Lately I've been playing with gtk in c and now rust and it's fantastic how simple gui development is.
https://developer.tizen.org/development/training/native-appl...
https://developer.tizen.org/development/api-references/nativ...
And the upcoming .NET SDK here
https://developer.tizen.org/development/tizen-.net-preview/i...
Here you can have a look how C++ SDK used to look like, before the Enlightenment guys took over the show on Tizen 2.3.
http://mikeasoft.com/~mike/tizen2-native-dev-draft/
https://developer.tizen.org/ko/forums/native-application-dev...
Nice for you to enjoy doing GUIs in C, but having been coding since the 80's and exposed to so many more productive ways to do GUI development, I don't enjoy it at all, and many that do UI/UX as part of their daily job think the same way.
I've use qt, gtk, win32, swing, winforms, etc, right up to more modern approaches like wpf with mvvm and similar JavaScript ones. After going back to c and gtk I think we've really lost our way and made some really simple problems really complicated.