The two exceptions mentioned above were done years ago in perl and that was a PITA. Never going back there, getting user input from STDIN is much easier.
Python also has some cool tools in this department apart from TkInter like XGui, Lucid and Kivy (touchscreen support!), but I'd prefer something that I can use in C/C++.
But what library to use?
Actually a better question is: What library do you portable freeware users prefer to see?
Qt (formerly by TrollTech) isn't stealth and rather bloated (no need for a complete framework), GTK is ok to work with as I've heard but can look crap in certain OS-es (this was maybe only true 5 years ago) and wxWidgets is afaik just a wrapper for GTK but I could be wrong. And then I've also found Ultimate++ and eGUI++.
Like I said, I've got no experience with any of them, so it's hard for me to judge them and make a choice. I'm a bit reluctant to go with one of the lesser known libraries as it's hard to tell if it will still be around in 5 years. Google turns up a lot of them, but a lot also seem quite dead...
- Portable and if possible completely stealth.
- Cross-platform. Since I don't use Apple I personally don't care for supporting it, but support for all three major OS would be great.
- I prefer source that can be used and included at compilation over an external dll that has to be linked. Not a big priority though.
- freeware-friendly licensing. Open-source preferred, studying source is the best teacher.
- Lightweight. Or at least as lean as it can be.