I just noticed your comment, so sorry for the belated reply. I just wanted to mention that the tecgraf, makers of IUP, has thankfully simplified their build sy

I just noticed your comment, so sorry for the belated reply. I just wanted to mention that the tecgraf, makers of IUP, has thankfully simplified their build system -- no more custom build system. Also, they've started releasing pre-built binaries for all major OSs, including Linux and OSX. So now it's as easy and downloading a file and running sudo ./install. And if you want to build it yourself, it's as simple as running a few make files (make; make install each for the IUP, CD, and IM libraries). But absolutely, the first time I tried to use IUP a few years ago, I couldn't get it build due to the complexity of the build system. Fortunately, that's all changed now.