WIP - Make poll_events and run_forever take &mut self

This removes the need for the EventsLoop::interrupt method by inroducing
a ControlFlow type. This new type is to be returned by the user's
callback and indicates whether the `EventsLoop` should continue waiting
for events or break from the loop.

Only the wayland, x11 and api_transition backends have been updated so
far, and only the wayland backend has actually been tested.

examples/window.rs

@@ -12,8 +12,10 @@ fn main() {
         println!("{:?}", event);
 
         match event {
-            winit::Event::WindowEvent { event: winit::WindowEvent::Closed, .. } => events_loop.interrupt(),
+            winit::Event::WindowEvent { event: winit::WindowEvent::Closed, .. } => {
-            _ => ()
+                winit::ControlFlow::Complete
+            },
+            _ => winit::ControlFlow::Continue,
         }
     });
 }

src/api_transition.rs

@@ -8,7 +8,7 @@
 macro_rules! gen_api_transition {
     () => {
         pub struct EventsLoop {
-            windows: ::std::sync::Mutex<Vec<::std::sync::Arc<Window>>>,
+            windows: ::std::sync::Arc<::std::sync::Mutex<Vec<::std::sync::Arc<Window>>>>,
             interrupted: ::std::sync::atomic::AtomicBool,
             awakened: ::std::sync::Arc<::std::sync::atomic::AtomicBool>,
         }
@@ -20,7 +20,7 @@ macro_rules! gen_api_transition {
         impl EventsLoop {
             pub fn new() -> EventsLoop {
                 EventsLoop {
-                    windows: ::std::sync::Mutex::new(vec![]),
+                    windows: ::std::sync::Arc::new(::std::sync::Mutex::new(vec![])),
                     interrupted: ::std::sync::atomic::AtomicBool::new(false),
                     awakened: ::std::sync::Arc::new(::std::sync::atomic::AtomicBool::new(false)),
                 }
@@ -92,7 +92,7 @@ macro_rules! gen_api_transition {
 
         pub struct Window2 {
             pub window: ::std::sync::Arc<Window>,
-            events_loop: ::std::sync::Weak<EventsLoop>,
+            windows: ::std::sync::Weak<::std::sync::Mutex<Vec<::std::sync::Arc<Window>>>>
         }
 
         impl ::std::ops::Deref for Window2 {
@@ -104,7 +104,8 @@ macro_rules! gen_api_transition {
         }
 
         impl Window2 {
-            pub fn new(events_loop: ::std::sync::Arc<EventsLoop>, window: &::WindowAttributes,
+            pub fn new(events_loop: &EventsLoop,
+                       window: &::WindowAttributes,
                        pl_attribs: &PlatformSpecificWindowBuilderAttributes)
                        -> Result<Window2, CreationError>
             {
@@ -112,7 +113,7 @@ macro_rules! gen_api_transition {
                 events_loop.windows.lock().unwrap().push(win.clone());
                 Ok(Window2 {
                     window: win,
-                    events_loop: ::std::sync::Arc::downgrade(&events_loop),
+                    events_loop: ::std::sync::Arc::downgrade(&events_loop.windows),
                 })
             }
 
@@ -124,8 +125,8 @@ macro_rules! gen_api_transition {
 
         impl Drop for Window2 {
             fn drop(&mut self) {
-                if let Some(ev) = self.events_loop.upgrade() {
+                if let Some(windows) = self.windows.upgrade() {
-                    let mut windows = ev.windows.lock().unwrap();
+                    let mut windows = windows.lock().unwrap();
                     windows.retain(|w| &**w as *const Window != &*self.window as *const _);
                 }
             }

src/lib.rs

@@ -119,8 +119,6 @@ extern crate x11_dl;
 #[macro_use(wayland_env,declare_handler)]
 extern crate wayland_client;
 
-use std::sync::Arc;
-
 pub use events::*;
 pub use window::{AvailableMonitorsIter, MonitorId, get_available_monitors, get_primary_monitor};
 pub use native_monitor::NativeMonitorId;
@@ -189,21 +187,32 @@ pub struct ButtonId(u32);
 ///
 /// To wake up an `EventsLoop` from a another thread, see the `EventsLoopProxy` docs.
 pub struct EventsLoop {
-    events_loop: Arc<platform::EventsLoop>,
+    events_loop: platform::EventsLoop,
+}
+
+/// Returned by the user callback given to the `EventsLoop::run_forever` method.
+///
+/// Indicates whether the `run_forever` method should continue or complete.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum ControlFlow {
+    /// Continue looping and waiting for events.
+    Continue,
+    /// Exit from the event loop.
+    Complete,
 }
 
 impl EventsLoop {
     /// Builds a new events loop.
     pub fn new() -> EventsLoop {
         EventsLoop {
-            events_loop: Arc::new(platform::EventsLoop::new()),
+            events_loop: platform::EventsLoop::new(),
         }
     }
 
     /// Fetches all the events that are pending, calls the callback function for each of them,
     /// and returns.
     #[inline]
-    pub fn poll_events<F>(&self, callback: F)
+    pub fn poll_events<F>(&mut self, callback: F)
         where F: FnMut(Event)
     {
         self.events_loop.poll_events(callback)
@@ -211,18 +220,12 @@ impl EventsLoop {
 
     /// Runs forever until `interrupt()` is called. Whenever an event happens, calls the callback.
     #[inline]
-    pub fn run_forever<F>(&self, callback: F)
+    pub fn run_forever<F>(&mut self, callback: F)
-        where F: FnMut(Event)
+        where F: FnMut(Event) -> ControlFlow
     {
         self.events_loop.run_forever(callback)
     }
 
-    /// If we called `run_forever()`, stops the process of waiting for events.
-    #[inline]
-    pub fn interrupt(&self) {
-        self.events_loop.interrupt()
-    }
-
     /// Creates an `EventsLoopProxy` that can be used to wake up the `EventsLoop` from another
     /// thread.
     pub fn create_proxy(&self) -> EventsLoopProxy {

src/platform/linux/mod.rs

@@ -3,7 +3,7 @@
 use std::collections::VecDeque;
 use std::sync::Arc;
 
-use {CreationError, CursorState, EventsLoopClosed, MouseCursor};
+use {CreationError, CursorState, EventsLoopClosed, MouseCursor, ControlFlow};
 use libc;
 
 use self::x11::XConnection;
@@ -129,9 +129,10 @@ impl MonitorId {
 
 impl Window2 {
     #[inline]
-    pub fn new(events_loop: ::std::sync::Arc<EventsLoop>, window: &::WindowAttributes,
+    pub fn new(events_loop: &EventsLoop,
+               window: &::WindowAttributes,
                pl_attribs: &PlatformSpecificWindowBuilderAttributes)
-               -> Result<Window2, CreationError>
+               -> Result<Self, CreationError>
     {
         match *UNIX_BACKEND {
             UnixBackend::Wayland(ref ctxt) => {
@@ -336,28 +337,21 @@ impl EventsLoop {
         }
     }
 
-    pub fn interrupt(&self) {
+    pub fn poll_events<F>(&mut self, callback: F)
-        match *self {
-            EventsLoop::Wayland(ref evlp) => evlp.interrupt(),
-            EventsLoop::X(ref evlp) => evlp.interrupt()
-        }
-    }
-
-    pub fn poll_events<F>(&self, callback: F)
         where F: FnMut(::Event)
     {
         match *self {
-            EventsLoop::Wayland(ref evlp) => evlp.poll_events(callback),
+            EventsLoop::Wayland(ref mut evlp) => evlp.poll_events(callback),
-            EventsLoop::X(ref evlp) => evlp.poll_events(callback)
+            EventsLoop::X(ref mut evlp) => evlp.poll_events(callback)
         }
     }
 
-    pub fn run_forever<F>(&self, callback: F)
+    pub fn run_forever<F>(&mut self, callback: F)
-        where F: FnMut(::Event)
+        where F: FnMut(::Event) -> ControlFlow
     {
         match *self {
-            EventsLoop::Wayland(ref evlp) => evlp.run_forever(callback),
+            EventsLoop::Wayland(ref mut evlp) => evlp.run_forever(callback),
-            EventsLoop::X(ref evlp) => evlp.run_forever(callback)
+            EventsLoop::X(ref mut evlp) => evlp.run_forever(callback)
         }
     }
 }

src/platform/linux/wayland/event_loop.rs

@@ -1,4 +1,5 @@
-use {WindowEvent as Event, ElementState, MouseButton, MouseScrollDelta, TouchPhase, ModifiersState, KeyboardInput, EventsLoopClosed};
+use {WindowEvent as Event, ElementState, MouseButton, MouseScrollDelta, TouchPhase, ModifiersState,
+     KeyboardInput, EventsLoopClosed, ControlFlow};
 
 use std::sync::{Arc, Mutex, Weak};
 use std::sync::atomic::{self, AtomicBool};
@@ -53,7 +54,9 @@ impl EventsLoopSink {
         ::std::mem::replace(&mut self.callback, cb)
     }
 
-    fn with_callback<F: FnOnce(&mut FnMut(::Event))>(&mut self, f: F) {
+    fn with_callback<F>(&mut self, f: F)
+        where F: FnOnce(&mut FnMut(::Event)),
+    {
         f(&mut *self.callback)
     }
 }
@@ -67,8 +70,6 @@ pub struct EventsLoop {
     decorated_ids: Mutex<Vec<(usize, Arc<wl_surface::WlSurface>)>>,
     // our sink, receiver of callbacks, shared with some handlers
     sink: Arc<Mutex<EventsLoopSink>>,
-    // trigger interruption of the run
-    interrupted: AtomicBool,
     // trigger cleanup of the dead surfaces
     cleanup_needed: Arc<AtomicBool>,
     // Whether or not there is a pending `Awakened` event to be emitted.
@@ -115,7 +116,6 @@ impl EventsLoop {
             evq: Arc::new(Mutex::new(evq)),
             decorated_ids: Mutex::new(Vec::new()),
             sink: sink,
-            interrupted: AtomicBool::new(false),
             pending_wakeup: Arc::new(AtomicBool::new(false)),
             cleanup_needed: Arc::new(AtomicBool::new(false)),
             hid: hid
@@ -158,10 +158,6 @@ impl EventsLoop {
         }
     }
 
-    pub fn interrupt(&self) {
-        self.interrupted.store(true, atomic::Ordering::Relaxed);
-    }
-
     fn prune_dead_windows(&self) {
         self.decorated_ids.lock().unwrap().retain(|&(_, ref w)| w.is_alive());
         let mut evq_guard = self.evq.lock().unwrap();
@@ -175,7 +171,7 @@ impl EventsLoop {
         }
     }
 
-    pub fn poll_events<F>(&self, callback: F)
+    pub fn poll_events<F>(&mut self, callback: F)
         where F: FnMut(::Event)
     {
         // send pending requests to the server...
@@ -219,38 +215,45 @@ impl EventsLoop {
         }
     }
 
-    pub fn run_forever<F>(&self, callback: F)
+    pub fn run_forever<F>(&mut self, mut callback: F)
-        where F: FnMut(::Event)
+        where F: FnMut(::Event) -> ControlFlow,
     {
-        self.interrupted.store(false, atomic::Ordering::Relaxed);
-
         // send pending requests to the server...
         self.ctxt.flush();
 
         // first of all, get exclusive access to this event queue
         let mut evq_guard = self.evq.lock().unwrap();
 
+        // Check for control flow by wrapping the callback.
+        let control_flow = ::std::cell::Cell::new(ControlFlow::Continue);
+        let callback = |event| if let ControlFlow::Complete = callback(event) {
+            control_flow.set(ControlFlow::Complete);
+        };
+
         // set the callback into the sink
         // we extend the lifetime of the closure to 'static to be able to put it in
         // the sink, but we'll explicitly drop it at the end of this function, so it's fine
         let static_cb = unsafe { ::std::mem::transmute(Box::new(callback) as Box<FnMut(_)>) };
         let old_cb = unsafe { self.sink.lock().unwrap().set_callback(static_cb) };
 
-        while !self.interrupted.load(atomic::Ordering::Relaxed) {
+        loop {
             self.ctxt.dispatch();
             evq_guard.dispatch_pending().expect("Wayland connection unexpectedly lost");
 
             self.emit_pending_wakeup();
 
             let ids_guard = self.decorated_ids.lock().unwrap();
-            self.sink.lock().unwrap().with_callback(
+            self.sink.lock().unwrap()
-                |cb| Self::process_resize(&mut evq_guard, &ids_guard, cb)
+                .with_callback(|cb| Self::process_resize(&mut evq_guard, &ids_guard, cb));
-            );
             self.ctxt.flush();
 
             if self.cleanup_needed.swap(false, atomic::Ordering::Relaxed) {
                 self.prune_dead_windows()
             }
+
+            if let ControlFlow::Complete = control_flow.get() {
+                break;
+            }
         }
 
         // replace the old noop callback

src/platform/linux/x11/mod.rs

@@ -7,7 +7,8 @@ pub use self::xdisplay::{XConnection, XNotSupported, XError};
 pub mod ffi;
 
 use platform::PlatformSpecificWindowBuilderAttributes;
-use {CreationError, Event, EventsLoopClosed, WindowEvent, DeviceEvent, AxisId, ButtonId, KeyboardInput};
+use {CreationError, Event, EventsLoopClosed, WindowEvent, DeviceEvent, AxisId, ButtonId,
+     KeyboardInput, ControlFlow};
 
 use std::{mem, ptr, slice};
 use std::sync::{Arc, Mutex, Weak};
@@ -30,10 +31,9 @@ mod xdisplay;
 // the one generated by the macro.
 
 pub struct EventsLoop {
-    interrupted: AtomicBool,
     display: Arc<XConnection>,
     wm_delete_window: ffi::Atom,
-    windows: Mutex<HashMap<WindowId, WindowData>>,
+    windows: Arc<Mutex<HashMap<WindowId, WindowData>>>,
     devices: Mutex<HashMap<DeviceId, Device>>,
     xi2ext: XExtension,
     pending_wakeup: Arc<AtomicBool>,
@@ -81,11 +81,10 @@ impl EventsLoop {
         let root = unsafe { (display.xlib.XDefaultRootWindow)(display.display) };
 
         let result = EventsLoop {
-            interrupted: AtomicBool::new(false),
             pending_wakeup: Arc::new(AtomicBool::new(false)),
             display: display,
             wm_delete_window: wm_delete_window,
-            windows: Mutex::new(HashMap::new()),
+            windows: Arc::new(Mutex::new(HashMap::new())),
             devices: Mutex::new(HashMap::new()),
             xi2ext: xi2ext,
             root: root,
@@ -118,14 +117,9 @@ impl EventsLoop {
         }
     }
 
-    pub fn interrupt(&self) {
-        self.interrupted.store(true, atomic::Ordering::Relaxed);
-    }
-
     pub fn poll_events<F>(&self, mut callback: F)
         where F: FnMut(Event)
     {
-        self.interrupted.store(false, atomic::Ordering::Relaxed);
         let xlib = &self.display.xlib;
 
         let mut xev = unsafe { mem::uninitialized() };
@@ -141,16 +135,12 @@ impl EventsLoop {
                 (xlib.XNextEvent)(self.display.display, &mut xev);
             }
             self.process_event(&mut xev, &mut callback);
-            if self.interrupted.load(atomic::Ordering::Relaxed) {
-                break;
-            }
         }
     }
 
-    pub fn run_forever<F>(&self, mut callback: F)
+    pub fn run_forever<F>(&mut self, mut callback: F)
-        where F: FnMut(Event)
+        where F: FnMut(Event) -> ControlFlow
     {
-        self.interrupted.store(false, atomic::Ordering::Relaxed);
         self.pending_wakeup.store(false, atomic::Ordering::Relaxed);
 
         let xlib = &self.display.xlib;
@@ -160,13 +150,25 @@ impl EventsLoop {
         loop {
             unsafe { (xlib.XNextEvent)(self.display.display, &mut xev) }; // Blocks as necessary
 
+            let mut control_flow = ControlFlow::Continue;
+
             if self.pending_wakeup.load(atomic::Ordering::Relaxed) {
                 self.pending_wakeup.store(false, atomic::Ordering::Relaxed);
-                callback(Event::Awakened);
+                control_flow = callback(Event::Awakened);
             }
 
-            self.process_event(&mut xev, &mut callback);
+            // Track whether or not `Complete` was returned when processing the event.
-            if self.interrupted.load(atomic::Ordering::Relaxed) {
+            {
+                let mut cb = |event| {
+                    if let ControlFlow::Complete = callback(event) {
+                        control_flow = ControlFlow::Complete;
+                    }
+                };
+                    
+                self.process_event(&mut xev, &mut cb);
+            }
+
+            if let ControlFlow::Complete = control_flow {
                 break;
             }
         }
@@ -178,7 +180,7 @@ impl EventsLoop {
         device.name.clone()
     }
 
-    fn process_event<F>(&self, xev: &mut ffi::XEvent, callback: &mut F)
+    fn process_event<F>(&self, xev: &mut ffi::XEvent, mut callback: F)
         where F: FnMut(Event)
     {
         let xlib = &self.display.xlib;
@@ -312,7 +314,11 @@ impl EventsLoop {
                     };
 
                     for chr in written.chars() {
-                        callback(Event::WindowEvent { window_id: wid, event: WindowEvent::ReceivedCharacter(chr) })
+                        let event = Event::WindowEvent {
+                            window_id: wid,
+                            event: WindowEvent::ReceivedCharacter(chr),
+                        };
+                        callback(event);
                     }
                 }
             }
@@ -603,7 +609,8 @@ pub struct DeviceId(c_int);
 
 pub struct Window2 {
     pub window: Arc<Window>,
-    events_loop: Weak<::platform::EventsLoop>,
+    display: Weak<XConnection>,
+    windows: Weak<Mutex<HashMap<WindowId, WindowData>>>,
 }
 
 impl ::std::ops::Deref for Window2 {
@@ -620,9 +627,10 @@ lazy_static! {      // TODO: use a static mutex when that's possible, and put me
 }
 
 impl Window2 {
-    pub fn new(events_loop: Arc<::platform::EventsLoop>,
+    pub fn new(events_loop: &::platform::EventsLoop,
-               window: &::WindowAttributes, pl_attribs: &PlatformSpecificWindowBuilderAttributes)
+               window: &::WindowAttributes,
-               -> Result<Window2, CreationError>
+               pl_attribs: &PlatformSpecificWindowBuilderAttributes)
+               -> Result<Self, CreationError>
     {
         let x_events_loop = if let ::platform::EventsLoop::X(ref e) = *events_loop { e } else { unreachable!() };
         let win = ::std::sync::Arc::new(try!(Window::new(&x_events_loop, window, pl_attribs)));
@@ -662,7 +670,8 @@ impl Window2 {
 
         Ok(Window2 {
             window: win,
-            events_loop: Arc::downgrade(&events_loop),
+            windows: Arc::downgrade(&x_events_loop.windows),
+            display: Arc::downgrade(&x_events_loop.display),
         })
     }
 
@@ -674,17 +683,13 @@ impl Window2 {
 
 impl Drop for Window2 {
     fn drop(&mut self) {
-        if let Some(ev) = self.events_loop.upgrade() {
+        if let (Some(windows), Some(display)) = (self.windows.upgrade(), self.display.upgrade()) {
-            if let ::platform::EventsLoop::X(ref ev) = *ev {
+            let mut windows = windows.lock().unwrap();
-                let mut windows = ev.windows.lock().unwrap();
-
-
             let w = windows.remove(&self.window.id()).unwrap();
             let _lock = GLOBAL_XOPENIM_LOCK.lock().unwrap();
             unsafe {
-                    (ev.display.xlib.XDestroyIC)(w.ic);
+                (display.xlib.XDestroyIC)(w.ic);
-                    (ev.display.xlib.XCloseIM)(w.im);
+                (display.xlib.XCloseIM)(w.im);
-                }
             }
         }
     }

src/window.rs

@@ -110,7 +110,7 @@ impl WindowBuilder {
         }
 
         // building
-        let w = try!(platform::Window2::new(events_loop.events_loop.clone(), &self.window, &self.platform_specific));
+        let w = try!(platform::Window2::new(&events_loop.events_loop, &self.window, &self.platform_specific));
 
         Ok(Window { window: w })
     }