api: make EventLoopProxy wrap an opaque type

The proxy is intended to be Clone, thus use `Arc` for it internally and
don't require backends for it to be `Clone`. Use `EventLoopProxyProvider`
to hide the backend's proxy implementation details.

Co-authored-by: daxpedda <daxpedda@gmail.com>

src/platform_impl/web/event_loop/mod.rs

@@ -10,7 +10,6 @@ pub(crate) mod runner;
 mod state;
 mod window_target;
 
-pub(crate) use proxy::EventLoopProxy;
 pub(crate) use window_target::{ActiveEventLoop, OwnedDisplayHandle};
 
 pub struct EventLoop {

src/platform_impl/web/event_loop/proxy.rs

@@ -1,17 +1,101 @@
-use super::runner::WeakShared;
-use crate::platform_impl::platform::r#async::Waker;
+use std::future;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::task::Poll;
 
-#[derive(Clone)]
-pub struct EventLoopProxy {
-    runner: Waker<WeakShared>,
+use super::super::main_thread::MainThreadMarker;
+use crate::event_loop::EventLoopProxyProvider;
+use crate::platform_impl::web::event_loop::runner::WeakShared;
+use crate::platform_impl::web::r#async::{AtomicWaker, Wrapper};
+
+pub struct EventLoopProxy(Wrapper<WeakShared, Arc<State>, ()>);
+
+struct State {
+    awoken: AtomicBool,
+    waker: AtomicWaker,
+    closed: AtomicBool,
 }
 
 impl EventLoopProxy {
-    pub fn new(runner: Waker<WeakShared>) -> Self {
-        Self { runner }
+    pub fn new(main_thread: MainThreadMarker, runner: WeakShared) -> Self {
+        let state = Arc::new(State {
+            awoken: AtomicBool::new(false),
+            waker: AtomicWaker::new(),
+            closed: AtomicBool::new(false),
+        });
+
+        Self(Wrapper::new(
+            main_thread,
+            runner,
+            |runner, _| {
+                let runner = runner.borrow();
+                let runner = runner.as_ref().unwrap();
+
+                if let Some(runner) = runner.upgrade() {
+                    runner.send_proxy_wake_up(true);
+                }
+            },
+            {
+                let state = Arc::clone(&state);
+
+                move |runner| async move {
+                    while future::poll_fn(|cx| {
+                        if state.awoken.swap(false, Ordering::Relaxed) {
+                            Poll::Ready(true)
+                        } else {
+                            state.waker.register(cx.waker());
+
+                            if state.awoken.swap(false, Ordering::Relaxed) {
+                                Poll::Ready(true)
+                            } else {
+                                if state.closed.load(Ordering::Relaxed) {
+                                    return Poll::Ready(false);
+                                }
+
+                                Poll::Pending
+                            }
+                        }
+                    })
+                    .await
+                    {
+                        let runner = runner.borrow();
+                        let runner = runner.as_ref().unwrap();
+
+                        if let Some(runner) = runner.upgrade() {
+                            runner.send_proxy_wake_up(false);
+                        }
+                    }
+                }
+            },
+            state,
+            |state, _| {
+                state.awoken.store(true, Ordering::Relaxed);
+                state.waker.wake();
+            },
+        ))
     }
 
-    pub fn wake_up(&self) {
-        self.runner.wake();
+    pub fn take(&self) -> bool {
+        debug_assert!(
+            MainThreadMarker::new().is_some(),
+            "this should only be called from the main thread"
+        );
+
+        self.0.with_sender_data(|state| state.awoken.swap(false, Ordering::Relaxed))
+    }
+}
+
+impl Drop for EventLoopProxy {
+    fn drop(&mut self) {
+        self.0.with_sender_data(|state| {
+            state.closed.store(true, Ordering::Relaxed);
+            state.waker.wake();
+        });
+    }
+}
+
+impl EventLoopProxyProvider for EventLoopProxy {
+    fn wake_up(&self) {
+        self.0.send(())
     }
 }

src/platform_impl/web/event_loop/runner.rs

@@ -3,6 +3,7 @@ use std::collections::{HashSet, VecDeque};
 use std::iter;
 use std::ops::Deref;
 use std::rc::{Rc, Weak};
+use std::sync::Arc;
 
 use wasm_bindgen::prelude::Closure;
 use wasm_bindgen::JsCast;
@@ -13,13 +14,14 @@ use super::super::event;
 use super::super::main_thread::MainThreadMarker;
 use super::super::monitor::MonitorHandler;
 use super::backend;
+use super::proxy::EventLoopProxy;
 use super::state::State;
 use crate::dpi::PhysicalSize;
 use crate::event::{DeviceEvent, ElementState, Event, RawKeyEvent, StartCause, WindowEvent};
 use crate::event_loop::{ControlFlow, DeviceEvents};
 use crate::platform::web::{PollStrategy, WaitUntilStrategy};
 use crate::platform_impl::platform::backend::EventListenerHandle;
-use crate::platform_impl::platform::r#async::{DispatchRunner, Waker, WakerSpawner};
+use crate::platform_impl::platform::r#async::DispatchRunner;
 use crate::platform_impl::platform::window::Inner;
 use crate::window::WindowId;
 
@@ -37,7 +39,7 @@ type OnEventHandle<T> = RefCell<Option<EventListenerHandle<dyn FnMut(T)>>>;
 
 struct Execution {
     main_thread: MainThreadMarker,
-    proxy_spawner: WakerSpawner<WeakShared>,
+    event_loop_proxy: Arc<EventLoopProxy>,
     control_flow: Cell<ControlFlow>,
     poll_strategy: Cell<PollStrategy>,
     wait_until_strategy: Cell<WaitUntilStrategy>,
@@ -140,12 +142,7 @@ impl Shared {
         let document = window.document().expect("Failed to obtain document");
 
         Shared(Rc::<Execution>::new_cyclic(|weak| {
-            let proxy_spawner =
-                WakerSpawner::new(main_thread, WeakShared(weak.clone()), |runner, local| {
-                    if let Some(runner) = runner.upgrade() {
-                        runner.send_proxy_wake_up(local);
-                    }
-                });
+            let proxy_spawner = EventLoopProxy::new(main_thread, WeakShared(weak.clone()));
 
             let monitor = MonitorHandler::new(
                 main_thread,
@@ -156,7 +153,7 @@ impl Shared {
 
             Execution {
                 main_thread,
-                proxy_spawner,
+                event_loop_proxy: Arc::new(proxy_spawner),
                 control_flow: Cell::new(ControlFlow::default()),
                 poll_strategy: Cell::new(PollStrategy::default()),
                 wait_until_strategy: Cell::new(WaitUntilStrategy::default()),
@@ -653,7 +650,7 @@ impl Shared {
                 // Pre-fetch `UserEvent`s to avoid having to wait until the next event loop cycle.
                 events.extend(
                     self.0
-                        .proxy_spawner
+                        .event_loop_proxy
                         .take()
                         .then_some(Event::UserWakeUp)
                         .map(EventWrapper::from),
@@ -818,8 +815,8 @@ impl Shared {
         self.0.wait_until_strategy.get()
     }
 
-    pub(crate) fn waker(&self) -> Waker<WeakShared> {
-        self.0.proxy_spawner.waker()
+    pub(crate) fn event_loop_proxy(&self) -> &Arc<EventLoopProxy> {
+        &self.0.event_loop_proxy
     }
 
     pub(crate) fn weak(&self) -> WeakShared {

src/platform_impl/web/event_loop/window_target.rs

@@ -2,13 +2,14 @@ use std::cell::Cell;
 use std::clone::Clone;
 use std::iter;
 use std::rc::Rc;
+use std::sync::Arc;
 
 use web_sys::Element;
 
 use super::super::monitor::MonitorPermissionFuture;
 use super::super::{lock, KeyEventExtra};
-use super::runner::{EventWrapper, WeakShared};
-use super::{backend, runner, EventLoopProxy};
+use super::runner::EventWrapper;
+use super::{backend, runner};
 use crate::error::{NotSupportedError, RequestError};
 use crate::event::{ElementState, Event, KeyEvent, TouchPhase, WindowEvent};
 use crate::event_loop::{
@@ -19,7 +20,7 @@ use crate::keyboard::ModifiersState;
 use crate::monitor::MonitorHandle as RootMonitorHandle;
 use crate::platform::web::{CustomCursorFuture, PollStrategy, WaitUntilStrategy};
 use crate::platform_impl::platform::cursor::CustomCursor;
-use crate::platform_impl::platform::r#async::Waker;
+use crate::platform_impl::web::event_loop::proxy::EventLoopProxy;
 use crate::platform_impl::Window;
 use crate::window::{CustomCursor as RootCustomCursor, CustomCursorSource, Theme, WindowId};
 
@@ -476,15 +477,15 @@ impl ActiveEventLoop {
         self.runner.monitor().has_detailed_monitor_permission()
     }
 
-    pub(crate) fn waker(&self) -> Waker<WeakShared> {
-        self.runner.waker()
+    pub(crate) fn event_loop_proxy(&self) -> Arc<EventLoopProxy> {
+        self.runner.event_loop_proxy().clone()
     }
 }
 
 impl RootActiveEventLoop for ActiveEventLoop {
     fn create_proxy(&self) -> RootEventLoopProxy {
-        let event_loop_proxy = EventLoopProxy::new(self.waker());
-        RootEventLoopProxy { event_loop_proxy }
+        let event_loop_proxy = self.event_loop_proxy();
+        RootEventLoopProxy::new(event_loop_proxy)
     }
 
     fn create_window(