cegui VS NanoGUI

CEGUI

You could have a look at CEGUI or MyGUI. I haven't used either, but as far as I remember both of them implement multiple rendering backends and are/were used in some more or less notable projects.

NanoGUI

With 2.5 days you probably don't want anything that requires much setup, so Qt is probably a non-starter. You could try this one: https://github.com/wjakob/nanogui, the examples are not the platonic ideal of modern C++ programming, but that also means you don't need much mastery of the language to hammer a program until it has a GUI.

I've dipped my toes into GUI development just enough to know you can have "simple," or you can have "native," but not both. There are smaller projects like nanogui[0] and microgui[1] out there, but of course they're only as small as they are because they don't use native widgets.

[0]https://github.com/wjakob/nanogui/tree/master/src

[1]https://github.com/ryankurte/micro-gui

### [NanoGUI](https://github.com/wjakob/nanogui)

I have only played with this briefly, but after the initial setup NanoGUI seemed pretty intuitive https://github.com/wjakob/nanogui

There's GTK which is all LGPL (ok to dynamic link to) and things like nanogui which is BSD (just attribution).

Wondering if this was inspired by Wenzel Jakob's nanogui [0] by any chance. (cz that's what I wanted to do, rewrite nanogui in C, so I don't have to rely on a C++ compiler).

[0] https://github.com/wjakob/nanogui