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/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 }
+    }
+}