CUI is immediate-mode C99. Bring your own window and renderer, call functions, get data grids, node editors, curve editors, flame graphs, a log console and a hex viewer.
Zero dependencies. Drops into any engine.
also new overhauled, redesigned components coming soon.
Checkout the new components as well:
https://t.co/TAEAaGGQkP
ps: the new components were inspired by @PostiauxCharles