This example is the default XCode "OpenGL" example code, modified to support IMGUI and Synergy.
Synergy (remote keyboard/mouse) is not required, but it's pretty hard to use IMGUI without it. Synergy includes a "uSynergy" library that allows embedding a synergy client, this is what is used here. IMGUI supports "Touch Padding", and this is enabled when Synergy is not active.
Things that would be nice but I didn't get around to doing:
IMGUI is a c++ library. If you want to include it directly, rename your Obj-C file to have the ".mm" extension.
Alternatively, you can wrap your debug code in a C interface, this is what I am demonstrating here with the "debug_hud.h" interface. Either approach works, use whatever you prefer.
In my case, most of my game code is already in C++ so it's not really an issue and I can use IMGUI directly.