Remove 'static requirement on run

There's no need to force the static on the users, given that internally
some backends were not using static in the first place.

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

src/event_loop.rs

@@ -310,11 +310,14 @@ impl<T> EventLoop<T> {
     ///   asynchronously (via the browser's own, internal, event loop) and doesn't block the
     ///   current thread of execution like it does on other platforms.
     ///
+    ///   This function won't be available with `target_feature = "exception-handling"`.
+    ///
     /// [`ControlFlow`]: crate::event_loop::ControlFlow
     #[inline]
+    #[cfg(not(all(wasm_platform, target_feature = "exception-handling")))]
     pub fn run<F>(self, event_handler: F) -> Result<(), RunLoopError>
     where
-        F: 'static + FnMut(Event<T>, &EventLoopWindowTarget<T>, &mut ControlFlow),
+        F: FnMut(Event<T>, &EventLoopWindowTarget<T>, &mut ControlFlow),
     {
         self.event_loop.run(event_handler)
     }

src/platform_impl/android/mod.rs

@@ -526,8 +526,7 @@ impl<T: 'static> EventLoop<T> {
 
     pub fn run<F>(mut self, event_handler: F) -> Result<(), RunLoopError>
     where
-        F: 'static
+        F: FnMut(event::Event<T>, &event_loop::EventLoopWindowTarget<T>, &mut ControlFlow),
-            + FnMut(event::Event<T>, &event_loop::EventLoopWindowTarget<T>, &mut ControlFlow),
     {
         self.run_ondemand(event_handler)
     }

src/platform_impl/ios/event_loop.rs

@@ -106,7 +106,7 @@ impl<T: 'static> EventLoop<T> {
 
     pub fn run<F>(self, event_handler: F) -> !
     where
-        F: 'static + FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
+        F: FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
     {
         unsafe {
             let application = UIApplication::shared(MainThreadMarker::new().unwrap());
@@ -116,10 +116,18 @@ impl<T: 'static> EventLoop<T> {
                 `EventLoop` cannot be `run` after a call to `UIApplicationMain` on iOS\n\
                  Note: `EventLoop::run` calls `UIApplicationMain` on iOS",
             );
-            app_state::will_launch(Box::new(EventLoopHandler {
+
+            let event_handler = std::mem::transmute::<
+                Box<dyn FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow)>,
+                Box<EventHandlerCallback<T>>,
+            >(Box::new(event_handler));
+
+            let handler = EventLoopHandler {
                 f: event_handler,
                 event_loop: self.window_target,
-            }));
+            };
+
+            app_state::will_launch(Box::new(handler));
 
             // Ensure application delegate is initialized
             view::WinitApplicationDelegate::class();
@@ -314,17 +322,20 @@ fn setup_control_flow_observers() {
 #[derive(Debug)]
 pub enum Never {}
 
+type EventHandlerCallback<T> =
+    dyn FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow) + 'static;
+
 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> {
+struct EventLoopHandler<T: 'static> {
-    f: F,
+    f: Box<EventHandlerCallback<T>>,
     event_loop: RootEventLoopWindowTarget<T>,
 }
 
-impl<F, T: 'static> Debug for EventLoopHandler<F, T> {
+impl<T: 'static> Debug for EventLoopHandler<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("EventLoopHandler")
             .field("event_loop", &self.event_loop)
@@ -332,11 +343,7 @@ impl<F, T: 'static> Debug for EventLoopHandler<F, T> {
     }
 }
 
-impl<F, T> EventHandler for EventLoopHandler<F, T>
+impl<T: 'static> EventHandler for EventLoopHandler<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(),

src/platform_impl/macos/event_loop.rs

@@ -195,7 +195,7 @@ impl<T> EventLoop<T> {
 
     pub fn run<F>(mut self, callback: F) -> Result<(), RunLoopError>
     where
-        F: 'static + FnMut(Event<T>, &RootWindowTarget<T>, &mut ControlFlow),
+        F: FnMut(Event<T>, &RootWindowTarget<T>, &mut ControlFlow),
     {
         self.run_ondemand(callback)
     }

src/platform_impl/orbital/event_loop.rs

@@ -445,8 +445,7 @@ impl<T: 'static> EventLoop<T> {
 
     pub fn run<F>(mut self, mut event_handler_inner: F) -> Result<(), RunLoopError>
     where
-        F: 'static
+        F: FnMut(event::Event<T>, &event_loop::EventLoopWindowTarget<T>, &mut ControlFlow),
-            + FnMut(event::Event<T>, &event_loop::EventLoopWindowTarget<T>, &mut ControlFlow),
     {
         // Wrapper for event handler function that prevents ExitWithCode from being unset.
         let mut event_handler =

src/platform_impl/web/event_loop/mod.rs

@@ -29,11 +29,23 @@ impl<T> EventLoop<T> {
         }
     }
 
-    pub fn run<F>(self, event_handler: F) -> !
+    pub fn run<F>(self, mut event_handler: F) -> !
     where
-        F: 'static + FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
+        F: FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
     {
-        self.spawn_inner(event_handler, false);
+        let target = RootEventLoopWindowTarget {
+            p: self.elw.p.clone(),
+            _marker: PhantomData,
+        };
+
+        // SAFETY: Don't use `move` to make sure we leak the `event_handler` and `target`.
+        let handler: Box<dyn FnMut(_, _)> =
+            Box::new(|event, flow| event_handler(event, &target, flow));
+        // SAFETY: The `transmute` is necessary because `run()` requires `'static`. This is safe
+        // because this function will never return and all resources not cleaned up by the point we
+        // `throw` will leak, making this actually `'static`.
+        let handler = unsafe { std::mem::transmute(handler) };
+        self.elw.p.run(handler, false);
 
         // Throw an exception to break out of Rust execution and use unreachable to tell the
         // compiler this function won't return, giving it a return type of '!'
@@ -44,14 +56,7 @@ impl<T> EventLoop<T> {
         unreachable!();
     }
 
-    pub fn spawn<F>(self, event_handler: F)
+    pub fn spawn<F>(self, mut event_handler: F)
-    where
-        F: 'static + FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
-    {
-        self.spawn_inner(event_handler, true);
-    }
-
-    fn spawn_inner<F>(self, mut event_handler: F, event_loop_recreation: bool)
     where
         F: 'static + FnMut(Event<T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
     {
@@ -62,7 +67,7 @@ impl<T> EventLoop<T> {
 
         self.elw.p.run(
             Box::new(move |event, flow| event_handler(event, &target, flow)),
-            event_loop_recreation,
+            true,
         );
     }
 

src/platform_impl/windows/event_loop.rs

@@ -248,7 +248,7 @@ impl<T: 'static> EventLoop<T> {
 
     pub fn run<F>(mut self, event_handler: F) -> Result<(), RunLoopError>
     where
-        F: 'static + FnMut(Event<T>, &RootELW<T>, &mut ControlFlow),
+        F: FnMut(Event<T>, &RootELW<T>, &mut ControlFlow),
     {
         self.run_ondemand(event_handler)
     }