https://people.freedesktop.org/~ajax/WhyX.pdf ref: https://dblp.org/pid/m/MarkSManasse.html
ref: https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.4380201409
It's a shame it's historical. I was hoping that X had been lurking around all this time and was about to stage a comeback.I have fond memories of Quaterdeck's DESQview/X system.