Built to power a new generation of game development tools, Ultra App Kit provides an easy-to-use C++ programming SDK for creating desktop GUI applications.
Unlike other alternatives like Dear ImGui, the Ultra App Kit GUI renders in retained mode rather than immediate mode and is specifically designed for desktop GUI applications instead of games. This makes applications snappy and responsive when resizing or refreshing a window.
DPI scaling is baked into the design for resolution-independent graphics on any screen.
Version 1.1 adds support for Linux and Mac development, so GUI applications can be developed for multiple operating systems with a single code base.
Link to Article:
https://www.ultraengine.com/community/blogs/entry/2672-ultra-app-kit-released/