Connecting/Disconnecting monitors can crash winit

[MolotovCherry]

I was writing a monitor control application (which can connect and disconnect monitors at runtime), and if you connect and disconnect monitors enough times, eventually winit will just up and crash (I'm using egui, and the window is ONLY on the main monitor which never gets disconnected).

This is reproducible, but can be very hard to cause since it's sporadic. Just keep connecting and disconnecting a secondary monitor a lot of times, eventually it'll crash. Sometimes I can't get it to, sometimes I can.

Note: This is on Windows 11. If any other info is needed, don't hesitate to ask.

I suspect that, here, the monitor is_some() when it asks, so it goes through and calls size()
eframe-0.22.0\src\native\epi_integration.rs:431

    let monitor = window.current_monitor().is_some();
    let monitor_size = if monitor {
        let size = window
            .current_monitor()
            .unwrap()
            .size()
            .to_logical::<f32>(pixels_per_point.into());
        Some(egui::vec2(size.width, size.height))
    } else {
        None
    };

Which goes into wininit, winit-0.28.6\src\platform_impl\windows\monitor.rs:186, and the monitor disappears within that short timeframe, so when get_monitor_info() is called, now it's gone

    #[inline]
    pub fn size(&self) -> PhysicalSize<u32> {
        let rc_monitor = get_monitor_info(self.0).unwrap().monitorInfo.rcMonitor;
        PhysicalSize {
            width: (rc_monitor.right - rc_monitor.left) as u32,
            height: (rc_monitor.bottom - rc_monitor.top) as u32,
        }
    }

Stacktrace

panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 1461, kind: Uncategorized, message: "Invalid monitor handle." }', C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\monitor.rs:186:51

stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library\std\src\panicking.rs:593
   1: core::panicking::panic_fmt
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library\core\src\panicking.rs:67
   2: core::result::unwrap_failed
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be/library\core\src\result.rs:1651
   3: enum2$<core::result::Result<windows_sys::Windows::Win32::Graphics::Gdi::MONITORINFOEXW,std::io::error::Error> >::unwrap<windows_sys::Windows::Win32::Graphics::Gdi::MONITORINFOEXW,std::io::error::Error>
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\core\src\result.rs:1076
   4: winit::platform_impl::platform::monitor::MonitorHandle::size
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\monitor.rs:186
   5: winit::monitor::MonitorHandle::size
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\monitor.rs:130
   6: eframe::native::epi_integration::read_window_info
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\epi_integration.rs:43
   7: eframe::native::epi_integration::EpiIntegration::update
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\epi_integration.rs:494
   8: eframe::native::run::glow_integration::impl$2::run_ui_and_paint
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:829
   9: eframe::native::run::run_and_return::closure$0<eframe::native::run::glow_integration::GlowWinitApp>
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:148
  10: winit::platform_impl::platform::event_loop::impl$3::run_return::closure$0<enum2$<eframe::native::run::UserEvent>,eframe::native::run::run_and_return::closure_env$0<eframe::native::run::glow_integration::GlowWinitApp> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop.rs:260
  11: alloc::boxed::impl$48::call_mut<tuple$<enum2$<winit::event::Event<enum2$<eframe::native::run::UserEvent> > >,ref_mut$<enum2$<winit::event_loop::ControlFlow> > >,dyn$<core::ops::function::FnMut<tuple$<enum2$<winit::event::Event<enum2$<eframe::native::run::
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\alloc\src\boxed.rs:2000
  12: winit::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure$0<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:250
  13: core::panic::unwind_safe::impl$23::call_once<tuple$<>,winit::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure_env$0<enum2$<eframe::native::run::UserEvent> > >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\core\src\panic\unwind_safe.rs:271
  14: std::panicking::try::do_call<core::panic::unwind_safe::AssertUnwindSafe<winit::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure_env$0<enum2$<eframe::native::run::UserEvent> > >,tuple$<> >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\panicking.rs:500
  15: eframe::epi::backend::impl$2::default
  16: std::panicking::try<tuple$<>,core::panic::unwind_safe::AssertUnwindSafe<winit::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure_env$0<enum2$<eframe::native::run::UserEvent> > > >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\panicking.rs:464
  17: std::panic::catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<winit::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure_env$0<enum2$<eframe::native::run::UserEvent> > >,tuple$<> >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\panic.rs:142
  18: winit::platform_impl::platform::event_loop::runner::EventLoopRunner<enum2$<eframe::native::run::UserEvent> >::catch_unwind<enum2$<eframe::native::run::UserEvent>,tuple$<>,winit::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::clos
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:157
  19: winit::platform_impl::platform::event_loop::runner::EventLoopRunner<enum2$<eframe::native::run::UserEvent> >::call_event_handler<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:242
  20: winit::platform_impl::platform::event_loop::runner::EventLoopRunner<enum2$<eframe::native::run::UserEvent> >::call_redraw_events_cleared<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:409
  21: winit::platform_impl::platform::event_loop::runner::EventLoopRunner<enum2$<eframe::native::run::UserEvent> >::move_state_to<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:358
  22: winit::platform_impl::platform::event_loop::runner::EventLoopRunner<enum2$<eframe::native::run::UserEvent> >::redraw_events_cleared<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:234
  23: winit::platform_impl::platform::event_loop::thread_event_target_callback::closure$0<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop.rs:2371
  24: core::ops::function::FnOnce::call_once<winit::platform_impl::platform::event_loop::thread_event_target_callback::closure_env$0<enum2$<eframe::native::run::UserEvent> >,tuple$<> >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\core\src\ops\function.rs:250
  25: core::panic::unwind_safe::impl$23::call_once<isize,winit::platform_impl::platform::event_loop::thread_event_target_callback::closure_env$0<enum2$<eframe::native::run::UserEvent> > >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\core\src\panic\unwind_safe.rs:271
  26: std::panicking::try::do_call<core::panic::unwind_safe::AssertUnwindSafe<winit::platform_impl::platform::event_loop::thread_event_target_callback::closure_env$0<enum2$<eframe::native::run::UserEvent> > >,isize>
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\panicking.rs:500
  27: eframe::epi::backend::impl$2::default
  28: std::panicking::try<isize,core::panic::unwind_safe::AssertUnwindSafe<winit::platform_impl::platform::event_loop::thread_event_target_callback::closure_env$0<enum2$<eframe::native::run::UserEvent> > > >
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\panicking.rs:464
  29: std::panic::catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<winit::platform_impl::platform::event_loop::thread_event_target_callback::closure_env$0<enum2$<eframe::native::run::UserEvent> > >,isize>
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\panic.rs:142
  30: winit::platform_impl::platform::event_loop::runner::EventLoopRunner<enum2$<eframe::native::run::UserEvent> >::catch_unwind<enum2$<eframe::native::run::UserEvent>,isize,winit::platform_impl::platform::event_loop::thread_event_target_callback::closure_env$0
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop\runner.rs:157
  31: winit::platform_impl::platform::event_loop::thread_event_target_callback<enum2$<eframe::native::run::UserEvent> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop.rs:2547
  32: DispatchMessageW
  33: DispatchMessageW
  34: GetClassLongW
  35: KiUserCallbackDispatcher
  36: NtUserDispatchMessage
  37: DispatchMessageW
  38: winit::platform_impl::platform::event_loop::EventLoop<enum2$<eframe::native::run::UserEvent> >::run_return<enum2$<eframe::native::run::UserEvent>,eframe::native::run::run_and_return::closure_env$0<eframe::native::run::glow_integration::GlowWinitApp> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform_impl\windows\event_loop.rs:282
  39: winit::platform::run_return::impl$0::run_return<enum2$<eframe::native::run::UserEvent>,eframe::native::run::run_and_return::closure_env$0<eframe::native::run::glow_integration::GlowWinitApp> >
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\winit-0.28.6\src\platform\run_return.rs:51
  40: eframe::native::run::run_and_return<eframe::native::run::glow_integration::GlowWinitApp>
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:132
  41: eframe::native::run::glow_integration::run_glow::closure$0
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:1043
  42: eframe::native::run::with_event_loop::closure$0<enum2$<core::result::Result<tuple$<>,enum2$<eframe::Error> > >,eframe::native::run::glow_integration::run_glow::closure_env$0>
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:116
  43: std::thread::local::LocalKey<core::cell::RefCell<enum2$<core::option::Option<winit::event_loop::EventLoop<enum2$<eframe::native::run::UserEvent> > > > > >::try_with<core::cell::RefCell<enum2$<core::option::Option<winit::event_loop::EventLoop<enum2$<eframe
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\thread\local.rs:270
  44: std::thread::local::LocalKey<core::cell::RefCell<enum2$<core::option::Option<winit::event_loop::EventLoop<enum2$<eframe::native::run::UserEvent> > > > > >::with<core::cell::RefCell<enum2$<core::option::Option<winit::event_loop::EventLoop<enum2$<eframe::na
             at /rustc/5680fa18feaa87f3ff04063800aec256c3d4b4be\library\std\src\thread\local.rs:246
  45: eframe::native::run::with_event_loop<enum2$<core::result::Result<tuple$<>,enum2$<eframe::Error> > >,eframe::native::run::glow_integration::run_glow::closure_env$0>
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:109
  46: eframe::native::run::glow_integration::run_glow
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\native\run.rs:1040
  47: eframe::run_native
             at C:\Users\<user>\.cargo\registry\src\index.crates.io-6f17d22bba15001f\eframe-0.22.0\src\lib.rs:220

[MolotovCherry]

If anyone is ever affected, this patch works for now (no guarantee it's correct though, but it works enough)

# patch bug which causes egui crash when changing monitors
[patch.crates-io]
winit = { path = "path/to/vendored/winit" }

    pub fn size(&self) -> PhysicalSize<u32> {
        let Ok(rc_monitor) = get_monitor_info(self.0) else {
            return PhysicalSize {
                width: 0,
                height: 0,
            };
        };

        let rc_monitor = rc_monitor.monitorInfo.rcMonitor;

        PhysicalSize {
            width: (rc_monitor.right - rc_monitor.left) as u32,
            height: (rc_monitor.bottom - rc_monitor.top) as u32,
        }
    }

[fredizzimo]

I think this might be an issue on Wayland as well

• Crash when external display is disconnected in Wayland neovide/neovide#2066

But it might also be some error condition that we don't handle properly inside Neovide. I will investigate that in more depth a bit later, but I'm reporting it here first in case you see the issue immediately. There does not seem to be any panics on our main thread, so my guess is that the main event loop either hangs or even more likely just exits, causing the other threads to panic since there's no receiver for the channel.

[bleonard252]

I think this is related to that issue but not quite. OP is talking about a window on the main monitor; it seems to disappear consistently if it's on an external monitor that gets unplugged, at least in neovide/neovide#2066.