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Auto merge of #23574 - asajeffrey:glutin-reduce-borrow-duration, r=paulrouget

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Don't process events while borrowing the event loop

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At the moment, the glutin embedder holds onto a borrow of the events loop while processing events, which is dangerous if any of the event handlers end up using the events loop reentrantly. (This caused a panic while integrating https://github.com/servo/rust-webvr/pull/84.)

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because this is low-level embedding code

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This commit is contained in:
bors-servo 2019-07-01 10:01:46 -04:00 • committed by GitHub
commit 18477d1e1e
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1 changed files with 28 additions and 24 deletions
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52
ports/glutin/app.rs
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@ -69,11 +69,8 @@ impl App {
mem::replace(&mut *self.event_queue.borrow_mut(), Vec::new())
}
fn has_events(&self) -> bool {
!self.event_queue.borrow().is_empty() || self.window.has_events()
}
fn winit_event_to_servo_event(&self, event: glutin::Event) {
// This function decides whether the event should be handled during `run_forever`.
fn winit_event_to_servo_event(&self, event: glutin::Event) -> glutin::ControlFlow {
match event {
// App level events
glutin::Event::Suspended(suspended) => {
@ -94,36 +91,43 @@ impl App {
if Some(window_id) != self.window.id() {
warn!("Got an event from unknown window");
} else {
// Resize events need to be handled during run_forever
let cont = if let glutin::WindowEvent::Resized(_) = event {
glutin::ControlFlow::Continue
} else {
glutin::ControlFlow::Break
};
self.window.winit_event_to_servo_event(event);
return cont;
}
},
}
glutin::ControlFlow::Break
}
fn run_loop(self) {
let mut stop = false;
loop {
let mut events_loop = self.events_loop.borrow_mut();
if self.window.is_animating() && !self.suspended.get() {
// We block on compositing (self.handle_events() ends up calling swap_buffers)
events_loop.poll_events(|e| {
self.winit_event_to_servo_event(e);
});
stop = self.handle_events();
} else {
// We block on winit's event loop (window events)
events_loop.run_forever(|e| {
self.winit_event_to_servo_event(e);
if self.has_events() && !self.suspended.get() {
stop = self.handle_events();
}
if stop || self.window.is_animating() && !self.suspended.get() {
glutin::ControlFlow::Break
} else {
glutin::ControlFlow::Continue
if !self.window.is_animating() || self.suspended.get() {
// If there's no animations running then we block on the window event loop.
self.events_loop.borrow_mut().run_forever(|e| {
let cont = self.winit_event_to_servo_event(e);
if cont == glutin::ControlFlow::Continue {
// Note we need to be careful to make sure that any events
// that are handled during run_forever aren't re-entrant,
// since we are handling them while holding onto a mutable borrow
// of the events loop
self.handle_events();
}
cont
});
}
// Grab any other events that may have happened
self.events_loop.borrow_mut().poll_events(|e| {
self.winit_event_to_servo_event(e);
});
// If animations are running, we block on compositing
// (self.handle_events() ends up calling swap_buffers)
let stop = self.handle_events();
if stop {
break;
}