Indeed. I attached a clumsy patch to
https://bitbucket.org/rsc/plan9port/issue/107/devdraw-macbook-retina-support
that does most of the necessary expansion for retina, but it does it
always (it doesn't even consult devdrawretina). I'd like whatever we
end up doing in the tree to be more adaptive, ideally leading to
getting rid of the devdrawretina setting entirely.
As a first start toward a real solution, I just committed
 http://codereview.appspot.com/6856091 adds display->dpi
 http://codereview.appspot.com/6858071 adds DefaultDPI
 http://codereview.appspot.com/6855092 adds scalesize (see graphics(3))
The new field display->dpi field is refreshed on each window resize.
Right now it is always set to DefaultDPI (100), but if the Cocoa code
in devdraw sets the global displaydpi variable when creating the new
image, that value will filter through to display->dpi in the graphical
program.
My suggested plan, then, is:
1. Set displaydpi correctly in devdraw, probably during initimg.
2. Make the libframe tick code scale the tick size using scalesize. I
think you probably want to use FRTICKW*scalesize(display, 1) instead
of scalesize(display, FRTICKW) so that the tick width splits nicely
into thirds as it always has. For the current retina displays where
actual dpi is around 220, that will end up being a 6-pixel tick.
3. Adjust the fixed-size elements like lines in acme according to
display->dpi too. Probably start with scalesize, but we can tweak
things according to whether it looks good. (See bitbucket patch for
places that need changing. I also missed the line between tag and
body, wherever that is.) It may be that we should make DefaultDPI 133
instead of 100. That will still produce scalesize(d, 1) = 2 on 225 dpi
retina, but it will produce scalesize(d, 2) = 3, scalesize(d, 4) = 7,
and scalesize(d, 12) = 20. When I was playing around those seemed a
bit nicer than strict doubling.
4. Eventually it might be nice to make references to fontsrv fonts
auto-scale, so that if you ask for /mnt/font/LucidaGrande/14a/font (a
reasonable approximation to the default acme font), you get 31pt on
retina. That will require both reloading fonts on resize and also
making apps understand that a font's metrics can change as a result of
a resize. This is also an argument for DefaultDPI = 135, as that would
produce 24pt, which is what I've actually found to work well with acme
on this machine.
So as far as this CL is concerned, I suggest changing it to use
scalesize, so that it forms step 2 of this plan.
Thanks.
Russ