I was totally sold on this and already preparing to try this out on a simple game using OpenGL I'm working on as a pet project, until I saw the code examples. The amount of highly-specific OpenGL code that's apparently needed to embed an ImgUI popover is completely prohibitive to my use case, the GLEW and GLFW examples literally have 3 times the number of OpenGL calls my own rendering function has, I see custom shaders used just for the UI, setting up clipping rectangles, loading font textures, etc. And that's just to manage renderer state, not even to setup the popover itself.

I can understand that it's an advantage to have something like this renderer-agnostic, and embeddable anywhere in your render flow, but the way you have to use this completely defeats its purpose IMO. I would love a higher-level abstraction layer on top of this that deals with all the render state setup, so I only have to setup the UI itself and populate it, and can throw in a one-liner somewhere in my render function that draws it. In this case, I would happily trade the fact that this would break render-independence and would clobber render state, for ease of integration.

That said, the end result looks immensely useful and very-well done, it's just too involved to setup and use I think...