Fix multi-window interaction with the single process work

[halgari]

Fixes #968 and #965.

This fixes the above bugs by reworking how we open multiple windows. Namely:

• Whenever a window opens, create a main process director token to keep the single process director alive
• Startup Avalonia in a mode that only shuts down when a cancellation token exits
• Link that cancellation token to the single process director cancellation token
• Only run the Avalonia startup and the first window on the creation thread, run the rest via the UI dispatcher (this fixes the Regression: Opening a second instance of the App doesn't create a new Window #968 regression)

[erri120]

See comments.

The app now doesn't open anymore, it like the following exists immediately:

_logger.LogInformation("Starting application loop.");
app.Run(MainThreadData.GlobalShutdownToken);
_logger.LogInformation("Application loop ended.");

00:00:01.793 [INFO] Starting UI application
00:00:02.104 [INFO] Starting application loop.
00:00:02.105 [INFO] Application loop ended.
00:00:02.105 [DEBUG] Startup handler returned 0

Edit: MainThreadData.GlobalShutdownToken appears to already be canceled.

[halgari]

Is this in debug mode? Works fine in debug without a debugger attached on my machine (dotnet run). Looks like with a debugger attached it no longer works, I'll look into that

[erri120]

Is this in debug mode? Works fine in debug without a debugger attached on my machine (dotnet run). Looks like with a debugger attached it no longer works, I'll look into that

NexusMods.App/src/NexusMods.App/StartupHandler.cs

Lines 50 to 63 in 9232312

	// Otherwise we need to startup Avalonia. This results in lazy loading of avalonia
	MainThreadData.MainThreadActions.Enqueue( () =>
	{
	tcs.SetResult(0);
	if (!MainThreadData.IsStartingThread)
	{
	logger.LogCritical("UI should only start from the main thread");
	return -1;
	}
	provider.GetRequiredService<NxmRpcListener>();
	Startup.Main(provider, []);
	return 0;
	});

tcs.SetResult(0) will "finish" StartUiWindowAsync which finishes await startup.Start(args, _isDebug); in Program.cs.

[halgari]

This gets us up back and running. I don't like how there's two paths for the code now, where some things only happen under Debug mode, but I need to think how to better manage this in a way where the code is a bit cleaner. Perhaps a lot of this logic can be moved into the SingleProcess project

[erri120]

Multiple windows now work again, however, you're unable to close any windows. If you close a window, an exception is thrown due to AvaloniaUI/Avalonia#14437 and the window stays frozen on screen. The only way to solve this is by manually killing the main process of the app.

This wasn't an issue before. Previously, the exception from AvaloniaUI/Avalonia#14437 would just be thrown, and the window would close without issues.

[halgari]

What process are you going through to get this to happen? I just opened and closed a bunch of windows with this branch and didn't see this exception?

[erri120]

What process are you going through to get this to happen? I just opened and closed a bunch of windows with this branch and didn't see this exception?

The exception should always appear in the log, since the underlying issue AvaloniaUI/Avalonia#14437 hasn't been fixed yet.

However, the last two commits of this PR introduced another issue: the window doesn't close properly, and the main process is still running. I had to manually kill the main process before the windows disappeared. This happens when running with a debugger and without.

[halgari]

I can't get this error at all, it all cleanly shuts down for me, I'll switch over to my ubuntu machine and see if I can get it to happen there.

[Al12rs]

I'm testing the merge with main and I can reproduce on windows 11.
Make sure you have managed at least one game to create an additional workspace, I think you might need a LoadoutWorkspace to trigger the crash on close.

The issue is that when you have two windows open and close one, that one crashes on close, which in turn crashes the other window as well. For me the second window closes automatically a few seconds after the crash instead of forcing me to close it manually.

[halgari]

Ah I haven't managed a game yet, let me try that

[github-actions]

This PR conflicts with main. You need to rebase the PR before it can be merged.

[Al12rs]

@halgari The app crash on close issue was fixed in:

• Fix crash on close #1068

That should unblock work on this PR again.
The changes from main need to be merged in.

[github-actions]

This PR doesn't conflict with main anymore. It can be merged after all status checks have passed and it has been reviewed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 2.17391% with 90 lines in your changes are missing coverage. Please review.

Project coverage is 54.18%. Comparing base (ce086a3) to head (904c274).

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #972      +/-   ##
==========================================
- Coverage   54.89%   54.18%   -0.72%     
==========================================
  Files         669      669              
  Lines       22126    22177      +51     
  Branches     1710     1713       +3     
==========================================
- Hits        12147    12017     -130     
- Misses       9580     9758     +178     
- Partials      399      402       +3     

Flag	Coverage Δ
Linux	54.12% <2.17%> (-0.13%)	⬇️
Windows	?
clean_environment_tests	54.18% <2.17%> (-0.71%)	⬇️
macOS	53.52% <2.17%> (-0.17%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...rc/NexusMods.App.UI/Windows/MainWindowViewModel.cs	69.81% <ø> (-1.36%)	⬇️
src/NexusMods.App/MainThreadData.cs	0.00% <0.00%> (ø)
src/NexusMods.App/StartupHandler.cs	0.00% <0.00%> (ø)
src/NexusMods.App/Program.cs	0.00% <0.00%> (ø)
src/NexusMods.App/Startup.cs	21.31% <5.26%> (-26.69%)	⬇️

... and 28 files with indirect coverage changes

[erri120]

Running the app without an attached debugger via dotnet run, the processes remain running after closing the window.

When running the app with an attached debugger and running two instances, you get two processes, not a single process.

[Sewer56]

When Running on Linux, this PR makes it so you can't run the App in an IDE without the debugger attached.

First process spawns 2nd process, then it dies, as far as I can tell.