calDPI(NV) != calDPI(NOUVEAU|RANDR12_ON)

nouveauのlive git ebuildが動いたので調子にコいてemergeしまくっていたら、
Xorgが起動しなくなるほどぶっ壊れた。 :P
で、#nouveauで泣きをイれてみる。
[nouveau just worked, so I remerge it sometimes. It b0rk0rz my X. :P
So I asked devs at #nouveau.]

05/08 00:25:58 hiyuh
    hmm, updating nouveau on my pb. it breaks my X. :p
05/08 00:38:29 marcheu
    hiyuh: bisect, and then blame someone :)
05/08 00:41:17 hiyuh
    zomg :)
05/08 00:44:30 hiyuh
    I can't startx w/ nouveau by using the overlay atm. it seems to b0rk
    at loading (or initializing) nouveau_drv.so.
05/08 00:47:50 pq
    so look in Xorg's log
05/08 00:49:27 hiyuh
    pq: any easy way to bisect by using the overlay's
    xf86-video-nouveau? setting EGIT_blah?
05/08 00:49:54 pq
    hmm... I don't that would be an easier option
05/08 00:50:41 pq
    git-clone the nouveau DDX repo, build it, and make a symlink from
    where the ebuild installed the driver to the hand-built drv.so
05/08 00:51:33 pq
    for instance, I have
    /usr/lib/xorg/modules/drivers/nouveau_drv.so.devel ->
    /home/pq/nouveau/xf86-video-nouveau/src/.libs/nouveau_drv.so
05/08 00:52:01 hiyuh
    ah ok.
05/08 00:52:09 pq
    then I just do the link nouveau_drv.so -> nouveau_drv.so.devel when
    I want to switch to the hand-built version

05/08 01:57:11 hiyuh
    pq, marcheu: http://dev.gentoo.gr.jp/~hiyuh/misc/nouveau-bisect.log
05/08 01:57:52 marcheu
    hiyuh: you're saying it's 52e58c7e799697989fcfbf95050ce10a4c3d1f8f ?
05/08 02:04:32 hiyuh
    marcheu: I guess so.
05/08 02:05:34 pq
    hiyuh, when the bisection completes, git says something like "the
    first bad commit is..."
05/08 02:06:06 pq
    I'm not sure how to read the bisect log
05/08 02:07:06 hiyuh
    http://dev.gentoo.gr.jp/~hiyuh/misc/b0rk-Xorg.0.log
05/08 02:07:55 hiyuh
    all bad rev does vomit like this.
05/08 02:09:36 pq
    hm, script execution segfaults
05/08 02:09:44 pq
    hiyuh, btw. please enable randr12
05/08 02:09:47 marcheu
    hiyuh: I blame malc0  :)
05/08 02:10:13 hiyuh
    lol
05/08 02:12:54 hiyuh
    pq: randr12 works kinda bit. but it shows me larger and bolder fonts
    on gtk app.
05/08 02:12:59 hiyuh
    for testing is ok, but "do enable it always" is not good for me atm.
05/08 02:13:09 marcheu
    hiyuh: what are the issues with it ?
05/08 02:13:26 marcheu
    hiyuh: can't you force another dpi ? AFAIK what randr12 does is
    correct
05/08 02:13:30 marcheu
    or use smaller fonts..
05/08 02:15:35 hiyuh
    well, I'm not good at tuning xorg.conf. I just replaced "nv" to
    "nouveau". http://dev.gentoo.gr.jp/~hiyuh/misc/xorg.conf
05/08 02:16:00 marcheu
    I think "nv" has incorrect dpi computation...
05/08 02:16:07 hiyuh
    zomg :)
05/08 02:16:25 marcheu
    the right thing to do is configure your font size in whatever app
    you use
05/08 02:16:35 marcheu
    or force dpi but that's pretty dirty
05/08 02:16:57 pq
    you can also calculate what the true dpi is and see which one
    is closer
05/08 02:17:09 marcheu
    I think I've been looking at pb12 logs before (yours ?) and they
    reported proper size with randr12 but not default
05/08 02:22:19 hiyuh
    heh
05/08 02:24:47 marcheu
    they didn't ?
05/08 02:25:02 marcheu
    the detected size should be displayed in the logs
05/08 02:27:03 hiyuh
    marcheu: hmm? are you saying "show me the Xorg log w/ randr12
    enabled"?
05/08 02:27:28 marcheu
    I'm saying you should check the reported size is correct
05/08 02:27:41 marcheu
    which would mean the dpi is in turn correct
05/08 02:27:46 marcheu
    I don't want the logs, I'm pretty sure it is
05/08 02:30:06 hiyuh
    well, how can I check whether it was correct or not?
05/08 02:30:09 hiyuh
    running Xorg w/ randr12 enabled then what?
05/08 02:30:39 marcheu
    the screen size is in the logs
05/08 02:36:03 hiyuh
    nv sets (75, 75). w/ randr12 off, nouveau sets (75, 75). w/ randr12
    on, nouveau sets (108, 144)
05/08 02:38:16 marcheu
    sure, because nouveau with randr12 takes the screen size into account,
    which is the correct thing to do
05/08 02:38:21 marcheu
    look in the logs for the screen size
05/08 02:38:27 marcheu
    you'll see that it's the right one
05/08 02:38:32 marcheu
    but I'm repeating myself somehow
05/08 02:40:23 hiyuh
    so, (108, 144) is correct DPI?
05/08 02:40:44 marcheu
    so.
05/08 02:41:09 marcheu
    to compute the DPI, you divide the size in pixels by the size
    in inches
05/08 02:41:16 marcheu
    the size in pixels is the same
05/08 02:41:34 marcheu
    now feel free to do the computation yourself
05/08 02:41:59 marcheu
    and really I'm leaving before this stuff drives me crazy
05/08 02:42:04 pmdata
    !INCREASE your dpi! PLIZ YOUR EYES
05/08 02:42:54 marcheu
    and really, we're not going to fuck up dpi calculation because it
    makes font too big or too small. it's up to the apps to be configured
05/08 02:42:57 marcheu
    bbl
05/08 02:43:15 pq
    btw. the size in inches is horizontal or vertical, not diagonal
    marketing inches :-)

つーことで、git repoの方はmalc0様々がそのうち直してくれるだろうと勝手に期待して待つことにする。
randr12 onなnouveauはnvとDPIがモロ違うっぽいのでフォントはアプリ側で調整する方法で行くかな。
[So I'm waiting official fix for this b0rkage by malc0 or someone who read t3h log.
ATM, w/ randr12 on, nouveau sets different DPI from nv's (is incorrect?).
T3h way to stick nouveau w/ randr12 on, I'll set appropriated font size as the app side setting.]