Running egui app outside main thread

[kubo-von]

Hello, I've created my app by modifying the eframe native template and when trying to run it in a new thread from other crate using ThreadPool, I get this:

thread '<unnamed>' panicked at 'Initializing the event loop outside of the main thread is a significant cross-platform compatibility hazard. If you really, absolutely need to create an EventLoop on a different thread, please use the EventLoopExtUnix::new_any_thread function.'

Is there any simple way of fixing it without patching egui or eframe ? I really only need this to work on Linux for now.
Thanks a lot!

[willser]

Seems there no way.Maybe you could run them independent and communicate between them using other protocols instead of channel.

[exbucks]

@kubo-von This package does not support running a even loop outside of the main thread, and I suggest you to use winsafe. It supports that well.

[ghost]

Actually there is a way under Linux to do this:
Add this to your Cargo.toml

[dependencies.winit]
default-features = false
features = ["wayland"]
version = "0.28.7"

[dependencies.eframe]
default-features = false
features = ["default_fonts", "glow", "wayland"]
version = "0.23.0"

Then do this in rust:

use std::thread;

use eframe::egui;
use eframe::EventLoopBuilderHook;
use winit::platform::wayland::EventLoopBuilderExtWayland;

fn main() {
	let _handle = thread::spawn(|| {
		let event_loop_builder: Option<EventLoopBuilderHook> = Some(Box::new(|event_loop_builder| {
			event_loop_builder.with_any_thread(true);
		}));
		let native_options = eframe::NativeOptions {
			event_loop_builder,
			..Default::default()
		};
		eframe::run_simple_native("App", native_options, update).expect("failed to run app");
	});
	loop {}
}

fn update(ctx: &eframe::egui::Context, _: &mut eframe::Frame) {
	egui::CentralPanel::default().show(ctx, |ui| {
		ui.heading("hello");
	});
}

[buxx]

I have an error with this solution. Import seems not working for with_any_thread trait :

error[E0599]: no method named `with_any_thread` found for mutable reference `&mut eframe::EventLoopBuilder<eframe::UserEvent>` in the current scope
  --> gui/src/window/mod.rs:25:36
   |
25 |                 event_loop_builder.with_any_thread(true);
   |                                    ^^^^^^^^^^^^^^^ method not found in `&mut EventLoopBuilder<UserEvent>`
   |
   = help: items from traits can only be used if the trait is in scope
help: the following traits which provide `with_any_thread` are implemented but not in scope; perhaps you want to import one of them
   |
1  + use winit::platform::wayland::EventLoopBuilderExtWayland;
   |
1  + use winit::platform::wayland::EventLoopBuilderExtWayland;
   |
1  + use winit::platform::x11::EventLoopBuilderExtX11;
   |

warning: unused import: `winit::platform::wayland::EventLoopBuilderExtWayland`
 --> gui/src/window/mod.rs:3:5
  |
3 | use winit::platform::wayland::EventLoopBuilderExtWayland;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

[tomas-vancura-nlk]

I ran into the same issue, please double check that your version of egui/eframe is new enough to itself depend on winit v30+, which introduces the EventLoopBuiilderExtX11/Wayland traits. (e.g. egui v0.29.1 works but v0.28.1 doesn't).

[Levitanus]

I've stopped on a solution, when the main thread spawns a separate executable GUI process, and communicates with it on websockets. In case of panic in main ‒ both are being killed.