Stephan,
Thank you, I have seen this reference, but the framework seems to be written in VisualWorks. While it looks like what I need, I am not ready to put the effort into the process of getting up to speed in the VisualWorks ecosystem. There does appear to be a way to download it, but, since I am focused on my (hobby) project and the learning opportunity it provides, I will continue to develop a framework in Squeak.
There is a page referenced on the link you provided that discusses porting, so perhaps, someday, I will take a look at it. From what I have learned so far PDF is a gnarly mess of pointers and offsets which have to be carefully managed - hard fun!
BTW, I owe the list a reply to this thread about my discovery of the answer to my question.
jrm