The best one in terms of LoC I've seen: ImGUI. Next best in terms of complexity: WxWidgets Next best: Qt The most productive way to produce a complex GUI is

The best one in terms of LoC I've seen: ImGUI. Next best in terms of complexity: WxWidgets Next best: Qt The most productive way to produce a complex GUI is always through an editor + resource compiler. You always have the option of going part HTML+part native callback. I have to admit, I've not been much of a fan of GUI programming.