[Linux] Gtk-CRITICAL **: 22:23:23.129: gtk_main_quit: assertion 'main_loops != NULL' failed

[ianmjones]

Description

When running an app built with Wails v2.0.0-beta.42 (and some earlier versions), whether as a built binary or via wails dev, when the app is quit, the following is displayed on the console:

Gtk-CRITICAL **: 22:23:23.129: gtk_main_quit: assertion 'main_loops != NULL' failed

To Reproduce

1. Update to wails v2.0.0-beta.42
2. wails init -t svelte -n wailsv2b42
3. cd wailsv2b42
4. wails build
5. build/bin/wailsv2b42
6. Quit the app.

Expected behaviour

No critical error displayed on console when app quits.

Screenshots

No response

Attempted Fixes

No response

System Details

Wails CLI v2.0.0-beta.42

Scanning system - Please wait (this may take a long time)...Done.

System
------
OS:             NixOS
Version:        22.11
ID:             nixos
Go Version:     go1.18.4
Platform:       linux
Architecture:   amd64

Wails
------
Version:                v2.0.0-beta.42
Package Manager:        nixpkgs

Dependency      Package Name    Status          Version
----------      ------------    ------          -------
*docker         nixos.docker    Installed       20.10.17
gcc             nixos.gcc       Installed       11.3.0
libgtk-3        nixos.gtk3      Installed       3.24.34
libwebkit       nixos.webkitgtk Installed       2.36.4
npm             nixos.nodejs    Installed       16.15.0
*nsis           nixos.nsis      Available       3.06.1
pkg-config      nixos.pkg-configInstalled       0.29.2
*upx            nixos.upx       Installed       3.96

* - Optional Dependency

Diagnosis
---------
Your system is ready for Wails development!
Optional package(s) installation details:
  - nsis: nix-env -iA nixos.nsis



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Additional context

No response

[leaanthony]

Potentially using g_application_quit() instead of gtk_main() may fix this: https://stackoverflow.com/questions/36905118/code-cannot-exit-from-gtk-application-apparently-no-message-loops

Just need to test that the Go code continues to run after calling this.

[stffabi]

The problem is frontend.Quit is called two times. The first time it is called e.g. when clicking the close button on the window. This call successfully executes gtk_main_quit. Then a second call to frontend.Quit will be initiated by the app.Shutdown method which is called after frontend.Run returns.

wails/v2/internal/appng/app_production.go

Lines 36 to 48 in 6e0c2f7

	func (a *App) Shutdown() {
	if a.shutdownCallback != nil {
	a.shutdownCallback(a.ctx)
	}
	a.frontend.Quit()
	}
	func (a *App) Run() error {
	err := a.frontend.Run(a.ctx)
	a.Shutdown()
	return err
	}

This second call will then issue the assertion because the main_loop has already been finished. This has been introduced with PR #1488

[leaanthony]

I think this one is covered by the PR and has been tested but not merged. Closing this to reduce noise 👍