Question: How to get the diagram to know the hosting div has changed size so as to get it to re-draw the part of the diagram that was not previously visible. Looking for a div resize event but ideally something built in to simply call.
Self-Answer: I searched the docs but could not seem to hit on the solution. Then as I was typing my question the new forum tool spat out a bunch of cases referring to diagram.requestUpdate() and links to the resizing sample http://gojs.net/latest/intro/resizing.html - the answer you seek is in the second set of code on that page.
Trying to find how I had missed that I went back to the diagram API page but found it to be absent. I then ran a Google site search site:http://gojs.net/latest requestUpdate which confirmed that this most useful of methods is not documented except in a sample.