El2.0 ios (#871)

* port ios winit el2.0 implementation to the new rust-windowing repo

* unimplemented! => unreachable
trailing comma in CFRunLoopTimerCallback

* implement get_fullscreen

* add iOS specific platform documentation. Add a TODO about how to possibly extend the iOS backend to work have methods callable from more than just the main thread

* assert that window is only dropped from the main thread

* assert_main_thread called from fewer places

src/event_loop.rs

@@ -94,6 +94,10 @@ impl Default for ControlFlow {
 
 impl EventLoop<()> {
     /// Builds a new event loop with a `()` as the user event type.
+    /// 
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Can only be called on the main thread.
     pub fn new() -> EventLoop<()> {
         EventLoop::<()>::new_user_event()
     }
@@ -106,6 +110,10 @@ impl<T> EventLoop<T> {
     /// using an environment variable `WINIT_UNIX_BACKEND`. Legal values are `x11` and `wayland`.
     /// If it is not set, winit will try to connect to a wayland connection, and if it fails will
     /// fallback on x11. If this variable is set with any other value, winit will panic.
+    /// 
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Can only be called on the main thread.
     pub fn new_user_event() -> EventLoop<T> {
         EventLoop {
             event_loop: platform_impl::EventLoop::new(),

src/platform/ios.rs

@@ -2,7 +2,21 @@
 
 use std::os::raw::c_void;
 
-use {MonitorHandle, Window, WindowBuilder};
+use event_loop::EventLoop;
+use monitor::MonitorHandle;
+use window::{Window, WindowBuilder};
+
+/// Additional methods on `EventLoop` that are specific to iOS.
+pub trait EventLoopExtIOS {
+    /// Returns the idiom (phone/tablet/tv/etc) for the current device.
+    fn get_idiom(&self) -> Idiom;
+}
+
+impl<T: 'static> EventLoopExtIOS for EventLoop<T> {
+    fn get_idiom(&self) -> Idiom {
+        self.event_loop.get_idiom()
+    }
+}
 
 /// Additional methods on `Window` that are specific to iOS.
 pub trait WindowExtIOS {
@@ -11,10 +25,25 @@ pub trait WindowExtIOS {
     /// The pointer will become invalid when the `Window` is destroyed.
     fn get_uiwindow(&self) -> *mut c_void;
 
+    /// Returns a pointer to the `UIViewController` that is used by this window.
+    ///
+    /// The pointer will become invalid when the `Window` is destroyed.
+    fn get_uiviewcontroller(&self) -> *mut c_void;
+
     /// Returns a pointer to the `UIView` that is used by this window.
     ///
     /// The pointer will become invalid when the `Window` is destroyed.
     fn get_uiview(&self) -> *mut c_void;
+
+    /// Sets the HiDpi factor used by this window.
+    /// 
+    /// This translates to `-[UIWindow setContentScaleFactor:hidpi_factor]`.
+    fn set_hidpi_factor(&self, hidpi_factor: f64);
+
+    /// Sets the valid orientations for screens showing this `Window`.
+    /// 
+    /// On iPhones and iPods upside down portrait is never enabled.
+    fn set_valid_orientations(&self, valid_orientations: ValidOrientations);
 }
 
 impl WindowExtIOS for Window {
@@ -23,10 +52,25 @@ impl WindowExtIOS for Window {
         self.window.get_uiwindow() as _
     }
 
+    #[inline]
+    fn get_uiviewcontroller(&self) -> *mut c_void {
+        self.window.get_uiviewcontroller() as _
+    }
+
     #[inline]
     fn get_uiview(&self) -> *mut c_void {
         self.window.get_uiview() as _
     }
+
+    #[inline]
+    fn set_hidpi_factor(&self, hidpi_factor: f64) {
+        self.window.set_hidpi_factor(hidpi_factor)
+    }
+
+    #[inline]
+    fn set_valid_orientations(&self, valid_orientations: ValidOrientations) {
+        self.window.set_valid_orientations(valid_orientations)
+    }
 }
 
 /// Additional methods on `WindowBuilder` that are specific to iOS.
@@ -35,6 +79,15 @@ pub trait WindowBuilderExtIOS {
     ///
     /// The class will be initialized by calling `[root_view initWithFrame:CGRect]`
     fn with_root_view_class(self, root_view_class: *const c_void) -> WindowBuilder;
+    
+    /// Sets the `contentScaleFactor` of the underlying `UIWindow` to `hidpi_factor`.
+    /// 
+    /// The default value is device dependent, and it's recommended GLES or Metal applications set
+    /// this to `MonitorHandle::get_hidpi_factor()`.
+    fn with_hidpi_factor(self, hidpi_factor: f64) -> WindowBuilder;
+    
+    /// Sets the valid orientations for the `Window`.
+    fn with_valid_orientations(self, valid_orientations: ValidOrientations) -> WindowBuilder;
 }
 
 impl WindowBuilderExtIOS for WindowBuilder {
@@ -43,6 +96,18 @@ impl WindowBuilderExtIOS for WindowBuilder {
         self.platform_specific.root_view_class = unsafe { &*(root_view_class as *const _) };
         self
     }
+
+    #[inline]
+    fn with_hidpi_factor(mut self, hidpi_factor: f64) -> WindowBuilder {
+        self.platform_specific.hidpi_factor = Some(hidpi_factor);
+        self
+    }
+
+    #[inline]
+    fn with_valid_orientations(mut self, valid_orientations: ValidOrientations) -> WindowBuilder {
+        self.platform_specific.valid_orientations = valid_orientations;
+        self
+    }
 }
 
 /// Additional methods on `MonitorHandle` that are specific to iOS.
@@ -57,3 +122,40 @@ impl MonitorHandleExtIOS for MonitorHandle {
         self.inner.get_uiscreen() as _
     }
 }
+
+/// Valid orientations for a particular `Window`.
+#[derive(Clone, Copy, Debug)]
+pub enum ValidOrientations {
+    /// Excludes `PortraitUpsideDown` on iphone
+    LandscapeAndPortrait,
+
+    Landscape,
+    
+    /// Excludes `PortraitUpsideDown` on iphone
+    Portrait,
+}
+
+impl Default for ValidOrientations {
+    #[inline]
+    fn default() -> ValidOrientations {
+        ValidOrientations::LandscapeAndPortrait
+    }
+}
+
+/// The device [idiom].
+/// 
+/// [idiom]: https://developer.apple.com/documentation/uikit/uidevice/1620037-userinterfaceidiom?language=objc
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Idiom {
+    Unspecified,
+
+    /// iPhone and iPod touch.
+    Phone,
+
+    /// iPad.
+    Pad,
+
+    /// tvOS and Apple TV.
+    TV,
+    CarPlay,
+}

src/platform_impl/ios/app_state.rs

@@ -0,0 +1,580 @@
+use std::{mem, ptr};
+use std::cell::{RefCell, RefMut};
+use std::mem::ManuallyDrop;
+use std::os::raw::c_void;
+use std::time::Instant;
+
+use event::{Event, StartCause};
+use event_loop::ControlFlow;
+
+use platform_impl::platform::event_loop::{EventHandler, Never};
+use platform_impl::platform::ffi::{
+    id,
+    CFAbsoluteTimeGetCurrent,
+    CFRelease,
+    CFRunLoopAddTimer,
+    CFRunLoopGetMain,
+    CFRunLoopRef,
+    CFRunLoopTimerCreate,
+    CFRunLoopTimerInvalidate,
+    CFRunLoopTimerRef,
+    CFRunLoopTimerSetNextFireDate,
+    kCFRunLoopCommonModes,
+    NSUInteger,
+};
+
+macro_rules! bug {
+    ($msg:expr) => {
+        panic!("winit iOS bug, file an issue: {}", $msg)
+    };
+}
+
+// this is the state machine for the app lifecycle
+#[derive(Debug)]
+enum AppStateImpl {
+    NotLaunched {
+        queued_windows: Vec<id>,
+        queued_events: Vec<Event<Never>>,
+    },
+    Launching {
+        queued_windows: Vec<id>,
+        queued_events: Vec<Event<Never>>,
+        queued_event_handler: Box<EventHandler>,
+    },
+    ProcessingEvents {
+        event_handler: Box<EventHandler>,
+        active_control_flow: ControlFlow,
+    },
+    // special state to deal with reentrancy and prevent mutable aliasing.
+    InUserCallback {
+        queued_events: Vec<Event<Never>>,
+    },
+    Waiting {
+        waiting_event_handler: Box<EventHandler>,
+        start: Instant,
+    },
+    PollFinished {
+        waiting_event_handler: Box<EventHandler>,
+    },
+    Terminated,
+}
+
+impl Drop for AppStateImpl {
+    fn drop(&mut self) {
+        match self {
+            &mut AppStateImpl::NotLaunched { ref mut queued_windows, .. } |
+            &mut AppStateImpl::Launching { ref mut queued_windows, .. } => unsafe {
+                for &mut window in queued_windows {
+                    let () = msg_send![window, release];
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+pub struct AppState {
+    app_state: AppStateImpl,
+    control_flow: ControlFlow,
+    waker: EventLoopWaker,
+}
+
+impl AppState {
+    // requires main thread
+    unsafe fn get_mut() -> 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);
+
+        if cfg!(debug_assertions) {
+            assert_main_thread!("bug in winit: `AppState::get_mut()` can only be called on the main thread");
+        }
+
+        let mut guard = APP_STATE.borrow_mut();
+        if guard.is_none() {
+            #[inline(never)]
+            #[cold]
+            unsafe fn init_guard(guard: &mut RefMut<'static, Option<AppState>>) {
+                let waker = EventLoopWaker::new(CFRunLoopGetMain());
+                **guard = Some(AppState {
+                    app_state: AppStateImpl::NotLaunched {
+                        queued_windows: Vec::new(),
+                        queued_events: Vec::new(),
+                    },
+                    control_flow: ControlFlow::default(),
+                    waker,
+                });
+            }
+            init_guard(&mut guard)
+        }
+        RefMut::map(guard, |state| {
+            state.as_mut().unwrap()
+        })
+    }
+    
+    // requires main thread and window is a UIWindow
+    // retains window
+    pub unsafe fn set_key_window(window: id) {
+        let mut this = AppState::get_mut();
+        match &mut this.app_state {
+            &mut AppStateImpl::NotLaunched { ref mut queued_windows, .. } => {
+                queued_windows.push(window);
+                msg_send![window, retain];
+                return;
+            }
+            &mut AppStateImpl::ProcessingEvents { .. } => {},
+            &mut AppStateImpl::InUserCallback { .. } => {},
+            &mut AppStateImpl::Terminated => panic!("Attempt to create a `Window` \
+                                                     after the app has terminated"),
+            app_state => unreachable!("unexpected state: {:#?}", app_state), // all other cases should be impossible
+        }
+        drop(this);
+        msg_send![window, makeKeyAndVisible]
+    }
+
+    // requires main thread
+    pub unsafe fn will_launch(queued_event_handler: Box<EventHandler>) {
+        let mut this = AppState::get_mut();
+        let (queued_windows, queued_events) = match &mut this.app_state {
+            &mut AppStateImpl::NotLaunched {
+                ref mut queued_windows,
+                ref mut queued_events,
+            } => {
+                let windows = ptr::read(queued_windows);
+                let events = ptr::read(queued_events);
+                (windows, events)
+            }
+            _ => panic!("winit iOS expected the app to be in a `NotLaunched` \
+                            state, but was not - please file an issue"),
+        };
+        ptr::write(&mut this.app_state, AppStateImpl::Launching {
+            queued_windows,
+            queued_events,
+            queued_event_handler,
+        });
+    }
+
+    // requires main thread
+    pub unsafe fn did_finish_launching() {
+        let mut this = AppState::get_mut();
+        let windows = match &mut this.app_state {
+            &mut AppStateImpl::Launching {
+                ref mut queued_windows,
+                ..
+            } => mem::replace(queued_windows, Vec::new()),
+            _ => panic!(
+                "winit iOS expected the app to be in a `Launching` \
+                 state, but was not - please file an issue"
+            ),
+        };
+        // have to drop RefMut because the window setup code below can trigger new events
+        drop(this);
+
+        for window in windows {
+            let count: NSUInteger = msg_send![window, retainCount];
+            // make sure the window is still referenced
+            if count > 1 {
+                // Do a little screen dance here to account for windows being created before
+                // `UIApplicationMain` is called. This fixes visual issues such as being
+                // offcenter and sized incorrectly. Additionally, to fix orientation issues, we
+                // gotta reset the `rootViewController`.
+                //
+                // relevant iOS log:
+                // ```
+                // [ApplicationLifecycle] Windows were created before application initialzation
+                // completed. This may result in incorrect visual appearance.
+                // ```
+                let screen: id = msg_send![window, screen];
+                let () = msg_send![screen, retain];
+                let () = msg_send![window, setScreen:0 as id];
+                let () = msg_send![window, setScreen:screen];
+                let () = msg_send![screen, release];
+                let controller: id = msg_send![window, rootViewController];
+                let () = msg_send![window, setRootViewController:ptr::null::<()>()];
+                let () = msg_send![window, setRootViewController:controller];
+                let () = msg_send![window, makeKeyAndVisible];
+            }
+            let () = msg_send![window, release];
+        }
+
+        let mut this = AppState::get_mut();
+        let (windows, events, event_handler) = match &mut this.app_state {
+            &mut AppStateImpl::Launching {
+                ref mut queued_windows,
+                ref mut queued_events,
+                ref mut queued_event_handler,
+            } => {
+                let windows = ptr::read(queued_windows);
+                let events = ptr::read(queued_events);
+                let event_handler = ptr::read(queued_event_handler);
+                (windows, events, event_handler)
+            }
+            _ => panic!("winit iOS expected the app to be in a `Launching` \
+                        state, but was not - please file an issue"),
+        };
+        ptr::write(&mut this.app_state, AppStateImpl::ProcessingEvents {
+            event_handler,
+            active_control_flow: ControlFlow::Poll,
+        });
+        drop(this);
+        
+        let events = std::iter::once(Event::NewEvents(StartCause::Init)).chain(events);
+        AppState::handle_nonuser_events(events);
+
+        // the above window dance hack, could possibly trigger new windows to be created.
+        // we can just set those windows up normally, as they were created after didFinishLaunching
+        for window in windows {
+            let count: NSUInteger = msg_send![window, retainCount];
+            // make sure the window is still referenced
+            if count > 1 {
+                let () = msg_send![window, makeKeyAndVisible];
+            }
+            let () = msg_send![window, release];
+        }
+    }
+
+    // requires main thread
+    // AppState::did_finish_launching handles the special transition `Init`
+    pub unsafe fn handle_wakeup_transition() {
+        let mut this = AppState::get_mut();
+        let event = match this.control_flow {
+            ControlFlow::Poll => {
+                let event_handler = match &mut this.app_state {
+                    &mut AppStateImpl::NotLaunched { .. } |
+                    &mut AppStateImpl::Launching { .. } => return,
+                    &mut AppStateImpl::PollFinished {
+                        ref mut waiting_event_handler,
+                    } => ptr::read(waiting_event_handler),
+                    _ => bug!("`EventHandler` unexpectedly started polling"),
+                };
+                ptr::write(&mut this.app_state, AppStateImpl::ProcessingEvents {
+                    event_handler,
+                    active_control_flow: ControlFlow::Poll,
+                });
+                Event::NewEvents(StartCause::Poll)
+            }
+            ControlFlow::Wait => {
+                let (event_handler, start) = match &mut this.app_state {
+                    &mut AppStateImpl::NotLaunched { .. } |
+                    &mut AppStateImpl::Launching { .. } => return,
+                    &mut AppStateImpl::Waiting {
+                        ref mut waiting_event_handler,
+                        ref mut start,
+                    } => (ptr::read(waiting_event_handler), *start),
+                    _ => bug!("`EventHandler` unexpectedly woke up"),
+                };
+                ptr::write(&mut this.app_state, AppStateImpl::ProcessingEvents {
+                    event_handler,
+                    active_control_flow: ControlFlow::Wait,
+                });
+                Event::NewEvents(StartCause::WaitCancelled {
+                    start,
+                    requested_resume: None,
+                })
+            }
+            ControlFlow::WaitUntil(requested_resume) => {
+                let (event_handler, start) = match &mut this.app_state {
+                    &mut AppStateImpl::NotLaunched { .. } |
+                    &mut AppStateImpl::Launching { .. } => return,
+                    &mut AppStateImpl::Waiting {
+                        ref mut waiting_event_handler,
+                        ref mut start,
+                    } => (ptr::read(waiting_event_handler), *start),
+                    _ => bug!("`EventHandler` unexpectedly woke up"),
+                };
+                ptr::write(&mut this.app_state, AppStateImpl::ProcessingEvents {
+                    event_handler,
+                    active_control_flow: ControlFlow::WaitUntil(requested_resume),
+                });
+                if Instant::now() >= requested_resume {
+                    Event::NewEvents(StartCause::ResumeTimeReached {
+                        start,
+                        requested_resume,
+                    })
+                } else {
+                    Event::NewEvents(StartCause::WaitCancelled {
+                        start,
+                        requested_resume: Some(requested_resume),
+                    })
+                }
+            }
+            ControlFlow::Exit => bug!("unexpected controlflow `Exit`"),
+        };
+        drop(this);
+        AppState::handle_nonuser_event(event)
+    }
+
+    // requires main thread
+    pub unsafe fn handle_nonuser_event(event: Event<Never>) {
+        AppState::handle_nonuser_events(std::iter::once(event))
+    }
+
+    // requires main thread
+    pub unsafe fn handle_nonuser_events<I: IntoIterator<Item = Event<Never>>>(events: I) {
+        let mut this = AppState::get_mut();
+        let mut control_flow = this.control_flow;
+        let (mut event_handler, active_control_flow) = match &mut this.app_state {
+            &mut AppStateImpl::Launching {
+                ref mut queued_events,
+                ..
+            }
+            | &mut AppStateImpl::NotLaunched {
+                ref mut queued_events,
+                ..
+            }
+            | &mut AppStateImpl::InUserCallback {
+                ref mut queued_events,
+                ..
+            } => {
+                queued_events.extend(events);
+                return
+            }
+            &mut AppStateImpl::ProcessingEvents {
+                ref mut event_handler,
+                ref mut active_control_flow,
+            } => (ptr::read(event_handler), *active_control_flow),
+            &mut AppStateImpl::PollFinished { .. }
+            | &mut AppStateImpl::Waiting { .. }
+            | &mut AppStateImpl::Terminated => bug!("unexpected attempted to process an event"),
+        };
+        ptr::write(&mut this.app_state, AppStateImpl::InUserCallback {
+            queued_events: Vec::new(),
+        });
+        drop(this);
+
+        for event in events {
+            event_handler.handle_nonuser_event(event, &mut control_flow)
+        }
+        loop {
+            let mut this = AppState::get_mut();
+            let queued_events = match &mut this.app_state {
+                &mut AppStateImpl::InUserCallback {
+                    ref mut queued_events,
+                } => mem::replace(queued_events, Vec::new()),
+                _ => bug!("unexpected `AppStateImpl`"),
+            };
+            if queued_events.is_empty() {
+                this.app_state = AppStateImpl::ProcessingEvents {
+                    event_handler,
+                    active_control_flow,
+                };
+                this.control_flow = control_flow;
+                break
+            }
+            drop(this);
+            for event in queued_events {
+                event_handler.handle_nonuser_event(event, &mut control_flow)
+            }
+        }
+    }
+
+    // requires main thread
+    pub unsafe fn handle_user_events() {
+        let mut this = AppState::get_mut();
+        let mut control_flow = this.control_flow;
+        let (mut event_handler, active_control_flow) = match &mut this.app_state {
+            &mut AppStateImpl::NotLaunched { .. } | &mut AppStateImpl::Launching { .. } => return,
+            &mut AppStateImpl::ProcessingEvents {
+                ref mut event_handler,
+                ref mut active_control_flow,
+            } => (ptr::read(event_handler), *active_control_flow),
+            &mut AppStateImpl::InUserCallback { .. }
+            | &mut AppStateImpl::PollFinished { .. }
+            | &mut AppStateImpl::Waiting { .. }
+            | &mut AppStateImpl::Terminated => bug!("unexpected attempted to process an event"),
+        };
+        ptr::write(&mut this.app_state, AppStateImpl::InUserCallback {
+            queued_events: Vec::new(),
+        });
+        drop(this);
+
+        event_handler.handle_user_events(&mut control_flow);
+        loop {
+            let mut this = AppState::get_mut();
+            let queued_events = match &mut this.app_state {
+                &mut AppStateImpl::InUserCallback {
+                    ref mut queued_events,
+                } => mem::replace(queued_events, Vec::new()),
+                _ => bug!("unexpected `AppStateImpl`"),
+            };
+            if queued_events.is_empty() {
+                this.app_state = AppStateImpl::ProcessingEvents {
+                    event_handler,
+                    active_control_flow,
+                };
+                this.control_flow = control_flow;
+                break
+            }
+            drop(this);
+            for event in queued_events {
+                event_handler.handle_nonuser_event(event, &mut control_flow)
+            }
+            event_handler.handle_user_events(&mut control_flow);
+        }
+    }
+
+    // requires main thread
+    pub unsafe fn handle_events_cleared() {
+        let mut this = AppState::get_mut();
+        match &mut this.app_state {
+            &mut AppStateImpl::NotLaunched { .. } | &mut AppStateImpl::Launching { .. } => return,
+            &mut AppStateImpl::ProcessingEvents { .. } => {}
+            _ => unreachable!(),
+        };
+        drop(this);
+
+        AppState::handle_user_events();
+        AppState::handle_nonuser_event(Event::EventsCleared);
+
+        let mut this = AppState::get_mut();
+        let (event_handler, old) = match &mut this.app_state {
+            &mut AppStateImpl::ProcessingEvents {
+                ref mut event_handler,
+                ref mut active_control_flow,
+            } => (ManuallyDrop::new(ptr::read(event_handler)), *active_control_flow),
+            _ => unreachable!(),
+        };
+
+        let new = this.control_flow;
+        match (old, new) {
+            (ControlFlow::Poll, ControlFlow::Poll) => {
+                ptr::write(
+                    &mut this.app_state,
+                    AppStateImpl::PollFinished {
+                        waiting_event_handler: ManuallyDrop::into_inner(event_handler),
+                    },
+                )
+            },
+            (ControlFlow::Wait, ControlFlow::Wait) => {
+                let start = Instant::now();
+                ptr::write(
+                    &mut this.app_state,
+                    AppStateImpl::Waiting {
+                        waiting_event_handler: ManuallyDrop::into_inner(event_handler),
+                        start,
+                    },
+                )
+            },
+            (ControlFlow::WaitUntil(old_instant), ControlFlow::WaitUntil(new_instant))
+                if old_instant == new_instant => {
+                let start = Instant::now();
+                ptr::write(
+                    &mut this.app_state,
+                    AppStateImpl::Waiting {
+                        waiting_event_handler: ManuallyDrop::into_inner(event_handler),
+                        start,
+                    },
+                )
+            }
+            (_, ControlFlow::Wait) => {
+                let start = Instant::now();
+                ptr::write(
+                    &mut this.app_state,
+                    AppStateImpl::Waiting {
+                        waiting_event_handler: ManuallyDrop::into_inner(event_handler),
+                        start,
+                    },
+                );
+                this.waker.stop()
+            },
+            (_, ControlFlow::WaitUntil(new_instant)) => {
+                let start = Instant::now();
+                ptr::write(
+                    &mut this.app_state,
+                    AppStateImpl::Waiting {
+                        waiting_event_handler: ManuallyDrop::into_inner(event_handler),
+                        start,
+                    },
+                );
+                this.waker.start_at(new_instant)
+            },
+            (_, ControlFlow::Poll) => {
+                ptr::write(
+                    &mut this.app_state,
+                    AppStateImpl::PollFinished {
+                        waiting_event_handler: ManuallyDrop::into_inner(event_handler),
+                    },
+                );
+                this.waker.start()
+            },
+            (_, ControlFlow::Exit) => {
+                // https://developer.apple.com/library/archive/qa/qa1561/_index.html
+                // it is not possible to quit an iOS app gracefully and programatically
+                warn!("`ControlFlow::Exit` ignored on iOS");
+                this.control_flow = old
+            }
+        }
+    }
+
+    pub fn terminated() {
+        let mut this = unsafe { AppState::get_mut() };
+        let mut old = mem::replace(&mut this.app_state, AppStateImpl::Terminated);
+        let mut control_flow = this.control_flow;
+        if let AppStateImpl::ProcessingEvents { ref mut event_handler, .. } = old {
+            drop(this);
+            event_handler.handle_nonuser_event(Event::LoopDestroyed, &mut control_flow)
+        } else {
+            bug!("`LoopDestroyed` happened while not processing events")
+        }
+    }
+}
+
+struct EventLoopWaker {
+    timer: CFRunLoopTimerRef,
+}
+
+impl Drop for EventLoopWaker {
+    fn drop(&mut self) {
+        unsafe {
+            CFRunLoopTimerInvalidate(self.timer);
+            CFRelease(self.timer as _);
+        }
+    }
+}
+
+impl EventLoopWaker {
+    fn new(rl: CFRunLoopRef) -> EventLoopWaker {
+        extern fn wakeup_main_loop(_timer: CFRunLoopTimerRef, _info: *mut c_void) {}
+        unsafe {
+            // create a timer with a 1microsec 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 immediatley in did_finish_launching
+            let timer = CFRunLoopTimerCreate(
+                ptr::null_mut(),
+                std::f64::MAX,
+                0.000_000_1,
+                0,
+                0,
+                wakeup_main_loop,
+                ptr::null_mut(),
+            );
+            CFRunLoopAddTimer(rl, timer, kCFRunLoopCommonModes);
+
+            EventLoopWaker { timer }
+        }
+    }
+
+    fn stop(&mut self) {
+        unsafe { CFRunLoopTimerSetNextFireDate(self.timer, std::f64::MAX) }
+    }
+
+    fn start(&mut self) {
+        unsafe { CFRunLoopTimerSetNextFireDate(self.timer, std::f64::MIN) }
+    }
+
+    fn start_at(&mut self, instant: Instant) {
+        let now = Instant::now();
+        if now >= instant {
+            self.start();
+        } else {
+            unsafe {
+                let current = CFAbsoluteTimeGetCurrent();
+                let duration = instant - now;
+                let fsecs =
+                    duration.subsec_nanos() as f64 / 1_000_000_000.0 + duration.as_secs() as f64;
+                CFRunLoopTimerSetNextFireDate(self.timer, current + fsecs)
+            }
+        }
+    }
+}

src/platform_impl/ios/event_loop.rs

@@ -0,0 +1,334 @@
+use std::{mem, ptr};
+use std::collections::VecDeque;
+use std::ffi::c_void;
+use std::fmt::{self, Debug, Formatter};
+use std::marker::PhantomData;
+use std::sync::mpsc::{self, Sender, Receiver};
+
+use event::Event;
+use event_loop::{
+    ControlFlow,
+    EventLoopWindowTarget as RootEventLoopWindowTarget,
+    EventLoopClosed,
+};
+use platform::ios::Idiom;
+
+use platform_impl::platform::app_state::AppState;
+use platform_impl::platform::ffi::{
+    id,
+    nil,
+    CFIndex,
+    CFRelease,
+    CFRunLoopActivity,
+    CFRunLoopAddObserver,
+    CFRunLoopAddSource,
+    CFRunLoopGetMain,
+    CFRunLoopObserverCreate,
+    CFRunLoopObserverRef,
+    CFRunLoopSourceContext,
+    CFRunLoopSourceCreate,
+    CFRunLoopSourceInvalidate,
+    CFRunLoopSourceRef,
+    CFRunLoopSourceSignal,
+    CFRunLoopWakeUp,
+    kCFRunLoopCommonModes,
+    kCFRunLoopDefaultMode,
+    kCFRunLoopEntry,
+    kCFRunLoopBeforeWaiting,
+    kCFRunLoopAfterWaiting,
+    kCFRunLoopExit,
+    NSOperatingSystemVersion,
+    NSString,
+    UIApplicationMain,
+    UIUserInterfaceIdiom,
+};
+use platform_impl::platform::monitor;
+use platform_impl::platform::MonitorHandle;
+use platform_impl::platform::view;
+
+pub struct EventLoopWindowTarget<T: 'static> {
+    receiver: Receiver<T>,
+    sender_to_clone: Sender<T>,
+    capabilities: Capabilities,
+}
+
+impl<T: 'static> EventLoopWindowTarget<T> {
+    pub fn capabilities(&self) -> &Capabilities {
+        &self.capabilities
+    }
+}
+
+pub struct EventLoop<T: 'static> {
+    window_target: RootEventLoopWindowTarget<T>,
+}
+
+impl<T: 'static> EventLoop<T> {
+    pub fn new() -> EventLoop<T> {
+        static mut SINGLETON_INIT: bool = false;
+        unsafe {
+            assert_main_thread!("`EventLoop` can only be created on the main thread on iOS");
+            assert!(!SINGLETON_INIT, "Only one `EventLoop` is supported on iOS. \
+                `EventLoopProxy` might be helpful");
+            SINGLETON_INIT = true;
+            view::create_delegate_class();
+        }
+
+        let (sender_to_clone, receiver) = mpsc::channel();
+
+        // this line sets up the main run loop before `UIApplicationMain`
+        setup_control_flow_observers();
+
+        let version: NSOperatingSystemVersion = unsafe {
+            let process_info: id = msg_send![class!(NSProcessInfo), processInfo];
+            msg_send![process_info, operatingSystemVersion]
+        };
+        let capabilities = version.into();
+
+        EventLoop {
+            window_target: RootEventLoopWindowTarget {
+                p: EventLoopWindowTarget {
+                    receiver,
+                    sender_to_clone,
+                    capabilities,
+                },
+                _marker: PhantomData,
+            }
+        }
+    }
+
+    pub fn run<F>(self, event_handler: F) -> !
+    where
+        F: 'static + FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow)
+    {
+        unsafe {
+            let application: *mut c_void = msg_send![class!(UIApplication), sharedApplication];
+            assert_eq!(application, ptr::null_mut(), "\
+                `EventLoop` cannot be `run` after a call to `UIApplicationMain` on iOS\n\
+                Note: `EventLoop::run` calls `UIApplicationMain` on iOS");
+            AppState::will_launch(Box::new(EventLoopHandler {
+                f: event_handler,
+                event_loop: self.window_target,
+            }));
+
+            UIApplicationMain(0, ptr::null(), nil, NSString::alloc(nil).init_str("AppDelegate"));
+            unreachable!()
+        }
+    }
+
+    pub fn create_proxy(&self) -> EventLoopProxy<T> {
+        EventLoopProxy::new(self.window_target.p.sender_to_clone.clone())
+    }
+
+    pub fn get_available_monitors(&self) -> VecDeque<MonitorHandle> {
+        // guaranteed to be on main thread
+        unsafe {
+            monitor::uiscreens()
+        }
+    }
+
+    pub fn get_primary_monitor(&self) -> MonitorHandle {
+        // guaranteed to be on main thread
+        unsafe {
+            monitor::main_uiscreen()
+        }
+    }
+
+    pub fn window_target(&self) -> &RootEventLoopWindowTarget<T> {
+        &self.window_target
+    }
+}
+
+// EventLoopExtIOS
+impl<T: 'static> EventLoop<T> {
+    pub fn get_idiom(&self) -> Idiom {
+        // guaranteed to be on main thread
+        unsafe {
+            self::get_idiom()
+        }
+    }
+}
+
+pub struct EventLoopProxy<T> {
+    sender: Sender<T>,
+    source: CFRunLoopSourceRef,
+}
+
+unsafe impl<T> Send for EventLoopProxy<T> {}
+unsafe impl<T> Sync for EventLoopProxy<T> {}
+
+impl<T> Clone for EventLoopProxy<T> {
+    fn clone(&self) -> EventLoopProxy<T> {
+        EventLoopProxy::new(self.sender.clone())
+    }
+}
+
+impl<T> Drop for EventLoopProxy<T> {
+    fn drop(&mut self) {
+        unsafe {
+            CFRunLoopSourceInvalidate(self.source);
+            CFRelease(self.source as _);
+        }
+    }
+}
+
+impl<T> EventLoopProxy<T> {
+    fn new(sender: Sender<T>) -> EventLoopProxy<T> {
+        unsafe {
+            // just wakeup the eventloop
+            extern "C" fn event_loop_proxy_handler(_: *mut c_void) {}
+
+            // adding a Source to the main CFRunLoop lets us wake it up and
+            // process user events through the normal OS EventLoop mechanisms.
+            let rl = CFRunLoopGetMain();
+            // we want all the members of context to be zero/null, except one
+            let mut context: CFRunLoopSourceContext = mem::zeroed();
+            context.perform = event_loop_proxy_handler;
+            let source = CFRunLoopSourceCreate(
+                ptr::null_mut(),
+                CFIndex::max_value() - 1,
+                &mut context,
+            );
+            CFRunLoopAddSource(rl, source, kCFRunLoopCommonModes);
+            CFRunLoopWakeUp(rl);
+
+            EventLoopProxy {
+                sender,
+                source,
+            }
+        }
+    }
+
+    pub fn send_event(&self, event: T) -> Result<(), EventLoopClosed> {
+        self.sender.send(event).map_err(|_| EventLoopClosed)?;
+        unsafe {
+            // let the main thread know there's a new event
+            CFRunLoopSourceSignal(self.source);
+            let rl = CFRunLoopGetMain();
+            CFRunLoopWakeUp(rl);
+        }
+        Ok(())
+    }
+}
+
+fn setup_control_flow_observers() {
+    unsafe {
+        // begin is queued with the highest priority to ensure it is processed before other observers
+        extern fn control_flow_begin_handler(
+            _: CFRunLoopObserverRef,
+            activity: CFRunLoopActivity,
+            _: *mut c_void,
+        ) {
+            unsafe {
+                #[allow(non_upper_case_globals)]
+                match activity {
+                    kCFRunLoopAfterWaiting => AppState::handle_wakeup_transition(),
+                    kCFRunLoopEntry => unimplemented!(), // not expected to ever happen
+                    _ => unreachable!(),
+                }
+            }
+        }
+
+        // end is queued with the lowest priority to ensure it is processed after other observers
+        // without that, LoopDestroyed will get sent after EventsCleared
+        extern fn control_flow_end_handler(
+            _: CFRunLoopObserverRef,
+            activity: CFRunLoopActivity,
+            _: *mut c_void,
+        ) {
+            unsafe {
+                #[allow(non_upper_case_globals)]
+                match activity {
+                    kCFRunLoopBeforeWaiting => AppState::handle_events_cleared(),
+                    kCFRunLoopExit => unimplemented!(), // not expected to ever happen
+                    _ => unreachable!(),
+                }
+            }
+        }
+
+        let main_loop = CFRunLoopGetMain();
+        let begin_observer = CFRunLoopObserverCreate(
+            ptr::null_mut(),
+            kCFRunLoopEntry | kCFRunLoopAfterWaiting,
+            1, // repeat = true
+            CFIndex::min_value(),
+            control_flow_begin_handler,
+            ptr::null_mut(),
+        );
+        CFRunLoopAddObserver(main_loop, begin_observer, kCFRunLoopDefaultMode);
+        let end_observer = CFRunLoopObserverCreate(
+            ptr::null_mut(),
+            kCFRunLoopExit | kCFRunLoopBeforeWaiting,
+            1, // repeat = true
+            CFIndex::max_value(),
+            control_flow_end_handler,
+            ptr::null_mut(),
+        );
+        CFRunLoopAddObserver(main_loop, end_observer, kCFRunLoopDefaultMode);
+    }
+}
+
+#[derive(Debug)]
+pub enum Never {}
+
+pub trait EventHandler: Debug {
+    fn handle_nonuser_event(&mut self, event: Event<Never>, control_flow: &mut ControlFlow);
+    fn handle_user_events(&mut self, control_flow: &mut ControlFlow);
+}
+
+struct EventLoopHandler<F, T: 'static> {
+    f: F,
+    event_loop: RootEventLoopWindowTarget<T>,
+}
+
+impl<F, T: 'static> Debug for EventLoopHandler<F, T> {
+    fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
+        formatter.debug_struct("EventLoopHandler")
+            .field("event_loop", &self.event_loop)
+            .finish()
+    }
+}
+
+impl<F, T> EventHandler for EventLoopHandler<F, T>
+where
+    F: 'static + FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
+    T: 'static,
+{
+    fn handle_nonuser_event(&mut self, event: Event<Never>, control_flow: &mut ControlFlow) {
+        (self.f)(
+            event.map_nonuser_event().unwrap(),
+            &self.event_loop,
+            control_flow,
+        );
+    }
+
+    fn handle_user_events(&mut self, control_flow: &mut ControlFlow) {
+        for event in self.event_loop.p.receiver.try_iter() {
+            (self.f)(
+                Event::UserEvent(event),
+                &self.event_loop,
+                control_flow,
+            );
+        }
+    }
+}
+
+// must be called on main thread
+pub unsafe fn get_idiom() -> Idiom {
+    let device: id = msg_send![class!(UIDevice), currentDevice];
+    let raw_idiom: UIUserInterfaceIdiom = msg_send![device, userInterfaceIdiom];
+    raw_idiom.into()
+}
+
+pub struct Capabilities {
+    pub supports_safe_area: bool,
+}
+
+impl From<NSOperatingSystemVersion> for Capabilities {
+    fn from(os_version: NSOperatingSystemVersion) -> Capabilities {
+        assert!(os_version.major >= 8, "`winit` current requires iOS version 8 or greater");
+
+        let supports_safe_area = os_version.major >= 11;
+
+        Capabilities { supports_safe_area }
+    }
+}

src/platform_impl/ios/ffi.rs

@@ -1,24 +1,33 @@
 #![allow(non_camel_case_types, non_snake_case, non_upper_case_globals)]
 
 use std::ffi::CString;
+use std::ops::BitOr;
 use std::os::raw::*;
 
+use objc::{Encode, Encoding};
 use objc::runtime::Object;
 
+use platform::ios::{Idiom, ValidOrientations};
+
 pub type id = *mut Object;
 pub const nil: id = 0 as id;
 
-pub type CFStringRef = *const c_void;
-pub type CFTimeInterval = f64;
-pub type Boolean = u32;
-
-pub const kCFRunLoopRunHandledSource: i32 = 4;
-
 #[cfg(target_pointer_width = "32")]
 pub type CGFloat = f32;
 #[cfg(target_pointer_width = "64")]
 pub type CGFloat = f64;
 
+pub type NSInteger = isize;
+pub type NSUInteger = usize;
+
+#[repr(C)]
+#[derive(Clone, Debug)]
+pub struct NSOperatingSystemVersion {
+    pub major: NSInteger,
+    pub minor: NSInteger,
+    pub patch: NSInteger,
+}
+
 #[repr(C)]
 #[derive(Debug, Clone)]
 pub struct CGPoint {
@@ -26,13 +35,6 @@ pub struct CGPoint {
     pub y: CGFloat,
 }
 
-#[repr(C)]
-#[derive(Debug, Clone)]
-pub struct CGRect {
-    pub origin: CGPoint,
-    pub size: CGSize,
-}
-
 #[repr(C)]
 #[derive(Debug, Clone)]
 pub struct CGSize {
@@ -40,13 +42,134 @@ pub struct CGSize {
     pub height: CGFloat,
 }
 
+#[repr(C)]
+#[derive(Debug, Clone)]
+pub struct CGRect {
+    pub origin: CGPoint,
+    pub size: CGSize,
+}
+
+unsafe impl Encode for CGRect {
+    fn encode() -> Encoding {
+        unsafe {
+            if cfg!(target_pointer_width = "32") {
+                Encoding::from_str("{CGRect={CGPoint=ff}{CGSize=ff}}")
+            } else if cfg!(target_pointer_width = "64") {
+                Encoding::from_str("{CGRect={CGPoint=dd}{CGSize=dd}}")
+            } else {
+                unimplemented!()
+            }
+        }
+    }
+}
+#[derive(Debug)]
+#[allow(dead_code)]
+#[repr(isize)]
+pub enum UITouchPhase {
+    Began = 0,
+    Moved,
+    Stationary,
+    Ended,
+    Cancelled,
+}
+
+#[repr(C)]
+#[derive(Debug, Clone)]
+pub struct UIEdgeInsets {
+    pub top: CGFloat,
+    pub left: CGFloat,
+    pub bottom: CGFloat,
+    pub right: CGFloat,
+}
+
+#[repr(transparent)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct UIUserInterfaceIdiom(NSInteger);
+
+unsafe impl Encode for UIUserInterfaceIdiom {
+    fn encode() -> Encoding { NSInteger::encode() }
+}
+
+impl UIUserInterfaceIdiom {
+    pub const Unspecified: UIUserInterfaceIdiom = UIUserInterfaceIdiom(-1);
+    pub const Phone: UIUserInterfaceIdiom = UIUserInterfaceIdiom(0);
+    pub const Pad: UIUserInterfaceIdiom = UIUserInterfaceIdiom(1);
+    pub const TV: UIUserInterfaceIdiom = UIUserInterfaceIdiom(2);
+    pub const CarPlay: UIUserInterfaceIdiom = UIUserInterfaceIdiom(3);
+}
+
+impl From<Idiom> for UIUserInterfaceIdiom {
+    fn from(idiom: Idiom) -> UIUserInterfaceIdiom {
+        match idiom {
+            Idiom::Unspecified => UIUserInterfaceIdiom::Unspecified,
+            Idiom::Phone => UIUserInterfaceIdiom::Phone,
+            Idiom::Pad => UIUserInterfaceIdiom::Pad,
+            Idiom::TV => UIUserInterfaceIdiom::TV,
+            Idiom::CarPlay => UIUserInterfaceIdiom::CarPlay,
+        }
+    }
+}
+
+impl Into<Idiom> for UIUserInterfaceIdiom {
+    fn into(self) -> Idiom {
+        match self {
+            UIUserInterfaceIdiom::Unspecified => Idiom::Unspecified,
+            UIUserInterfaceIdiom::Phone => Idiom::Phone,
+            UIUserInterfaceIdiom::Pad => Idiom::Pad,
+            UIUserInterfaceIdiom::TV => Idiom::TV,
+            UIUserInterfaceIdiom::CarPlay => Idiom::CarPlay,
+            _ => unreachable!(),
+        }
+    }
+}
+
+#[repr(transparent)]
+#[derive(Clone, Copy, Debug)]
+pub struct UIInterfaceOrientationMask(NSUInteger);
+
+unsafe impl Encode for UIInterfaceOrientationMask {
+    fn encode() -> Encoding { NSUInteger::encode() }
+}
+
+impl UIInterfaceOrientationMask {
+    pub const Portrait: UIInterfaceOrientationMask = UIInterfaceOrientationMask(1 << 1);
+    pub const PortraitUpsideDown: UIInterfaceOrientationMask = UIInterfaceOrientationMask(1 << 2);
+    pub const LandscapeLeft: UIInterfaceOrientationMask = UIInterfaceOrientationMask(1 << 4);
+    pub const LandscapeRight: UIInterfaceOrientationMask = UIInterfaceOrientationMask(1 << 3);
+    pub const Landscape: UIInterfaceOrientationMask = UIInterfaceOrientationMask(Self::LandscapeLeft.0 | Self::LandscapeRight.0);
+    pub const AllButUpsideDown: UIInterfaceOrientationMask = UIInterfaceOrientationMask(Self::Landscape.0 | Self::Portrait.0);
+    pub const All: UIInterfaceOrientationMask = UIInterfaceOrientationMask(Self::AllButUpsideDown.0 | Self::PortraitUpsideDown.0);
+}
+
+impl BitOr for UIInterfaceOrientationMask {
+    type Output = Self;
+
+    fn bitor(self, rhs: Self) -> Self {
+        UIInterfaceOrientationMask(self.0 | rhs.0)
+    }
+}
+
+impl UIInterfaceOrientationMask {
+    pub fn from_valid_orientations_idiom(
+        valid_orientations: ValidOrientations,
+        idiom: Idiom,
+    ) -> UIInterfaceOrientationMask {
+        match (valid_orientations, idiom) {
+            (ValidOrientations::LandscapeAndPortrait, Idiom::Phone) => UIInterfaceOrientationMask::AllButUpsideDown,
+            (ValidOrientations::LandscapeAndPortrait, _) => UIInterfaceOrientationMask::All,
+            (ValidOrientations::Landscape, _) => UIInterfaceOrientationMask::Landscape,
+            (ValidOrientations::Portrait, Idiom::Phone) => UIInterfaceOrientationMask::Portrait,
+            (ValidOrientations::Portrait, _) => UIInterfaceOrientationMask::Portrait | UIInterfaceOrientationMask::PortraitUpsideDown,
+        }
+    }
+}
+
 #[link(name = "UIKit", kind = "framework")]
 #[link(name = "CoreFoundation", kind = "framework")]
-#[link(name = "GlKit", kind = "framework")]
 extern {
-    pub static kCFRunLoopDefaultMode: CFStringRef;
+    pub static kCFRunLoopDefaultMode: CFRunLoopMode;
+    pub static kCFRunLoopCommonModes: CFRunLoopMode;
 
-    // int UIApplicationMain ( int argc, char *argv[], NSString *principalClassName, NSString *delegateClassName );
     pub fn UIApplicationMain(
         argc: c_int,
         argv: *const c_char,
@@ -54,31 +177,115 @@ extern {
         delegateClassName: id,
     ) -> c_int;
 
-    // SInt32 CFRunLoopRunInMode ( CFStringRef mode, CFTimeInterval seconds, Boolean returnAfterSourceHandled );
-    pub fn CFRunLoopRunInMode(
-        mode: CFStringRef,
-        seconds: CFTimeInterval,
-        returnAfterSourceHandled: Boolean,
-    ) -> i32;
+    pub fn CFRunLoopGetMain() -> CFRunLoopRef;
+    pub fn CFRunLoopWakeUp(rl: CFRunLoopRef);
+
+    pub fn CFRunLoopObserverCreate(
+        allocator: CFAllocatorRef,
+        activities: CFOptionFlags,
+        repeats: Boolean,
+        order: CFIndex,
+        callout: CFRunLoopObserverCallBack,
+        context: *mut CFRunLoopObserverContext,
+    ) -> CFRunLoopObserverRef;
+    pub fn CFRunLoopAddObserver(
+        rl: CFRunLoopRef,
+        observer: CFRunLoopObserverRef,
+        mode: CFRunLoopMode,
+    );
+
+    pub fn CFRunLoopTimerCreate(
+        allocator: CFAllocatorRef,
+        fireDate: CFAbsoluteTime,
+        interval: CFTimeInterval,
+        flags: CFOptionFlags,
+        order: CFIndex,
+        callout: CFRunLoopTimerCallBack,
+        context: *mut CFRunLoopTimerContext,
+    ) -> CFRunLoopTimerRef;
+    pub fn CFRunLoopAddTimer(
+        rl: CFRunLoopRef,
+        timer: CFRunLoopTimerRef,
+        mode: CFRunLoopMode,
+    );
+    pub fn CFRunLoopTimerSetNextFireDate(
+        timer: CFRunLoopTimerRef,
+        fireDate: CFAbsoluteTime,
+    );
+    pub fn CFRunLoopTimerInvalidate(time: CFRunLoopTimerRef);
+
+    pub fn CFRunLoopSourceCreate(
+        allocator: CFAllocatorRef,
+        order: CFIndex,
+        context: *mut CFRunLoopSourceContext,
+    ) -> CFRunLoopSourceRef;
+    pub fn CFRunLoopAddSource(
+        rl: CFRunLoopRef,
+        source: CFRunLoopSourceRef,
+        mode: CFRunLoopMode,
+    );
+    pub fn CFRunLoopSourceInvalidate(source: CFRunLoopSourceRef);
+    pub fn CFRunLoopSourceSignal(source: CFRunLoopSourceRef);
+
+    pub fn CFAbsoluteTimeGetCurrent() -> CFAbsoluteTime;
+    pub fn CFRelease(cftype: *const c_void);
 }
 
-extern {
-    pub fn setjmp(env: *mut c_void) -> c_int;
-    pub fn longjmp(env: *mut c_void, val: c_int) -> !;
+pub type Boolean = u8;
+pub enum CFAllocator {}
+pub type CFAllocatorRef = *mut CFAllocator;
+pub enum CFRunLoop {}
+pub type CFRunLoopRef = *mut CFRunLoop;
+pub type CFRunLoopMode = CFStringRef;
+pub enum CFRunLoopObserver {}
+pub type CFRunLoopObserverRef = *mut CFRunLoopObserver;
+pub enum CFRunLoopTimer {}
+pub type CFRunLoopTimerRef = *mut CFRunLoopTimer;
+pub enum CFRunLoopSource {}
+pub type CFRunLoopSourceRef = *mut CFRunLoopSource;
+pub enum CFString {}
+pub type CFStringRef = *const CFString;
+
+pub type CFHashCode = c_ulong;
+pub type CFIndex = c_long;
+pub type CFOptionFlags = c_ulong;
+pub type CFRunLoopActivity = CFOptionFlags;
+
+pub type CFAbsoluteTime = CFTimeInterval;
+pub type CFTimeInterval = f64;
+
+pub const kCFRunLoopEntry: CFRunLoopActivity = 0;
+pub const kCFRunLoopBeforeWaiting: CFRunLoopActivity = 1 << 5;
+pub const kCFRunLoopAfterWaiting: CFRunLoopActivity = 1 << 6;
+pub const kCFRunLoopExit: CFRunLoopActivity = 1 << 7;
+
+pub type CFRunLoopObserverCallBack = extern "C" fn(
+    observer: CFRunLoopObserverRef,
+    activity: CFRunLoopActivity,
+    info: *mut c_void,
+);
+pub type CFRunLoopTimerCallBack = extern "C" fn(
+    timer: CFRunLoopTimerRef,
+    info: *mut c_void,
+);
+
+pub enum CFRunLoopObserverContext {}
+pub enum CFRunLoopTimerContext {}
+
+#[repr(C)]
+pub struct CFRunLoopSourceContext {
+    pub version: CFIndex,
+    pub info: *mut c_void,
+    pub retain: extern "C" fn(*const c_void) -> *const c_void,
+    pub release: extern "C" fn(*const c_void),
+    pub copyDescription: extern "C" fn(*const c_void) -> CFStringRef,
+    pub equal: extern "C" fn(*const c_void, *const c_void) -> Boolean,
+    pub hash: extern "C" fn(*const c_void) -> CFHashCode,
+    pub schedule: extern "C" fn(*mut c_void, CFRunLoopRef, CFRunLoopMode),
+    pub cancel: extern "C" fn(*mut c_void, CFRunLoopRef, CFRunLoopMode),
+    pub perform: extern "C" fn(*mut c_void),
 }
 
-// values taken from "setjmp.h" header in xcode iPhoneOS/iPhoneSimulator SDK
-#[cfg(any(target_arch = "x86_64"))]
-pub const JBLEN: usize = (9 * 2) + 3 + 16;
-#[cfg(any(target_arch = "x86"))]
-pub const JBLEN: usize = 18;
-#[cfg(target_arch = "arm")]
-pub const JBLEN: usize = 10 + 16 + 2;
-#[cfg(target_arch = "aarch64")]
-pub const JBLEN: usize = (14 + 8 + 2) * 2;
-
-pub type JmpBuf = [c_int; JBLEN];
-
 pub trait NSString: Sized {
     unsafe fn alloc(_: Self) -> id {
         msg_send![class!(NSString), alloc]

src/platform_impl/ios/mod.rs

@@ -47,663 +47,55 @@
 //!
 //! This is how those event are represented in winit:
 //!
-//!  - applicationDidBecomeActive is Focused(true)
-//!  - applicationWillResignActive is Focused(false)
-//!  - applicationDidEnterBackground is Suspended(true)
-//!  - applicationWillEnterForeground is Suspended(false)
-//!  - applicationWillTerminate is Destroyed
+//!  - applicationDidBecomeActive is Suspended(false)
+//!  - applicationWillResignActive is Suspended(true)
+//!  - applicationWillTerminate is LoopDestroyed
 //!
-//! Keep in mind that after Destroyed event is received every attempt to draw with
+//! Keep in mind that after LoopDestroyed event is received every attempt to draw with
 //! opengl will result in segfault.
 //!
-//! Also note that app will not receive Destroyed event if suspended, it will be SIGKILL'ed
+//! Also note that app may not receive the LoopDestroyed event if suspended; it might be SIGKILL'ed.
 
 #![cfg(target_os = "ios")]
 
-use std::{fmt, mem, ptr};
-use std::cell::RefCell;
-use std::collections::VecDeque;
-use std::os::raw::*;
-use std::sync::Arc;
-
-use objc::declare::ClassDecl;
-use objc::runtime::{BOOL, Class, Object, Sel, YES};
-
-use {
-    CreationError,
-    Event,
-    LogicalPosition,
-    LogicalSize,
-    MouseCursor,
-    PhysicalPosition,
-    PhysicalSize,
-    WindowAttributes,
-    WindowEvent,
-    WindowId as RootEventId,
-};
-use events::{Touch, TouchPhase};
-use window::MonitorHandle as RootMonitorHandle;
+// TODO: (mtak-) UIKit requires main thread for virtually all function/method calls. This could be
+// worked around in the future by using GCD (grand central dispatch) and/or caching of values like
+// window size/position.
+macro_rules! assert_main_thread {
+    ($($t:tt)*) => {
+        if !msg_send![class!(NSThread), isMainThread] {
+            panic!($($t)*);
+        }
+    };
+}
 
+mod app_state;
+mod event_loop;
 mod ffi;
-use self::ffi::{
-    CFTimeInterval,
-    CFRunLoopRunInMode,
-    CGFloat,
-    CGPoint,
-    CGRect,
-    id,
-    JBLEN,
-    JmpBuf,
-    kCFRunLoopDefaultMode,
-    kCFRunLoopRunHandledSource,
-    longjmp,
-    nil,
-    NSString,
-    setjmp,
-    UIApplicationMain,
- };
+mod monitor;
+mod view;
+mod window;
 
-static mut JMPBUF: Option<Box<JmpBuf>> = None;
-
-pub struct Window {
-    _events_queue: Arc<RefCell<VecDeque<Event>>>,
-    delegate_state: Box<DelegateState>,
-}
-
-unsafe impl Send for Window {}
-unsafe impl Sync for Window {}
-
-#[derive(Debug)]
-struct DelegateState {
-    window: id,
-    controller: id,
-    view: id,
-    size: LogicalSize,
-    scale: f64,
-}
-
-impl DelegateState {
-    fn new(window: id, controller: id, view: id, size: LogicalSize, scale: f64) -> DelegateState {
-        DelegateState {
-            window,
-            controller,
-            view,
-            size,
-            scale,
-        }
-    }
-}
-
-impl Drop for DelegateState {
-    fn drop(&mut self) {
-        unsafe {
-            let _: () = msg_send![self.window, release];
-            let _: () = msg_send![self.controller, release];
-            let _: () = msg_send![self.view, release];
-        }
-    }
-}
-
-#[derive(Clone)]
-pub struct MonitorHandle;
-
-impl fmt::Debug for MonitorHandle {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        #[derive(Debug)]
-        struct MonitorHandle {
-            name: Option<String>,
-            dimensions: PhysicalSize,
-            position: PhysicalPosition,
-            hidpi_factor: f64,
-        }
-
-        let monitor_id_proxy = MonitorHandle {
-            name: self.get_name(),
-            dimensions: self.get_dimensions(),
-            position: self.get_position(),
-            hidpi_factor: self.get_hidpi_factor(),
-        };
-
-        monitor_id_proxy.fmt(f)
-    }
-}
-
-impl MonitorHandle {
-    #[inline]
-    pub fn get_uiscreen(&self) -> id {
-        let class = class!(UIScreen);
-        unsafe { msg_send![class, mainScreen] }
-    }
-
-    #[inline]
-    pub fn get_name(&self) -> Option<String> {
-        Some("Primary".to_string())
-    }
-
-    #[inline]
-    pub fn get_dimensions(&self) -> PhysicalSize {
-        let bounds: CGRect = unsafe { msg_send![self.get_uiscreen(), nativeBounds] };
-        (bounds.size.width as f64, bounds.size.height as f64).into()
-    }
-
-    #[inline]
-    pub fn get_position(&self) -> PhysicalPosition {
-        // iOS assumes single screen
-        (0, 0).into()
-    }
-
-    #[inline]
-    pub fn get_hidpi_factor(&self) -> f64 {
-        let scale: CGFloat = unsafe { msg_send![self.get_uiscreen(), nativeScale] };
-        scale as f64
-    }
-}
-
-pub struct EventLoop {
-    events_queue: Arc<RefCell<VecDeque<Event>>>,
-}
-
-#[derive(Clone)]
-pub struct EventLoopProxy;
-
-impl EventLoop {
-    pub fn new() -> EventLoop {
-        unsafe {
-            if !msg_send![class!(NSThread), isMainThread] {
-                panic!("`EventLoop` can only be created on the main thread on iOS");
-            }
-        }
-        EventLoop { events_queue: Default::default() }
-    }
-
-    #[inline]
-    pub fn get_available_monitors(&self) -> VecDeque<MonitorHandle> {
-        let mut rb = VecDeque::with_capacity(1);
-        rb.push_back(MonitorHandle);
-        rb
-    }
-
-    #[inline]
-    pub fn get_primary_monitor(&self) -> MonitorHandle {
-        MonitorHandle
-    }
-
-    pub fn poll_events<F>(&mut self, mut callback: F)
-        where F: FnMut(::Event)
-    {
-        if let Some(event) = self.events_queue.borrow_mut().pop_front() {
-            callback(event);
-            return;
-        }
-
-        unsafe {
-            // jump hack, so we won't quit on willTerminate event before processing it
-            assert!(JMPBUF.is_some(), "`EventLoop::poll_events` must be called after window creation on iOS");
-            if setjmp(mem::transmute_copy(&mut JMPBUF)) != 0 {
-                if let Some(event) = self.events_queue.borrow_mut().pop_front() {
-                    callback(event);
-                    return;
-                }
-            }
-        }
-
-        unsafe {
-            // run runloop
-            let seconds: CFTimeInterval = 0.000002;
-            while CFRunLoopRunInMode(kCFRunLoopDefaultMode, seconds, 1) == kCFRunLoopRunHandledSource {}
-        }
-
-        if let Some(event) = self.events_queue.borrow_mut().pop_front() {
-            callback(event)
-        }
-    }
-
-    pub fn run_forever<F>(&mut self, mut callback: F)
-        where F: FnMut(::Event) -> ::ControlFlow,
-    {
-        // Yeah that's a very bad implementation.
-        loop {
-            let mut control_flow = ::ControlFlow::Continue;
-            self.poll_events(|e| {
-                if let ::ControlFlow::Break = callback(e) {
-                    control_flow = ::ControlFlow::Break;
-                }
-            });
-            if let ::ControlFlow::Break = control_flow {
-                break;
-            }
-            ::std::thread::sleep(::std::time::Duration::from_millis(5));
-        }
-    }
-
-    pub fn create_proxy(&self) -> EventLoopProxy {
-        EventLoopProxy
-    }
-}
-
-impl EventLoopProxy {
-    pub fn wakeup(&self) -> Result<(), ::EventLoopClosed> {
-        unimplemented!()
-    }
-}
+pub use self::event_loop::{EventLoop, EventLoopProxy, EventLoopWindowTarget};
+pub use self::monitor::MonitorHandle;
+pub use self::window::{
+    PlatformSpecificWindowBuilderAttributes,
+    Window,
+    WindowId,
+};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct WindowId;
-
-impl WindowId {
-    pub unsafe fn dummy() -> Self {
-        WindowId
-    }
+pub struct DeviceId {
+    uiscreen: ffi::id,
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct DeviceId;
-
 impl DeviceId {
     pub unsafe fn dummy() -> Self {
-        DeviceId
-    }
-}
-
-#[derive(Clone)]
-pub struct PlatformSpecificWindowBuilderAttributes {
-    pub root_view_class: &'static Class,
-}
-
-impl Default for PlatformSpecificWindowBuilderAttributes {
-    fn default() -> Self {
-        PlatformSpecificWindowBuilderAttributes {
-            root_view_class: class!(UIView),
+        DeviceId {
+            uiscreen: std::ptr::null_mut(),
         }
     }
 }
 
-// TODO: AFAIK transparency is enabled by default on iOS,
-// so to be consistent with other platforms we have to change that.
-impl Window {
-    pub fn new(
-        ev: &EventLoop,
-        _attributes: WindowAttributes,
-        pl_attributes: PlatformSpecificWindowBuilderAttributes,
-    ) -> Result<Window, CreationError> {
-        unsafe {
-            debug_assert!(mem::size_of_val(&JMPBUF) == mem::size_of::<Box<JmpBuf>>());
-            assert!(mem::replace(&mut JMPBUF, Some(Box::new([0; JBLEN]))).is_none(), "Only one `Window` is supported on iOS");
-        }
-
-        unsafe {
-            if setjmp(mem::transmute_copy(&mut JMPBUF)) != 0 {
-                let app_class = class!(UIApplication);
-                let app: id = msg_send![app_class, sharedApplication];
-                let delegate: id = msg_send![app, delegate];
-                let state: *mut c_void = *(&*delegate).get_ivar("winitState");
-                let mut delegate_state = Box::from_raw(state as *mut DelegateState);
-                let events_queue = &*ev.events_queue;
-                (&mut *delegate).set_ivar("eventsQueue", mem::transmute::<_, *mut c_void>(events_queue));
-
-                // easiest? way to get access to PlatformSpecificWindowBuilderAttributes to configure the view
-                let rect: CGRect = msg_send![MonitorHandle.get_uiscreen(), bounds];
-
-                let uiview_class = class!(UIView);
-                let root_view_class = pl_attributes.root_view_class;
-                let is_uiview: BOOL = msg_send![root_view_class, isSubclassOfClass:uiview_class];
-                assert!(is_uiview == YES, "`root_view_class` must inherit from `UIView`");
-
-                delegate_state.view = msg_send![root_view_class, alloc];
-                assert!(!delegate_state.view.is_null(), "Failed to create `UIView` instance");
-                delegate_state.view = msg_send![delegate_state.view, initWithFrame:rect];
-                assert!(!delegate_state.view.is_null(), "Failed to initialize `UIView` instance");
-
-                let _: () = msg_send![delegate_state.controller, setView:delegate_state.view];
-                let _: () = msg_send![delegate_state.window, makeKeyAndVisible];
-
-                return Ok(Window {
-                    _events_queue: ev.events_queue.clone(),
-                    delegate_state,
-                });
-            }
-        }
-
-        create_delegate_class();
-        start_app();
-
-        panic!("Couldn't create `UIApplication`!")
-    }
-
-    #[inline]
-    pub fn get_uiwindow(&self) -> id {
-        self.delegate_state.window
-    }
-
-    #[inline]
-    pub fn get_uiview(&self) -> id {
-        self.delegate_state.view
-    }
-
-    #[inline]
-    pub fn set_title(&self, _title: &str) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn show(&self) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn hide(&self) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn get_position(&self) -> Option<LogicalPosition> {
-        // N/A
-        None
-    }
-
-    #[inline]
-    pub fn get_inner_position(&self) -> Option<LogicalPosition> {
-        // N/A
-        None
-    }
-
-    #[inline]
-    pub fn set_position(&self, _position: LogicalPosition) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn get_inner_size(&self) -> Option<LogicalSize> {
-        Some(self.delegate_state.size)
-    }
-
-    #[inline]
-    pub fn get_outer_size(&self) -> Option<LogicalSize> {
-        self.get_inner_size()
-    }
-
-    #[inline]
-    pub fn set_inner_size(&self, _size: LogicalSize) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_min_dimensions(&self, _dimensions: Option<LogicalSize>) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_max_dimensions(&self, _dimensions: Option<LogicalSize>) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_resizable(&self, _resizable: bool) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_cursor(&self, _cursor: MouseCursor) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn grab_cursor(&self, _grab: bool) -> Result<(), String> {
-        Err("Cursor grabbing is not possible on iOS.".to_owned())
-    }
-
-    #[inline]
-    pub fn hide_cursor(&self, _hide: bool) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn get_hidpi_factor(&self) -> f64 {
-        self.delegate_state.scale
-    }
-
-    #[inline]
-    pub fn set_cursor_position(&self, _position: LogicalPosition) -> Result<(), String> {
-        Err("Setting cursor position is not possible on iOS.".to_owned())
-    }
-
-    #[inline]
-    pub fn set_maximized(&self, _maximized: bool) {
-        // N/A
-        // iOS has single screen maximized apps so nothing to do
-    }
-
-    #[inline]
-    pub fn get_fullscreen(&self) -> Option<RootMonitorHandle> {
-        // N/A
-        // iOS has single screen maximized apps so nothing to do
-        None
-    }
-
-    #[inline]
-    pub fn set_fullscreen(&self, _monitor: Option<RootMonitorHandle>) {
-        // N/A
-        // iOS has single screen maximized apps so nothing to do
-    }
-
-    #[inline]
-    pub fn set_decorations(&self, _decorations: bool) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_always_on_top(&self, _always_on_top: bool) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_window_icon(&self, _icon: Option<::Icon>) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn set_ime_spot(&self, _logical_spot: LogicalPosition) {
-        // N/A
-    }
-
-    #[inline]
-    pub fn get_current_monitor(&self) -> RootMonitorHandle {
-        RootMonitorHandle { inner: MonitorHandle }
-    }
-
-    #[inline]
-    pub fn get_available_monitors(&self) -> VecDeque<MonitorHandle> {
-        let mut rb = VecDeque::with_capacity(1);
-        rb.push_back(MonitorHandle);
-        rb
-    }
-
-    #[inline]
-    pub fn get_primary_monitor(&self) -> MonitorHandle {
-        MonitorHandle
-    }
-
-    #[inline]
-    pub fn id(&self) -> WindowId {
-        WindowId
-    }
-}
-
-fn create_delegate_class() {
-    extern fn did_finish_launching(this: &mut Object, _: Sel, _: id, _: id) -> BOOL {
-        let screen_class = class!(UIScreen);
-        let window_class = class!(UIWindow);
-        let controller_class = class!(UIViewController);
-        unsafe {
-            let main_screen: id = msg_send![screen_class, mainScreen];
-            let bounds: CGRect = msg_send![main_screen, bounds];
-            let scale: CGFloat = msg_send![main_screen, nativeScale];
-
-            let window: id = msg_send![window_class, alloc];
-            let window: id = msg_send![window, initWithFrame:bounds.clone()];
-
-            let size = (bounds.size.width as f64, bounds.size.height as f64).into();
-
-            let view_controller: id = msg_send![controller_class, alloc];
-            let view_controller: id = msg_send![view_controller, init];
-
-            let _: () = msg_send![window, setRootViewController:view_controller];
-
-            let state = Box::new(DelegateState::new(window, view_controller, ptr::null_mut(), size, scale as f64));
-            let state_ptr: *mut DelegateState = mem::transmute(state);
-            this.set_ivar("winitState", state_ptr as *mut c_void);
-
-            // The `UIView` is setup in `Window::new` which gets `longjmp`'ed to here.
-            // This makes it easier to configure the specific `UIView` type.
-            let _: () = msg_send![this, performSelector:sel!(postLaunch:) withObject:nil afterDelay:0.0];
-        }
-        YES
-    }
-
-    extern fn post_launch(_: &Object, _: Sel, _: id) {
-        unsafe { longjmp(mem::transmute_copy(&mut JMPBUF), 1); }
-    }
-
-    extern fn did_become_active(this: &Object, _: Sel, _: id) {
-        unsafe {
-            let events_queue: *mut c_void = *this.get_ivar("eventsQueue");
-            let events_queue = &*(events_queue as *const RefCell<VecDeque<Event>>);
-            events_queue.borrow_mut().push_back(Event::WindowEvent {
-                window_id: RootEventId(WindowId),
-                event: WindowEvent::Focused(true),
-            });
-        }
-    }
-
-    extern fn will_resign_active(this: &Object, _: Sel, _: id) {
-        unsafe {
-            let events_queue: *mut c_void = *this.get_ivar("eventsQueue");
-            let events_queue = &*(events_queue as *const RefCell<VecDeque<Event>>);
-            events_queue.borrow_mut().push_back(Event::WindowEvent {
-                window_id: RootEventId(WindowId),
-                event: WindowEvent::Focused(false),
-            });
-        }
-    }
-
-    extern fn will_enter_foreground(this: &Object, _: Sel, _: id) {
-        unsafe {
-            let events_queue: *mut c_void = *this.get_ivar("eventsQueue");
-            let events_queue = &*(events_queue as *const RefCell<VecDeque<Event>>);
-            events_queue.borrow_mut().push_back(Event::Suspended(false));
-        }
-    }
-
-    extern fn did_enter_background(this: &Object, _: Sel, _: id) {
-        unsafe {
-            let events_queue: *mut c_void = *this.get_ivar("eventsQueue");
-            let events_queue = &*(events_queue as *const RefCell<VecDeque<Event>>);
-            events_queue.borrow_mut().push_back(Event::Suspended(true));
-        }
-    }
-
-    extern fn will_terminate(this: &Object, _: Sel, _: id) {
-        unsafe {
-            let events_queue: *mut c_void = *this.get_ivar("eventsQueue");
-            let events_queue = &*(events_queue as *const RefCell<VecDeque<Event>>);
-            // push event to the front to garantee that we'll process it
-            // immidiatly after jump
-            events_queue.borrow_mut().push_front(Event::WindowEvent {
-                window_id: RootEventId(WindowId),
-                event: WindowEvent::Destroyed,
-            });
-            longjmp(mem::transmute_copy(&mut JMPBUF), 1);
-        }
-    }
-
-    extern fn handle_touches(this: &Object, _: Sel, touches: id, _:id) {
-        unsafe {
-            let events_queue: *mut c_void = *this.get_ivar("eventsQueue");
-            let events_queue = &*(events_queue as *const RefCell<VecDeque<Event>>);
-
-            let touches_enum: id = msg_send![touches, objectEnumerator];
-
-            loop {
-                let touch: id = msg_send![touches_enum, nextObject];
-                if touch == nil {
-                    break
-                }
-                let location: CGPoint = msg_send![touch, locationInView:nil];
-                let touch_id = touch as u64;
-                let phase: i32 = msg_send![touch, phase];
-
-                events_queue.borrow_mut().push_back(Event::WindowEvent {
-                    window_id: RootEventId(WindowId),
-                    event: WindowEvent::Touch(Touch {
-                        device_id: DEVICE_ID,
-                        id: touch_id,
-                        location: (location.x as f64, location.y as f64).into(),
-                        phase: match phase {
-                            0 => TouchPhase::Started,
-                            1 => TouchPhase::Moved,
-                            // 2 is UITouchPhaseStationary and is not expected here
-                            3 => TouchPhase::Ended,
-                            4 => TouchPhase::Cancelled,
-                            _ => panic!("unexpected touch phase: {:?}", phase)
-                        }
-                    }),
-                });
-            }
-        }
-    }
-
-    let ui_responder = class!(UIResponder);
-    let mut decl = ClassDecl::new("AppDelegate", ui_responder).expect("Failed to declare class `AppDelegate`");
-
-    unsafe {
-        decl.add_method(sel!(application:didFinishLaunchingWithOptions:),
-                        did_finish_launching as extern fn(&mut Object, Sel, id, id) -> BOOL);
-
-        decl.add_method(sel!(applicationDidBecomeActive:),
-                        did_become_active as extern fn(&Object, Sel, id));
-
-        decl.add_method(sel!(applicationWillResignActive:),
-                        will_resign_active as extern fn(&Object, Sel, id));
-
-        decl.add_method(sel!(applicationWillEnterForeground:),
-                        will_enter_foreground as extern fn(&Object, Sel, id));
-
-        decl.add_method(sel!(applicationDidEnterBackground:),
-                        did_enter_background as extern fn(&Object, Sel, id));
-
-        decl.add_method(sel!(applicationWillTerminate:),
-                        will_terminate as extern fn(&Object, Sel, id));
-
-
-        decl.add_method(sel!(touchesBegan:withEvent:),
-                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
-
-        decl.add_method(sel!(touchesMoved:withEvent:),
-                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
-
-        decl.add_method(sel!(touchesEnded:withEvent:),
-                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
-
-        decl.add_method(sel!(touchesCancelled:withEvent:),
-                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
-
-
-        decl.add_method(sel!(postLaunch:),
-                        post_launch as extern fn(&Object, Sel, id));
-
-        decl.add_ivar::<*mut c_void>("winitState");
-        decl.add_ivar::<*mut c_void>("eventsQueue");
-
-        decl.register();
-    }
-}
-
-#[inline]
-fn start_app() {
-    unsafe {
-        UIApplicationMain(0, ptr::null(), nil, NSString::alloc(nil).init_str("AppDelegate"));
-    }
-}
-
-// Constant device ID, to be removed when this backend is updated to report real device IDs.
-const DEVICE_ID: ::DeviceId = ::DeviceId(DeviceId);
+unsafe impl Send for DeviceId {}
+unsafe impl Sync for DeviceId {}

src/platform_impl/ios/monitor.rs

@@ -0,0 +1,171 @@
+use std::{
+    collections::VecDeque,
+    fmt,
+    ops::{Deref, DerefMut},
+};
+
+use dpi::{PhysicalPosition, PhysicalSize};
+
+use platform_impl::platform::ffi::{
+    id,
+    nil,
+    CGFloat,
+    CGRect,
+    NSUInteger,
+};
+
+pub struct Inner {
+    uiscreen: id,
+}
+
+impl Drop for Inner {
+    fn drop(&mut self) {
+        unsafe {
+            let () = msg_send![self.uiscreen, release];
+        }
+    }
+}
+
+pub struct MonitorHandle {
+    inner: Inner,
+}
+
+impl Deref for MonitorHandle {
+    type Target = Inner;
+
+    fn deref(&self) -> &Inner {
+        unsafe {
+            assert_main_thread!("`MonitorHandle` methods can only be run on the main thread on iOS");
+        }
+        &self.inner
+    }
+}
+
+impl DerefMut for MonitorHandle {
+    fn deref_mut(&mut self) -> &mut Inner {
+        unsafe {
+            assert_main_thread!("`MonitorHandle` methods can only be run on the main thread on iOS");
+        }
+        &mut self.inner
+    }
+}
+
+unsafe impl Send for MonitorHandle {}
+unsafe impl Sync for MonitorHandle {}
+
+impl Clone for MonitorHandle {
+    fn clone(&self) -> MonitorHandle {
+        MonitorHandle::retained_new(self.uiscreen)
+    }
+}
+
+impl Drop for MonitorHandle {
+    fn drop(&mut self) {
+        unsafe {
+            assert_main_thread!("`MonitorHandle` can only be dropped on the main thread on iOS");
+        }
+    }
+}
+
+impl fmt::Debug for MonitorHandle {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        #[derive(Debug)]
+        struct MonitorHandle {
+            name: Option<String>,
+            dimensions: PhysicalSize,
+            position: PhysicalPosition,
+            hidpi_factor: f64,
+        }
+
+        let monitor_id_proxy = MonitorHandle {
+            name: self.get_name(),
+            dimensions: self.get_dimensions(),
+            position: self.get_position(),
+            hidpi_factor: self.get_hidpi_factor(),
+        };
+
+        monitor_id_proxy.fmt(f)
+    }
+}
+
+impl MonitorHandle {
+    pub fn retained_new(uiscreen: id) -> MonitorHandle {
+        unsafe {
+            assert_main_thread!("`MonitorHandle` can only be cloned on the main thread on iOS");
+            let () = msg_send![uiscreen, retain];
+        }
+        MonitorHandle { inner: Inner { uiscreen } }
+    }
+}
+
+impl Inner {
+    pub fn get_name(&self) -> Option<String> {
+        unsafe {
+            if self.uiscreen == main_uiscreen().uiscreen {
+                Some("Primary".to_string())
+            } else if self.uiscreen == mirrored_uiscreen().uiscreen {
+                Some("Mirrored".to_string())
+            } else {
+                uiscreens()
+                    .iter()
+                    .position(|rhs| rhs.uiscreen == self.uiscreen)
+                    .map(|idx| idx.to_string())
+            }
+        }
+    }
+    
+    pub fn get_dimensions(&self) -> PhysicalSize {
+        unsafe {
+            let bounds: CGRect = msg_send![self.get_uiscreen(), nativeBounds];
+            (bounds.size.width as f64, bounds.size.height as f64).into()
+        }
+    }
+    
+    pub fn get_position(&self) -> PhysicalPosition {
+        unsafe {
+            let bounds: CGRect = msg_send![self.get_uiscreen(), nativeBounds];
+            (bounds.origin.x as f64, bounds.origin.y as f64).into()
+        }
+    }
+    
+    pub fn get_hidpi_factor(&self) -> f64 {
+        unsafe {
+            let scale: CGFloat = msg_send![self.get_uiscreen(), nativeScale];
+            scale as f64
+        }
+    }
+}
+
+// MonitorHandleExtIOS
+impl Inner {
+    pub fn get_uiscreen(&self) -> id {
+        self.uiscreen
+    }
+}
+
+// requires being run on main thread
+pub unsafe fn main_uiscreen() -> MonitorHandle {
+    let uiscreen: id = msg_send![class!(UIScreen), mainScreen];
+    MonitorHandle::retained_new(uiscreen)
+}
+
+// requires being run on main thread
+unsafe fn mirrored_uiscreen() -> MonitorHandle {
+    let uiscreen: id = msg_send![class!(UIScreen), mirroredScreen];
+    MonitorHandle::retained_new(uiscreen)
+}
+
+// requires being run on main thread
+pub unsafe fn uiscreens() -> VecDeque<MonitorHandle> {
+    let screens: id = msg_send![class!(UIScreen), screens];
+    let count: NSUInteger = msg_send![screens, count];
+    let mut result = VecDeque::with_capacity(count as _);
+    let screens_enum: id = msg_send![screens, objectEnumerator];
+    loop {
+        let screen: id = msg_send![screens_enum, nextObject];
+        if screen == nil {
+            break result
+        }
+        result.push_back(MonitorHandle::retained_new(screen));
+    }
+}

src/platform_impl/ios/view.rs

@@ -0,0 +1,395 @@
+use std::collections::HashMap;
+
+use objc::declare::ClassDecl;
+use objc::runtime::{BOOL, Class, NO, Object, Sel, YES};
+
+use event::{
+    DeviceId as RootDeviceId,
+    Event,
+    Touch,
+    TouchPhase,
+    WindowEvent
+};
+use platform::ios::MonitorHandleExtIOS;
+use window::{WindowAttributes, WindowId as RootWindowId};
+
+use platform_impl::platform::app_state::AppState;
+use platform_impl::platform::DeviceId;
+use platform_impl::platform::event_loop;
+use platform_impl::platform::ffi::{
+    id,
+    nil,
+    CGFloat,
+    CGPoint,
+    CGRect,
+    UIInterfaceOrientationMask,
+    UITouchPhase,
+};
+use platform_impl::platform::window::{PlatformSpecificWindowBuilderAttributes};
+
+// requires main thread
+unsafe fn get_view_class(root_view_class: &'static Class) -> &'static Class {
+    static mut CLASSES: Option<HashMap<*const Class, &'static Class>> = None;
+    static mut ID: usize = 0;
+    
+    if CLASSES.is_none() {
+        CLASSES = Some(HashMap::default());
+    }
+
+    let classes = CLASSES.as_mut().unwrap();
+
+    classes.entry(root_view_class).or_insert_with(move || {
+        let uiview_class = class!(UIView);
+        let is_uiview: BOOL = msg_send![root_view_class, isSubclassOfClass:uiview_class];
+        assert_eq!(is_uiview, YES, "`root_view_class` must inherit from `UIView`");
+
+        extern fn draw_rect(object: &Object, _: Sel, rect: CGRect) {
+            unsafe {
+                let window: id = msg_send![object, window];
+                AppState::handle_nonuser_event(Event::WindowEvent {
+                    window_id: RootWindowId(window.into()),
+                    event: WindowEvent::RedrawRequested,
+                });
+                let superclass: &'static Class = msg_send![object, superclass];
+                let () = msg_send![super(object, superclass), drawRect: rect];
+            }
+        }
+
+        extern fn layout_subviews(object: &Object, _: Sel) {
+            unsafe {
+                let window: id = msg_send![object, window];
+                let bounds: CGRect = msg_send![window, bounds];
+                let screen: id = msg_send![window, screen];
+                let screen_space: id = msg_send![screen, coordinateSpace];
+                let screen_frame: CGRect = msg_send![object, convertRect:bounds toCoordinateSpace:screen_space];
+                let size = crate::dpi::LogicalSize {
+                    width: screen_frame.size.width,
+                    height: screen_frame.size.height,
+                };
+                AppState::handle_nonuser_event(Event::WindowEvent {
+                    window_id: RootWindowId(window.into()),
+                    event: WindowEvent::Resized(size),
+                });
+                let superclass: &'static Class = msg_send![object, superclass];
+                let () = msg_send![super(object, superclass), layoutSubviews];
+            }
+        }
+
+        let mut decl = ClassDecl::new(&format!("WinitUIView{}", ID), root_view_class)
+            .expect("Failed to declare class `WinitUIView`");
+        ID += 1;
+        decl.add_method(sel!(drawRect:),
+                        draw_rect as extern fn(&Object, Sel, CGRect));
+        decl.add_method(sel!(layoutSubviews),
+                        layout_subviews as extern fn(&Object, Sel));
+        decl.register()
+    })
+}
+
+// requires main thread
+unsafe fn get_view_controller_class() -> &'static Class {
+    static mut CLASS: Option<&'static Class> = None;
+    if CLASS.is_none() {
+        let uiviewcontroller_class = class!(UIViewController);
+
+        extern fn set_prefers_status_bar_hidden(object: &mut Object, _: Sel, hidden: BOOL) {
+            unsafe {
+                object.set_ivar::<BOOL>("_prefers_status_bar_hidden", hidden);
+                let () = msg_send![object, setNeedsStatusBarAppearanceUpdate];
+            }
+        }
+
+        extern fn prefers_status_bar_hidden(object: &Object, _: Sel) -> BOOL {
+            unsafe {
+                *object.get_ivar::<BOOL>("_prefers_status_bar_hidden")
+            }
+        }
+
+        extern fn set_supported_orientations(object: &mut Object, _: Sel, orientations: UIInterfaceOrientationMask) {
+            unsafe {
+                object.set_ivar::<UIInterfaceOrientationMask>("_supported_orientations", orientations);
+                let () = msg_send![class!(UIViewController), attemptRotationToDeviceOrientation];
+            }
+        }
+
+        extern fn supported_orientations(object: &Object, _: Sel) -> UIInterfaceOrientationMask {
+            unsafe {
+                *object.get_ivar::<UIInterfaceOrientationMask>("_supported_orientations")
+            }
+        }
+
+        extern fn should_autorotate(_: &Object, _: Sel) -> BOOL {
+            YES
+        }
+
+        let mut decl = ClassDecl::new("WinitUIViewController", uiviewcontroller_class)
+            .expect("Failed to declare class `WinitUIViewController`");
+        decl.add_ivar::<BOOL>("_prefers_status_bar_hidden");
+        decl.add_ivar::<UIInterfaceOrientationMask>("_supported_orientations");
+        decl.add_method(sel!(setPrefersStatusBarHidden:),
+                        set_prefers_status_bar_hidden as extern fn(&mut Object, Sel, BOOL));
+        decl.add_method(sel!(prefersStatusBarHidden),
+                        prefers_status_bar_hidden as extern fn(&Object, Sel) -> BOOL);
+        decl.add_method(sel!(setSupportedInterfaceOrientations:),
+                        set_supported_orientations as extern fn(&mut Object, Sel, UIInterfaceOrientationMask));
+        decl.add_method(sel!(supportedInterfaceOrientations),
+                        supported_orientations as extern fn(&Object, Sel) -> UIInterfaceOrientationMask);
+        decl.add_method(sel!(shouldAutorotate),
+                        should_autorotate as extern fn(&Object, Sel) -> BOOL);
+        CLASS = Some(decl.register());
+    }
+    CLASS.unwrap()
+}
+
+// requires main thread
+unsafe fn get_window_class() -> &'static Class {
+    static mut CLASS: Option<&'static Class> = None;
+    if CLASS.is_none() {
+        let uiwindow_class = class!(UIWindow);
+
+        extern fn become_key_window(object: &Object, _: Sel) {
+            unsafe {
+                AppState::handle_nonuser_event(Event::WindowEvent {
+                    window_id: RootWindowId(object.into()),
+                    event: WindowEvent::Focused(true),
+                });
+                let () = msg_send![super(object, class!(UIWindow)), becomeKeyWindow];
+            }
+        }
+
+        extern fn resign_key_window(object: &Object, _: Sel) {
+            unsafe {
+                AppState::handle_nonuser_event(Event::WindowEvent {
+                    window_id: RootWindowId(object.into()),
+                    event: WindowEvent::Focused(false),
+                });
+                let () = msg_send![super(object, class!(UIWindow)), resignKeyWindow];
+            }
+        }
+
+        extern fn handle_touches(object: &Object, _: Sel, touches: id, _:id) {
+            unsafe {
+                let uiscreen = msg_send![object, screen];
+                let touches_enum: id = msg_send![touches, objectEnumerator];
+                let mut touch_events = Vec::new();
+                loop {
+                    let touch: id = msg_send![touches_enum, nextObject];
+                    if touch == nil {
+                        break
+                    }
+                    let location: CGPoint = msg_send![touch, locationInView:nil];
+                    let touch_id = touch as u64;
+                    let phase: UITouchPhase = msg_send![touch, phase];
+                    let phase = match phase {
+                        UITouchPhase::Began => TouchPhase::Started,
+                        UITouchPhase::Moved => TouchPhase::Moved,
+                        // 2 is UITouchPhase::Stationary and is not expected here
+                        UITouchPhase::Ended => TouchPhase::Ended,
+                        UITouchPhase::Cancelled => TouchPhase::Cancelled,
+                        _ => panic!("unexpected touch phase: {:?}", phase as i32),
+                    };
+
+                    touch_events.push(Event::WindowEvent {
+                        window_id: RootWindowId(object.into()),
+                        event: WindowEvent::Touch(Touch {
+                            device_id: RootDeviceId(DeviceId { uiscreen }),
+                            id: touch_id,
+                            location: (location.x as f64, location.y as f64).into(),
+                            phase,
+                        }),
+                    });
+                }
+                AppState::handle_nonuser_events(touch_events);
+            }
+        }
+
+        extern fn set_content_scale_factor(object: &mut Object, _: Sel, hidpi_factor: CGFloat) {
+            unsafe {
+                let () = msg_send![super(object, class!(UIWindow)), setContentScaleFactor:hidpi_factor];
+                let view_controller: id = msg_send![object, rootViewController];
+                let view: id = msg_send![view_controller, view];
+                let () = msg_send![view, setContentScaleFactor:hidpi_factor];
+                let bounds: CGRect = msg_send![object, bounds];
+                let screen: id = msg_send![object, screen];
+                let screen_space: id = msg_send![screen, coordinateSpace];
+                let screen_frame: CGRect = msg_send![object, convertRect:bounds toCoordinateSpace:screen_space];
+                let size = crate::dpi::LogicalSize {
+                    width: screen_frame.size.width,
+                    height: screen_frame.size.height,
+                };
+                AppState::handle_nonuser_events(
+                    std::iter::once(Event::WindowEvent {
+                        window_id: RootWindowId(object.into()),
+                        event: WindowEvent::HiDpiFactorChanged(hidpi_factor as _),
+                    }).chain(std::iter::once(Event::WindowEvent {
+                        window_id: RootWindowId(object.into()),
+                        event: WindowEvent::Resized(size),
+                    }))
+                );
+            }
+        }
+
+        let mut decl = ClassDecl::new("WinitUIWindow", uiwindow_class)
+            .expect("Failed to declare class `WinitUIWindow`");
+        decl.add_method(sel!(becomeKeyWindow),
+                        become_key_window as extern fn(&Object, Sel));
+        decl.add_method(sel!(resignKeyWindow),
+                        resign_key_window as extern fn(&Object, Sel));
+
+        decl.add_method(sel!(touchesBegan:withEvent:),
+                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
+        decl.add_method(sel!(touchesMoved:withEvent:),
+                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
+        decl.add_method(sel!(touchesEnded:withEvent:),
+                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
+        decl.add_method(sel!(touchesCancelled:withEvent:),
+                        handle_touches as extern fn(this: &Object, _: Sel, _: id, _:id));
+
+        decl.add_method(sel!(setContentScaleFactor:),
+                        set_content_scale_factor as extern fn(&mut Object, Sel, CGFloat));
+
+        CLASS = Some(decl.register());
+    }
+    CLASS.unwrap()
+}
+
+// requires main thread
+pub unsafe fn create_view(
+    window_attributes: &WindowAttributes,
+    platform_attributes: &PlatformSpecificWindowBuilderAttributes,
+    frame: CGRect,
+) -> id {
+    let class = get_view_class(platform_attributes.root_view_class);
+
+    let view: id = msg_send![class, alloc];
+    assert!(!view.is_null(), "Failed to create `UIView` instance");
+    let view: id = msg_send![view, initWithFrame:frame];
+    assert!(!view.is_null(), "Failed to initialize `UIView` instance");
+    if window_attributes.multitouch {
+        let () = msg_send![view, setMultipleTouchEnabled:YES];
+    }
+
+    view
+}
+
+// requires main thread
+pub unsafe fn create_view_controller(
+    window_attributes: &WindowAttributes,
+    platform_attributes: &PlatformSpecificWindowBuilderAttributes,
+    view: id,
+) -> id {
+    let class = get_view_controller_class();
+
+    let view_controller: id = msg_send![class, alloc];
+    assert!(!view_controller.is_null(), "Failed to create `UIViewController` instance");
+    let view_controller: id = msg_send![view_controller, init];
+    assert!(!view_controller.is_null(), "Failed to initialize `UIViewController` instance");
+    let status_bar_hidden = if window_attributes.decorations {
+        NO
+    } else {
+        YES
+    };
+    let idiom = event_loop::get_idiom();
+    let supported_orientations = UIInterfaceOrientationMask::from_valid_orientations_idiom(
+        platform_attributes.valid_orientations,
+        idiom,
+    );
+    let () = msg_send![view_controller, setPrefersStatusBarHidden:status_bar_hidden];
+    let () = msg_send![view_controller, setSupportedInterfaceOrientations:supported_orientations];
+    let () = msg_send![view_controller, setView:view];
+    view_controller
+}
+
+// requires main thread
+pub unsafe fn create_window(
+    window_attributes: &WindowAttributes,
+    platform_attributes: &PlatformSpecificWindowBuilderAttributes,
+    frame: CGRect,
+    view_controller: id,
+) -> id {
+    let class = get_window_class();
+
+    let window: id = msg_send![class, alloc];
+    assert!(!window.is_null(), "Failed to create `UIWindow` instance");
+    let window: id = msg_send![window, initWithFrame:frame];
+    assert!(!window.is_null(), "Failed to initialize `UIWindow` instance");
+    let () = msg_send![window, setRootViewController:view_controller];
+    if let Some(hidpi_factor) = platform_attributes.hidpi_factor {
+        let () = msg_send![window, setContentScaleFactor:hidpi_factor as CGFloat];
+    }
+    if let &Some(ref monitor) = &window_attributes.fullscreen {
+        let () = msg_send![window, setScreen:monitor.get_uiscreen()];
+    }
+
+    window
+}
+
+pub fn create_delegate_class() {
+    extern fn did_finish_launching(_: &mut Object, _: Sel, _: id, _: id) -> BOOL {
+        unsafe {
+            AppState::did_finish_launching();
+        }
+        YES
+    }
+
+    extern fn did_become_active(_: &Object, _: Sel, _: id) {
+        unsafe {
+            AppState::handle_nonuser_event(Event::Suspended(false))
+        }
+    }
+
+    extern fn will_resign_active(_: &Object, _: Sel, _: id) {
+        unsafe {
+            AppState::handle_nonuser_event(Event::Suspended(true))
+        }
+    }
+
+    extern fn will_enter_foreground(_: &Object, _: Sel, _: id) {}
+    extern fn did_enter_background(_: &Object, _: Sel, _: id) {}
+
+    extern fn will_terminate(_: &Object, _: Sel, _: id) {
+        unsafe {
+            let app: id = msg_send![class!(UIApplication), sharedApplication];
+            let windows: id = msg_send![app, windows];
+            let windows_enum: id = msg_send![windows, objectEnumerator];
+            let mut events = Vec::new();
+            loop {
+                let window: id = msg_send![windows_enum, nextObject];
+                if window == nil {
+                    break
+                }
+                let is_winit_window: BOOL = msg_send![window, isKindOfClass:class!(WinitUIWindow)];
+                if is_winit_window == YES {
+                    events.push(Event::WindowEvent {
+                        window_id: RootWindowId(window.into()),
+                        event: WindowEvent::Destroyed,
+                    });
+                }
+            }
+            AppState::handle_nonuser_events(events);
+            AppState::terminated();
+        }
+    }
+
+    let ui_responder = class!(UIResponder);
+    let mut decl = ClassDecl::new("AppDelegate", ui_responder).expect("Failed to declare class `AppDelegate`");
+
+    unsafe {
+        decl.add_method(sel!(application:didFinishLaunchingWithOptions:),
+                        did_finish_launching as extern fn(&mut Object, Sel, id, id) -> BOOL);
+
+        decl.add_method(sel!(applicationDidBecomeActive:),
+                        did_become_active as extern fn(&Object, Sel, id));
+        decl.add_method(sel!(applicationWillResignActive:),
+                        will_resign_active as extern fn(&Object, Sel, id));
+        decl.add_method(sel!(applicationWillEnterForeground:),
+                        will_enter_foreground as extern fn(&Object, Sel, id));
+        decl.add_method(sel!(applicationDidEnterBackground:),
+                        did_enter_background as extern fn(&Object, Sel, id));
+
+        decl.add_method(sel!(applicationWillTerminate:),
+                        will_terminate as extern fn(&Object, Sel, id));
+
+        decl.register();
+    }
+}

src/platform_impl/ios/window.rs

@@ -0,0 +1,488 @@
+use std::{
+    collections::VecDeque,
+    ops::{Deref, DerefMut},
+};
+
+use objc::runtime::{Class, NO, Object, YES};
+
+use dpi::{self, LogicalPosition, LogicalSize};
+use icon::Icon;
+use monitor::MonitorHandle as RootMonitorHandle;
+use platform::ios::{MonitorHandleExtIOS, ValidOrientations};
+use window::{
+    CreationError,
+    MouseCursor,
+    WindowAttributes,
+};
+use platform_impl::{
+    platform::{
+        app_state::AppState,
+        event_loop,
+        ffi::{
+            id,
+            CGFloat,
+            CGPoint,
+            CGRect,
+            CGSize,
+            UIEdgeInsets,
+            UIInterfaceOrientationMask,
+        },
+        monitor,
+        view,
+        EventLoopWindowTarget,
+        MonitorHandle
+    },
+};
+
+pub struct Inner {
+    pub window: id,
+    pub view_controller: id,
+    pub view: id,
+    supports_safe_area: bool,
+}
+
+impl Drop for Inner {
+    fn drop(&mut self) {
+        unsafe {
+            let () = msg_send![self.view, release];
+            let () = msg_send![self.view_controller, release];
+            let () = msg_send![self.window, release];
+        }
+    }
+}
+
+impl Inner {
+    pub fn set_title(&self, _title: &str) {
+        debug!("`Window::set_title` is ignored on iOS")
+    }
+
+    pub fn show(&self) {
+        unsafe {
+            let () = msg_send![self.window, setHidden:NO];
+        }
+    }
+
+    pub fn hide(&self) {
+        unsafe {
+            let () = msg_send![self.window, setHidden:YES];
+        }
+    }
+
+    pub fn request_redraw(&self) {
+        unsafe {
+            let () = msg_send![self.view, setNeedsDisplay];
+        }
+    }
+    
+    pub fn get_inner_position(&self) -> Option<LogicalPosition> {
+        unsafe {
+            let safe_area = self.safe_area_screen_space();
+            Some(LogicalPosition {
+                x: safe_area.origin.x,
+                y: safe_area.origin.y,
+            })
+        }
+    }
+
+    pub fn get_position(&self) -> Option<LogicalPosition> {
+        unsafe {
+            let screen_frame = self.screen_frame();
+            Some(LogicalPosition {
+                x: screen_frame.origin.x,
+                y: screen_frame.origin.y,
+            })
+        }
+    }
+
+    pub fn set_position(&self, position: LogicalPosition) {
+        unsafe {
+            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.from_screen_space(new_screen_frame);
+            let () = msg_send![self.window, setBounds:bounds];
+        }
+    }
+
+    pub fn get_inner_size(&self) -> Option<LogicalSize> {
+        unsafe {
+            let safe_area = self.safe_area_screen_space();
+            Some(LogicalSize {
+                width: safe_area.size.width,
+                height: safe_area.size.height,
+            })
+        }
+    }
+
+    pub fn get_outer_size(&self) -> Option<LogicalSize> {
+        unsafe {
+            let screen_frame = self.screen_frame();
+            Some(LogicalSize {
+                width: screen_frame.size.width,
+                height: screen_frame.size.height,
+            })
+        }
+    }
+
+    pub fn set_inner_size(&self, _size: LogicalSize) {
+        unimplemented!("not clear what `Window::set_inner_size` means on iOS");
+    }
+
+    pub fn set_min_dimensions(&self, _dimensions: Option<LogicalSize>) {
+        warn!("`Window::set_min_dimensions` is ignored on iOS")
+    }
+
+    pub fn set_max_dimensions(&self, _dimensions: Option<LogicalSize>) {
+        warn!("`Window::set_max_dimensions` is ignored on iOS")
+    }
+
+    pub fn set_resizable(&self, _resizable: bool) {
+        warn!("`Window::set_resizable` is ignored on iOS")
+    }
+
+    pub fn get_hidpi_factor(&self) -> f64 {
+        unsafe {
+            let hidpi: CGFloat = msg_send![self.view, contentScaleFactor];
+            hidpi as _
+        }
+    }
+
+    pub fn set_cursor(&self, _cursor: MouseCursor) {
+        debug!("`Window::set_cursor` ignored on iOS")
+    }
+
+    pub fn set_cursor_position(&self, _position: LogicalPosition) -> Result<(), String> {
+        Err("Setting cursor position is not possible on iOS.".to_owned())
+    }
+
+    pub fn grab_cursor(&self, _grab: bool) -> Result<(), String> {
+        Err("Cursor grabbing is not possible on iOS.".to_owned())
+    }
+
+    pub fn hide_cursor(&self, _hide: bool) {
+        debug!("`Window::hide_cursor` is ignored on iOS")
+    }
+
+    pub fn set_maximized(&self, _maximized: bool) {
+        warn!("`Window::set_maximized` is ignored on iOS")
+    }
+
+    pub fn set_fullscreen(&self, monitor: Option<RootMonitorHandle>) {
+        unsafe {
+            match monitor {
+                Some(monitor) => {
+                    let uiscreen = monitor.get_uiscreen() as id;
+                    let current: id = msg_send![self.window, screen];
+                    let bounds: CGRect = msg_send![uiscreen, bounds];
+
+                    // this is pretty slow on iOS, so avoid doing it if we can
+                    if uiscreen != current {
+                        let () = msg_send![self.window, setScreen:uiscreen];
+                    }
+                    let () = msg_send![self.window, setFrame:bounds];
+                }
+                None => warn!("`Window::set_fullscreen(None)` ignored on iOS"),
+            }
+        }
+    }
+
+    pub fn get_fullscreen(&self) -> Option<RootMonitorHandle> {
+        unsafe {
+            let monitor = self.get_current_monitor();
+            let uiscreen = monitor.inner.get_uiscreen();
+            let screen_space_bounds = self.screen_frame();
+            let screen_bounds: CGRect = msg_send![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(monitor)
+            } else {
+                None
+            }
+        }
+    }
+
+    pub fn set_decorations(&self, decorations: bool) {
+        unsafe {
+            let status_bar_hidden = if decorations { NO } else { YES };
+            let () = msg_send![self.view_controller, setPrefersStatusBarHidden:status_bar_hidden];
+        }
+    }
+
+    pub fn set_always_on_top(&self, _always_on_top: bool) {
+        warn!("`Window::set_always_on_top` 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_spot(&self, _position: LogicalPosition) {
+        warn!("`Window::set_ime_spot` is ignored on iOS")
+    }
+
+    pub fn get_current_monitor(&self) -> RootMonitorHandle {
+        unsafe {
+            let uiscreen: id = msg_send![self.window, screen];
+            RootMonitorHandle { inner: MonitorHandle::retained_new(uiscreen) }
+        }
+    }
+
+    pub fn get_available_monitors(&self) -> VecDeque<MonitorHandle> {
+        unsafe {
+            monitor::uiscreens()
+        }
+    }
+
+    pub fn get_primary_monitor(&self) -> MonitorHandle {
+        unsafe {
+            monitor::main_uiscreen()
+        }
+    }
+
+    pub fn id(&self) -> WindowId {
+        self.window.into()
+    }
+}
+
+pub struct Window {
+    pub inner: Inner,
+}
+
+impl Drop for Window {
+    fn drop(&mut self) {
+        unsafe {
+            assert_main_thread!("`Window::drop` can only be run on the main thread on iOS");
+        }
+    }
+}
+
+unsafe impl Send for Window {}
+unsafe impl Sync for Window {}
+
+impl Deref for Window {
+    type Target = Inner;
+
+    fn deref(&self) -> &Inner {
+        unsafe {
+            assert_main_thread!("`Window` methods can only be run on the main thread on iOS");
+        }
+        &self.inner
+    }
+}
+
+impl DerefMut for Window {
+    fn deref_mut(&mut self) -> &mut Inner {
+        unsafe {
+            assert_main_thread!("`Window` methods can only be run on the main thread on iOS");
+        }
+        &mut self.inner
+    }
+}
+
+impl Window {
+    pub fn new<T>(
+        event_loop: &EventLoopWindowTarget<T>,
+        window_attributes: WindowAttributes,
+        platform_attributes: PlatformSpecificWindowBuilderAttributes,
+    ) -> Result<Window, CreationError> {
+        if let Some(_) = window_attributes.min_dimensions {
+            warn!("`WindowAttributes::min_dimensions` is ignored on iOS");
+        }
+        if let Some(_) = window_attributes.max_dimensions {
+            warn!("`WindowAttributes::max_dimensions` is ignored on iOS");
+        }
+        if window_attributes.always_on_top {
+            warn!("`WindowAttributes::always_on_top` is unsupported on iOS");
+        }
+        // TODO: transparency, visible
+
+        unsafe {
+            let screen = window_attributes.fullscreen
+                .as_ref()
+                .map(|screen| screen.get_uiscreen() as _)
+                .unwrap_or_else(|| monitor::main_uiscreen().get_uiscreen());
+            let screen_bounds: CGRect = msg_send![screen, bounds];
+
+            let frame = match window_attributes.dimensions {
+                Some(dim) => CGRect {
+                    origin: screen_bounds.origin,
+                    size: CGSize { width: dim.width, height: dim.height },
+                },
+                None => screen_bounds,
+            };
+
+            let view = view::create_view(&window_attributes, &platform_attributes, frame.clone());
+            let view_controller = view::create_view_controller(&window_attributes, &platform_attributes, view);
+            let window = view::create_window(&window_attributes, &platform_attributes, frame, view_controller);
+
+            let supports_safe_area = event_loop.capabilities().supports_safe_area;
+
+            let result = Window {
+                inner: Inner {
+                    window,
+                    view_controller,
+                    view,
+                    supports_safe_area,
+                },
+            };
+            AppState::set_key_window(window);
+            Ok(result)
+        }
+    }
+}
+
+// WindowExtIOS
+impl Inner {
+    pub fn get_uiwindow(&self) -> id { self.window }
+    pub fn get_uiviewcontroller(&self) -> id { self.view_controller }
+    pub fn get_uiview(&self) -> id { self.view }
+
+    pub fn set_hidpi_factor(&self, hidpi_factor: f64) {
+        unsafe {
+            assert!(dpi::validate_hidpi_factor(hidpi_factor), "`WindowExtIOS::set_hidpi_factor` received an invalid hidpi factor");
+            let hidpi_factor = hidpi_factor as CGFloat;
+            let () = msg_send![self.view, setContentScaleFactor:hidpi_factor];
+        }
+    }
+
+    pub fn set_valid_orientations(&self, valid_orientations: ValidOrientations) {
+        unsafe {
+            let idiom = event_loop::get_idiom();
+            let supported_orientations = UIInterfaceOrientationMask::from_valid_orientations_idiom(valid_orientations, idiom);
+            msg_send![self.view_controller, setSupportedInterfaceOrientations:supported_orientations];
+        }
+    }
+}
+
+impl Inner {
+    // requires main thread
+    unsafe fn screen_frame(&self) -> CGRect {
+        self.to_screen_space(msg_send![self.window, bounds])
+    }
+
+    // requires main thread
+    unsafe fn to_screen_space(&self, rect: CGRect) -> CGRect {
+        let screen: id = msg_send![self.window, screen];
+        if !screen.is_null() {
+            let screen_space: id = msg_send![screen, coordinateSpace];
+            msg_send![self.window, convertRect:rect toCoordinateSpace:screen_space]
+        } else {
+            rect
+        }
+    }
+
+    // requires main thread
+    unsafe fn from_screen_space(&self, rect: CGRect) -> CGRect {
+        let screen: id = msg_send![self.window, screen];
+        if !screen.is_null() {
+            let screen_space: id = msg_send![screen, coordinateSpace];
+            msg_send![self.window, convertRect:rect fromCoordinateSpace:screen_space]
+        } else {
+            rect
+        }
+    }
+
+    // requires main thread
+    unsafe fn safe_area_screen_space(&self) -> CGRect {
+        let bounds: CGRect = msg_send![self.window, bounds];
+        if self.supports_safe_area {
+            let safe_area: UIEdgeInsets = msg_send![self.window, safeAreaInsets];
+            let safe_bounds = CGRect {
+                origin: CGPoint {
+                    x: bounds.origin.x + safe_area.left,
+                    y: bounds.origin.y + safe_area.top,
+                },
+                size: CGSize {
+                    width: bounds.size.width - safe_area.left - safe_area.right,
+                    height: bounds.size.height - safe_area.top - safe_area.bottom,
+                },
+            };
+            self.to_screen_space(safe_bounds)
+        } else {
+            let screen_frame = self.to_screen_space(bounds);
+            let status_bar_frame: CGRect = {
+                let app: id = msg_send![class!(UIApplication), sharedApplication];
+                assert!(!app.is_null(), "`Window::get_inner_position` cannot be called before `EventLoop::run` on iOS");
+                msg_send![app, statusBarFrame]
+            };
+            let (y, height) = if screen_frame.origin.y > status_bar_frame.size.height {
+                (screen_frame.origin.y, screen_frame.size.height)
+            } else {
+                let y = status_bar_frame.size.height;
+                let height = screen_frame.size.height - (status_bar_frame.size.height - screen_frame.origin.y);
+                (y, height)
+            };
+            CGRect {
+                origin: CGPoint {
+                    x: screen_frame.origin.x,
+                    y,
+                },
+                size: CGSize {
+                    width: screen_frame.size.width,
+                    height,
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WindowId {
+    window: id,
+}
+
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId {
+            window: std::ptr::null_mut(),
+        }
+    }
+}
+
+unsafe impl Send for WindowId {}
+unsafe impl Sync for WindowId {}
+
+impl From<&Object> for WindowId {
+    fn from(window: &Object) -> WindowId {
+        WindowId { window: window as *const _ as _ }
+    }
+}
+
+impl From<&mut Object> for WindowId {
+    fn from(window: &mut Object) -> WindowId {
+        WindowId { window: window as _ }
+    }
+}
+
+impl From<id> for WindowId {
+    fn from(window: id) -> WindowId {
+        WindowId { window }
+    }
+}
+
+#[derive(Clone)]
+pub struct PlatformSpecificWindowBuilderAttributes {
+    pub root_view_class: &'static Class,
+    pub hidpi_factor: Option<f64>,
+    pub valid_orientations: ValidOrientations,
+}
+
+impl Default for PlatformSpecificWindowBuilderAttributes {
+    fn default() -> PlatformSpecificWindowBuilderAttributes {
+        PlatformSpecificWindowBuilderAttributes {
+            root_view_class: class!(UIView),
+            hidpi_factor: None,
+            valid_orientations: Default::default(),
+        }
+    }
+}

src/window.rs

@@ -330,6 +330,10 @@ impl Window {
     /// Modifies the title of the window.
     ///
     /// This is a no-op if the window has already been closed.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - Has no effect on iOS.
     #[inline]
     pub fn set_title(&self, title: &str) {
         self.window.set_title(title)
@@ -339,8 +343,8 @@ impl Window {
     ///
     /// ## Platform-specific
     ///
-    /// - Has no effect on Android
-    ///
+    /// - **Android:** Has no effect.
+    /// - **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn show(&self) {
         self.window.show()
@@ -350,8 +354,8 @@ impl Window {
     ///
     /// ## Platform-specific
     ///
-    /// - Has no effect on Android
-    ///
+    /// - **Android:** Has no effect.
+    /// - **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn hide(&self) {
         self.window.hide()
@@ -368,6 +372,10 @@ impl Window {
     /// * While processing `EventsCleared`.
     /// * While processing a `RedrawRequested` event that was sent during `EventsCleared` or any
     ///   directly subsequent `RedrawRequested` event.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Can only be called on the main thread.
     pub fn request_redraw(&self) {
         self.window.request_redraw()
     }
@@ -383,6 +391,11 @@ impl Window {
     ///  of the visible screen region.
     ///
     /// Returns `None` if the window no longer exists.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Can only be called on the main thread. Returns the top left coordinates of the
+    ///   window in the screen space coordinate system.
     #[inline]
     pub fn get_position(&self) -> Option<LogicalPosition> {
         self.window.get_position()
@@ -392,6 +405,13 @@ impl Window {
     /// top-left hand corner of the desktop.
     ///
     /// The same conditions that apply to `get_position` apply to this method.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Can only be called on the main thread. Returns the top left coordinates of the
+    ///   window's [safe area] in the screen space coordinate system.
+    /// 
+    /// [safe area]: https://developer.apple.com/documentation/uikit/uiview/2891103-safeareainsets?language=objc
     #[inline]
     pub fn get_inner_position(&self) -> Option<LogicalPosition> {
         self.window.get_inner_position()
@@ -402,6 +422,11 @@ impl Window {
     /// See `get_position` for more information about the coordinates.
     ///
     /// This is a no-op if the window has already been closed.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Can only be called on the main thread. Sets the top left coordinates of the
+    ///   window in the screen space coordinate system.
     #[inline]
     pub fn set_position(&self, position: LogicalPosition) {
         self.window.set_position(position)
@@ -414,6 +439,13 @@ impl Window {
     /// Converting the returned `LogicalSize` to `PhysicalSize` produces the size your framebuffer should be.
     ///
     /// Returns `None` if the window no longer exists.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Can only be called on the main thread. Returns the `LogicalSize` of the window's
+    ///   [safe area] in screen space coordinates.
+    /// 
+    /// [safe area]: https://developer.apple.com/documentation/uikit/uiview/2891103-safeareainsets?language=objc
     #[inline]
     pub fn get_inner_size(&self) -> Option<LogicalSize> {
         self.window.get_inner_size()
@@ -425,6 +457,11 @@ impl Window {
     /// use `get_inner_size` instead.
     ///
     /// Returns `None` if the window no longer exists.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Can only be called on the main thread. Returns the `LogicalSize` of the window in
+    ///   screen space coordinates.
     #[inline]
     pub fn get_outer_size(&self) -> Option<LogicalSize> {
         self.window.get_outer_size()
@@ -435,18 +472,31 @@ impl Window {
     /// See `get_inner_size` for more information about the values.
     ///
     /// This is a no-op if the window has already been closed.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Unimplemented. Currently this panics, as it's not clear what `set_inner_size`
+    ///   would mean for iOS.
     #[inline]
     pub fn set_inner_size(&self, size: LogicalSize) {
         self.window.set_inner_size(size)
     }
 
     /// Sets a minimum dimension size for the window.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Has no effect.
     #[inline]
     pub fn set_min_dimensions(&self, dimensions: Option<LogicalSize>) {
         self.window.set_min_dimensions(dimensions)
     }
 
     /// Sets a maximum dimension size for the window.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Has no effect.
     #[inline]
     pub fn set_max_dimensions(&self, dimensions: Option<LogicalSize>) {
         self.window.set_max_dimensions(dimensions)
@@ -462,6 +512,10 @@ impl Window {
     /// This only has an effect on desktop platforms.
     ///
     /// Due to a bug in XFCE, this has no effect on Xfwm.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Has no effect.
     #[inline]
     pub fn set_resizable(&self, resizable: bool) {
         self.window.set_resizable(resizable)
@@ -479,19 +533,31 @@ impl Window {
     ///
     /// - **X11:** This respects Xft.dpi, and can be overridden using the `WINIT_HIDPI_FACTOR` environment variable.
     /// - **Android:** Always returns 1.0.
+    /// - **iOS:** Can only be called on the main thread. Returns the underlying `UIView`'s
+    ///   [`contentScaleFactor`].
+    /// 
+    /// [`contentScaleFactor`]: https://developer.apple.com/documentation/uikit/uiview/1622657-contentscalefactor?language=objc
     #[inline]
     pub fn get_hidpi_factor(&self) -> f64 {
         self.window.get_hidpi_factor()
     }
 
     /// Modifies the mouse cursor of the window.
-    /// Has no effect on Android.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Has no effect.
+    /// - **Android:** Has no effect.
     #[inline]
     pub fn set_cursor(&self, cursor: MouseCursor) {
         self.window.set_cursor(cursor);
     }
 
     /// Changes the position of the cursor in window coordinates.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS:** Always returns an `Err`.
     #[inline]
     pub fn set_cursor_position(&self, position: LogicalPosition) -> Result<(), String> {
         self.window.set_cursor_position(position)
@@ -501,9 +567,10 @@ impl Window {
     ///
     /// ## Platform-specific
     ///
-    /// On macOS, this presently merely locks the cursor in a fixed location, which looks visually awkward.
-    ///
-    /// This has no effect on Android or iOS.
+    /// - **macOS:** This presently merely locks the cursor in a fixed location, which looks visually
+    ///   awkward.
+    /// - **Android:** Has no effect.
+    /// - **iOS:** Always returns an Err.
     #[inline]
     pub fn grab_cursor(&self, grab: bool) -> Result<(), String> {
         self.window.grab_cursor(grab)
@@ -513,42 +580,65 @@ impl Window {
     ///
     /// ## Platform-specific
     ///
-    /// On Windows and X11, the cursor is only hidden within the confines of the window.
-    ///
-    /// On macOS, the cursor is hidden as long as the window has input focus, even if the cursor is outside of the
-    /// window.
-    ///
-    /// This has no effect on Android or iOS.
+    /// - **Windows:** The cursor is only hidden within the confines of the window.
+    /// - **X11:** The cursor is only hidden within the confines of the window.
+    /// - **macOS:** The cursor is hidden as long as the window has input focus, even if the cursor is
+    ///   outside of the window.
+    /// - **iOS:** Has no effect.
+    /// - **Android:** Has no effect.
     #[inline]
     pub fn hide_cursor(&self, hide: bool) {
         self.window.hide_cursor(hide)
     }
 
-    /// Sets the window to maximized or back
+    /// Sets the window to maximized or back.
+    ///
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Has no effect.
     #[inline]
     pub fn set_maximized(&self, maximized: bool) {
         self.window.set_maximized(maximized)
     }
 
-    /// Sets the window to fullscreen or back
+    /// Sets the window to fullscreen or back.
+    ///
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn set_fullscreen(&self, monitor: Option<MonitorHandle>) {
         self.window.set_fullscreen(monitor)
     }
 
     /// Gets the window's current fullscreen state.
+    ///
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn get_fullscreen(&self) -> Option<MonitorHandle> {
         self.window.get_fullscreen()
     }
 
     /// Turn window decorations on or off.
+    ///
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Can only be called on the main thread. Controls whether the status bar is hidden
+    ///   via [`setPrefersStatusBarHidden`].
+    /// 
+    /// [`setPrefersStatusBarHidden`]: https://developer.apple.com/documentation/uikit/uiviewcontroller/1621440-prefersstatusbarhidden?language=objc
     #[inline]
     pub fn set_decorations(&self, decorations: bool) {
         self.window.set_decorations(decorations)
     }
 
     /// Change whether or not the window will always be on top of other windows.
+    ///
+    /// ## Platform-specific
+    /// 
+    /// - **iOS:** Has no effect.
     #[inline]
     pub fn set_always_on_top(&self, always_on_top: bool) {
         self.window.set_always_on_top(always_on_top)
@@ -568,12 +658,20 @@ impl Window {
     }
 
     /// Sets location of IME candidate box in client area coordinates relative to the top left.
+    ///
+    /// ## Platform-specific
+    ///
+    /// **iOS:** Has no effect.
     #[inline]
     pub fn set_ime_spot(&self, position: LogicalPosition) {
         self.window.set_ime_spot(position)
     }
 
     /// Returns the monitor on which the window currently resides
+    ///
+    /// ## Platform-specific
+    ///
+    /// **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn get_current_monitor(&self) -> MonitorHandle {
         self.window.get_current_monitor()
@@ -582,6 +680,10 @@ impl Window {
     /// Returns the list of all the monitors available on the system.
     ///
     /// This is the same as `EventLoop::get_available_monitors`, and is provided for convenience.
+    ///
+    /// ## Platform-specific
+    ///
+    /// **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn get_available_monitors(&self) -> AvailableMonitorsIter {
         let data = self.window.get_available_monitors();
@@ -591,6 +693,10 @@ impl Window {
     /// Returns the primary monitor of the system.
     ///
     /// This is the same as `EventLoop::get_primary_monitor`, and is provided for convenience.
+    ///
+    /// ## Platform-specific
+    ///
+    /// **iOS:** Can only be called on the main thread.
     #[inline]
     pub fn get_primary_monitor(&self) -> MonitorHandle {
         MonitorHandle { inner: self.window.get_primary_monitor() }