[bug] Panic on Windows if a native window is created

[dceddia]

Describe the bug

When a native window is created with AppHandle::create_tao_window, then doing anything to the app causes it to panic. I think anything that causes a window event causes a panic.

With tauri-1.0.0-rc.4 and tao 0.6.4 this was working fine, but after updating to tauri-1.0.0-rc.6 and tao 0.7.0 it's started panicing.

Reproduction

This repo has a minimal reproduction: https://github.com/dceddia/tauri-window-hang-repro

See the stack trace below. I think the relevant part is #5 - tauri-runtime-wry-0.3.5\src\lib.rs:2447, here. That section looks like it's handling window events, and it seems to make the assumption that an event will definitely come from a window with a webview.

The webview_id_map, too, assumes that a call to get() will find an associated window, and unwraps the Option, which causes the panic.

Event::WindowEvent {
    event, window_id, ..
} => {
    let window_id = webview_id_map.get(&window_id);
    ...

Expected behavior

No panic :)

Platform and versions

$ yarn tauri info
yarn run v1.22.17
$ tauri info

Environment
  › OS: Windows 10.0.19044 X64
  › Webview2: 100.0.1185.36
  › MSVC:
      - Visual Studio Build Tools 2019
      - Visual Studio Community 2019
  › Node.js: 16.9.0
  › npm: 7.22.0
  › pnpm: Not installed!
  › yarn: 1.22.17
  › rustup: 1.24.3
  › rustc: 1.58.1
  › cargo: 1.58.0
  › Rust toolchain: stable-x86_64-pc-windows-msvc

Packages
  › @tauri-apps/cli [NPM]: 1.0.0-rc.7
  › @tauri-apps/api [NPM]: 1.0.0-rc.3
  › tauri [RUST]: 1.0.0-rc.6,
  › tauri-build [RUST]: 1.0.0-rc.5,
  › tao [RUST]: 0.7.0,
  › wry [RUST]: 0.14.0,

App
  › build-type: bundle
  › CSP: unset
  › distDir: ../public
  › devPath: http://localhost:8080/
  › framework: Svelte
  › bundler: Rollup

App directory structure
  ├─ .git
  ├─ .vscode
  ├─ node_modules
  ├─ public
  ├─ src
  └─ src-tauri

Stack trace

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tauri-runtime-wry-0.3.5\src\lib.rs:128:36
stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\/library\std\src\panicking.rs:498
   1: core::panicking::panic_fmt
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\/library\core\src\panicking.rs:107
   2: core::panicking::panic
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\/library\core\src\panicking.rs:48
   3: enum$<core::option::Option<ref$<u64> >, 1, 18446744073709551615, Some>::unwrap<ref$<u64> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\core\src\option.rs:746
   4: tauri_runtime_wry::WebviewIdStore::get
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tauri-runtime-wry-0.3.5\src\lib.rs:128
   5: tauri_runtime_wry::handle_event_loop<enum$<tauri::EventLoopMessage> >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tauri-runtime-wry-0.3.5\src\lib.rs:2447
   6: tauri_runtime_wry::impl$49::run::closure$0<enum$<tauri::EventLoopMessage>,tauri::app::impl$17::run::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tauri-runtime-wry-0.3.5\src\lib.rs:1954
   7: tao::platform_impl::platform::event_loop::impl$2::run_return::closure$0<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > >,tauri_runtime_wry::impl$49::run::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:225
   8: alloc::boxed::impl$45::call_mut<tuple$<enum$<tao::event::Event<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > > >,ref_mut$<enum$<tao::event_loop::ControlFlow> > >,dyn$<core::ops::function::FnMut<tuple$<enum$<tao::event::Event<enum$<ta
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\alloc\src\boxed.rs:1701
   9: tao::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure$0<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop\runner.rs:249
  10: core::panic::unwind_safe::impl$23::call_once<tuple$<>,tao::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure$0>
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\core\src\panic\unwind_safe.rs:271
  11: std::panicking::try::do_call<core::panic::unwind_safe::AssertUnwindSafe<tao::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure$0>,tuple$<> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\std\src\panicking.rs:406
  12: core::option::impl$41::from_residual<tuple$<alloc::string::String,alloc::string::String> >
  13: std::panicking::try<tuple$<>,core::panic::unwind_safe::AssertUnwindSafe<tao::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure$0> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\std\src\panicking.rs:370
  14: std::panic::catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<tao::platform_impl::platform::event_loop::runner::impl$3::call_event_handler::closure$0>,tuple$<> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\std\src\panic.rs:133
  15: tao::platform_impl::platform::event_loop::runner::EventLoopRunner<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::catch_unwind<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > >,tuple$<>,tao::platform_impl::platform
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop\runner.rs:155
  16: tao::platform_impl::platform::event_loop::runner::EventLoopRunner<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::call_event_handler<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop\runner.rs:241
  17: tao::platform_impl::platform::event_loop::runner::EventLoopRunner<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::send_event<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop\runner.rs:223
  18: tao::platform_impl::platform::event_loop::SubclassInput<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::send_event<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:107
  19: tao::platform_impl::platform::event_loop::public_window_callback_inner::closure$6<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:1632
  20: core::ops::function::FnOnce::call_once<tao::platform_impl::platform::event_loop::public_window_callback_inner::closure$6,tuple$<> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\core\src\ops\function.rs:227
  21: core::panic::unwind_safe::impl$23::call_once<tuple$<>,tao::platform_impl::platform::event_loop::public_window_callback_inner::closure$6>
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\core\src\panic\unwind_safe.rs:271
  22: std::panicking::try::do_call<core::panic::unwind_safe::AssertUnwindSafe<tao::platform_impl::platform::event_loop::public_window_callback_inner::closure$6>,tuple$<> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\std\src\panicking.rs:406
  23: core::option::impl$41::from_residual<tuple$<alloc::string::String,alloc::string::String> >
  24: std::panicking::try<tuple$<>,core::panic::unwind_safe::AssertUnwindSafe<tao::platform_impl::platform::event_loop::public_window_callback_inner::closure$6> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\std\src\panicking.rs:370
  25: std::panic::catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<tao::platform_impl::platform::event_loop::public_window_callback_inner::closure$6>,tuple$<> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\std\src\panic.rs:133
  26: tao::platform_impl::platform::event_loop::runner::EventLoopRunner<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::catch_unwind<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > >,tuple$<>,tao::platform_impl::platform
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop\runner.rs:155
  27: tao::platform_impl::platform::event_loop::public_window_callback_inner<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:1978
  28: tao::platform_impl::platform::event_loop::public_window_callback<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:848
  29: DefSubclassProc
  30: DefSubclassProc
  31: CallWindowProcW
  32: DispatchMessageW
  33: SendMessageTimeoutW
  34: KiUserCallbackDispatcher
  35: NtUserGetMessage
  36: GetMessageW
  37: windows::Windows::Win32::UI::WindowsAndMessaging::GetMessageW<windows::Windows::Win32::Foundation::HWND>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\windows-0.30.0\src\Windows\Win32\UI\WindowsAndMessaging\mod.rs:4336
  38: tao::platform_impl::platform::event_loop::EventLoop<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::run_return<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > >,tauri_runtime_wry::impl$49::run::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:236
  39: tao::platform_impl::platform::event_loop::EventLoop<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::run<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > >,tauri_runtime_wry::impl$49::run::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\platform_impl\windows\event_loop.rs:209
  40: tao::event_loop::EventLoop<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > > >::run<enum$<tauri_runtime_wry::Message<enum$<tauri::EventLoopMessage> > >,tauri_runtime_wry::impl$49::run::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tao-0.7.0\src\event_loop.rs:177
  41: tauri_runtime_wry::impl$49::run<enum$<tauri::EventLoopMessage>,tauri::app::impl$17::run::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tauri-runtime-wry-0.3.5\src\lib.rs:1953
  42: tauri::app::App<tauri_runtime_wry::Wry<enum$<tauri::EventLoopMessage> > >::run<tauri_runtime_wry::Wry<enum$<tauri::EventLoopMessage> >,app::main::closure$0>
             at C:\Users\Dave\.cargo\registry\src\github.com-1ecc6299db9ec823\tauri-1.0.0-rc.6\src\app.rs:614
  43: app::main
             at .\src\main.rs:15
  44: core::ops::function::FnOnce::call_once<void (*)(),tuple$<> >
             at /rustc/db9d1b20bba1968c1ec1fc49616d4742c1725b4b\library\core\src\ops\function.rs:227
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
[0410/215004.211:ERROR:window_impl.cc(114)] Failed to unregister class Chrome_WidgetWin_0. Error = 0

Additional context

I'm not sure if I'm creating this window at the right time, or if I should be depending on tao directly here or if there's a better way, so let me know if anything could be better.

The goal of having this native window is to make an empty overlay that I can draw in with wgpu.

[lucasfernog]

Thanks for the report, fix will be published soon. Really interesting use case btw :)

[dceddia]

Awesome, thanks Lucas!

[dceddia]

@lucasfernog I finally got around to updating, and this panic is fixed, but now there's a deadlock 😅 It's around the same place, right here when it receives a WindowEvent:

    Event::WindowEvent {
      event, window_id, ..
    } => {
      let window_id = webview_id_map.get(&window_id); // <<< hangs here

The event it's hanging on is Moved, and I imagine that both the parent and my child window are getting the Moved event and then both try to lock the webview_id_map. Does this mean I'm creating the window on the wrong thread or something? Do I need to give it its own event loop?

I've put in a bunch of println's in my code to narrow it down and it seems like it's able to at least create the window and send + finish a couple resize events, so it's not immediately broken, but from a user standpoint it looks like the app hangs immediately on startup. My code that creates the window looks like

pub fn add_overlay(app_handle: &AppHandle) -> impl OverlayView {
    let window = app_handle
        .get_window("main")
        .expect("failed to get main window");

    let hwnd = window.hwnd().expect("failed to get HWND");
    let overlay = app_handle
        .create_tao_window(move || {
            let window_builder = tao::window::WindowBuilder::new()
                .with_always_on_top(false)
                .with_decorations(false)
                .with_resizable(false)
                .with_visible(false)
                .with_position(tao::dpi::LogicalPosition::<u32>::new(30, 30))
                .with_owner_window(hwnd) 
                .with_inner_size(tao::dpi::LogicalSize::<u32>::new(200, 200));

            ("WGPU Target".to_string(), window_builder)
        })
        .expect("failed to create overlay window");
...
}

I put this as a reply here since there's already some context, but I can create a separate issue if that makes more sense.

[lucasfernog]

@dceddia can you file a separate issue with an example I can use to reproduce it? tried with your tauri-window-hang-repro but couldn't reproduce it. Thanks!

[dceddia]

Ah, sorry - should've tried that first! I just went to update the example and realized that the overlay didn't have much to do with it.

The problem was that I was making changes to the window in a tauri::command that wasn't async. Making the commands async fixed the issue. I had the same problem (hung window) when I tried to create a new window in a non-async command. I guess window operations need to happen in another thread!

[lucasfernog]

Can you file an issue with your command? If it doesn't work in the main thread it's a bug.