Immediate mode GUI (IMGUI) is a GUI that uses immediate mode to create interface (as opposed to retained mode). i.e., the interface is created on every render.
In retained mode, you create widgets and they persist / store state. In immediate mode, every widget is basically re-created on every render and create/redraw functions are unified.
For me, this is very similar to React-like frontend UI libraries.
- www.iki.fi/sol - Tutorials - IMGUI—how to implement a simple IMGUI library