[BUG] Conflict between popups and AppShell Title

[brendanrempel]

Is there an existing issue for this?

• I have searched the existing issues

Did you read the "Reporting a bug" section on Contributing file?

• I have read the "Reporting a bug" section on Contributing file: https://github.com/CommunityToolkit/Maui/blob/main/CONTRIBUTING.md#reporting-a-bug

Current Behavior

This appears to be a conflict between the latest Popup functionality and AppShell/TitleBar. While the two operate correctly, they are causing a conflict that causes the application to crash when exiting. No stack dump is available and can be reproduced on a hello world app. Specifically, the unhandled exception occurs:

Exception: Value does not fall within the expected range.
Message: Invalid window; it belongs to other thread.

Expected Behavior

Exiting the application should not have an error.

Steps To Reproduce

1. Create a MAUI project on Windows, DotNet9. Target the build/debug for localhost.
2. I believe this is optional, but in NUGET, perform all updates (should only be a couple)
3. Add Community Toolkit needed for Popups
4. Create a new view, change the parent to Popup.
5. I changed the popup constructor to accept an action, call the action on button click
6. In MainPage.xaml.cs, add this code to bring up the popup:

`protected override async void OnAppearing()
{
if (!firstLoad) return;

firstLoad = false;

CancellationToken token = new();

var popup = new PageTest(async () =>
{
await this.ClosePopupAsync(token);
});

await this.ShowPopupAsync(
//await Shell.Current.ShowPopupAsync(
popup,
new PopupOptions(),
token);
}`

7. Run the app, close the popup, then close the app. It should close correctly.
8. Change this method in the App.xaml.cs:

protected override Window CreateWindow(IActivationState? activationState) { return new Window(new AppShell()) { // BUG - this option causes popups to crash TitleBar = new TitleBar() { Title = "title", Subtitle = "subject" } }; }

9. Repeat running the app. Close the popup, close the app.
10. An unhandled exception should occur.
11. Alternatively, comment out the popup also fixes the crash.

Link to public reproduction project repository

https://github.com/brendanrempel/popupcrash/tree/main/MauiPopup

Environment

- .NET MAUI CommunityToolkit: 12.2.0
- OS: Windows 24H2 26120.5770
- .NET MAUI: DotNet 9
- Version 17.14.14

Anything else?

Duplicate of 2877 which was closed without resolving.

[brendanrempel]

Not sure if this helps, I debugged from source but was unable to track down the root cause. It might be under MAUI in WinUI.

The workaround is to not use Title/SubTitle but it would be good to fix. This kind of bug is going to throw off anybody updating to the latest CommunityToolkit forcing them to comment everything out until the crashing stops because the debugger isn't pointing to the actual bug.

[bijington]

One thing to try would be to create a ContentPage, set Shell.PresentationMode to Modal with a title bar and navigate to it. If that fails then it is a MAUI issue

[cjorgens79]

I am also running into this issue, i don't use Shell, so its not a shell specific thing. The problem is definitely caused by having a combination of a TitleBar on the window and using the MCT popup.

Its really as simple as having a custom TitleBar on the window, displaying a MCT popup at some point and then closing the application.

I have created a really simple repo of the issue here (which doesn't use shell)
https://github.com/cjorgens79/MauiMCTPopupWithWindowTitleBarIssue

Not sure if its the MCT popup causing the issue, or the TitleBar.. so unsure whether this is an issue for this repo or for the main MAUI repo?

Just for reference and search-ability, the unhandled exception that occurs is in app.g.i.cs and is
System.ArgumentException: Value does not fall within the expected range. at WinRT.ExceptionHelpers.<ThrowExceptionForHR>g__Throw|38_0(Int32 hr) at ABI.Microsoft.UI.Input.IInputNonClientPointerSourceStaticsMethods.GetForWindowId(IObjectReference _obj, WindowId windowId) at Microsoft.UI.Input.InputNonClientPointerSource.GetForWindowId(WindowId windowId) at Microsoft.Maui.Platform.WindowRootView.UpdateTitleBarContentSize() at Microsoft.Maui.Platform.WindowRootView.PlatformView_LayoutUpdated(Object sender, Object e) at WinRT.GenericTypeInstantiations.Windows_Foundation_EventHandler_1_object.Do_Abi_Invoke(IntPtr thisPtr, IntPtr sender, IntPtr args)

[cjorgens79]

FYI i have now posted a bug for this report on the MAUI repo too given the stack trace seems to point to MAUI internals

dotnet/maui#32194

[brendanrempel]

I think neither CommunityToolkit not Maui want to investigate given that my bug is still unverified and Maui wants a repro without MCT's implementation of the popup. If we can get an actual stack trace of the bounds exception, that would help. Otherwise this bug is in a standoff.

[cjorgens79]

I've now proven its a MAUI bug and have given them a repo without MCT to work from.

[TheCodeTraveler]

Thanks for confirming @cjorgens79!