This is more of a useful exemplar than a specific issue, but basically, the current version of PsychoPy has the following behavior on my 2017 MacBook Pro running MacOS Catalina, when attached to a non-Retina external display:
A non-fullscreen window that specifies which screen it should be opened on (the retina display or the external display) seems to work fine.
Fullscreen windows opened on the retina display work fine. Those opened on the non-retina display seem to be ‘misplaced’, that is, in a window with a gray background, there is a large black bar on the bottom 1/5 or 1/4 of the screen and everything seems to be shifted ‘upward’ by that amount (see image)
While this has no practical impact, if you move a non-fullscreen window back and forth between displays, you can see the canvas scaling issue happen in real time.
The only one of these that’s still a serious problem is the fullscreen on non-retina displays issue. However, I don’t know if people using newer versions of MacOS have encountered this again. Mostly, I was hoping to just have a record of the nature of the problem since it seems to recur periodically over MacOS updates and changes to PsychoPy’s display system