I put a breakpoint in drawRect just at the entrance . Thread1 showed a history of greyed calls that weren't in my source . One of these object calls associated with lower right corner dragging was something like resize titled window . I couldn't put breakpoints at this call to see if it was called on the faulty zoom.

I still can't fathom what in Michele's code makes the zoom go wierd though I still think it is related to the image size tracking the window size , but it is necessary for me to go in the dark so I can appreciate when the light comes in the column.