What Marius wrote is mostly accurate. If you set devdrawretina=1 you get
tinier pixels; acme, sam, and 9term know to draw thicker lines in response;
other programs do not.

If you want fonts that look somewhat like the Plan 9 bitmaps, I use this
with acme:

#!/bin/bash
export devdrawretina=1
/usr/local/plan9/bin/acme -f /mnt/font/LucidaGrande/25a/font -F
/mnt/font/Menlo-Regular/25a/font "$@"

It would be nice if acme, sam, 9term adjusted the font size to match the
display DPI accordingly. I have code that does this (I lied above; I
actually start acme with size 15a fonts and it scales to decide to use the
25a fonts), but I am not happy enough with it yet. The main thing that is
missing is that if the window changes from retina to non-retina or vice
versa (for example, you use a retina laptop with an external monitor and
drag a window from one screen to the other), acme and sam know to redraw
with thicker or thinner lines but I don't quite have to font adjustment
during resize correct.

The lack of on-the-fly font resizing is a continual source of pain for me
(I end up having to restart acme a lot), and at some point I will finish
it. Ideally I want to get to the point where devdrawretina=1 acme (no other
arguments) just works.

For fun, try 'devdrawretina=1 9term -f /mnt/font/Menlo-Regular/80a/font'
and then in that window run 'unicode fffe'.

Russ