But the README says the build process it just a couple of files so I figured I could just build it by hand. This involved downloading a couple more repos from the author's repo and setting up some symlinks, includes, and defines that I figured out through trial and error, but in the end I was not successful in getting the demo to build. I tried a combo of SDL2 and OpenGL3 but it bombed out with a C++ error about too many initalizers. The only good news is that I was able to cleanly build the demo_im_app code, but the main requires the ImPlatform which appears to be buggy.
Update: I figured out that you need to run a git submodule update command first. The shell script is supposed to tell you this but it is broken. This does a bunch of work but then dies because g++ doesn't stick the string ".exe" on the end of executibles. Also, the script looks in the wrong place for the output. A few text fixes in the bootstrap.sh and generate_projects.sh files and it gets to a point where the build is dying due to not having "main" or "sharpmake" objects in the current context, whatever that means. I don't know enough about C# to go further, especially for what was supposed to be a quickie 10 minute test. I'm hoping someone else figures this out and updates the repo.
Installation
Add two files to your project:
src/im_anim.h
src/im_anim.cpp
That's it. No build system changes, no external dependencies.