So, I added support for retina on the Macbook Pro. Text looks great.
I made icons double size and draw them at half size on canvas. This makes them look sharp on retina and fine on normal Macs with no conditional drawing needed. I use code like this in the Canvas.paint event:
g.DrawPicture currentPic, 0, 0, currentPic.Width *.5, currentPic.Height *.5, 0, 0, currentpic.Width, currentPic.Height
However, when running on Windows, my half size icons have unacceptable artifacts from the halving. I assume the Windows graphics renderer is not as spiffy.
Do I need to create 2 versions of all my icons or is there some trick I've missed?