Move UIKit backend to winit-uikit

winit-uikit/src/event_loop.rs

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