How to properly persist WebView state at exit?

[CrendKing]

I want to persist some state from the frontend right before the app exits. It doesn't seem to be as easy as I expect.

My initial attempt is simply create a window.onbeforeunload handler and let it call a command. It doesn't work because this is not an unload event. That event is usually triggered on refresh.

Second attempt is to emit an message to frontend inside WindowEvent::CloseRequested handler, block until for the Javascript to call my command, unblock and let the app exit. It doesn't work (I think) because sleeping in the event handler causes the whole event loop to stop, thus my command will never be triggered.

I got it work by preventing the WindowEvent::CloseRequested from closing by api.prevent_close(), emit the message, and finally app_handle.exit() inside the command. What's wrong is that I always get an error message in the console:

[0816/225145.587:ERROR:window_impl.cc(114)] Failed to unregister class Chrome_WidgetWin_0. Error = 0

I assume we shouldn't call app_handle.exit() inside a command?

Is there a more standard way to do this?

[abisar]

If you're handling the state from javascript and it has nothing to do with rust, simply handle it only on javasscript side:
https://tauri.app/v1/api/js/classes/window.webviewwindow/#oncloserequested

What's wrong is that I always get an error message in the console:

https://bugs.chromium.org/p/chromium/issues/detail?id=113008
I wouldn't worry about it.