For those interested, I believe the blank canvas / black canvas is due to a change in macOS 10.14 and Tk needs to be updated:

https://stackoverflow.com/questions/52316783/nsscrollview-not-refreshing-its...

I can confirm that it's an issue with Tk 8.5 built on macOS 10.14. This will most like *not* be fixed as 8.5 is pretty old nor do I have any desire to look into fixing it with a patch right now.