Much worse? I don't understand how this is possible. You opened this ticket two months ago and I don't see what change (in the macosx folder, the only changed file in this timeframe is macosx/tkMacOSXDialog.c) could trigger this worsening. That's strange.

If it's really much worse now than at the time you opened this ticket, could you please try bisecting and identify the faulty commit?

I'm wondering: Did it ever work on OS X with Cocoa? Or did we always have such refresh problems with Cocoa?

We are told below that there is no such effects with Carbon on 8.5.9.