Thanks for the pointers.
I finally did some sleuthing and experimentation.
Indeed, devdraw now knows about a display’s DPI, and launching a devdraw app
with environment devdrawretina=1 enables detection of retina displays, and
setting the current DPI accordingly.
DPI seems to affect a few things:
1. computing geometries of fixed-sized UI elements like scroll bars
2. computing scroll “ticks”
⌘-R toggles the current DPI from “retina” (220 DPI) to “non-retina” (110 DPI).
There doesn’t seem to be any sort of built-in font scaling at the moment. So
when you launch, say, acme on a retina machine, you’ll have to supply your own
(larger) font. I ended up using fontsrv with system fonts:
% devdrawretina=1 acme -f /mnt/font/HelveticaNeue-Medium/24a/font -F
/mnt/font/Menlo-Regular/22a/font
seems to work pretty well.
-m.
