Depends on the complexity of the GUI you need and on other factors. QT is OK if your GUI is very complex and you're targeting a desktop OS. For simple GUI QT

Depends on the complexity of the GUI you need and on other factors. QT is OK if your GUI is very complex and you're targeting a desktop OS. For simple GUI QT is just too big. For GUIs without a desktop OS (mobile, embedded), QT is not a good fit either, not enough mobile support, and their embedded license can be prohibitively expensive. I have positive experience building moderately complex commercial quality GUIs on top of this: https://github.com/memononen/nanovg https://github.com/memononen/nanovg