Skia Targets allows to change the UI on Background thread

[pedrojesus-work]

Current behavior

If I try to edit a TextBox.Text on a Background thread that will work and the text will be updated.

Expected behavior

Some exception saying that I can't change the UI outside the UIThread.

How to reproduce it (as minimally and precisely as possible)

In order to run the issue, just try out this sample. IF you run the Windows target it will fail when the code hits ContinueWith, on Skia targets it will work.
GTKUIBackgroundThread.zip

Workaround

None

Works on UWP/WinUI

Yes

Environment

Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia

NuGet package version(s)

No response

Affected platforms

No response

IDE

No response

IDE version

No response

Relevant plugins

No response

Anything else we need to know?

No response

[jeromelaban]

@pedrojesus-work this is fixed in the latest 5.2 builds, background operations are blocked. Is this a version you tested with?

[pedrojesus-work]

@jeromelaban, no it's 5.1.87, I'll try the 5.2 and see how that goes

[pedrojesus-work]

Changed the sdk version to 5.2.0 "Uno.Sdk": "5.2.0-dev.1921", and still reproduce the error

[jeromelaban]

@Youssef1313 could you take a look?

[Youssef1313]

@jeromelaban The added check was in a specific code path that's known to be very problematic when accessed concurrently. It doesn't cover all SetValue calls, but only subset that end up calling DependencyProperty.GetProperty (e.g, it happens for inherited properties for example).

To fix this issue, the check will need to happen in InnerSetValue, but that's a larger breaking change than what was recently introduced. I'll open a PR anyway.