What is the purpose of this border? My guess is that the dropshadow that is applied to the menu cannot be reliably applied on Windows, so the border is a way of ensuring that the menu has sufficient contrast with its background?
I suspect that code is very old indeed, but probably the original reason was that OSX always adds a 1px border around its menus, so this made it look consistent when you run your code on other OSes.
Thanks Jules. It sounds like I can safely remove that snippet from my drawPopupMenuBackground override? On Mac the menu is being rendered without a border, but with a dropshadow, and I’d like it to look like that on Windows too.