NullReferenceException when accessing ColorScheme in View.cs

[heinrich-ulbricht]

Describe the bug

Got a NullReferenceException in View.cs when working with message boxes.

To Reproduce

This is a currently a sporadic error and probably a timing issue. Cannot reliably reproduce. I nevertheless want to document this in case it becomes relevant/reproducible or anybody immediately sees what's up.

Expected behavior
I expect such an error not to happen.

Screenshots
Here's the debugger halting (View.cs):

And here the call stack:

>	Terminal.Gui.dll!Terminal.Gui.View.GetNormalColor() Line 3003	C#
 	Terminal.Gui.dll!Terminal.Gui.Border.DrawTitle(Terminal.Gui.View view) Line 950	C#
 	Terminal.Gui.dll!Terminal.Gui.Border.DrawChildBorder(Terminal.Gui.Rect frame, bool fill) Line 718	C#
 	Terminal.Gui.dll!Terminal.Gui.Border.DrawContent(Terminal.Gui.View view, bool fill) Line 519	C#
 	Terminal.Gui.dll!Terminal.Gui.Window.Redraw(Terminal.Gui.Rect bounds) Line 300	C#
 	Terminal.Gui.dll!Terminal.Gui.Application.Refresh() Line 943	C#
 	Terminal.Gui.dll!Terminal.Gui.Application.RunMainLoopIteration(ref Terminal.Gui.Application.RunState state, bool wait, ref bool firstIteration) Line 1024	C#
 	Terminal.Gui.dll!Terminal.Gui.Application.RunLoop(Terminal.Gui.Application.RunState state, bool wait) Line 996	C#
 	Terminal.Gui.dll!Terminal.Gui.Application.Run(Terminal.Gui.Toplevel view, System.Func<System.Exception, bool> errorHandler) Line 1172	C#
 	Terminal.Gui.dll!Terminal.Gui.MessageBox.QueryFull(bool useErrorColors, int width, int height, NStack.ustring title, NStack.ustring message, int defaultButton, Terminal.Gui.Border border, NStack.ustring[] buttons) Line 310	C#
 	Terminal.Gui.dll!Terminal.Gui.MessageBox.Query(NStack.ustring title, NStack.ustring message, NStack.ustring[] buttons) Line 58	C#
 	MyApp.dll!MyApp.LoginViewModel.TestTargetConnectionAsync() Line 217	C#

SuperView is null, thus making the ColorScheme being null when being accessed in the first screenshot.

(View.cs)

This crash-exits the app.

(Note: since SuperView is marked nullable ("?") the ColorScheme should be marked nullable as well?)

Desktop (please complete the following information):

• OS: Windows 11
• Version: dev branch from 6 days ago: 8a90453

I looked at the recent commits and could see nothing that immediately looks like fixing this.

Edit: just pulled in the latest changes and the error persists.

[heinrich-ulbricht]

The Border has a child with null ColorScheme, if that helps.

[tznind]

From the stack trace it looks like you are calling query from an async method called TestTargetConnectionAsync.

Can you please try using the follow:

Application.MainLoop.Invoke(()=>{

/*make UI changes here (including popup message boxes)*/

});

This will ensure UI code runs on the correct UI Thread

[heinrich-ulbricht]

@tznind That's it! Was just about to ask if I can just like this invoke message boxes from async methods. I can not :) Problem solved. Thank you.