wxWidgets or QtWidgets if you want a proper desktop GUI app.

My problem with wxWidgets was I kinda wish its API was more elegant

There were also some subtle issues like the child windows leaking a lot of memory in the GTK implementations when idle (something like spamming gobjects).

I wouldn't touch Qt even with a ten foot pole, too much bloated for me.

Heck, Tcl/Tk could work as well.

that's funny, most of the time I don't even want to USE apps written in those because they're dated and janky as hell, must less write in them