Based on our record, IUP Portable User Interface seems to be more popular. It has been mentiond 1 time since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
As C libraries, I can recommend IUP. You can also choose immediate mode which has the same look on all platforms, there are some wrappers around imgui in Zig like zig-upaya. Source: almost 4 years ago
Qt - Powerful, flexible and easy to use, Qt will help you not only meet your tight deadline, but also reduce the maintainable code by an astonishing percentage.
FLTK - Fast Light Toolkit - Fast Light Toolkit (FLTK)
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
wxWidgets - wxWidgets: Cross-Platform GUI Library
Avalonia - A multi-platform .NET UI framework
gtkmm - gtkmm is the official C++ interface for the popular GUI library GTK+.