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eframe: Switch to winit ApplicationManager api #4709

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The next version of winit will remove the run APIs: rust-windowing/winit#3683. This pretty extensively breaks code like

event_loop.run_on_demand(|event, event_loop_window_target| {
crate::profile_scope!("winit_event", short_event_description(&event));
log::trace!("winit event: {event:?}");
if matches!(event, winit::event::Event::AboutToWait) {
return; // early-out: don't trigger another wait
}
let event_result = match &event {
winit::event::Event::LoopExiting => {
// On Mac, Cmd-Q we get here and then `run_on_demand` doesn't return (despite its name),
// so we need to save state now:
log::debug!("Received Event::LoopExiting - saving app state…");
winit_app.save_and_destroy();
return;
}
winit::event::Event::WindowEvent {
event: winit::event::WindowEvent::RedrawRequested,
window_id,
} => {
windows_next_repaint_times.remove(window_id);
winit_app.run_ui_and_paint(event_loop_window_target, *window_id)
}
winit::event::Event::UserEvent(UserEvent::RequestRepaint {
when,
frame_nr,
viewport_id,
}) => {
let current_frame_nr = winit_app.frame_nr(*viewport_id);
if current_frame_nr == *frame_nr || current_frame_nr == *frame_nr + 1 {
log::trace!("UserEvent::RequestRepaint scheduling repaint at {when:?}");
if let Some(window_id) = winit_app.window_id_from_viewport_id(*viewport_id) {
EventResult::RepaintAt(window_id, *when)
} else {
EventResult::Wait
}
} else {
log::trace!("Got outdated UserEvent::RequestRepaint");
EventResult::Wait // old request - we've already repainted
}
}
winit::event::Event::NewEvents(winit::event::StartCause::ResumeTimeReached {
..
}) => {
log::trace!("Woke up to check next_repaint_time");
EventResult::Wait
}
event => match winit_app.on_event(event_loop_window_target, event) {
Ok(event_result) => {
log::trace!("event_result: {event_result:?}");
event_result
}
Err(err) => {
log::error!("Exiting because of error: {err} during event {event:?}");
returned_result = Err(err);
EventResult::Exit
}
},
};
match event_result {
EventResult::Wait => {
event_loop_window_target.set_control_flow(ControlFlow::Wait);
}
EventResult::RepaintNow(window_id) => {
log::trace!(
"RepaintNow of {window_id:?} caused by {}",
short_event_description(&event)
);
if cfg!(target_os = "windows") {
// Fix flickering on Windows, see https://github.com/emilk/egui/pull/2280
windows_next_repaint_times.remove(&window_id);
winit_app.run_ui_and_paint(event_loop_window_target, window_id);
} else {
// Fix for https://github.com/emilk/egui/issues/2425
windows_next_repaint_times.insert(window_id, Instant::now());
}
}
EventResult::RepaintNext(window_id) => {
log::trace!(
"RepaintNext of {window_id:?} caused by {}",
short_event_description(&event)
);
windows_next_repaint_times.insert(window_id, Instant::now());
}
EventResult::RepaintAt(window_id, repaint_time) => {
windows_next_repaint_times.insert(
window_id,
windows_next_repaint_times
.get(&window_id)
.map_or(repaint_time, |last| (*last).min(repaint_time)),
);
}
EventResult::Exit => {
log::debug!("Asking to exit event loop…");
winit_app.save_and_destroy();
event_loop_window_target.exit();
return;
}
}
let mut next_repaint_time = windows_next_repaint_times.values().min().copied();
windows_next_repaint_times.retain(|window_id, repaint_time| {
if Instant::now() < *repaint_time {
return true; // not yet ready
};
next_repaint_time = None;
event_loop_window_target.set_control_flow(ControlFlow::Poll);
if let Some(window) = winit_app.window(*window_id) {
log::trace!("request_redraw for {window_id:?}");
let is_minimized = window.is_minimized().unwrap_or(false);
if is_minimized {
false
} else {
window.request_redraw();
true
}
} else {
log::trace!("No window found for {window_id:?}");
false
}
});
if let Some(next_repaint_time) = next_repaint_time {
event_loop_window_target.set_control_flow(ControlFlow::WaitUntil(next_repaint_time));
};
})?;
. I'm not sure how much effort it will be to fix, but it might make sense to do that sooner-rather-than-later.

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