Can't get Screens in Design Preview?

[Coloryr]

10:03:18.175 [Error] 28276 <= "Unhandled exception. System.InvalidOperationException: Windowing backend wasn't properly initialized."
10:03:18.177 [Error] 28276 <= "   at Avalonia.Controls.WindowBase.get_Screens()"
10:03:18.177 [Error] 28276 <= "   at ColorMC.Gui.UI.Windows.ABaseWindow.SetWindowState() in E:\code\ColorMC\src\ColorMC.Gui\UI\Windows\ABaseWindow.cs:line 114"
10:03:18.178 [Error] 28276 <= "   at ColorMC.Gui.UI.Windows.AMultiWindow.FindGoodPos() in E:\code\ColorMC\src\ColorMC.Gui\UI\Windows\AMultiWindow.cs:line 140"
10:03:18.178 [Error] 28276 <= "   at ColorMC.Gui.UI.Windows.AMultiWindow.InitMultiWindow(BaseUserControl con) in E:\code\ColorMC\src\ColorMC.Gui\UI\Windows\AMultiWindow.cs:line 62"
10:03:18.178 [Error] 28276 <= "   at ColorMC.Gui.UI.Windows.MultiWindow..ctor(BaseUserControl con) in E:\code\ColorMC\src\ColorMC.Gui\UI\Windows\MultiWindow.axaml.cs:line 22"
10:03:18.179 [Error] 28276 <= "   at ColorMC.Gui.Manager.WindowManager.ShowWindow(BaseUserControl con) in E:\code\ColorMC\src\ColorMC.Gui\Manager\WindowManager.cs:line 212"
10:03:18.179 [Error] 28276 <= "   at ColorMC.Gui.Manager.WindowManager.AWindow(BaseUserControl con, Boolean newwindow) in E:\code\ColorMC\src\ColorMC.Gui\Manager\WindowManager.cs:line 238"
10:03:18.179 [Error] 28276 <= "   at ColorMC.Gui.Manager.WindowManager.ShowMain() in E:\code\ColorMC\src\ColorMC.Gui\Manager\WindowManager.cs:line 366"
10:03:18.179 [Error] 28276 <= "   at ColorMC.Gui.Manager.WindowManager.Init(String path) in E:\code\ColorMC\src\ColorMC.Gui\Manager\WindowManager.cs:line 120"
10:03:18.180 [Error] 28276 <= "   at ColorMC.Gui.App.OnFrameworkInitializationCompleted() in E:\code\ColorMC\src\ColorMC.Gui\App.axaml.cs:line 103"
10:03:18.180 [Error] 28276 <= "   at Avalonia.AppBuilder.SetupUnsafe()"
10:03:18.180 [Error] 28276 <= "   at Avalonia.AppBuilder.Setup()"
10:03:18.182 [Error] 28276 <= "   at Avalonia.AppBuilder.SetupWithoutStarting()"
10:03:18.182 [Error] 28276 <= "   at Avalonia.DesignerSupport.Remote.RemoteDesignerEntryPoint.AppInitializer.ConfigureApp(IAvaloniaRemoteTransportConnection transport, CommandLineArgs args, Object obj)"
10:03:18.182 [Error] 28276 <= "   at Avalonia.DesignerSupport.Remote.RemoteDesignerEntryPoint.Main(String[] cmdline)"
10:03:18.183 [Error] 28276 <= "   at Avalonia.Designer.HostApp.Program.Main(String[] args)"

https://github.com/Coloryr/ColorMC/blob/9c0fe2d4e543e38d7d26c06f57a3f77f194c832c/src/ColorMC.Gui/UI/Windows/ABaseWindow.cs#L114

[thevortexcloud]

The designer uses a special backend from memory. Not sure if the Screen stuff is even implemented properly?

[maxkatz6]

It should be https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.DesignerSupport/Remote/Stubs.cs#L245

[thevortexcloud]

Hmm, well it looks like that error can only happen if the screens are null.

Avalonia/src/Avalonia.Controls/WindowBase.cs

Lines 112 to 113 in 282f844

	public new Screens Screens => base.Screens
	?? throw new InvalidOperationException("Windowing backend wasn't properly initialized.");

But I can't see how it can be unless I am not reading the right code/this method is just not being called:

Avalonia/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs

Lines 97 to 110 in 680a5e2

	public override object TryGetFeature(Type featureType)
	{
	if (featureType == typeof(IStorageProvider))
	{
	return new NoopStorageProvider();
	}
	if (featureType == typeof(IScreenImpl))
	{
	return new ScreenStub();
	}
	return base.TryGetFeature(featureType);
	}

But It looks like it should always be getting called:

Avalonia/src/Avalonia.Controls/TopLevel.cs

Lines 556 to 560 in 680a5e2

	/// <summary>
	/// Gets platform screens implementation.
	/// </summary>
	public Screens? Screens => _screens ??=
	PlatformImpl?.TryGetFeature<IScreenImpl>() is { } screenImpl ? new Screens(screenImpl) : null;

So just from doing a brief look at the code, I am not clear what's happening here.