http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.78.5331
Paul Haeberli, ConMan: A Visual Programming Language for Interactive
Graphics (1988)
I supervised a student who did an implementation for a Blit-like
environment on the Sun3 as a project;
unfortunately I didn't keep a copy. I remember there were several things
left to work out based on the paper.
(The Blit-like environment replaced megabytes of Sunview, in case you were
wondering, and enabled some serious fun.
Sunview enabled some serious head-banging.)