On Tue, 2009-09-15 at 12:06 -0400, Adam Jackson wrote: > In attempting to document how displays are expected to work in F12 [1], > I realized we still don't have a decent heuristic for some cases. > > Broadly, displays are either fixed-format or variable-format. FF means > you have some set number of pixels, like an LCD. VF means you don't, > like a CRT. (Projectors are often somewhere in between, we'll pretend > they don't exist for a moment.) We get FF displays pretty much right, > since they tend to describe themselves well enough in EDID to figure out > what their native size is. Some VF displays are polite enough to define > a preferred mode, and for that case we'll default to that. > > But, many VF displays don't define a preferred mode. How are we to > choose? What's currently implemented will pick something along the > lines of "the largest available mode that matches our guess at the > physical aspect ratio and that fits in the card's DAC and memory > bandwidth limits". Which is awful. So I'm thinking something like (in > wretched pseudopython): > > def mode_dpi_cmp(x, y): > return cmp(abs(x.dpi - 96), abs(y.dpi - 96)) > > def mode_size_cmp(x, y): > return cmp(x.width * x.height, y.width * y.height) > > def best_mode(modes, dpi_known = True): > l = filter(lambda x: x.refresh >= 72, modes) > if l == []: > l = modes > if dpi_known: > l.sort(cmp=mode_dpi_cmp) > else: > l.sort(cmp=mode_size_cmp) > return l[0] > > Which is _pretty_ good, except you'd kinda like to match aspect ratio if > you happen to know AR but not DPI. Which is trivial to add, but starts > to be hard to read. > > If anyone has ideas I'm all ears, but I'd like to get this implemented > sometime this week, so speak up. I know that, in the dinosaur days of CRT, I could 'see' flicker (and get flicker-generated headaches) at anything under 80Hz, and I know there are even more sensitive people than that. So 72Hz may be a bit of a low 'safe refresh rate' cutoff. I'd like it to be 80 at least. 72/75 were better than 65 for me, but definitely not acceptable for long-term work. (/me remembers the days when you could gain any office worker's everlasting friendship by changing their refresh rate from 60Hz to 85Hz...ahhh, good times.) -- Adam Williamson Fedora QA Community Monkey IRC: adamw | Fedora Talk: adamwill AT fedoraproject DOT org http://www.happyassassin.net -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
