Received unexpected nullPtr in "windowGet".

[Magicloud]

This might be a bug in the introspection data, or perhaps a use-after-free bug.
If in doubt, please report it at
        https://github.com/haskell-gi/haskell-gi/issues
CallStack (from HasCallStack):
  checkUnexpectedReturnNULL, called at ./GI/Wnck/Objects/Window.hs:6230:5 in gi-wnck-3.0.8-975HXvshBOwJHSsSkhyvoF:GI.Wnck.Objects.Window
  windowGet, called at src/X11.hs:16:43 in clipper-0.1.0.0-JCPHnGWuHrDJyDFlArW9uN:X11

OS: ArchLinux

Some system packages versions:

libwnck3 3.36.0-1
gtk3 1:3.24.21-1

Source: https://github.com/Magicloud/clipper

Tried #getEffectiveToplevel before castTo X11Window. No luck

Also using traceShowId to see the XID passing to windowGet, it is a reasonable number, but nothing like the window ID reported by xprop tool.

[Magicloud]

Not sure if the problem is triggered by my usage of WNCK. Per the doc, windowGet returns a preexisting WNCK window. Maybe not suit my case.

[garetxe]

Thanks for the report!

The immediate cause of the crash is that the function is returning NULL, but the introspection data says that the function cannot return NULL. This is a common problem with the introspection data, I have just released gi-wnck-3.0.9 with a fix, please take a look.

The bigger issue is probably that you were expecting a valid Window being returned here, but it isn't. I am unfortunately not familiar with the Wnck API, so I am afraid that I cannot help too much there.

[Magicloud]

Ye, I am guessing there is some GTK trick I need. Not a problem with Haskell-GI.

Since I see the new version returns "Maybe Wnck.Window" as fixed. I am closing this.