Comment 6 for bug 1959673

I've made an attempted fix (https://github.com/PintaProject/Pinta/actions/runs/3759973148) which needs some testing on various platforms to see if it actually fixes the issue :)

It seems to work on macOS and Windows in my testing. The one minor issue it introduces is when pasting or creating a large image that needs to be zoomed out to fit in the window - there's now a small flicker of the image at 100% zoom before it's redrawn zoomed out