Move UIKit backend to winit-uikit

winit-uikit/src/app_state.rs

@@ -0,0 +1,597 @@
+#![deny(unused_results)]
+
+use std::cell::{OnceCell, RefCell, RefMut};
+use std::collections::HashSet;
+use std::os::raw::c_void;
+use std::sync::{Arc, Mutex};
+use std::time::Instant;
+use std::{mem, ptr};
+
+use dispatch2::MainThreadBound;
+use dpi::PhysicalSize;
+use objc2::rc::Retained;
+use objc2::MainThreadMarker;
+use objc2_core_foundation::{
+    kCFRunLoopCommonModes, CFAbsoluteTimeGetCurrent, CFRetained, CFRunLoop, CFRunLoopTimer, CGRect,
+    CGSize,
+};
+use objc2_ui_kit::{UIApplication, UICoordinateSpace, UIView};
+use winit_common::core_foundation::EventLoopProxy;
+use winit_common::event_handler::EventHandler;
+use winit_core::application::ApplicationHandler;
+use winit_core::event::{StartCause, SurfaceSizeWriter, WindowEvent};
+use winit_core::event_loop::ControlFlow;
+use winit_core::window::WindowId;
+
+use crate::event_loop::ActiveEventLoop;
+use crate::window::WinitUIWindow;
+
+macro_rules! bug {
+    ($($msg:tt)*) => {
+        panic!("winit iOS bug, file an issue: {}", format!($($msg)*))
+    };
+}
+
+macro_rules! bug_assert {
+    ($test:expr, $($msg:tt)*) => {
+        assert!($test, "winit iOS bug, file an issue: {}", format!($($msg)*))
+    };
+}
+
+/// Get the global event handler for the application.
+///
+/// This is stored separately from AppState, since AppState needs to be accessible while the handler
+/// is executing.
+fn get_handler(mtm: MainThreadMarker) -> &'static EventHandler {
+    // SAFETY: Creating `StaticMainThreadBound` in a `const` context, where there is no concept
+    // of the main thread.
+    static GLOBAL: MainThreadBound<OnceCell<EventHandler>> =
+        MainThreadBound::new(OnceCell::new(), unsafe { MainThreadMarker::new_unchecked() });
+
+    GLOBAL.get(mtm).get_or_init(EventHandler::new)
+}
+
+#[derive(Debug)]
+pub(crate) enum EventWrapper {
+    Window { window_id: WindowId, event: WindowEvent },
+    ScaleFactorChanged(ScaleFactorChanged),
+}
+
+#[derive(Debug)]
+pub struct ScaleFactorChanged {
+    pub(super) window: Retained<WinitUIWindow>,
+    pub(super) suggested_size: PhysicalSize<u32>,
+    pub(super) scale_factor: f64,
+}
+
+impl EventWrapper {
+    fn is_redraw(&self) -> bool {
+        matches!(self, Self::Window { event: WindowEvent::RedrawRequested, .. })
+    }
+}
+
+// this is the state machine for the app lifecycle
+#[derive(Debug)]
+#[must_use = "dropping `AppStateImpl` without inspecting it is probably a bug"]
+enum AppStateImpl {
+    Initial {
+        queued_gpu_redraws: HashSet<Retained<WinitUIWindow>>,
+    },
+    ProcessingEvents {
+        queued_gpu_redraws: HashSet<Retained<WinitUIWindow>>,
+        active_control_flow: ControlFlow,
+    },
+    ProcessingRedraws {
+        active_control_flow: ControlFlow,
+    },
+    Waiting {
+        start: Instant,
+    },
+    PollFinished,
+    Terminated,
+}
+
+pub(crate) struct AppState {
+    // This should never be `None`, except for briefly during a state transition.
+    app_state: Option<AppStateImpl>,
+    control_flow: ControlFlow,
+    waker: EventLoopWaker,
+    event_loop_proxy: Arc<EventLoopProxy>,
+    queued_events: Vec<EventWrapper>,
+}
+
+impl AppState {
+    pub(crate) fn get_mut(mtm: MainThreadMarker) -> RefMut<'static, AppState> {
+        // basically everything in UIKit requires the main thread, so it's pointless to use the
+        // std::sync APIs.
+        // must be mut because plain `static` requires `Sync`
+        static mut APP_STATE: RefCell<Option<AppState>> = RefCell::new(None);
+
+        #[allow(unknown_lints)] // New lint below
+        #[allow(static_mut_refs)] // TODO: Use `MainThreadBound` instead.
+        let mut guard = unsafe { APP_STATE.borrow_mut() };
+        if guard.is_none() {
+            #[inline(never)]
+            #[cold]
+            fn init_guard(guard: &mut RefMut<'static, Option<AppState>>, mtm: MainThreadMarker) {
+                let waker = EventLoopWaker::new(CFRunLoop::main().unwrap());
+                let event_loop_proxy = Arc::new(EventLoopProxy::new(mtm, move || {
+                    get_handler(mtm).handle(|app| app.proxy_wake_up(&ActiveEventLoop { mtm }));
+                }));
+
+                **guard = Some(AppState {
+                    app_state: Some(AppStateImpl::Initial { queued_gpu_redraws: HashSet::new() }),
+                    control_flow: ControlFlow::default(),
+                    waker,
+                    event_loop_proxy,
+                    queued_events: Vec::new(),
+                });
+            }
+            init_guard(&mut guard, mtm);
+        }
+        RefMut::map(guard, |state| state.as_mut().unwrap())
+    }
+
+    fn state(&self) -> &AppStateImpl {
+        match &self.app_state {
+            Some(ref state) => state,
+            None => bug!("`AppState` previously failed a state transition"),
+        }
+    }
+
+    fn state_mut(&mut self) -> &mut AppStateImpl {
+        match &mut self.app_state {
+            Some(ref mut state) => state,
+            None => bug!("`AppState` previously failed a state transition"),
+        }
+    }
+
+    fn take_state(&mut self) -> AppStateImpl {
+        match self.app_state.take() {
+            Some(state) => state,
+            None => bug!("`AppState` previously failed a state transition"),
+        }
+    }
+
+    fn set_state(&mut self, new_state: AppStateImpl) {
+        bug_assert!(
+            self.app_state.is_none(),
+            "attempted to set an `AppState` without calling `take_state` first {:?}",
+            self.app_state
+        );
+        self.app_state = Some(new_state)
+    }
+
+    fn replace_state(&mut self, new_state: AppStateImpl) -> AppStateImpl {
+        match &mut self.app_state {
+            Some(ref mut state) => mem::replace(state, new_state),
+            None => bug!("`AppState` previously failed a state transition"),
+        }
+    }
+
+    fn has_launched(&self) -> bool {
+        !matches!(self.state(), AppStateImpl::Initial { .. })
+    }
+
+    fn has_terminated(&self) -> bool {
+        matches!(self.state(), AppStateImpl::Terminated)
+    }
+
+    fn did_finish_launching_transition(&mut self) {
+        let queued_gpu_redraws = match self.take_state() {
+            AppStateImpl::Initial { queued_gpu_redraws } => queued_gpu_redraws,
+            s => bug!("unexpected state {:?}", s),
+        };
+        self.set_state(AppStateImpl::ProcessingEvents {
+            active_control_flow: self.control_flow,
+            queued_gpu_redraws,
+        });
+    }
+
+    fn wakeup_transition(&mut self) -> Option<StartCause> {
+        // before `AppState::did_finish_launching` is called, pretend there is no running
+        // event loop.
+        if !self.has_launched() || self.has_terminated() {
+            return None;
+        }
+
+        let start_cause = match (self.control_flow, self.take_state()) {
+            (ControlFlow::Poll, AppStateImpl::PollFinished) => StartCause::Poll,
+            (ControlFlow::Wait, AppStateImpl::Waiting { start }) => {
+                StartCause::WaitCancelled { start, requested_resume: None }
+            },
+            (ControlFlow::WaitUntil(requested_resume), AppStateImpl::Waiting { start }) => {
+                if Instant::now() >= requested_resume {
+                    StartCause::ResumeTimeReached { start, requested_resume }
+                } else {
+                    StartCause::WaitCancelled { start, requested_resume: Some(requested_resume) }
+                }
+            },
+            s => bug!("`EventHandler` unexpectedly woke up {:?}", s),
+        };
+
+        self.set_state(AppStateImpl::ProcessingEvents {
+            queued_gpu_redraws: Default::default(),
+            active_control_flow: self.control_flow,
+        });
+        Some(start_cause)
+    }
+
+    fn main_events_cleared_transition(&mut self) -> HashSet<Retained<WinitUIWindow>> {
+        let (queued_gpu_redraws, active_control_flow) = match self.take_state() {
+            AppStateImpl::ProcessingEvents { queued_gpu_redraws, active_control_flow } => {
+                (queued_gpu_redraws, active_control_flow)
+            },
+            s => bug!("unexpected state {:?}", s),
+        };
+        self.set_state(AppStateImpl::ProcessingRedraws { active_control_flow });
+        queued_gpu_redraws
+    }
+
+    fn events_cleared_transition(&mut self) {
+        if !self.has_launched() || self.has_terminated() {
+            return;
+        }
+        let old = match self.take_state() {
+            AppStateImpl::ProcessingRedraws { active_control_flow } => active_control_flow,
+            s => bug!("unexpected state {:?}", s),
+        };
+
+        let new = self.control_flow;
+        match (old, new) {
+            (ControlFlow::Wait, ControlFlow::Wait) => {
+                let start = Instant::now();
+                self.set_state(AppStateImpl::Waiting { start });
+                self.waker.stop()
+            },
+            (ControlFlow::WaitUntil(old_instant), ControlFlow::WaitUntil(new_instant))
+                if old_instant == new_instant =>
+            {
+                let start = Instant::now();
+                self.set_state(AppStateImpl::Waiting { start });
+            },
+            (_, ControlFlow::Wait) => {
+                let start = Instant::now();
+                self.set_state(AppStateImpl::Waiting { start });
+                self.waker.stop()
+            },
+            (_, ControlFlow::WaitUntil(new_instant)) => {
+                let start = Instant::now();
+                self.set_state(AppStateImpl::Waiting { start });
+                self.waker.start_at(new_instant)
+            },
+            // Unlike on macOS, handle Poll to Poll transition here to call the waker
+            (_, ControlFlow::Poll) => {
+                self.set_state(AppStateImpl::PollFinished);
+                self.waker.start()
+            },
+        }
+    }
+
+    fn terminated_transition(&mut self) {
+        match self.replace_state(AppStateImpl::Terminated) {
+            AppStateImpl::ProcessingEvents { .. } => {},
+            s => bug!("terminated while not processing events {:?}", s),
+        }
+    }
+
+    pub fn event_loop_proxy(&self) -> &Arc<EventLoopProxy> {
+        &self.event_loop_proxy
+    }
+
+    pub(crate) fn set_control_flow(&mut self, control_flow: ControlFlow) {
+        self.control_flow = control_flow;
+    }
+
+    pub(crate) fn control_flow(&self) -> ControlFlow {
+        self.control_flow
+    }
+}
+
+pub(crate) fn queue_gl_or_metal_redraw(mtm: MainThreadMarker, window: Retained<WinitUIWindow>) {
+    let mut this = AppState::get_mut(mtm);
+    match this.state_mut() {
+        &mut AppStateImpl::Initial { ref mut queued_gpu_redraws, .. }
+        | &mut AppStateImpl::ProcessingEvents { ref mut queued_gpu_redraws, .. } => {
+            let _ = queued_gpu_redraws.insert(window);
+        },
+        s @ &mut AppStateImpl::ProcessingRedraws { .. }
+        | s @ &mut AppStateImpl::Waiting { .. }
+        | s @ &mut AppStateImpl::PollFinished => bug!("unexpected state {:?}", s),
+        &mut AppStateImpl::Terminated => {
+            panic!("Attempt to create a `Window` after the app has terminated")
+        },
+    }
+}
+
+pub(crate) fn launch<R>(
+    mtm: MainThreadMarker,
+    app: impl ApplicationHandler,
+    run: impl FnOnce() -> R,
+) -> R {
+    get_handler(mtm).set(Box::new(app), run)
+}
+
+pub fn did_finish_launching(mtm: MainThreadMarker) {
+    let mut this = AppState::get_mut(mtm);
+
+    this.waker.start();
+
+    // have to drop RefMut because the window setup code below can trigger new events
+    drop(this);
+
+    AppState::get_mut(mtm).did_finish_launching_transition();
+
+    get_handler(mtm).handle(|app| app.new_events(&ActiveEventLoop { mtm }, StartCause::Init));
+    get_handler(mtm).handle(|app| app.can_create_surfaces(&ActiveEventLoop { mtm }));
+    handle_nonuser_events(mtm, []);
+}
+
+// AppState::did_finish_launching handles the special transition `Init`
+pub fn handle_wakeup_transition(mtm: MainThreadMarker) {
+    let mut this = AppState::get_mut(mtm);
+    let cause = match this.wakeup_transition() {
+        None => return,
+        Some(cause) => cause,
+    };
+    drop(this);
+
+    get_handler(mtm).handle(|app| app.new_events(&ActiveEventLoop { mtm }, cause));
+    handle_nonuser_events(mtm, []);
+}
+
+pub(crate) fn handle_nonuser_event(mtm: MainThreadMarker, event: EventWrapper) {
+    handle_nonuser_events(mtm, std::iter::once(event))
+}
+
+pub(crate) fn handle_nonuser_events<I: IntoIterator<Item = EventWrapper>>(
+    mtm: MainThreadMarker,
+    events: I,
+) {
+    let mut this = AppState::get_mut(mtm);
+    if this.has_terminated() {
+        return;
+    }
+
+    if !get_handler(mtm).ready() {
+        // Prevent re-entrancy; queue the events up for once we're done handling the event instead.
+        this.queued_events.extend(events);
+        return;
+    }
+
+    let processing_redraws = matches!(this.state(), AppStateImpl::ProcessingRedraws { .. });
+    drop(this);
+
+    for event in events {
+        if !processing_redraws && event.is_redraw() {
+            tracing::info!("processing `RedrawRequested` during the main event loop");
+        } else if processing_redraws && !event.is_redraw() {
+            tracing::warn!(
+                "processing non `RedrawRequested` event after the main event loop: {:#?}",
+                event
+            );
+        }
+        handle_wrapped_event(mtm, event)
+    }
+
+    loop {
+        let mut this = AppState::get_mut(mtm);
+        let queued_events = mem::take(&mut this.queued_events);
+        if queued_events.is_empty() {
+            break;
+        }
+        drop(this);
+
+        for event in queued_events {
+            if !processing_redraws && event.is_redraw() {
+                tracing::info!("processing `RedrawRequested` during the main event loop");
+            } else if processing_redraws && !event.is_redraw() {
+                tracing::warn!(
+                    "processing non-`RedrawRequested` event after the main event loop: {:#?}",
+                    event
+                );
+            }
+            handle_wrapped_event(mtm, event);
+        }
+    }
+}
+
+fn handle_user_events(mtm: MainThreadMarker) {
+    let this = AppState::get_mut(mtm);
+    if matches!(this.state(), AppStateImpl::ProcessingRedraws { .. }) {
+        bug!("user events attempted to be sent out while `ProcessingRedraws`");
+    }
+    drop(this);
+
+    loop {
+        let mut this = AppState::get_mut(mtm);
+        let queued_events = mem::take(&mut this.queued_events);
+        if queued_events.is_empty() {
+            break;
+        }
+        drop(this);
+
+        for event in queued_events {
+            handle_wrapped_event(mtm, event);
+        }
+    }
+}
+
+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 let Ok(window) = window.downcast::<WinitUIWindow>() {
+            events.push(EventWrapper::Window {
+                window_id: 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() {
+        return;
+    }
+    match this.state_mut() {
+        AppStateImpl::ProcessingEvents { .. } => {},
+        _ => bug!("`ProcessingRedraws` happened unexpectedly"),
+    };
+    drop(this);
+
+    handle_user_events(mtm);
+
+    let mut this = AppState::get_mut(mtm);
+    let redraw_events: Vec<EventWrapper> = this
+        .main_events_cleared_transition()
+        .into_iter()
+        .map(|window| EventWrapper::Window {
+            window_id: window.id(),
+            event: WindowEvent::RedrawRequested,
+        })
+        .collect();
+    drop(this);
+
+    handle_nonuser_events(mtm, redraw_events);
+    get_handler(mtm).handle(|app| app.about_to_wait(&ActiveEventLoop { mtm }));
+    handle_nonuser_events(mtm, []);
+}
+
+pub fn handle_events_cleared(mtm: MainThreadMarker) {
+    AppState::get_mut(mtm).events_cleared_transition();
+}
+
+pub(crate) fn handle_resumed(mtm: MainThreadMarker) {
+    get_handler(mtm).handle(|app| app.resumed(&ActiveEventLoop { mtm }));
+    handle_nonuser_events(mtm, []);
+}
+
+pub(crate) fn handle_suspended(mtm: MainThreadMarker) {
+    get_handler(mtm).handle(|app| app.suspended(&ActiveEventLoop { mtm }));
+    handle_nonuser_events(mtm, []);
+}
+
+pub(crate) fn handle_memory_warning(mtm: MainThreadMarker) {
+    get_handler(mtm).handle(|app| app.memory_warning(&ActiveEventLoop { mtm }));
+    handle_nonuser_events(mtm, []);
+}
+
+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 let Ok(window) = window.downcast::<WinitUIWindow>() {
+            events.push(EventWrapper::Window {
+                window_id: window.id(),
+                event: WindowEvent::Destroyed,
+            });
+        }
+    }
+    handle_nonuser_events(mtm, events);
+
+    let mut this = AppState::get_mut(mtm);
+    this.terminated_transition();
+    // Prevent EventLoopProxy from firing again.
+    this.event_loop_proxy.invalidate();
+    drop(this);
+
+    get_handler(mtm).terminate();
+}
+
+fn handle_wrapped_event(mtm: MainThreadMarker, event: EventWrapper) {
+    match event {
+        EventWrapper::Window { window_id, event } => get_handler(mtm)
+            .handle(|app| app.window_event(&ActiveEventLoop { mtm }, window_id, event)),
+        EventWrapper::ScaleFactorChanged(event) => handle_hidpi_proxy(mtm, event),
+    }
+}
+
+fn handle_hidpi_proxy(mtm: MainThreadMarker, event: ScaleFactorChanged) {
+    let ScaleFactorChanged { suggested_size, scale_factor, window } = event;
+    let new_surface_size = Arc::new(Mutex::new(suggested_size));
+    get_handler(mtm).handle(|app| {
+        app.window_event(&ActiveEventLoop { mtm }, window.id(), WindowEvent::ScaleFactorChanged {
+            scale_factor,
+            surface_size_writer: SurfaceSizeWriter::new(Arc::downgrade(&new_surface_size)),
+        });
+    });
+    let (view, screen_frame) = get_view_and_screen_frame(&window);
+    let physical_size = *new_surface_size.lock().unwrap();
+    drop(new_surface_size);
+    let logical_size = physical_size.to_logical(scale_factor);
+    let size = CGSize::new(logical_size.width, logical_size.height);
+    let new_frame: CGRect = CGRect::new(screen_frame.origin, size);
+    view.setFrame(new_frame);
+}
+
+fn get_view_and_screen_frame(window: &WinitUIWindow) -> (Retained<UIView>, CGRect) {
+    let view_controller = window.rootViewController().unwrap();
+    let view = view_controller.view().unwrap();
+    let bounds = window.bounds();
+    let screen = window.screen();
+    let screen_space = screen.coordinateSpace();
+    let screen_frame = window.convertRect_toCoordinateSpace(bounds, &screen_space);
+    (view, screen_frame)
+}
+
+struct EventLoopWaker {
+    timer: CFRetained<CFRunLoopTimer>,
+}
+
+impl Drop for EventLoopWaker {
+    fn drop(&mut self) {
+        self.timer.invalidate();
+    }
+}
+
+impl EventLoopWaker {
+    fn new(rl: CFRetained<CFRunLoop>) -> EventLoopWaker {
+        extern "C-unwind" fn wakeup_main_loop(_timer: *mut CFRunLoopTimer, _info: *mut c_void) {}
+        unsafe {
+            // Create a timer with a 0.1µs interval (1ns does not work) to mimic polling.
+            // It is initially setup with a first fire time really far into the
+            // future, but that gets changed to fire immediately in did_finish_launching
+            let timer = CFRunLoopTimer::new(
+                None,
+                f64::MAX,
+                0.000_000_1,
+                0,
+                0,
+                Some(wakeup_main_loop),
+                ptr::null_mut(),
+            )
+            .unwrap();
+            rl.add_timer(Some(&timer), kCFRunLoopCommonModes);
+
+            EventLoopWaker { timer }
+        }
+    }
+
+    fn stop(&mut self) {
+        self.timer.set_next_fire_date(f64::MAX);
+    }
+
+    fn start(&mut self) {
+        self.timer.set_next_fire_date(f64::MIN);
+    }
+
+    fn start_at(&mut self, instant: Instant) {
+        let now = Instant::now();
+        if now >= instant {
+            self.start();
+        } else {
+            let current = CFAbsoluteTimeGetCurrent();
+            let duration = instant - now;
+            let fsecs =
+                duration.subsec_nanos() as f64 / 1_000_000_000.0 + duration.as_secs() as f64;
+            self.timer.set_next_fire_date(current + fsecs);
+        }
+    }
+}

winit-uikit/src/event_loop.rs

@@ -0,0 +1,356 @@
+use std::ffi::c_void;
+use std::ptr;
+use std::sync::Arc;
+
+use objc2::rc::Retained;
+use objc2::runtime::ProtocolObject;
+use objc2::{msg_send, ClassType, MainThreadMarker};
+use objc2_core_foundation::{
+    kCFRunLoopDefaultMode, CFIndex, CFRunLoop, CFRunLoopActivity, CFRunLoopObserver,
+};
+use objc2_foundation::{NSNotificationCenter, NSObjectProtocol};
+use objc2_ui_kit::{
+    UIApplication, UIApplicationDidBecomeActiveNotification,
+    UIApplicationDidEnterBackgroundNotification, UIApplicationDidFinishLaunchingNotification,
+    UIApplicationDidReceiveMemoryWarningNotification, UIApplicationWillEnterForegroundNotification,
+    UIApplicationWillResignActiveNotification, UIApplicationWillTerminateNotification, UIScreen,
+};
+use rwh_06::HasDisplayHandle;
+use winit_core::application::ApplicationHandler;
+use winit_core::cursor::{CustomCursor, CustomCursorSource};
+use winit_core::error::{EventLoopError, NotSupportedError, RequestError};
+use winit_core::event_loop::{
+    ActiveEventLoop as RootActiveEventLoop, ControlFlow, DeviceEvents,
+    EventLoopProxy as CoreEventLoopProxy, OwnedDisplayHandle as CoreOwnedDisplayHandle,
+};
+use winit_core::monitor::MonitorHandle as CoreMonitorHandle;
+use winit_core::window::{Theme, Window as CoreWindow};
+
+use super::app_state::{send_occluded_event_for_all_windows, AppState};
+use super::notification_center::create_observer;
+use crate::monitor::MonitorHandle;
+use crate::window::Window;
+use crate::{app_state, monitor};
+
+#[derive(Debug)]
+pub struct ActiveEventLoop {
+    pub(super) mtm: MainThreadMarker,
+}
+
+impl RootActiveEventLoop for ActiveEventLoop {
+    fn create_proxy(&self) -> CoreEventLoopProxy {
+        CoreEventLoopProxy::new(AppState::get_mut(self.mtm).event_loop_proxy().clone())
+    }
+
+    fn create_window(
+        &self,
+        window_attributes: winit_core::window::WindowAttributes,
+    ) -> Result<Box<dyn CoreWindow>, RequestError> {
+        Ok(Box::new(Window::new(self, window_attributes)?))
+    }
+
+    fn create_custom_cursor(
+        &self,
+        _source: CustomCursorSource,
+    ) -> Result<CustomCursor, RequestError> {
+        Err(NotSupportedError::new("create_custom_cursor is not supported").into())
+    }
+
+    fn available_monitors(&self) -> Box<dyn Iterator<Item = CoreMonitorHandle>> {
+        Box::new(
+            monitor::uiscreens(self.mtm)
+                .into_iter()
+                .map(|monitor| CoreMonitorHandle(Arc::new(monitor))),
+        )
+    }
+
+    fn primary_monitor(&self) -> Option<winit_core::monitor::MonitorHandle> {
+        #[allow(deprecated)]
+        let monitor = MonitorHandle::new(UIScreen::mainScreen(self.mtm));
+        Some(CoreMonitorHandle(Arc::new(monitor)))
+    }
+
+    fn listen_device_events(&self, _allowed: DeviceEvents) {}
+
+    fn set_control_flow(&self, control_flow: ControlFlow) {
+        AppState::get_mut(self.mtm).set_control_flow(control_flow)
+    }
+
+    fn system_theme(&self) -> Option<Theme> {
+        None
+    }
+
+    fn control_flow(&self) -> ControlFlow {
+        AppState::get_mut(self.mtm).control_flow()
+    }
+
+    fn exit(&self) {
+        // https://developer.apple.com/library/archive/qa/qa1561/_index.html
+        // it is not possible to quit an iOS app gracefully and programmatically
+        tracing::warn!("`ControlFlow::Exit` ignored on iOS");
+    }
+
+    fn exiting(&self) -> bool {
+        false
+    }
+
+    fn owned_display_handle(&self) -> CoreOwnedDisplayHandle {
+        CoreOwnedDisplayHandle::new(Arc::new(OwnedDisplayHandle))
+    }
+
+    fn rwh_06_handle(&self) -> &dyn rwh_06::HasDisplayHandle {
+        self
+    }
+}
+
+impl rwh_06::HasDisplayHandle for ActiveEventLoop {
+    fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
+        let raw = rwh_06::RawDisplayHandle::UiKit(rwh_06::UiKitDisplayHandle::new());
+        unsafe { Ok(rwh_06::DisplayHandle::borrow_raw(raw)) }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
+pub(crate) struct OwnedDisplayHandle;
+
+impl HasDisplayHandle for OwnedDisplayHandle {
+    fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
+        let raw = rwh_06::RawDisplayHandle::UiKit(rwh_06::UiKitDisplayHandle::new());
+        unsafe { Ok(rwh_06::DisplayHandle::borrow_raw(raw)) }
+    }
+}
+
+#[derive(Debug)]
+pub struct EventLoop {
+    mtm: MainThreadMarker,
+    window_target: ActiveEventLoop,
+
+    // Since iOS 9.0, we no longer need to remove the observers before they are deallocated; the
+    // system instead cleans it up next time it would have posted a notification to it.
+    //
+    // Though we do still need to keep the observers around to prevent them from being deallocated.
+    _did_finish_launching_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+    _did_become_active_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+    _will_resign_active_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+    _will_enter_foreground_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+    _did_enter_background_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+    _will_terminate_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+    _did_receive_memory_warning_observer: Retained<ProtocolObject<dyn NSObjectProtocol>>,
+}
+
+#[derive(Default, Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct PlatformSpecificEventLoopAttributes {}
+
+impl EventLoop {
+    pub fn new(_: &PlatformSpecificEventLoopAttributes) -> Result<EventLoop, EventLoopError> {
+        let mtm = MainThreadMarker::new()
+            .expect("On iOS, `EventLoop` must be created on the main thread");
+
+        static mut SINGLETON_INIT: bool = false;
+        unsafe {
+            assert!(
+                !SINGLETON_INIT,
+                "Only one `EventLoop` is supported on iOS. `EventLoopProxy` might be helpful"
+            );
+            SINGLETON_INIT = true;
+        }
+
+        // this line sets up the main run loop before `UIApplicationMain`
+        setup_control_flow_observers();
+
+        let center = unsafe { NSNotificationCenter::defaultCenter() };
+
+        let _did_finish_launching_observer = create_observer(
+            &center,
+            // `application:didFinishLaunchingWithOptions:`
+            unsafe { UIApplicationDidFinishLaunchingNotification },
+            move |_| {
+                app_state::did_finish_launching(mtm);
+            },
+        );
+        let _did_become_active_observer = create_observer(
+            &center,
+            // `applicationDidBecomeActive:`
+            unsafe { UIApplicationDidBecomeActiveNotification },
+            move |_| app_state::handle_resumed(mtm),
+        );
+        let _will_resign_active_observer = create_observer(
+            &center,
+            // `applicationWillResignActive:`
+            unsafe { UIApplicationWillResignActiveNotification },
+            move |_| app_state::handle_suspended(mtm),
+        );
+        let _will_enter_foreground_observer = create_observer(
+            &center,
+            // `applicationWillEnterForeground:`
+            unsafe { UIApplicationWillEnterForegroundNotification },
+            move |notification| {
+                let app = unsafe { notification.object() }.expect(
+                    "UIApplicationWillEnterForegroundNotification to have application object",
+                );
+                // The `object` in `UIApplicationWillEnterForegroundNotification` is documented to
+                // be `UIApplication`.
+                let app = app.downcast::<UIApplication>().unwrap();
+                send_occluded_event_for_all_windows(&app, false);
+            },
+        );
+        let _did_enter_background_observer = create_observer(
+            &center,
+            // `applicationDidEnterBackground:`
+            unsafe { UIApplicationDidEnterBackgroundNotification },
+            move |notification| {
+                let app = unsafe { notification.object() }.expect(
+                    "UIApplicationDidEnterBackgroundNotification to have application object",
+                );
+                // The `object` in `UIApplicationDidEnterBackgroundNotification` is documented to be
+                // `UIApplication`.
+                let app = app.downcast::<UIApplication>().unwrap();
+                send_occluded_event_for_all_windows(&app, true);
+            },
+        );
+        let _will_terminate_observer = create_observer(
+            &center,
+            // `applicationWillTerminate:`
+            unsafe { UIApplicationWillTerminateNotification },
+            move |notification| {
+                let app = unsafe { notification.object() }
+                    .expect("UIApplicationWillTerminateNotification to have application object");
+                // The `object` in `UIApplicationWillTerminateNotification` is (somewhat) documented
+                // to be `UIApplication`.
+                let app = app.downcast::<UIApplication>().unwrap();
+                app_state::terminated(&app);
+            },
+        );
+        let _did_receive_memory_warning_observer = create_observer(
+            &center,
+            // `applicationDidReceiveMemoryWarning:`
+            unsafe { UIApplicationDidReceiveMemoryWarningNotification },
+            move |_| app_state::handle_memory_warning(mtm),
+        );
+
+        Ok(EventLoop {
+            mtm,
+            window_target: ActiveEventLoop { mtm },
+            _did_finish_launching_observer,
+            _did_become_active_observer,
+            _will_resign_active_observer,
+            _will_enter_foreground_observer,
+            _did_enter_background_observer,
+            _will_terminate_observer,
+            _did_receive_memory_warning_observer,
+        })
+    }
+
+    pub fn run_app<A: ApplicationHandler>(self, app: A) -> ! {
+        let application: Option<Retained<UIApplication>> =
+            unsafe { msg_send![UIApplication::class(), sharedApplication] };
+        assert!(
+            application.is_none(),
+            "\
+                `EventLoop` cannot be `run` after a call to `UIApplicationMain` on iOS\nNote: \
+             `EventLoop::run_app` calls `UIApplicationMain` on iOS",
+        );
+
+        // We intentionally override neither the application nor the delegate,
+        // to allow the user to do so themselves!
+        app_state::launch(self.mtm, app, || UIApplication::main(None, None, self.mtm))
+    }
+
+    pub fn window_target(&self) -> &dyn RootActiveEventLoop {
+        &self.window_target
+    }
+}
+
+fn setup_control_flow_observers() {
+    unsafe {
+        // begin is queued with the highest priority to ensure it is processed before other
+        // observers
+        extern "C-unwind" fn control_flow_begin_handler(
+            _: *mut CFRunLoopObserver,
+            activity: CFRunLoopActivity,
+            _: *mut c_void,
+        ) {
+            let mtm = MainThreadMarker::new().unwrap();
+            #[allow(non_upper_case_globals)]
+            match activity {
+                CFRunLoopActivity::AfterWaiting => app_state::handle_wakeup_transition(mtm),
+                _ => unreachable!(),
+            }
+        }
+
+        // Core Animation registers its `CFRunLoopObserver` that performs drawing operations in
+        // `CA::Transaction::ensure_implicit` with a priority of `0x1e8480`. We set the main_end
+        // priority to be 0, in order to send AboutToWait before RedrawRequested. This value was
+        // chosen conservatively to guard against apple using different priorities for their redraw
+        // observers in different OS's or on different devices. If it so happens that it's too
+        // conservative, the main symptom would be non-redraw events coming in after `AboutToWait`.
+        //
+        // The value of `0x1e8480` was determined by inspecting stack traces and the associated
+        // registers for every `CFRunLoopAddObserver` call on an iPad Air 2 running iOS 11.4.
+        //
+        // Also tested to be `0x1e8480` on iPhone 8, iOS 13 beta 4.
+        extern "C-unwind" fn control_flow_main_end_handler(
+            _: *mut CFRunLoopObserver,
+            activity: CFRunLoopActivity,
+            _: *mut c_void,
+        ) {
+            let mtm = MainThreadMarker::new().unwrap();
+            #[allow(non_upper_case_globals)]
+            match activity {
+                CFRunLoopActivity::BeforeWaiting => app_state::handle_main_events_cleared(mtm),
+                CFRunLoopActivity::Exit => {}, // may happen when running on macOS
+                _ => unreachable!(),
+            }
+        }
+
+        // end is queued with the lowest priority to ensure it is processed after other observers
+        extern "C-unwind" fn control_flow_end_handler(
+            _: *mut CFRunLoopObserver,
+            activity: CFRunLoopActivity,
+            _: *mut c_void,
+        ) {
+            let mtm = MainThreadMarker::new().unwrap();
+            #[allow(non_upper_case_globals)]
+            match activity {
+                CFRunLoopActivity::BeforeWaiting => app_state::handle_events_cleared(mtm),
+                CFRunLoopActivity::Exit => {}, // may happen when running on macOS
+                _ => unreachable!(),
+            }
+        }
+
+        let main_loop = CFRunLoop::main().unwrap();
+
+        let begin_observer = CFRunLoopObserver::new(
+            None,
+            CFRunLoopActivity::AfterWaiting.0,
+            true,
+            CFIndex::MIN,
+            Some(control_flow_begin_handler),
+            ptr::null_mut(),
+        )
+        .unwrap();
+        main_loop.add_observer(Some(&begin_observer), kCFRunLoopDefaultMode);
+
+        let main_end_observer = CFRunLoopObserver::new(
+            None,
+            (CFRunLoopActivity::Exit | CFRunLoopActivity::BeforeWaiting).0,
+            true,
+            0, // see comment on `control_flow_main_end_handler`
+            Some(control_flow_main_end_handler),
+            ptr::null_mut(),
+        )
+        .unwrap();
+        main_loop.add_observer(Some(&main_end_observer), kCFRunLoopDefaultMode);
+
+        let end_observer = CFRunLoopObserver::new(
+            None,
+            (CFRunLoopActivity::Exit | CFRunLoopActivity::BeforeWaiting).0,
+            true,
+            CFIndex::MAX,
+            Some(control_flow_end_handler),
+            ptr::null_mut(),
+        )
+        .unwrap();
+        main_loop.add_observer(Some(&end_observer), kCFRunLoopDefaultMode);
+    }
+}

winit-uikit/src/lib.rs

@@ -0,0 +1,457 @@
+//! # Winit's UIKit (iOS/tvOS/visionOS) backend
+//!
+//! Winit has [the same iOS version requirements as `rustc`][rustc-ios-version], although it's
+//! frequently only tested on newer iOS versions.
+//!
+//! [rustc-ios-version]: https://doc.rust-lang.org/rustc/platform-support/apple-ios.html#os-version
+//!
+//! ## Running on Mac Catalyst
+//!
+//! Mac Catalyst allows running applications using UIKit on macOS, which can be very useful for
+//! testing. See [`rustc`'s documentation on Mac Catalyst][rustc-mac-catalyst] for details on how to
+//! use these targets. To use these with Winit, you'll need to bundle your application before
+//! running it, otherwise UIKit will exit with an error.
+//!
+//! To run e.g. the `window` example in the Winit repository, you can use [`cargo-bundle`] as
+//! follows:
+//!
+//! ```console
+//! $ cargo +nightly bundle --format=ios --target=aarch64-apple-ios-macabi --example=window
+//! $ ./target/aarch64-apple-ios-macabi/debug/examples/bundle/ios/winit.app/window
+//! ```
+//!
+//! [rustc-mac-catalyst]: https://doc.rust-lang.org/rustc/platform-support/apple-ios-macabi.html
+//! [`cargo-bundle`]: https://github.com/burtonageo/cargo-bundle
+//!
+//! ## Introduction to building an app
+//!
+//! Building and running your application in the iOS simulator, or on a real device, is a bit more
+//! complicated than Mac Catalyst - fundamentally, you must use Xcode, since the binary needs to be
+//! bundled, signed, notarized and uploaded to the device (there is [an open source work-in-progress
+//! on re-implementing parts of this][apple-platform-rs], but the user-story around it is not yet
+//! clear).
+//!
+//! This means that you're left with effectively two options: Use a tool that manages the Xcode
+//! configuration for you, or use Xcode directly. [`cargo-dinghy`] and [`cargo-mobile2`] are notable
+//! projects in the ecosystem that attempt the former, and [`cargo-xcode`] is an excellent project
+//! that attempts the latter. We will also attempt to describe here how you would go about using
+//! Xcode directly:
+//!
+//! First off, you'll need the correct Rust targets, see [`rustc`'s documentation on iOS][rustc-ios]
+//! for details. Nowadays, the correct targets are usually `aarch64-apple-ios-sim` for the
+//! simulator, and `aarch64-apple-ios` for the actual device.
+//!
+//! Next, create a new Xcode project using the "App" template. The exact configuration does not
+//! really matter, as we're going to delete most of it, since it's tailored for Objective-C and/or
+//! Swift, and Rust/Winit is neither. Specifically, we need to delete:
+//! - Everything relating to storyboards (unless you want to use e.g. a launch screen). This
+//!   includes the relevant keys in `Info.plist`.
+//! - All the generated C header, Objective-C and/or Swift files.
+//!
+//! Now that we have a fairly clean slate that we can build upon, you can add a "run script" build
+//! phase to your Xcode target, which will get invoked instead of the "compile sources" and "link
+//! binary" steps. The basic script should look something like:
+//!
+//! ```sh
+//! # Build desired targets based on `ARCHS` environment variable
+//! cargo build --target=aarch64-apple-ios --target=armv7s-apple-ios
+//! # Merge these with `lipo`, and place the result in "$TARGET_BUILD_DIR/$EXECUTABLE_PATH", which
+//! # is understood by Xcode
+//! lipo "$TARGET_BUILD_DIR/$EXECUTABLE_PATH" target/aarch64-apple-ios/debug/my_app target/armv7s-apple-ios/debug/my_app
+//! ```
+//!
+//! Note that this is very much the overall idea; the script needs to be much more involved to
+//! properly deal with different target architectures, invoking `lipo` when needed, incremental
+//! rebuild change detection, and so on. `cargo-xcode` has a script [here][cargo-xcode-script] that
+//! handles most of this complexity, you might be able to build upon that.
+//!
+//! Apologies that we're not able to provide you with more than this; work is in-progress on
+//! improving the situation, but it's slow-going.
+//!
+//! [apple-platform-rs]: https://github.com/indygreg/apple-platform-rs
+//! [`cargo-dinghy`]: https://github.com/sonos/dinghy
+//! [`cargo-mobile2`]: https://github.com/tauri-apps/cargo-mobile2
+//! [`cargo-xcode`]: https://crates.io/crates/cargo-xcode
+//! [rustc-ios]: https://doc.rust-lang.org/rustc/platform-support/apple-ios.html
+//! [cargo-xcode-script]: https://gitlab.com/kornelski/cargo-xcode/-/blob/main/src/xcodebuild.sh
+//!
+//! ## App lifecycle and events
+//!
+//! iOS environment is very different from other platforms and you must be very
+//! careful with it's events. Familiarize yourself with
+//! [app lifecycle](https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplicationDelegate_Protocol/).
+//!
+//! This is how those event are represented in winit:
+//!
+//!  - applicationDidBecomeActive is Resumed
+//!  - applicationWillResignActive is Suspended
+//!  - applicationWillTerminate corresponds to `Drop`ping the application handler.
+//!
+//! Note that an app may not receive the `Drop` event if suspended; it might be SIGKILL'ed.
+//!
+//! ## Custom `UIApplicationDelegate`
+//!
+//! Winit usually handles everything related to the lifecycle events of the application. Sometimes,
+//! though, you might want to access some of the more niche stuff that [the application
+//! delegate][app-delegate] provides. This functionality is not exposed directly in Winit, since it
+//! would increase the API surface by quite a lot. Instead, Winit guarantees that it will not
+//! register an application delegate, so you can set up a custom one in a nib file instead.
+//!
+//! [app-delegate]: https://developer.apple.com/documentation/uikit/uiapplicationdelegate?language=objc
+#![cfg(target_vendor = "apple")] // TODO: Remove once `objc2` allows compiling on all platforms
+
+mod app_state;
+mod event_loop;
+mod monitor;
+mod notification_center;
+mod view;
+mod view_controller;
+mod window;
+
+use std::os::raw::c_void;
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+use winit_core::monitor::{MonitorHandle, VideoMode};
+use winit_core::window::{PlatformWindowAttributes, Window};
+
+pub use self::event_loop::{EventLoop, PlatformSpecificEventLoopAttributes};
+use self::monitor::MonitorHandle as UIKitMonitorHandle;
+use self::window::Window as UIKitWindow;
+
+/// Additional methods on [`Window`] that are specific to iOS.
+pub trait WindowExtIOS {
+    /// Sets the [`contentScaleFactor`] of the underlying [`UIWindow`] to `scale_factor`.
+    ///
+    /// The default value is device dependent, and it's recommended GLES or Metal applications set
+    /// this to [`MonitorHandleProvider::scale_factor()`].
+    ///
+    /// [`UIWindow`]: https://developer.apple.com/documentation/uikit/uiwindow?language=objc
+    /// [`contentScaleFactor`]: https://developer.apple.com/documentation/uikit/uiview/1622657-contentscalefactor?language=objc
+    /// [`MonitorHandleProvider::scale_factor()`]: crate::monitor::MonitorHandleProvider::scale_factor()
+    fn set_scale_factor(&self, scale_factor: f64);
+
+    /// Sets the valid orientations for the [`Window`].
+    ///
+    /// The default value is [`ValidOrientations::LandscapeAndPortrait`].
+    ///
+    /// This changes the value returned by
+    /// [`-[UIViewController supportedInterfaceOrientations]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621435-supportedinterfaceorientations?language=objc),
+    /// and then calls
+    /// [`-[UIViewController attemptRotationToDeviceOrientation]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621400-attemptrotationtodeviceorientati?language=objc).
+    fn set_valid_orientations(&self, valid_orientations: ValidOrientations);
+
+    /// Sets whether the [`Window`] prefers the home indicator hidden.
+    ///
+    /// The default is to prefer showing the home indicator.
+    ///
+    /// This changes the value returned by
+    /// [`-[UIViewController prefersHomeIndicatorAutoHidden]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/2887510-prefershomeindicatorautohidden?language=objc),
+    /// and then calls
+    /// [`-[UIViewController setNeedsUpdateOfHomeIndicatorAutoHidden]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/2887509-setneedsupdateofhomeindicatoraut?language=objc).
+    ///
+    /// This only has an effect on iOS 11.0+.
+    fn set_prefers_home_indicator_hidden(&self, hidden: bool);
+
+    /// Sets the screen edges for which the system gestures will take a lower priority than the
+    /// application's touch handling.
+    ///
+    /// This changes the value returned by
+    /// [`-[UIViewController preferredScreenEdgesDeferringSystemGestures]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/2887512-preferredscreenedgesdeferringsys?language=objc),
+    /// and then calls
+    /// [`-[UIViewController setNeedsUpdateOfScreenEdgesDeferringSystemGestures]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/2887507-setneedsupdateofscreenedgesdefer?language=objc).
+    ///
+    /// This only has an effect on iOS 11.0+.
+    fn set_preferred_screen_edges_deferring_system_gestures(&self, edges: ScreenEdge);
+
+    /// Sets whether the [`Window`] prefers the status bar hidden.
+    ///
+    /// The default is to prefer showing the status bar.
+    ///
+    /// This sets the value of the
+    /// [`prefersStatusBarHidden`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621440-prefersstatusbarhidden?language=objc)
+    /// property.
+    ///
+    /// [`setNeedsStatusBarAppearanceUpdate()`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621354-setneedsstatusbarappearanceupdat?language=objc)
+    /// is also called for you.
+    fn set_prefers_status_bar_hidden(&self, hidden: bool);
+
+    /// Sets the preferred status bar style for the [`Window`].
+    ///
+    /// The default is system-defined.
+    ///
+    /// This sets the value of the
+    /// [`preferredStatusBarStyle`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621416-preferredstatusbarstyle?language=objc)
+    /// property.
+    ///
+    /// [`setNeedsStatusBarAppearanceUpdate()`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621354-setneedsstatusbarappearanceupdat?language=objc)
+    /// is also called for you.
+    fn set_preferred_status_bar_style(&self, status_bar_style: StatusBarStyle);
+
+    /// Sets whether the [`Window`] should recognize pinch gestures.
+    ///
+    /// The default is to not recognize gestures.
+    fn recognize_pinch_gesture(&self, should_recognize: bool);
+
+    /// Sets whether the [`Window`] should recognize pan gestures.
+    ///
+    /// The default is to not recognize gestures.
+    /// Installs [`UIPanGestureRecognizer`](https://developer.apple.com/documentation/uikit/uipangesturerecognizer) onto view
+    ///
+    /// Set the minimum number of touches required: [`minimumNumberOfTouches`](https://developer.apple.com/documentation/uikit/uipangesturerecognizer/1621208-minimumnumberoftouches)
+    ///
+    /// Set the maximum number of touches recognized: [`maximumNumberOfTouches`](https://developer.apple.com/documentation/uikit/uipangesturerecognizer/1621208-maximumnumberoftouches)
+    fn recognize_pan_gesture(
+        &self,
+        should_recognize: bool,
+        minimum_number_of_touches: u8,
+        maximum_number_of_touches: u8,
+    );
+
+    /// Sets whether the [`Window`] should recognize double tap gestures.
+    ///
+    /// The default is to not recognize gestures.
+    fn recognize_doubletap_gesture(&self, should_recognize: bool);
+
+    /// Sets whether the [`Window`] should recognize rotation gestures.
+    ///
+    /// The default is to not recognize gestures.
+    fn recognize_rotation_gesture(&self, should_recognize: bool);
+}
+
+impl WindowExtIOS for dyn Window + '_ {
+    #[inline]
+    fn set_scale_factor(&self, scale_factor: f64) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.set_scale_factor(scale_factor));
+    }
+
+    #[inline]
+    fn set_valid_orientations(&self, valid_orientations: ValidOrientations) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.set_valid_orientations(valid_orientations));
+    }
+
+    #[inline]
+    fn set_prefers_home_indicator_hidden(&self, hidden: bool) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.set_prefers_home_indicator_hidden(hidden));
+    }
+
+    #[inline]
+    fn set_preferred_screen_edges_deferring_system_gestures(&self, edges: ScreenEdge) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| {
+            w.set_preferred_screen_edges_deferring_system_gestures(edges)
+        });
+    }
+
+    #[inline]
+    fn set_prefers_status_bar_hidden(&self, hidden: bool) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.set_prefers_status_bar_hidden(hidden));
+    }
+
+    #[inline]
+    fn set_preferred_status_bar_style(&self, status_bar_style: StatusBarStyle) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.set_preferred_status_bar_style(status_bar_style))
+    }
+
+    #[inline]
+    fn recognize_pinch_gesture(&self, should_recognize: bool) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.recognize_pinch_gesture(should_recognize));
+    }
+
+    #[inline]
+    fn recognize_pan_gesture(
+        &self,
+        should_recognize: bool,
+        minimum_number_of_touches: u8,
+        maximum_number_of_touches: u8,
+    ) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| {
+            w.recognize_pan_gesture(
+                should_recognize,
+                minimum_number_of_touches,
+                maximum_number_of_touches,
+            )
+        });
+    }
+
+    #[inline]
+    fn recognize_doubletap_gesture(&self, should_recognize: bool) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.recognize_doubletap_gesture(should_recognize));
+    }
+
+    #[inline]
+    fn recognize_rotation_gesture(&self, should_recognize: bool) {
+        let window = self.cast_ref::<UIKitWindow>().unwrap();
+        window.maybe_wait_on_main(move |w| w.recognize_rotation_gesture(should_recognize));
+    }
+}
+
+/// Ios specific window attributes.
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct WindowAttributesIos {
+    pub(crate) scale_factor: Option<f64>,
+    pub(crate) valid_orientations: ValidOrientations,
+    pub(crate) prefers_home_indicator_hidden: bool,
+    pub(crate) prefers_status_bar_hidden: bool,
+    pub(crate) preferred_status_bar_style: StatusBarStyle,
+    pub(crate) preferred_screen_edges_deferring_system_gestures: ScreenEdge,
+}
+
+impl WindowAttributesIos {
+    /// Sets the [`contentScaleFactor`] of the underlying [`UIWindow`] to `scale_factor`.
+    ///
+    /// The default value is device dependent, and it's recommended GLES or Metal applications set
+    /// this to [`MonitorHandleProvider::scale_factor()`].
+    ///
+    /// [`UIWindow`]: https://developer.apple.com/documentation/uikit/uiwindow?language=objc
+    /// [`contentScaleFactor`]: https://developer.apple.com/documentation/uikit/uiview/1622657-contentscalefactor?language=objc
+    /// [`MonitorHandleProvider::scale_factor()`]: crate::monitor::MonitorHandleProvider::scale_factor()
+    pub fn with_scale_factor(mut self, scale_factor: f64) -> Self {
+        self.scale_factor = Some(scale_factor);
+        self
+    }
+
+    /// Sets the valid orientations for the [`Window`].
+    ///
+    /// The default value is [`ValidOrientations::LandscapeAndPortrait`].
+    ///
+    /// This sets the initial value returned by
+    /// [`-[UIViewController supportedInterfaceOrientations]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621435-supportedinterfaceorientations?language=objc).
+    pub fn with_valid_orientations(mut self, valid_orientations: ValidOrientations) -> Self {
+        self.valid_orientations = valid_orientations;
+        self
+    }
+
+    /// Sets whether the [`Window`] prefers the home indicator hidden.
+    ///
+    /// The default is to prefer showing the home indicator.
+    ///
+    /// This sets the initial value returned by
+    /// [`-[UIViewController prefersHomeIndicatorAutoHidden]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/2887510-prefershomeindicatorautohidden?language=objc).
+    ///
+    /// This only has an effect on iOS 11.0+.
+    pub fn with_prefers_home_indicator_hidden(mut self, hidden: bool) -> Self {
+        self.prefers_home_indicator_hidden = hidden;
+        self
+    }
+
+    /// Sets the screen edges for which the system gestures will take a lower priority than the
+    /// application's touch handling.
+    ///
+    /// This sets the initial value returned by
+    /// [`-[UIViewController preferredScreenEdgesDeferringSystemGestures]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/2887512-preferredscreenedgesdeferringsys?language=objc).
+    ///
+    /// This only has an effect on iOS 11.0+.
+    pub fn with_preferred_screen_edges_deferring_system_gestures(
+        mut self,
+        edges: ScreenEdge,
+    ) -> Self {
+        self.preferred_screen_edges_deferring_system_gestures = edges;
+        self
+    }
+
+    /// Sets whether the [`Window`] prefers the status bar hidden.
+    ///
+    /// The default is to prefer showing the status bar.
+    ///
+    /// This sets the initial value returned by
+    /// [`-[UIViewController prefersStatusBarHidden]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621440-prefersstatusbarhidden?language=objc).
+    pub fn with_prefers_status_bar_hidden(mut self, hidden: bool) -> Self {
+        self.prefers_status_bar_hidden = hidden;
+        self
+    }
+
+    /// Sets the style of the [`Window`]'s status bar.
+    ///
+    /// The default is system-defined.
+    ///
+    /// This sets the initial value returned by
+    /// [`-[UIViewController preferredStatusBarStyle]`](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621416-preferredstatusbarstyle?language=objc),
+    pub fn with_preferred_status_bar_style(mut self, status_bar_style: StatusBarStyle) -> Self {
+        self.preferred_status_bar_style = status_bar_style;
+        self
+    }
+}
+
+impl PlatformWindowAttributes for WindowAttributesIos {
+    fn box_clone(&self) -> Box<dyn PlatformWindowAttributes> {
+        Box::from(self.clone())
+    }
+}
+
+/// Additional methods on [`MonitorHandle`] that are specific to iOS.
+pub trait MonitorHandleExtIOS {
+    /// Returns a pointer to the [`UIScreen`] that is used by this monitor.
+    ///
+    /// [`UIScreen`]: https://developer.apple.com/documentation/uikit/uiscreen?language=objc
+    fn ui_screen(&self) -> *mut c_void;
+
+    /// Returns the preferred [`VideoMode`] for this monitor.
+    ///
+    /// This translates to a call to [`-[UIScreen preferredMode]`](https://developer.apple.com/documentation/uikit/uiscreen/1617823-preferredmode?language=objc).
+    fn preferred_video_mode(&self) -> VideoMode;
+}
+
+impl MonitorHandleExtIOS for MonitorHandle {
+    #[inline]
+    fn ui_screen(&self) -> *mut c_void {
+        // SAFETY: The marker is only used to get the pointer of the screen
+        let mtm = unsafe { objc2::MainThreadMarker::new_unchecked() };
+        let monitor = self.cast_ref::<UIKitMonitorHandle>().unwrap();
+        objc2::rc::Retained::as_ptr(monitor.ui_screen(mtm)) as *mut c_void
+    }
+
+    #[inline]
+    fn preferred_video_mode(&self) -> VideoMode {
+        let monitor = self.cast_ref::<UIKitMonitorHandle>().unwrap();
+        monitor.preferred_video_mode()
+    }
+}
+
+/// Valid orientations for a particular [`Window`].
+#[derive(Default, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum ValidOrientations {
+    /// Excludes `PortraitUpsideDown` on iphone
+    #[default]
+    LandscapeAndPortrait,
+
+    Landscape,
+
+    /// Excludes `PortraitUpsideDown` on iphone
+    Portrait,
+}
+
+bitflags::bitflags! {
+    /// The [edges] of a screen.
+    ///
+    /// [edges]: https://developer.apple.com/documentation/uikit/uirectedge?language=objc
+    #[derive(Default, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+    #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+    pub struct ScreenEdge: u8 {
+        const NONE   = 0;
+        const TOP    = 1 << 0;
+        const LEFT   = 1 << 1;
+        const BOTTOM = 1 << 2;
+        const RIGHT  = 1 << 3;
+        const ALL = ScreenEdge::TOP.bits() | ScreenEdge::LEFT.bits()
+            | ScreenEdge::BOTTOM.bits() | ScreenEdge::RIGHT.bits();
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum StatusBarStyle {
+    #[default]
+    Default,
+    LightContent,
+    DarkContent,
+}

winit-uikit/src/monitor.rs

@@ -0,0 +1,278 @@
+#![allow(clippy::unnecessary_cast)]
+
+use std::collections::VecDeque;
+use std::num::NonZeroU32;
+use std::{fmt, hash, ptr};
+
+use dispatch2::{run_on_main, MainThreadBound};
+use dpi::PhysicalPosition;
+use objc2::rc::Retained;
+use objc2::{available, MainThreadMarker, Message};
+use objc2_foundation::NSInteger;
+use objc2_ui_kit::{UIScreen, UIScreenMode};
+use winit_core::monitor::{MonitorHandleProvider, VideoMode};
+
+// Workaround for `MainThreadBound` implementing almost no traits
+#[derive(Debug)]
+struct MainThreadBoundDelegateImpls<T>(MainThreadBound<Retained<T>>);
+
+impl<T: Message> Clone for MainThreadBoundDelegateImpls<T> {
+    fn clone(&self) -> Self {
+        Self(run_on_main(|mtm| MainThreadBound::new(Retained::clone(self.0.get(mtm)), mtm)))
+    }
+}
+
+impl<T: Message> hash::Hash for MainThreadBoundDelegateImpls<T> {
+    fn hash<H: hash::Hasher>(&self, state: &mut H) {
+        // SAFETY: Marker only used to get the pointer
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        Retained::as_ptr(self.0.get(mtm)).hash(state);
+    }
+}
+
+impl<T: Message> PartialEq for MainThreadBoundDelegateImpls<T> {
+    fn eq(&self, other: &Self) -> bool {
+        // SAFETY: Marker only used to get the pointer
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        Retained::as_ptr(self.0.get(mtm)) == Retained::as_ptr(other.0.get(mtm))
+    }
+}
+
+impl<T: Message> Eq for MainThreadBoundDelegateImpls<T> {}
+
+#[derive(Debug, PartialEq, Eq, Hash, Clone)]
+pub struct VideoModeHandle {
+    pub(crate) mode: VideoMode,
+    screen_mode: MainThreadBoundDelegateImpls<UIScreenMode>,
+}
+
+impl VideoModeHandle {
+    fn new(
+        uiscreen: Retained<UIScreen>,
+        screen_mode: Retained<UIScreenMode>,
+        mtm: MainThreadMarker,
+    ) -> VideoModeHandle {
+        let refresh_rate_millihertz = refresh_rate_millihertz(&uiscreen);
+        let size = screen_mode.size();
+        let mode = VideoMode::new(
+            (size.width as u32, size.height as u32).into(),
+            None,
+            refresh_rate_millihertz,
+        );
+
+        VideoModeHandle {
+            mode,
+            screen_mode: MainThreadBoundDelegateImpls(MainThreadBound::new(screen_mode, mtm)),
+        }
+    }
+
+    pub(super) fn screen_mode(&self, mtm: MainThreadMarker) -> &Retained<UIScreenMode> {
+        self.screen_mode.0.get(mtm)
+    }
+}
+
+pub struct MonitorHandle {
+    ui_screen: MainThreadBound<Retained<UIScreen>>,
+}
+
+impl MonitorHandleProvider for MonitorHandle {
+    fn id(&self) -> u128 {
+        self.native_id() as _
+    }
+
+    fn native_id(&self) -> u64 {
+        // SAFETY: Only getting the pointer.
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        Retained::as_ptr(self.ui_screen.get(mtm)) as u64
+    }
+
+    fn name(&self) -> Option<std::borrow::Cow<'_, str>> {
+        run_on_main(|mtm| {
+            #[allow(deprecated)]
+            let main = UIScreen::mainScreen(mtm);
+            if *self.ui_screen(mtm) == main {
+                Some("Primary".into())
+            } else if Some(self.ui_screen(mtm)) == main.mirroredScreen().as_ref() {
+                Some("Mirrored".into())
+            } else {
+                #[allow(deprecated)]
+                UIScreen::screens(mtm)
+                    .iter()
+                    .position(|rhs| rhs == *self.ui_screen(mtm))
+                    .map(|idx| idx.to_string().into())
+            }
+        })
+    }
+
+    fn position(&self) -> Option<PhysicalPosition<i32>> {
+        let bounds = self.ui_screen.get_on_main(|ui_screen| ui_screen.nativeBounds());
+        Some((bounds.origin.x as f64, bounds.origin.y as f64).into())
+    }
+
+    fn scale_factor(&self) -> f64 {
+        self.ui_screen.get_on_main(|ui_screen| ui_screen.nativeScale()) as f64
+    }
+
+    fn current_video_mode(&self) -> Option<VideoMode> {
+        Some(run_on_main(|mtm| {
+            VideoModeHandle::new(
+                self.ui_screen(mtm).clone(),
+                self.ui_screen(mtm).currentMode().unwrap(),
+                mtm,
+            )
+            .mode
+        }))
+    }
+
+    fn video_modes(&self) -> Box<dyn Iterator<Item = VideoMode>> {
+        Box::new(self.video_modes())
+    }
+}
+
+impl Clone for MonitorHandle {
+    fn clone(&self) -> Self {
+        run_on_main(|mtm| Self {
+            ui_screen: MainThreadBound::new(self.ui_screen.get(mtm).clone(), mtm),
+        })
+    }
+}
+
+impl hash::Hash for MonitorHandle {
+    fn hash<H: hash::Hasher>(&self, state: &mut H) {
+        // SAFETY: Only getting the pointer.
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        Retained::as_ptr(self.ui_screen.get(mtm)).hash(state);
+    }
+}
+
+impl PartialEq for MonitorHandle {
+    fn eq(&self, other: &Self) -> bool {
+        // SAFETY: Only getting the pointer.
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        ptr::eq(
+            Retained::as_ptr(self.ui_screen.get(mtm)),
+            Retained::as_ptr(other.ui_screen.get(mtm)),
+        )
+    }
+}
+
+impl Eq for MonitorHandle {}
+
+impl PartialOrd for MonitorHandle {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for MonitorHandle {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        // SAFETY: Only getting the pointer.
+        // TODO: Make a better ordering
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+        Retained::as_ptr(self.ui_screen.get(mtm)).cmp(&Retained::as_ptr(other.ui_screen.get(mtm)))
+    }
+}
+
+impl fmt::Debug for MonitorHandle {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("MonitorHandle")
+            .field("name", &self.name())
+            .field("position", &self.position())
+            .field("scale_factor", &self.scale_factor())
+            .finish_non_exhaustive()
+    }
+}
+
+impl MonitorHandle {
+    pub(crate) fn new(ui_screen: Retained<UIScreen>) -> Self {
+        // Holding `Retained<UIScreen>` implies we're on the main thread.
+        let mtm = MainThreadMarker::new().unwrap();
+        Self { ui_screen: MainThreadBound::new(ui_screen, mtm) }
+    }
+
+    pub fn video_modes_handles(&self) -> impl Iterator<Item = VideoModeHandle> {
+        run_on_main(|mtm| {
+            let ui_screen = self.ui_screen(mtm);
+
+            ui_screen
+                .availableModes()
+                .into_iter()
+                .map(|mode| VideoModeHandle::new(ui_screen.clone(), mode, mtm))
+                .collect::<Vec<_>>()
+                .into_iter()
+        })
+    }
+
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
+        self.video_modes_handles().map(|handle| handle.mode)
+    }
+
+    pub(crate) fn ui_screen(&self, mtm: MainThreadMarker) -> &Retained<UIScreen> {
+        self.ui_screen.get(mtm)
+    }
+
+    pub fn preferred_video_mode(&self) -> VideoMode {
+        run_on_main(|mtm| {
+            VideoModeHandle::new(
+                self.ui_screen(mtm).clone(),
+                self.ui_screen(mtm).preferredMode().unwrap(),
+                mtm,
+            )
+            .mode
+        })
+    }
+}
+
+fn refresh_rate_millihertz(uiscreen: &UIScreen) -> Option<NonZeroU32> {
+    let refresh_rate_millihertz: NSInteger = {
+        if available!(ios = 10.3, tvos = 10.2) {
+            uiscreen.maximumFramesPerSecond()
+        } else {
+            // https://developer.apple.com/library/archive/technotes/tn2460/_index.html
+            // https://en.wikipedia.org/wiki/IPad_Pro#Model_comparison
+            //
+            // All iOS devices support 60 fps, and on devices where `maximumFramesPerSecond` is not
+            // supported, they are all guaranteed to have 60hz refresh rates. This does not
+            // correctly handle external displays. ProMotion displays support 120fps, but they were
+            // introduced at the same time as the `maximumFramesPerSecond` API.
+            //
+            // FIXME: earlier OSs could calculate the refresh rate using
+            // `-[CADisplayLink duration]`.
+            tracing::warn!(
+                "`maximumFramesPerSecond` requires iOS 10.3+ or tvOS 10.2+. Defaulting to 60 fps"
+            );
+            60
+        }
+    };
+
+    NonZeroU32::new(refresh_rate_millihertz as u32 * 1000)
+}
+
+pub fn uiscreens(mtm: MainThreadMarker) -> VecDeque<MonitorHandle> {
+    #[allow(deprecated)]
+    UIScreen::screens(mtm).into_iter().map(MonitorHandle::new).collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use objc2_foundation::NSSet;
+
+    use super::*;
+
+    // Test that UIScreen pointer comparisons are correct.
+    #[test]
+    #[allow(deprecated)]
+    fn screen_comparisons() {
+        // Test code, doesn't matter that it's not thread safe
+        let mtm = unsafe { MainThreadMarker::new_unchecked() };
+
+        assert!(ptr::eq(&*UIScreen::mainScreen(mtm), &*UIScreen::mainScreen(mtm)));
+
+        let main = UIScreen::mainScreen(mtm);
+        assert!(UIScreen::screens(mtm).iter().any(|screen| ptr::eq(&*screen, &*main)));
+
+        assert!(unsafe {
+            NSSet::setWithArray(&UIScreen::screens(mtm)).containsObject(&UIScreen::mainScreen(mtm))
+        });
+    }
+}

winit-uikit/src/notification_center.rs

@@ -0,0 +1 @@
+../../src/platform_impl/apple/appkit/notification_center.rs

winit-uikit/src/view.rs

@@ -0,0 +1,684 @@
+#![allow(clippy::unnecessary_cast)]
+use std::cell::{Cell, RefCell};
+
+use dpi::PhysicalPosition;
+use objc2::rc::Retained;
+use objc2::runtime::{NSObjectProtocol, ProtocolObject};
+use objc2::{available, define_class, msg_send, sel, DefinedClass, MainThreadMarker};
+use objc2_core_foundation::{CGFloat, CGPoint, CGRect};
+use objc2_foundation::{NSObject, NSSet, NSString};
+use objc2_ui_kit::{
+    UIEvent, UIForceTouchCapability, UIGestureRecognizer, UIGestureRecognizerDelegate,
+    UIGestureRecognizerState, UIKeyInput, UIPanGestureRecognizer, UIPinchGestureRecognizer,
+    UIResponder, UIRotationGestureRecognizer, UITapGestureRecognizer, UITextInputTraits, UITouch,
+    UITouchPhase, UITouchType, UITraitEnvironment, UIView,
+};
+use tracing::debug;
+use winit_core::event::{
+    ButtonSource, ElementState, FingerId, Force, KeyEvent, PointerKind, PointerSource, TouchPhase,
+    WindowEvent,
+};
+use winit_core::keyboard::{Key, KeyCode, KeyLocation, NamedKey, NativeKeyCode, PhysicalKey};
+
+use super::app_state::{self, EventWrapper};
+use super::window::WinitUIWindow;
+
+pub struct WinitViewState {
+    pinch_gesture_recognizer: RefCell<Option<Retained<UIPinchGestureRecognizer>>>,
+    doubletap_gesture_recognizer: RefCell<Option<Retained<UITapGestureRecognizer>>>,
+    rotation_gesture_recognizer: RefCell<Option<Retained<UIRotationGestureRecognizer>>>,
+    pan_gesture_recognizer: RefCell<Option<Retained<UIPanGestureRecognizer>>>,
+
+    // for iOS delta references the start of the Gesture
+    rotation_last_delta: Cell<CGFloat>,
+    pinch_last_delta: Cell<CGFloat>,
+    pan_last_delta: Cell<CGPoint>,
+
+    primary_finger: Cell<Option<FingerId>>,
+    fingers: Cell<u8>,
+}
+
+define_class!(
+    #[unsafe(super(UIView, UIResponder, NSObject))]
+    #[name = "WinitUIView"]
+    #[ivars = WinitViewState]
+    pub(crate) struct WinitView;
+
+    /// This documentation attribute makes rustfmt work for some reason?
+    impl WinitView {
+        #[unsafe(method(drawRect:))]
+        fn draw_rect(&self, rect: CGRect) {
+            let mtm = MainThreadMarker::new().unwrap();
+            let window = self.window().unwrap();
+            app_state::handle_nonuser_event(mtm, EventWrapper::Window {
+                window_id: window.id(),
+                event: WindowEvent::RedrawRequested,
+            });
+            let _: () = unsafe { msg_send![super(self), drawRect: rect] };
+        }
+
+        #[unsafe(method(layoutSubviews))]
+        fn layout_subviews(&self) {
+            let mtm = MainThreadMarker::new().unwrap();
+            let _: () = unsafe { msg_send![super(self), layoutSubviews] };
+
+            let frame = self.frame();
+            let scale_factor = self.contentScaleFactor() as f64;
+            let size = dpi::LogicalSize {
+                width: frame.size.width as f64,
+                height: frame.size.height as f64,
+            }
+            .to_physical(scale_factor);
+
+            let window = self.window().unwrap();
+            app_state::handle_nonuser_event(mtm, EventWrapper::Window {
+                window_id: window.id(),
+                event: WindowEvent::SurfaceResized(size),
+            });
+        }
+
+        #[unsafe(method(setContentScaleFactor:))]
+        fn set_content_scale_factor(&self, untrusted_scale_factor: CGFloat) {
+            let mtm = MainThreadMarker::new().unwrap();
+            let _: () =
+                unsafe { msg_send![super(self), setContentScaleFactor: untrusted_scale_factor] };
+
+            // `window` is null when `setContentScaleFactor` is invoked prior to `[UIWindow
+            // makeKeyAndVisible]` at window creation time (either manually or internally by
+            // UIKit when the `UIView` is first created), in which case we send no events here
+            let window = match self.window() {
+                Some(window) => window,
+                None => return,
+            };
+            // `setContentScaleFactor` may be called with a value of 0, which means "reset the
+            // content scale factor to a device-specific default value", so we can't use the
+            // parameter here. We can query the actual factor using the getter
+            let scale_factor = self.contentScaleFactor();
+            assert!(
+                !scale_factor.is_nan()
+                    && scale_factor.is_finite()
+                    && scale_factor.is_sign_positive()
+                    && scale_factor > 0.0,
+                "invalid scale_factor set on UIView",
+            );
+            let scale_factor = scale_factor as f64;
+            let frame = self.frame();
+            let size = dpi::LogicalSize {
+                width: frame.size.width as f64,
+                height: frame.size.height as f64,
+            };
+            let window_id = window.id();
+            app_state::handle_nonuser_events(
+                mtm,
+                std::iter::once(EventWrapper::ScaleFactorChanged(app_state::ScaleFactorChanged {
+                    window,
+                    scale_factor,
+                    suggested_size: size.to_physical(scale_factor),
+                }))
+                .chain(std::iter::once(EventWrapper::Window {
+                    window_id,
+                    event: WindowEvent::SurfaceResized(size.to_physical(scale_factor)),
+                })),
+            );
+        }
+
+        #[unsafe(method(safeAreaInsetsDidChange))]
+        fn safe_area_changed(&self) {
+            debug!("safeAreaInsetsDidChange was called, requesting redraw");
+            // When the safe area changes we want to make sure to emit a redraw event
+            self.setNeedsDisplay();
+        }
+
+        #[unsafe(method(touchesBegan:withEvent:))]
+        fn touches_began(&self, touches: &NSSet<UITouch>, _event: Option<&UIEvent>) {
+            self.handle_touches(touches)
+        }
+
+        #[unsafe(method(touchesMoved:withEvent:))]
+        fn touches_moved(&self, touches: &NSSet<UITouch>, _event: Option<&UIEvent>) {
+            self.handle_touches(touches)
+        }
+
+        #[unsafe(method(touchesEnded:withEvent:))]
+        fn touches_ended(&self, touches: &NSSet<UITouch>, _event: Option<&UIEvent>) {
+            self.handle_touches(touches)
+        }
+
+        #[unsafe(method(touchesCancelled:withEvent:))]
+        fn touches_cancelled(&self, touches: &NSSet<UITouch>, _event: Option<&UIEvent>) {
+            self.handle_touches(touches)
+        }
+
+        #[unsafe(method(pinchGesture:))]
+        fn pinch_gesture(&self, recognizer: &UIPinchGestureRecognizer) {
+            let window = self.window().unwrap();
+
+            let (phase, delta) = match recognizer.state() {
+                UIGestureRecognizerState::Began => {
+                    self.ivars().pinch_last_delta.set(recognizer.scale());
+                    (TouchPhase::Started, 0.0)
+                },
+                UIGestureRecognizerState::Changed => {
+                    let last_scale: f64 = self.ivars().pinch_last_delta.replace(recognizer.scale());
+                    (TouchPhase::Moved, recognizer.scale() - last_scale)
+                },
+                UIGestureRecognizerState::Ended => {
+                    let last_scale: f64 = self.ivars().pinch_last_delta.replace(0.0);
+                    (TouchPhase::Moved, recognizer.scale() - last_scale)
+                },
+                UIGestureRecognizerState::Cancelled | UIGestureRecognizerState::Failed => {
+                    self.ivars().rotation_last_delta.set(0.0);
+                    // Pass -delta so that action is reversed
+                    (TouchPhase::Cancelled, -recognizer.scale())
+                },
+                state => panic!("unexpected recognizer state: {state:?}"),
+            };
+
+            let gesture_event = EventWrapper::Window {
+                window_id: window.id(),
+                event: WindowEvent::PinchGesture { device_id: None, delta: delta as f64, phase },
+            };
+
+            let mtm = MainThreadMarker::new().unwrap();
+            app_state::handle_nonuser_event(mtm, gesture_event);
+        }
+
+        #[unsafe(method(doubleTapGesture:))]
+        fn double_tap_gesture(&self, recognizer: &UITapGestureRecognizer) {
+            let window = self.window().unwrap();
+
+            if recognizer.state() == UIGestureRecognizerState::Ended {
+                let gesture_event = EventWrapper::Window {
+                    window_id: window.id(),
+                    event: WindowEvent::DoubleTapGesture { device_id: None },
+                };
+
+                let mtm = MainThreadMarker::new().unwrap();
+                app_state::handle_nonuser_event(mtm, gesture_event);
+            }
+        }
+
+        #[unsafe(method(rotationGesture:))]
+        fn rotation_gesture(&self, recognizer: &UIRotationGestureRecognizer) {
+            let window = self.window().unwrap();
+
+            let (phase, delta) = match recognizer.state() {
+                UIGestureRecognizerState::Began => {
+                    self.ivars().rotation_last_delta.set(0.0);
+
+                    (TouchPhase::Started, 0.0)
+                },
+                UIGestureRecognizerState::Changed => {
+                    let last_rotation =
+                        self.ivars().rotation_last_delta.replace(recognizer.rotation());
+
+                    (TouchPhase::Moved, recognizer.rotation() - last_rotation)
+                },
+                UIGestureRecognizerState::Ended => {
+                    let last_rotation = self.ivars().rotation_last_delta.replace(0.0);
+
+                    (TouchPhase::Ended, recognizer.rotation() - last_rotation)
+                },
+                UIGestureRecognizerState::Cancelled | UIGestureRecognizerState::Failed => {
+                    self.ivars().rotation_last_delta.set(0.0);
+
+                    // Pass -delta so that action is reversed
+                    (TouchPhase::Cancelled, -recognizer.rotation())
+                },
+                state => panic!("unexpected recognizer state: {state:?}"),
+            };
+
+            // Make delta negative to match macos, convert to degrees
+            let gesture_event = EventWrapper::Window {
+                window_id: window.id(),
+                event: WindowEvent::RotationGesture {
+                    device_id: None,
+                    delta: -delta.to_degrees() as _,
+                    phase,
+                },
+            };
+
+            let mtm = MainThreadMarker::new().unwrap();
+            app_state::handle_nonuser_event(mtm, gesture_event);
+        }
+
+        #[unsafe(method(panGesture:))]
+        fn pan_gesture(&self, recognizer: &UIPanGestureRecognizer) {
+            let window = self.window().unwrap();
+
+            let translation = recognizer.translationInView(Some(self));
+
+            let (phase, dx, dy) = match recognizer.state() {
+                UIGestureRecognizerState::Began => {
+                    self.ivars().pan_last_delta.set(translation);
+
+                    (TouchPhase::Started, 0.0, 0.0)
+                },
+                UIGestureRecognizerState::Changed => {
+                    let last_pan: CGPoint = self.ivars().pan_last_delta.replace(translation);
+
+                    let dx = translation.x - last_pan.x;
+                    let dy = translation.y - last_pan.y;
+
+                    (TouchPhase::Moved, dx, dy)
+                },
+                UIGestureRecognizerState::Ended => {
+                    let last_pan: CGPoint =
+                        self.ivars().pan_last_delta.replace(CGPoint { x: 0.0, y: 0.0 });
+
+                    let dx = translation.x - last_pan.x;
+                    let dy = translation.y - last_pan.y;
+
+                    (TouchPhase::Ended, dx, dy)
+                },
+                UIGestureRecognizerState::Cancelled | UIGestureRecognizerState::Failed => {
+                    let last_pan: CGPoint =
+                        self.ivars().pan_last_delta.replace(CGPoint { x: 0.0, y: 0.0 });
+
+                    // Pass -delta so that action is reversed
+                    (TouchPhase::Cancelled, -last_pan.x, -last_pan.y)
+                },
+                state => panic!("unexpected recognizer state: {state:?}"),
+            };
+
+            let gesture_event = EventWrapper::Window {
+                window_id: window.id(),
+                event: WindowEvent::PanGesture {
+                    device_id: None,
+                    delta: PhysicalPosition::new(dx as _, dy as _),
+                    phase,
+                },
+            };
+
+            let mtm = MainThreadMarker::new().unwrap();
+            app_state::handle_nonuser_event(mtm, gesture_event);
+        }
+
+        #[unsafe(method(canBecomeFirstResponder))]
+        fn can_become_first_responder(&self) -> bool {
+            true
+        }
+    }
+
+    unsafe impl NSObjectProtocol for WinitView {}
+
+    unsafe impl UIGestureRecognizerDelegate for WinitView {
+        #[unsafe(method(gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:))]
+        fn should_recognize_simultaneously(
+            &self,
+            _gesture_recognizer: &UIGestureRecognizer,
+            _other_gesture_recognizer: &UIGestureRecognizer,
+        ) -> bool {
+            true
+        }
+    }
+
+    unsafe impl UITextInputTraits for WinitView {}
+
+    unsafe impl UIKeyInput for WinitView {
+        #[unsafe(method(hasText))]
+        fn has_text(&self) -> bool {
+            true
+        }
+
+        #[unsafe(method(insertText:))]
+        fn insert_text(&self, text: &NSString) {
+            self.handle_insert_text(text)
+        }
+
+        #[unsafe(method(deleteBackward))]
+        fn delete_backward(&self) {
+            self.handle_delete_backward()
+        }
+    }
+);
+
+impl WinitView {
+    pub(crate) fn new(
+        mtm: MainThreadMarker,
+        scale_factor: Option<f64>,
+        frame: CGRect,
+    ) -> Retained<Self> {
+        let this = mtm.alloc().set_ivars(WinitViewState {
+            pinch_gesture_recognizer: RefCell::new(None),
+            doubletap_gesture_recognizer: RefCell::new(None),
+            rotation_gesture_recognizer: RefCell::new(None),
+            pan_gesture_recognizer: RefCell::new(None),
+
+            rotation_last_delta: Cell::new(0.0),
+            pinch_last_delta: Cell::new(0.0),
+            pan_last_delta: Cell::new(CGPoint { x: 0.0, y: 0.0 }),
+
+            primary_finger: Cell::new(None),
+            fingers: Cell::new(0),
+        });
+        let this: Retained<Self> = unsafe { msg_send![super(this), initWithFrame: frame] };
+
+        this.setMultipleTouchEnabled(true);
+
+        if let Some(scale_factor) = scale_factor {
+            this.setContentScaleFactor(scale_factor as _);
+        }
+
+        this
+    }
+
+    fn window(&self) -> Option<Retained<WinitUIWindow>> {
+        // `WinitView`s should always be installed in a `WinitUIWindow`
+        (**self).window().map(|window| window.downcast().unwrap())
+    }
+
+    pub(crate) fn recognize_pinch_gesture(&self, should_recognize: bool) {
+        let mtm = MainThreadMarker::from(self);
+        if should_recognize {
+            if self.ivars().pinch_gesture_recognizer.borrow().is_none() {
+                let pinch = unsafe {
+                    UIPinchGestureRecognizer::initWithTarget_action(
+                        mtm.alloc(),
+                        Some(self),
+                        Some(sel!(pinchGesture:)),
+                    )
+                };
+                pinch.setDelegate(Some(ProtocolObject::from_ref(self)));
+                self.addGestureRecognizer(&pinch);
+                self.ivars().pinch_gesture_recognizer.replace(Some(pinch));
+            }
+        } else if let Some(recognizer) = self.ivars().pinch_gesture_recognizer.take() {
+            self.removeGestureRecognizer(&recognizer);
+        }
+    }
+
+    pub(crate) fn recognize_pan_gesture(
+        &self,
+        should_recognize: bool,
+        minimum_number_of_touches: u8,
+        maximum_number_of_touches: u8,
+    ) {
+        let mtm = MainThreadMarker::from(self);
+        if should_recognize {
+            if self.ivars().pan_gesture_recognizer.borrow().is_none() {
+                let pan = unsafe {
+                    UIPanGestureRecognizer::initWithTarget_action(
+                        mtm.alloc(),
+                        Some(self),
+                        Some(sel!(panGesture:)),
+                    )
+                };
+                pan.setDelegate(Some(ProtocolObject::from_ref(self)));
+                pan.setMinimumNumberOfTouches(minimum_number_of_touches as _);
+                pan.setMaximumNumberOfTouches(maximum_number_of_touches as _);
+                self.addGestureRecognizer(&pan);
+                self.ivars().pan_gesture_recognizer.replace(Some(pan));
+            }
+        } else if let Some(recognizer) = self.ivars().pan_gesture_recognizer.take() {
+            self.removeGestureRecognizer(&recognizer);
+        }
+    }
+
+    pub(crate) fn recognize_doubletap_gesture(&self, should_recognize: bool) {
+        let mtm = MainThreadMarker::from(self);
+        if should_recognize {
+            if self.ivars().doubletap_gesture_recognizer.borrow().is_none() {
+                let tap = unsafe {
+                    UITapGestureRecognizer::initWithTarget_action(
+                        mtm.alloc(),
+                        Some(self),
+                        Some(sel!(doubleTapGesture:)),
+                    )
+                };
+                tap.setDelegate(Some(ProtocolObject::from_ref(self)));
+                tap.setNumberOfTapsRequired(2);
+                tap.setNumberOfTouchesRequired(1);
+                self.addGestureRecognizer(&tap);
+                self.ivars().doubletap_gesture_recognizer.replace(Some(tap));
+            }
+        } else if let Some(recognizer) = self.ivars().doubletap_gesture_recognizer.take() {
+            self.removeGestureRecognizer(&recognizer);
+        }
+    }
+
+    pub(crate) fn recognize_rotation_gesture(&self, should_recognize: bool) {
+        let mtm = MainThreadMarker::from(self);
+        if should_recognize {
+            if self.ivars().rotation_gesture_recognizer.borrow().is_none() {
+                let rotation = unsafe {
+                    UIRotationGestureRecognizer::initWithTarget_action(
+                        mtm.alloc(),
+                        Some(self),
+                        Some(sel!(rotationGesture:)),
+                    )
+                };
+                rotation.setDelegate(Some(ProtocolObject::from_ref(self)));
+                self.addGestureRecognizer(&rotation);
+                self.ivars().rotation_gesture_recognizer.replace(Some(rotation));
+            }
+        } else if let Some(recognizer) = self.ivars().rotation_gesture_recognizer.take() {
+            self.removeGestureRecognizer(&recognizer);
+        }
+    }
+
+    fn handle_touches(&self, touches: &NSSet<UITouch>) {
+        let window = self.window().unwrap();
+        let mut touch_events = Vec::new();
+        for touch in touches {
+            let logical_location = touch.locationInView(None);
+            let touch_type = touch.r#type();
+            let force = if let UITouchType::Pencil = touch_type {
+                None
+            } else if available!(ios = 9.0, tvos = 9.0, visionos = 1.0) {
+                let trait_collection = self.traitCollection();
+                let touch_capability = trait_collection.forceTouchCapability();
+                // Both the OS _and_ the device need to be checked for force touch support.
+                if touch_capability == UIForceTouchCapability::Available {
+                    let force = touch.force();
+                    let max_possible_force = touch.maximumPossibleForce();
+                    Some(Force::Calibrated {
+                        force: force as _,
+                        max_possible_force: max_possible_force as _,
+                    })
+                } else {
+                    None
+                }
+            } else {
+                None
+            };
+            let touch_id = Retained::as_ptr(&touch) as usize;
+            let phase = touch.phase();
+            let position = {
+                let scale_factor = self.contentScaleFactor();
+                PhysicalPosition::from_logical::<(f64, f64), f64>(
+                    (logical_location.x as _, logical_location.y as _),
+                    scale_factor as f64,
+                )
+            };
+            let window_id = window.id();
+            let finger_id = FingerId::from_raw(touch_id);
+
+            let ivars = self.ivars();
+
+            match phase {
+                UITouchPhase::Began => {
+                    let primary = if let UITouchType::Pencil = touch_type {
+                        true
+                    } else {
+                        ivars.fingers.set(ivars.fingers.get() + 1);
+                        // Keep the primary finger around until we clear all the fingers to
+                        // recognize it when user briefly removes it.
+                        match ivars.primary_finger.get() {
+                            Some(primary_id) => primary_id == finger_id,
+                            None => {
+                                debug_assert_eq!(
+                                    ivars.fingers.get(),
+                                    1,
+                                    "number of fingers were not counted correctly"
+                                );
+                                ivars.primary_finger.set(Some(finger_id));
+                                true
+                            },
+                        }
+                    };
+
+                    touch_events.push(EventWrapper::Window {
+                        window_id,
+                        event: WindowEvent::PointerEntered {
+                            device_id: None,
+                            primary,
+                            position,
+                            kind: if let UITouchType::Pencil = touch_type {
+                                PointerKind::Unknown
+                            } else {
+                                PointerKind::Touch(finger_id)
+                            },
+                        },
+                    });
+                    touch_events.push(EventWrapper::Window {
+                        window_id,
+                        event: WindowEvent::PointerButton {
+                            device_id: None,
+                            primary,
+                            state: ElementState::Pressed,
+                            position,
+                            button: if let UITouchType::Pencil = touch_type {
+                                ButtonSource::Unknown(0)
+                            } else {
+                                ButtonSource::Touch { finger_id, force }
+                            },
+                        },
+                    });
+                },
+                UITouchPhase::Moved => {
+                    let (primary, source) = if let UITouchType::Pencil = touch_type {
+                        (true, PointerSource::Unknown)
+                    } else {
+                        (ivars.primary_finger.get().unwrap() == finger_id, PointerSource::Touch {
+                            finger_id,
+                            force,
+                        })
+                    };
+
+                    touch_events.push(EventWrapper::Window {
+                        window_id,
+                        event: WindowEvent::PointerMoved {
+                            device_id: None,
+                            primary,
+                            position,
+                            source,
+                        },
+                    });
+                },
+                // 2 is UITouchPhase::Stationary and is not expected here
+                UITouchPhase::Ended | UITouchPhase::Cancelled => {
+                    let primary = if let UITouchType::Pencil = touch_type {
+                        true
+                    } else {
+                        ivars.fingers.set(ivars.fingers.get() - 1);
+                        let primary = ivars.primary_finger.get().unwrap() == finger_id;
+                        if ivars.fingers.get() == 0 {
+                            ivars.primary_finger.set(None);
+                        }
+                        primary
+                    };
+
+                    if let UITouchPhase::Ended = phase {
+                        touch_events.push(EventWrapper::Window {
+                            window_id,
+                            event: WindowEvent::PointerButton {
+                                device_id: None,
+                                primary,
+                                state: ElementState::Released,
+                                position,
+                                button: if let UITouchType::Pencil = touch_type {
+                                    ButtonSource::Unknown(0)
+                                } else {
+                                    ButtonSource::Touch { finger_id, force }
+                                },
+                            },
+                        });
+                    }
+
+                    touch_events.push(EventWrapper::Window {
+                        window_id,
+                        event: WindowEvent::PointerLeft {
+                            device_id: None,
+                            primary,
+                            position: Some(position),
+                            kind: if let UITouchType::Pencil = touch_type {
+                                PointerKind::Unknown
+                            } else {
+                                PointerKind::Touch(finger_id)
+                            },
+                        },
+                    });
+                },
+                _ => panic!("unexpected touch phase: {phase:?}"),
+            }
+        }
+        let mtm = MainThreadMarker::new().unwrap();
+        app_state::handle_nonuser_events(mtm, touch_events);
+    }
+
+    fn handle_insert_text(&self, text: &NSString) {
+        let window = self.window().unwrap();
+        let window_id = window.id();
+        let mtm = MainThreadMarker::new().unwrap();
+        // send individual events for each character
+        app_state::handle_nonuser_events(
+            mtm,
+            text.to_string().chars().flat_map(|c| {
+                let text = smol_str::SmolStr::from_iter([c]);
+                // Emit both press and release events
+                [ElementState::Pressed, ElementState::Released].map(|state| EventWrapper::Window {
+                    window_id,
+                    event: WindowEvent::KeyboardInput {
+                        device_id: None,
+                        event: KeyEvent {
+                            text: if state == ElementState::Pressed {
+                                Some(text.clone())
+                            } else {
+                                None
+                            },
+                            state,
+                            location: KeyLocation::Standard,
+                            repeat: false,
+                            logical_key: Key::Character(text.clone()),
+                            physical_key: PhysicalKey::Unidentified(NativeKeyCode::Unidentified),
+                            text_with_all_modifiers: if state == ElementState::Pressed {
+                                Some(text.clone())
+                            } else {
+                                None
+                            },
+                            key_without_modifiers: Key::Character(text.clone()),
+                        },
+                        is_synthetic: false,
+                    },
+                })
+            }),
+        );
+    }
+
+    fn handle_delete_backward(&self) {
+        let window = self.window().unwrap();
+        let window_id = window.id();
+        let mtm = MainThreadMarker::new().unwrap();
+        app_state::handle_nonuser_events(
+            mtm,
+            [ElementState::Pressed, ElementState::Released].map(|state| EventWrapper::Window {
+                window_id,
+                event: WindowEvent::KeyboardInput {
+                    device_id: None,
+                    event: KeyEvent {
+                        state,
+                        logical_key: Key::Named(NamedKey::Backspace),
+                        physical_key: PhysicalKey::Code(KeyCode::Backspace),
+                        repeat: false,
+                        location: KeyLocation::Standard,
+                        text: None,
+                        text_with_all_modifiers: None,
+                        key_without_modifiers: Key::Named(NamedKey::Backspace),
+                    },
+                    is_synthetic: false,
+                },
+            }),
+        );
+    }
+}

winit-uikit/src/view_controller.rs

@@ -0,0 +1,160 @@
+use std::cell::Cell;
+
+use objc2::rc::Retained;
+use objc2::{available, define_class, msg_send, DefinedClass, MainThreadMarker};
+use objc2_foundation::NSObject;
+use objc2_ui_kit::{
+    UIDevice, UIInterfaceOrientationMask, UIRectEdge, UIResponder, UIStatusBarStyle,
+    UIUserInterfaceIdiom, UIView, UIViewController,
+};
+
+use crate::{ScreenEdge, StatusBarStyle, ValidOrientations, WindowAttributesIos};
+
+pub struct ViewControllerState {
+    prefers_status_bar_hidden: Cell<bool>,
+    preferred_status_bar_style: Cell<UIStatusBarStyle>,
+    prefers_home_indicator_auto_hidden: Cell<bool>,
+    supported_orientations: Cell<UIInterfaceOrientationMask>,
+    preferred_screen_edges_deferring_system_gestures: Cell<UIRectEdge>,
+}
+
+define_class!(
+    #[unsafe(super(UIViewController, UIResponder, NSObject))]
+    #[name = "WinitUIViewController"]
+    #[ivars = ViewControllerState]
+    pub(crate) struct WinitViewController;
+
+    /// This documentation attribute makes rustfmt work for some reason?
+    impl WinitViewController {
+        #[unsafe(method(shouldAutorotate))]
+        fn should_autorotate(&self) -> bool {
+            true
+        }
+
+        #[unsafe(method(prefersStatusBarHidden))]
+        fn prefers_status_bar_hidden(&self) -> bool {
+            self.ivars().prefers_status_bar_hidden.get()
+        }
+
+        #[unsafe(method(preferredStatusBarStyle))]
+        fn preferred_status_bar_style(&self) -> UIStatusBarStyle {
+            self.ivars().preferred_status_bar_style.get()
+        }
+
+        #[unsafe(method(prefersHomeIndicatorAutoHidden))]
+        fn prefers_home_indicator_auto_hidden(&self) -> bool {
+            self.ivars().prefers_home_indicator_auto_hidden.get()
+        }
+
+        #[unsafe(method(supportedInterfaceOrientations))]
+        fn supported_orientations(&self) -> UIInterfaceOrientationMask {
+            self.ivars().supported_orientations.get()
+        }
+
+        #[unsafe(method(preferredScreenEdgesDeferringSystemGestures))]
+        fn preferred_screen_edges_deferring_system_gestures(&self) -> UIRectEdge {
+            self.ivars().preferred_screen_edges_deferring_system_gestures.get()
+        }
+    }
+);
+
+impl WinitViewController {
+    pub(crate) fn set_prefers_status_bar_hidden(&self, val: bool) {
+        self.ivars().prefers_status_bar_hidden.set(val);
+        self.setNeedsStatusBarAppearanceUpdate();
+    }
+
+    pub(crate) fn set_preferred_status_bar_style(&self, val: StatusBarStyle) {
+        let val = match val {
+            StatusBarStyle::Default => UIStatusBarStyle::Default,
+            StatusBarStyle::LightContent => UIStatusBarStyle::LightContent,
+            StatusBarStyle::DarkContent => UIStatusBarStyle::DarkContent,
+        };
+        self.ivars().preferred_status_bar_style.set(val);
+        self.setNeedsStatusBarAppearanceUpdate();
+    }
+
+    pub(crate) fn set_prefers_home_indicator_auto_hidden(&self, val: bool) {
+        self.ivars().prefers_home_indicator_auto_hidden.set(val);
+        if available!(ios = 11.0, visionos = 1.0) {
+            self.setNeedsUpdateOfHomeIndicatorAutoHidden();
+        } else {
+            tracing::warn!(
+                "`setNeedsUpdateOfHomeIndicatorAutoHidden` requires iOS 11.0+ or visionOS. \
+                 Ignoring"
+            );
+        }
+    }
+
+    pub(crate) fn set_preferred_screen_edges_deferring_system_gestures(&self, val: ScreenEdge) {
+        let val = {
+            assert_eq!(val.bits() & !ScreenEdge::ALL.bits(), 0, "invalid `ScreenEdge`");
+            UIRectEdge(val.bits().into())
+        };
+        self.ivars().preferred_screen_edges_deferring_system_gestures.set(val);
+        if available!(ios = 11.0, visionos = 1.0) {
+            self.setNeedsUpdateOfScreenEdgesDeferringSystemGestures();
+        } else {
+            tracing::warn!(
+                "`setNeedsUpdateOfScreenEdgesDeferringSystemGestures` requires iOS 11.0+ or \
+                 visionOS. Ignoring"
+            );
+        }
+    }
+
+    pub(crate) fn set_supported_interface_orientations(
+        &self,
+        mtm: MainThreadMarker,
+        valid_orientations: ValidOrientations,
+    ) {
+        let mask = match (valid_orientations, UIDevice::currentDevice(mtm).userInterfaceIdiom()) {
+            (ValidOrientations::LandscapeAndPortrait, UIUserInterfaceIdiom::Phone) => {
+                UIInterfaceOrientationMask::AllButUpsideDown
+            },
+            (ValidOrientations::LandscapeAndPortrait, _) => UIInterfaceOrientationMask::All,
+            (ValidOrientations::Landscape, _) => UIInterfaceOrientationMask::Landscape,
+            (ValidOrientations::Portrait, UIUserInterfaceIdiom::Phone) => {
+                UIInterfaceOrientationMask::Portrait
+            },
+            (ValidOrientations::Portrait, _) => {
+                UIInterfaceOrientationMask::Portrait
+                    | UIInterfaceOrientationMask::PortraitUpsideDown
+            },
+        };
+        self.ivars().supported_orientations.set(mask);
+        #[allow(deprecated)]
+        UIViewController::attemptRotationToDeviceOrientation(mtm);
+    }
+
+    pub(crate) fn new(
+        mtm: MainThreadMarker,
+        ios_attributes: &WindowAttributesIos,
+        view: &UIView,
+    ) -> Retained<Self> {
+        // These are set properly below, we just to set them to something in the meantime.
+        let this = mtm.alloc().set_ivars(ViewControllerState {
+            prefers_status_bar_hidden: Cell::new(false),
+            preferred_status_bar_style: Cell::new(UIStatusBarStyle::Default),
+            prefers_home_indicator_auto_hidden: Cell::new(false),
+            supported_orientations: Cell::new(UIInterfaceOrientationMask::All),
+            preferred_screen_edges_deferring_system_gestures: Cell::new(UIRectEdge::empty()),
+        });
+        let this: Retained<Self> = unsafe { msg_send![super(this), init] };
+
+        this.set_prefers_status_bar_hidden(ios_attributes.prefers_status_bar_hidden);
+
+        this.set_preferred_status_bar_style(ios_attributes.preferred_status_bar_style);
+
+        this.set_supported_interface_orientations(mtm, ios_attributes.valid_orientations);
+
+        this.set_prefers_home_indicator_auto_hidden(ios_attributes.prefers_home_indicator_hidden);
+
+        this.set_preferred_screen_edges_deferring_system_gestures(
+            ios_attributes.preferred_screen_edges_deferring_system_gestures,
+        );
+
+        this.setView(Some(view));
+
+        this
+    }
+}

winit-uikit/src/window.rs

@@ -0,0 +1,898 @@
+#![allow(clippy::unnecessary_cast)]
+
+use std::collections::VecDeque;
+use std::sync::Arc;
+
+use dispatch2::MainThreadBound;
+use dpi::{
+    LogicalInsets, LogicalPosition, LogicalSize, PhysicalInsets, PhysicalPosition, PhysicalSize,
+    Position, Size,
+};
+use objc2::rc::Retained;
+use objc2::{available, class, define_class, msg_send, MainThreadMarker};
+use objc2_core_foundation::{CGFloat, CGPoint, CGRect, CGSize};
+use objc2_foundation::{NSObject, NSObjectProtocol};
+use objc2_ui_kit::{
+    UIApplication, UICoordinateSpace, UIEdgeInsets, UIResponder, UIScreen,
+    UIScreenOverscanCompensation, UIViewController, UIWindow,
+};
+use tracing::{debug, warn};
+use winit_core::cursor::Cursor;
+use winit_core::error::{NotSupportedError, RequestError};
+use winit_core::event::WindowEvent;
+use winit_core::icon::Icon;
+use winit_core::monitor::{Fullscreen, MonitorHandle as CoreMonitorHandle};
+use winit_core::window::{
+    CursorGrabMode, ImePurpose, ResizeDirection, Theme, UserAttentionType, Window as CoreWindow,
+    WindowAttributes, WindowButtons, WindowId, WindowLevel,
+};
+
+use super::app_state::EventWrapper;
+use super::view::WinitView;
+use super::view_controller::WinitViewController;
+use super::{app_state, monitor};
+use crate::event_loop::ActiveEventLoop;
+use crate::monitor::MonitorHandle;
+use crate::{ScreenEdge, StatusBarStyle, ValidOrientations, WindowAttributesIos};
+
+define_class!(
+    #[unsafe(super(UIWindow, UIResponder, NSObject))]
+    #[name = "WinitUIWindow"]
+    #[derive(Debug, PartialEq, Eq, Hash)]
+    pub(crate) struct WinitUIWindow;
+
+    /// This documentation attribute makes rustfmt work for some reason?
+    impl WinitUIWindow {
+        #[unsafe(method(becomeKeyWindow))]
+        fn become_key_window(&self) {
+            let mtm = MainThreadMarker::new().unwrap();
+            app_state::handle_nonuser_event(mtm, EventWrapper::Window {
+                window_id: self.id(),
+                event: WindowEvent::Focused(true),
+            });
+            let _: () = unsafe { msg_send![super(self), becomeKeyWindow] };
+        }
+
+        #[unsafe(method(resignKeyWindow))]
+        fn resign_key_window(&self) {
+            let mtm = MainThreadMarker::new().unwrap();
+            app_state::handle_nonuser_event(mtm, EventWrapper::Window {
+                window_id: self.id(),
+                event: WindowEvent::Focused(false),
+            });
+            let _: () = unsafe { msg_send![super(self), resignKeyWindow] };
+        }
+    }
+);
+
+impl WinitUIWindow {
+    pub(crate) fn new(
+        mtm: MainThreadMarker,
+        window_attributes: &WindowAttributes,
+        frame: CGRect,
+        view_controller: &UIViewController,
+    ) -> Retained<Self> {
+        // NOTE: This should only be created after the application has started launching,
+        // (`application:willFinishLaunchingWithOptions:` at the earliest), otherwise you'll run
+        // into very confusing issues with the window not being properly activated.
+        //
+        // Winit ensures this by not allowing access to `ActiveEventLoop` before handling events.
+        let this: Retained<Self> = unsafe { msg_send![mtm.alloc(), initWithFrame: frame] };
+
+        this.setRootViewController(Some(view_controller));
+
+        match window_attributes.fullscreen.clone() {
+            Some(Fullscreen::Exclusive(monitor, ref video_mode)) => {
+                let monitor = monitor.cast_ref::<MonitorHandle>().unwrap();
+                let screen = monitor.ui_screen(mtm);
+                if let Some(video_mode) =
+                    monitor.video_modes_handles().find(|mode| &mode.mode == video_mode)
+                {
+                    screen.setCurrentMode(Some(video_mode.screen_mode(mtm)));
+                }
+                this.setScreen(screen);
+            },
+            Some(Fullscreen::Borderless(Some(ref monitor))) => {
+                let monitor = monitor.cast_ref::<MonitorHandle>().unwrap();
+                let screen = monitor.ui_screen(mtm);
+                this.setScreen(screen);
+            },
+            _ => (),
+        }
+
+        this
+    }
+
+    pub(crate) fn id(&self) -> WindowId {
+        WindowId::from_raw(self as *const Self as usize)
+    }
+}
+
+pub struct Inner {
+    window: Retained<WinitUIWindow>,
+    view_controller: Retained<WinitViewController>,
+    view: Retained<WinitView>,
+    gl_or_metal_backed: bool,
+}
+
+impl Inner {
+    pub fn set_title(&self, _title: &str) {
+        debug!("`Window::set_title` is ignored on iOS")
+    }
+
+    pub fn set_transparent(&self, _transparent: bool) {
+        debug!("`Window::set_transparent` is ignored on iOS")
+    }
+
+    pub fn set_blur(&self, _blur: bool) {
+        debug!("`Window::set_blur` is ignored on iOS")
+    }
+
+    pub fn set_visible(&self, visible: bool) {
+        self.window.setHidden(!visible)
+    }
+
+    pub fn is_visible(&self) -> Option<bool> {
+        warn!("`Window::is_visible` is ignored on iOS");
+        None
+    }
+
+    pub fn request_redraw(&self) {
+        if self.gl_or_metal_backed {
+            let mtm = MainThreadMarker::new().unwrap();
+            // `setNeedsDisplay` does nothing on UIViews which are directly backed by CAEAGLLayer or
+            // CAMetalLayer. Ordinarily the OS sets up a bunch of UIKit state before
+            // calling drawRect: on a UIView, but when using raw or gl/metal for drawing
+            // this work is completely avoided.
+            //
+            // The docs for `setNeedsDisplay` don't mention `CAMetalLayer`; however, this has been
+            // confirmed via testing.
+            //
+            // https://developer.apple.com/documentation/uikit/uiview/1622437-setneedsdisplay?language=objc
+            app_state::queue_gl_or_metal_redraw(mtm, self.window.clone());
+        } else {
+            self.view.setNeedsDisplay();
+        }
+    }
+
+    pub fn pre_present_notify(&self) {}
+
+    pub fn surface_position(&self) -> PhysicalPosition<i32> {
+        let view_position = self.view.frame().origin;
+        let position =
+            unsafe { self.window.convertPoint_fromView(view_position, Some(&self.view)) };
+        let position = LogicalPosition::new(position.x, position.y);
+        position.to_physical(self.scale_factor())
+    }
+
+    pub fn outer_position(&self) -> Result<PhysicalPosition<i32>, RequestError> {
+        let screen_frame = self.screen_frame();
+        let position =
+            LogicalPosition { x: screen_frame.origin.x as f64, y: screen_frame.origin.y as f64 };
+        Ok(position.to_physical(self.scale_factor()))
+    }
+
+    pub fn set_outer_position(&self, physical_position: Position) {
+        let scale_factor = self.scale_factor();
+        let position = physical_position.to_logical::<f64>(scale_factor);
+        let screen_frame = self.screen_frame();
+        let new_screen_frame = CGRect {
+            origin: CGPoint { x: position.x as _, y: position.y as _ },
+            size: screen_frame.size,
+        };
+        let bounds = self.rect_from_screen_space(new_screen_frame);
+        self.window.setBounds(bounds);
+    }
+
+    pub fn surface_size(&self) -> PhysicalSize<u32> {
+        let frame = self.view.frame();
+        let size = LogicalSize::new(frame.size.width, frame.size.height);
+        size.to_physical(self.scale_factor())
+    }
+
+    pub fn outer_size(&self) -> PhysicalSize<u32> {
+        let frame = self.window.frame();
+        let size = LogicalSize::new(frame.size.width, frame.size.height);
+        size.to_physical(self.scale_factor())
+    }
+
+    pub fn request_surface_size(&self, _size: Size) -> Option<PhysicalSize<u32>> {
+        Some(self.surface_size())
+    }
+
+    pub fn safe_area(&self) -> PhysicalInsets<u32> {
+        let insets = if available!(ios = 11.0, tvos = 11.0, visionos = 1.0) {
+            self.view.safeAreaInsets()
+        } else {
+            // Assume the status bar frame is the only thing that obscures the view
+            let app = UIApplication::sharedApplication(MainThreadMarker::new().unwrap());
+            #[allow(deprecated)]
+            let status_bar_frame = app.statusBarFrame();
+            UIEdgeInsets { top: status_bar_frame.size.height, left: 0.0, bottom: 0.0, right: 0.0 }
+        };
+        let insets = LogicalInsets::new(insets.top, insets.left, insets.bottom, insets.right);
+        insets.to_physical(self.scale_factor())
+    }
+
+    pub fn set_min_surface_size(&self, _dimensions: Option<Size>) {
+        warn!("`Window::set_min_surface_size` is ignored on iOS")
+    }
+
+    pub fn set_max_surface_size(&self, _dimensions: Option<Size>) {
+        warn!("`Window::set_max_surface_size` is ignored on iOS")
+    }
+
+    pub fn surface_resize_increments(&self) -> Option<PhysicalSize<u32>> {
+        None
+    }
+
+    #[inline]
+    pub fn set_surface_resize_increments(&self, _increments: Option<Size>) {
+        warn!("`Window::set_surface_resize_increments` is ignored on iOS")
+    }
+
+    pub fn set_resizable(&self, _resizable: bool) {
+        warn!("`Window::set_resizable` is ignored on iOS")
+    }
+
+    pub fn is_resizable(&self) -> bool {
+        warn!("`Window::is_resizable` is ignored on iOS");
+        false
+    }
+
+    #[inline]
+    pub fn set_enabled_buttons(&self, _buttons: WindowButtons) {
+        warn!("`Window::set_enabled_buttons` is ignored on iOS");
+    }
+
+    #[inline]
+    pub fn enabled_buttons(&self) -> WindowButtons {
+        warn!("`Window::enabled_buttons` is ignored on iOS");
+        WindowButtons::all()
+    }
+
+    pub fn scale_factor(&self) -> f64 {
+        self.view.contentScaleFactor() as _
+    }
+
+    pub fn set_cursor(&self, _cursor: Cursor) {
+        debug!("`Window::set_cursor` ignored on iOS")
+    }
+
+    pub fn set_cursor_position(&self, _position: Position) -> Result<(), NotSupportedError> {
+        Err(NotSupportedError::new("set_cursor_position is not supported"))
+    }
+
+    pub fn set_cursor_grab(&self, _: CursorGrabMode) -> Result<(), NotSupportedError> {
+        Err(NotSupportedError::new("set_cursor_grab is not supported"))
+    }
+
+    pub fn set_cursor_visible(&self, _visible: bool) {
+        debug!("`Window::set_cursor_visible` is ignored on iOS")
+    }
+
+    pub fn drag_window(&self) -> Result<(), NotSupportedError> {
+        Err(NotSupportedError::new("drag_window is not supported"))
+    }
+
+    pub fn drag_resize_window(&self, _direction: ResizeDirection) -> Result<(), NotSupportedError> {
+        Err(NotSupportedError::new("drag_resize_window is not supported"))
+    }
+
+    #[inline]
+    pub fn show_window_menu(&self, _position: Position) {}
+
+    pub fn set_cursor_hittest(&self, _hittest: bool) -> Result<(), NotSupportedError> {
+        Err(NotSupportedError::new("set_cursor_hittest is not supported"))
+    }
+
+    pub fn set_minimized(&self, _minimized: bool) {
+        warn!("`Window::set_minimized` is ignored on iOS")
+    }
+
+    pub fn is_minimized(&self) -> Option<bool> {
+        warn!("`Window::is_minimized` is ignored on iOS");
+        None
+    }
+
+    pub fn set_maximized(&self, _maximized: bool) {
+        warn!("`Window::set_maximized` is ignored on iOS")
+    }
+
+    pub fn is_maximized(&self) -> bool {
+        warn!("`Window::is_maximized` is ignored on iOS");
+        false
+    }
+
+    pub(crate) fn set_fullscreen(&self, monitor: Option<Fullscreen>) {
+        let mtm = MainThreadMarker::new().unwrap();
+        let uiscreen = match &monitor {
+            Some(Fullscreen::Exclusive(monitor, video_mode)) => {
+                let monitor = monitor.cast_ref::<MonitorHandle>().unwrap();
+                let uiscreen = monitor.ui_screen(mtm);
+                if let Some(video_mode) =
+                    monitor.video_modes_handles().find(|mode| &mode.mode == video_mode)
+                {
+                    uiscreen.setCurrentMode(Some(video_mode.screen_mode(mtm)));
+                }
+                uiscreen.clone()
+            },
+            Some(Fullscreen::Borderless(Some(monitor))) => {
+                monitor.cast_ref::<MonitorHandle>().unwrap().ui_screen(mtm).clone()
+            },
+            Some(Fullscreen::Borderless(None)) => {
+                self.current_monitor_inner().ui_screen(mtm).clone()
+            },
+            None => {
+                warn!("`Window::set_fullscreen(None)` ignored on iOS");
+                return;
+            },
+        };
+
+        // this is pretty slow on iOS, so avoid doing it if we can
+        let current = self.window.screen();
+        if uiscreen != current {
+            self.window.setScreen(&uiscreen);
+        }
+
+        let bounds = uiscreen.bounds();
+        self.window.setFrame(bounds);
+
+        // For external displays, we must disable overscan compensation or
+        // the displayed image will have giant black bars surrounding it on
+        // each side
+        uiscreen.setOverscanCompensation(UIScreenOverscanCompensation::None);
+    }
+
+    pub(crate) fn fullscreen(&self) -> Option<Fullscreen> {
+        let mtm = MainThreadMarker::new().unwrap();
+        let monitor = self.current_monitor_inner();
+        let uiscreen = monitor.ui_screen(mtm);
+        let screen_space_bounds = self.screen_frame();
+        let screen_bounds = uiscreen.bounds();
+
+        // TODO: track fullscreen instead of relying on brittle float comparisons
+        if screen_space_bounds.origin.x == screen_bounds.origin.x
+            && screen_space_bounds.origin.y == screen_bounds.origin.y
+            && screen_space_bounds.size.width == screen_bounds.size.width
+            && screen_space_bounds.size.height == screen_bounds.size.height
+        {
+            Some(Fullscreen::Borderless(Some(CoreMonitorHandle(Arc::new(monitor)))))
+        } else {
+            None
+        }
+    }
+
+    pub fn set_decorations(&self, _decorations: bool) {}
+
+    pub fn is_decorated(&self) -> bool {
+        true
+    }
+
+    pub fn set_window_level(&self, _level: WindowLevel) {
+        warn!("`Window::set_window_level` is ignored on iOS")
+    }
+
+    pub fn set_window_icon(&self, _icon: Option<Icon>) {
+        warn!("`Window::set_window_icon` is ignored on iOS")
+    }
+
+    pub fn set_ime_cursor_area(&self, _position: Position, _size: Size) {
+        warn!("`Window::set_ime_cursor_area` is ignored on iOS")
+    }
+
+    /// Show / hide the keyboard. To show the keyboard, we call `becomeFirstResponder`,
+    /// requesting focus for the [WinitView]. Since [WinitView] implements
+    /// [objc2_ui_kit::UIKeyInput], the keyboard will be shown.
+    /// <https://developer.apple.com/documentation/uikit/uiresponder/1621113-becomefirstresponder>
+    pub fn set_ime_allowed(&self, allowed: bool) {
+        if allowed {
+            unsafe {
+                self.view.becomeFirstResponder();
+            }
+        } else {
+            unsafe {
+                self.view.resignFirstResponder();
+            }
+        }
+    }
+
+    pub fn set_ime_purpose(&self, _purpose: ImePurpose) {
+        warn!("`Window::set_ime_purpose` is ignored on iOS")
+    }
+
+    pub fn focus_window(&self) {
+        warn!("`Window::set_focus` is ignored on iOS")
+    }
+
+    pub fn request_user_attention(&self, _request_type: Option<UserAttentionType>) {
+        warn!("`Window::request_user_attention` is ignored on iOS")
+    }
+
+    // Allow directly accessing the current monitor internally without unwrapping.
+    fn current_monitor_inner(&self) -> MonitorHandle {
+        MonitorHandle::new(self.window.screen())
+    }
+
+    pub fn current_monitor(&self) -> Option<MonitorHandle> {
+        Some(self.current_monitor_inner())
+    }
+
+    pub fn available_monitors(&self) -> VecDeque<MonitorHandle> {
+        monitor::uiscreens(MainThreadMarker::new().unwrap())
+    }
+
+    pub fn primary_monitor(&self) -> Option<MonitorHandle> {
+        #[allow(deprecated)]
+        Some(MonitorHandle::new(UIScreen::mainScreen(MainThreadMarker::new().unwrap())))
+    }
+
+    pub fn id(&self) -> WindowId {
+        self.window.id()
+    }
+
+    pub fn raw_window_handle_rwh_06(&self) -> rwh_06::RawWindowHandle {
+        let mut window_handle = rwh_06::UiKitWindowHandle::new({
+            let ui_view = Retained::as_ptr(&self.view) as _;
+            std::ptr::NonNull::new(ui_view).expect("Retained<T> should never be null")
+        });
+        window_handle.ui_view_controller =
+            std::ptr::NonNull::new(Retained::as_ptr(&self.view_controller) as _);
+        rwh_06::RawWindowHandle::UiKit(window_handle)
+    }
+
+    pub fn theme(&self) -> Option<Theme> {
+        warn!("`Window::theme` is ignored on iOS");
+        None
+    }
+
+    pub fn set_content_protected(&self, _protected: bool) {}
+
+    pub fn has_focus(&self) -> bool {
+        self.window.isKeyWindow()
+    }
+
+    #[inline]
+    pub fn set_theme(&self, _theme: Option<Theme>) {
+        warn!("`Window::set_theme` is ignored on iOS");
+    }
+
+    pub fn title(&self) -> String {
+        warn!("`Window::title` is ignored on iOS");
+        String::new()
+    }
+
+    pub fn reset_dead_keys(&self) {
+        // Noop
+    }
+}
+
+#[derive(Debug)]
+pub struct Window {
+    inner: MainThreadBound<Inner>,
+}
+
+impl Window {
+    pub(crate) fn new(
+        event_loop: &ActiveEventLoop,
+        mut window_attributes: WindowAttributes,
+    ) -> Result<Window, RequestError> {
+        let mtm = event_loop.mtm;
+
+        if window_attributes.min_surface_size.is_some() {
+            warn!("`WindowAttributes::min_surface_size` is ignored on iOS");
+        }
+        if window_attributes.max_surface_size.is_some() {
+            warn!("`WindowAttributes::max_surface_size` is ignored on iOS");
+        }
+
+        let ios_attributes = window_attributes
+            .platform
+            .take()
+            .and_then(|attrs| attrs.cast::<WindowAttributesIos>().ok())
+            .unwrap_or_default();
+
+        // TODO: transparency, visible
+
+        #[allow(deprecated)]
+        let main_screen = UIScreen::mainScreen(mtm);
+        let fullscreen = window_attributes.fullscreen.clone();
+        let screen = match fullscreen {
+            Some(Fullscreen::Exclusive(ref monitor, _))
+            | Some(Fullscreen::Borderless(Some(ref monitor))) => {
+                let monitor = monitor.cast_ref::<MonitorHandle>().unwrap();
+                monitor.ui_screen(mtm)
+            },
+            Some(Fullscreen::Borderless(None)) | None => &main_screen,
+        };
+
+        let screen_bounds = screen.bounds();
+
+        let frame = match window_attributes.surface_size {
+            Some(dim) => {
+                let scale_factor = screen.scale();
+                let size = dim.to_logical::<f64>(scale_factor as f64);
+                CGRect {
+                    origin: screen_bounds.origin,
+                    size: CGSize { width: size.width as _, height: size.height as _ },
+                }
+            },
+            None => screen_bounds,
+        };
+
+        let view = WinitView::new(mtm, ios_attributes.scale_factor, frame);
+
+        let gl_or_metal_backed =
+            view.isKindOfClass(class!(CAMetalLayer)) || view.isKindOfClass(class!(CAEAGLLayer));
+
+        let view_controller = WinitViewController::new(mtm, &ios_attributes, &view);
+        let window = WinitUIWindow::new(mtm, &window_attributes, frame, &view_controller);
+        window.makeKeyAndVisible();
+
+        let inner = Inner { window, view_controller, view, gl_or_metal_backed };
+        Ok(Window { inner: MainThreadBound::new(inner, mtm) })
+    }
+
+    pub(crate) fn maybe_wait_on_main<R: Send>(&self, f: impl FnOnce(&Inner) -> R + Send) -> R {
+        self.inner.get_on_main(|inner| f(inner))
+    }
+
+    #[inline]
+    pub(crate) fn raw_window_handle_rwh_06(
+        &self,
+    ) -> Result<rwh_06::RawWindowHandle, rwh_06::HandleError> {
+        if let Some(mtm) = MainThreadMarker::new() {
+            Ok(self.inner.get(mtm).raw_window_handle_rwh_06())
+        } else {
+            Err(rwh_06::HandleError::Unavailable)
+        }
+    }
+
+    #[inline]
+    pub(crate) fn raw_display_handle_rwh_06(
+        &self,
+    ) -> Result<rwh_06::RawDisplayHandle, rwh_06::HandleError> {
+        Ok(rwh_06::RawDisplayHandle::UiKit(rwh_06::UiKitDisplayHandle::new()))
+    }
+}
+
+impl rwh_06::HasDisplayHandle for Window {
+    fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
+        let raw = self.raw_display_handle_rwh_06()?;
+        unsafe { Ok(rwh_06::DisplayHandle::borrow_raw(raw)) }
+    }
+}
+
+impl rwh_06::HasWindowHandle for Window {
+    fn window_handle(&self) -> Result<rwh_06::WindowHandle<'_>, rwh_06::HandleError> {
+        let raw = self.raw_window_handle_rwh_06()?;
+        unsafe { Ok(rwh_06::WindowHandle::borrow_raw(raw)) }
+    }
+}
+
+impl CoreWindow for Window {
+    fn id(&self) -> winit_core::window::WindowId {
+        self.maybe_wait_on_main(|delegate| delegate.id())
+    }
+
+    fn scale_factor(&self) -> f64 {
+        self.maybe_wait_on_main(|delegate| delegate.scale_factor())
+    }
+
+    fn request_redraw(&self) {
+        self.maybe_wait_on_main(|delegate| delegate.request_redraw());
+    }
+
+    fn pre_present_notify(&self) {
+        self.maybe_wait_on_main(|delegate| delegate.pre_present_notify());
+    }
+
+    fn reset_dead_keys(&self) {
+        self.maybe_wait_on_main(|delegate| delegate.reset_dead_keys());
+    }
+
+    fn surface_position(&self) -> PhysicalPosition<i32> {
+        self.maybe_wait_on_main(|delegate| delegate.surface_position())
+    }
+
+    fn outer_position(&self) -> Result<PhysicalPosition<i32>, RequestError> {
+        self.maybe_wait_on_main(|delegate| delegate.outer_position())
+    }
+
+    fn set_outer_position(&self, position: Position) {
+        self.maybe_wait_on_main(|delegate| delegate.set_outer_position(position));
+    }
+
+    fn surface_size(&self) -> PhysicalSize<u32> {
+        self.maybe_wait_on_main(|delegate| delegate.surface_size())
+    }
+
+    fn request_surface_size(&self, size: Size) -> Option<PhysicalSize<u32>> {
+        self.maybe_wait_on_main(|delegate| delegate.request_surface_size(size))
+    }
+
+    fn outer_size(&self) -> PhysicalSize<u32> {
+        self.maybe_wait_on_main(|delegate| delegate.outer_size())
+    }
+
+    fn safe_area(&self) -> PhysicalInsets<u32> {
+        self.maybe_wait_on_main(|delegate| delegate.safe_area())
+    }
+
+    fn set_min_surface_size(&self, min_size: Option<Size>) {
+        self.maybe_wait_on_main(|delegate| delegate.set_min_surface_size(min_size))
+    }
+
+    fn set_max_surface_size(&self, max_size: Option<Size>) {
+        self.maybe_wait_on_main(|delegate| delegate.set_max_surface_size(max_size));
+    }
+
+    fn surface_resize_increments(&self) -> Option<PhysicalSize<u32>> {
+        self.maybe_wait_on_main(|delegate| delegate.surface_resize_increments())
+    }
+
+    fn set_surface_resize_increments(&self, increments: Option<Size>) {
+        self.maybe_wait_on_main(|delegate| delegate.set_surface_resize_increments(increments));
+    }
+
+    fn set_title(&self, title: &str) {
+        self.maybe_wait_on_main(|delegate| delegate.set_title(title));
+    }
+
+    fn set_transparent(&self, transparent: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_transparent(transparent));
+    }
+
+    fn set_blur(&self, blur: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_blur(blur));
+    }
+
+    fn set_visible(&self, visible: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_visible(visible));
+    }
+
+    fn is_visible(&self) -> Option<bool> {
+        self.maybe_wait_on_main(|delegate| delegate.is_visible())
+    }
+
+    fn set_resizable(&self, resizable: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_resizable(resizable))
+    }
+
+    fn is_resizable(&self) -> bool {
+        self.maybe_wait_on_main(|delegate| delegate.is_resizable())
+    }
+
+    fn set_enabled_buttons(&self, buttons: WindowButtons) {
+        self.maybe_wait_on_main(|delegate| delegate.set_enabled_buttons(buttons))
+    }
+
+    fn enabled_buttons(&self) -> WindowButtons {
+        self.maybe_wait_on_main(|delegate| delegate.enabled_buttons())
+    }
+
+    fn set_minimized(&self, minimized: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_minimized(minimized));
+    }
+
+    fn is_minimized(&self) -> Option<bool> {
+        self.maybe_wait_on_main(|delegate| delegate.is_minimized())
+    }
+
+    fn set_maximized(&self, maximized: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_maximized(maximized));
+    }
+
+    fn is_maximized(&self) -> bool {
+        self.maybe_wait_on_main(|delegate| delegate.is_maximized())
+    }
+
+    fn set_fullscreen(&self, fullscreen: Option<Fullscreen>) {
+        self.maybe_wait_on_main(|delegate| delegate.set_fullscreen(fullscreen))
+    }
+
+    fn fullscreen(&self) -> Option<Fullscreen> {
+        self.maybe_wait_on_main(|delegate| delegate.fullscreen())
+    }
+
+    fn set_decorations(&self, decorations: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_decorations(decorations));
+    }
+
+    fn is_decorated(&self) -> bool {
+        self.maybe_wait_on_main(|delegate| delegate.is_decorated())
+    }
+
+    fn set_window_level(&self, level: WindowLevel) {
+        self.maybe_wait_on_main(|delegate| delegate.set_window_level(level));
+    }
+
+    fn set_window_icon(&self, window_icon: Option<Icon>) {
+        self.maybe_wait_on_main(|delegate| delegate.set_window_icon(window_icon));
+    }
+
+    fn set_ime_cursor_area(&self, position: Position, size: Size) {
+        self.maybe_wait_on_main(|delegate| delegate.set_ime_cursor_area(position, size));
+    }
+
+    fn set_ime_allowed(&self, allowed: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_ime_allowed(allowed));
+    }
+
+    fn set_ime_purpose(&self, purpose: ImePurpose) {
+        self.maybe_wait_on_main(|delegate| delegate.set_ime_purpose(purpose));
+    }
+
+    fn focus_window(&self) {
+        self.maybe_wait_on_main(|delegate| delegate.focus_window());
+    }
+
+    fn has_focus(&self) -> bool {
+        self.maybe_wait_on_main(|delegate| delegate.has_focus())
+    }
+
+    fn request_user_attention(&self, request_type: Option<UserAttentionType>) {
+        self.maybe_wait_on_main(|delegate| delegate.request_user_attention(request_type));
+    }
+
+    fn set_theme(&self, theme: Option<Theme>) {
+        self.maybe_wait_on_main(|delegate| delegate.set_theme(theme));
+    }
+
+    fn theme(&self) -> Option<Theme> {
+        self.maybe_wait_on_main(|delegate| delegate.theme())
+    }
+
+    fn set_content_protected(&self, protected: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_content_protected(protected));
+    }
+
+    fn title(&self) -> String {
+        self.maybe_wait_on_main(|delegate| delegate.title())
+    }
+
+    fn set_cursor(&self, cursor: Cursor) {
+        self.maybe_wait_on_main(|delegate| delegate.set_cursor(cursor));
+    }
+
+    fn set_cursor_position(&self, position: Position) -> Result<(), RequestError> {
+        Ok(self.maybe_wait_on_main(|delegate| delegate.set_cursor_position(position))?)
+    }
+
+    fn set_cursor_grab(
+        &self,
+        mode: winit_core::window::CursorGrabMode,
+    ) -> Result<(), RequestError> {
+        Ok(self.maybe_wait_on_main(|delegate| delegate.set_cursor_grab(mode))?)
+    }
+
+    fn set_cursor_visible(&self, visible: bool) {
+        self.maybe_wait_on_main(|delegate| delegate.set_cursor_visible(visible))
+    }
+
+    fn drag_window(&self) -> Result<(), RequestError> {
+        Ok(self.maybe_wait_on_main(|delegate| delegate.drag_window())?)
+    }
+
+    fn drag_resize_window(
+        &self,
+        direction: winit_core::window::ResizeDirection,
+    ) -> Result<(), RequestError> {
+        Ok(self.maybe_wait_on_main(|delegate| delegate.drag_resize_window(direction))?)
+    }
+
+    fn show_window_menu(&self, position: Position) {
+        self.maybe_wait_on_main(|delegate| delegate.show_window_menu(position))
+    }
+
+    fn set_cursor_hittest(&self, hittest: bool) -> Result<(), RequestError> {
+        Ok(self.maybe_wait_on_main(|delegate| delegate.set_cursor_hittest(hittest))?)
+    }
+
+    fn current_monitor(&self) -> Option<CoreMonitorHandle> {
+        self.maybe_wait_on_main(|delegate| {
+            delegate.current_monitor().map(|monitor| CoreMonitorHandle(Arc::new(monitor)))
+        })
+    }
+
+    fn available_monitors(&self) -> Box<dyn Iterator<Item = CoreMonitorHandle>> {
+        self.maybe_wait_on_main(|delegate| {
+            Box::new(
+                delegate
+                    .available_monitors()
+                    .into_iter()
+                    .map(|monitor| CoreMonitorHandle(Arc::new(monitor))),
+            )
+        })
+    }
+
+    fn primary_monitor(&self) -> Option<CoreMonitorHandle> {
+        self.maybe_wait_on_main(|delegate| {
+            delegate.primary_monitor().map(|monitor| CoreMonitorHandle(Arc::new(monitor)))
+        })
+    }
+
+    fn rwh_06_display_handle(&self) -> &dyn rwh_06::HasDisplayHandle {
+        self
+    }
+
+    fn rwh_06_window_handle(&self) -> &dyn rwh_06::HasWindowHandle {
+        self
+    }
+}
+
+// WindowExtIOS
+impl Inner {
+    pub fn set_scale_factor(&self, scale_factor: f64) {
+        assert!(
+            dpi::validate_scale_factor(scale_factor),
+            "`WindowExtIOS::set_scale_factor` received an invalid hidpi factor"
+        );
+        let scale_factor = scale_factor as CGFloat;
+        self.view.setContentScaleFactor(scale_factor);
+    }
+
+    pub fn set_valid_orientations(&self, valid_orientations: ValidOrientations) {
+        self.view_controller.set_supported_interface_orientations(
+            MainThreadMarker::new().unwrap(),
+            valid_orientations,
+        );
+    }
+
+    pub fn set_prefers_home_indicator_hidden(&self, hidden: bool) {
+        self.view_controller.set_prefers_home_indicator_auto_hidden(hidden);
+    }
+
+    pub fn set_preferred_screen_edges_deferring_system_gestures(&self, edges: ScreenEdge) {
+        self.view_controller.set_preferred_screen_edges_deferring_system_gestures(edges);
+    }
+
+    pub fn set_prefers_status_bar_hidden(&self, hidden: bool) {
+        self.view_controller.set_prefers_status_bar_hidden(hidden);
+    }
+
+    pub fn set_preferred_status_bar_style(&self, status_bar_style: StatusBarStyle) {
+        self.view_controller.set_preferred_status_bar_style(status_bar_style);
+    }
+
+    pub fn recognize_pinch_gesture(&self, should_recognize: bool) {
+        self.view.recognize_pinch_gesture(should_recognize);
+    }
+
+    pub fn recognize_pan_gesture(
+        &self,
+        should_recognize: bool,
+        minimum_number_of_touches: u8,
+        maximum_number_of_touches: u8,
+    ) {
+        self.view.recognize_pan_gesture(
+            should_recognize,
+            minimum_number_of_touches,
+            maximum_number_of_touches,
+        );
+    }
+
+    pub fn recognize_doubletap_gesture(&self, should_recognize: bool) {
+        self.view.recognize_doubletap_gesture(should_recognize);
+    }
+
+    pub fn recognize_rotation_gesture(&self, should_recognize: bool) {
+        self.view.recognize_rotation_gesture(should_recognize);
+    }
+}
+
+impl Inner {
+    fn screen_frame(&self) -> CGRect {
+        self.rect_to_screen_space(self.window.frame())
+    }
+
+    fn rect_to_screen_space(&self, rect: CGRect) -> CGRect {
+        let screen_space = self.window.screen().coordinateSpace();
+        self.window.convertRect_toCoordinateSpace(rect, &screen_space)
+    }
+
+    fn rect_from_screen_space(&self, rect: CGRect) -> CGRect {
+        let screen_space = self.window.screen().coordinateSpace();
+        self.window.convertRect_fromCoordinateSpace(rect, &screen_space)
+    }
+}