Assuming, of course, you want to use GTK3. Which can be acceptable for Linux applications (and even there GTK3 has a horrible UX compared to GTK2), but it's not

Assuming, of course, you want to use GTK3. Which can be acceptable for Linux applications (and even there GTK3 has a horrible UX compared to GTK2), but it's not something you'd want to use on Windows or OSX.