatch a placeholder `UserEvent`,
+                        // when we received the placeholder event here, the
+                        // real UserEvent(T) should already be put in the
+                        // mpsc channel and ready to be pulled
+                        Event::UserEvent(_) => {
+                            let event = user_event_receiver
                                 .try_recv()
-                                .expect("user event signaled but not received"),
-                        ),
-                    };
-                    event_handler(event, event_loop_windows_ref)
+                                .expect("user event signaled but not received");
+                            app.user_event(event_loop_windows_ref, event);
+                        },
+                        Event::Suspended => app.suspended(event_loop_windows_ref),
+                        Event::Resumed => app.resumed(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),
+                    }
                 });
             }
         }
@@ -284,10 +293,11 @@ impl<T: 'static> EventLoop<T> {
         }
     }
 
-    pub fn pump_events<F>(&mut self, timeout: Option<Duration>, mut event_handler: F) -> PumpStatus
-    where
-        F: FnMut(Event<T>, &RootAEL),
-    {
+    pub fn pump_app_events<A: ApplicationHandler<T>>(
+        &mut self,
+        timeout: Option<Duration>,
+        app: &mut A,
+    ) -> PumpStatus {
         {
             let runner = &self.window_target.p.runner_shared;
             let event_loop_windows_ref = &self.window_target;
@@ -302,16 +312,34 @@ impl<T: 'static> EventLoop<T> {
             // event handler.
             unsafe {
                 runner.set_event_handler(move |event| {
-                    let event = match event.map_nonuser_event() {
-                        Ok(non_user_event) => non_user_event,
-                        Err(_user_event_placeholder) => Event::UserEvent(
-                            user_event_receiver
-                                .recv()
-                                .expect("user event signaled but not received"),
-                        ),
-                    };
-                    event_handler(event, event_loop_windows_ref)
+                    match event {
+                        Event::NewEvents(cause) => app.new_events(event_loop_windows_ref, cause),
+                        Event::WindowEvent { window_id, event } => {
+                            app.window_event(event_loop_windows_ref, window_id, event)
+                        },
+                        Event::DeviceEvent { device_id, event } => {
+                            app.device_event(event_loop_windows_ref, device_id, event)
+                        },
+                        // The shared `EventLoopRunner` is not parameterized
+                        // `EventLoopProxy::send_event()` calls `PostMessage`
+                        // to wakeup and dispatch a placeholder `UserEvent`,
+                        // when we received the placeholder event here, the
+                        // real UserEvent(T) should already be put in the
+                        // mpsc channel and ready to be pulled
+                        Event::UserEvent(_) => {
+                            let event = user_event_receiver
+                                .try_recv()
+                                .expect("user event signaled but not received");
+                            app.user_event(event_loop_windows_ref, event);
+                        },
+                        Event::Suspended => app.suspended(event_loop_windows_ref),
+                        Event::Resumed => app.resumed(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),
+                    }
                 });
+
                 runner.wakeup();
             }
         }

src/window.rs

@@ -632,8 +632,7 @@ impl Window {
     ///
     /// ## Platform-specific
     ///
-    /// - **Android / iOS / X11 / Web / Windows / macOS / Orbital:** Unsupported.
-    /// - **Wayland:** Schedules a frame callback to throttle [`WindowEvent::RedrawRequested`].
+    /// **Wayland:** - schedules a frame callback to throttle [`WindowEvent::RedrawRequested`].
     ///
     /// [`WindowEvent::RedrawRequested`]: crate::event::WindowEvent::RedrawRequested
     #[inline]