On Tue, 2014-11-25 at 09:14 +0100, Lukas Zapletal wrote:
my desktop was completely broken this morning because my startup
rely on xrandr utility. An older update from this summer which I applied
recently changed it's output so device ids now contain dash characters
(e.g. instead VGA0 I see VGA-1).
No it didn't. xorg-x11-server-utils did update from xrandr 1.4.0 to
1.4.2 between F20 gold and current updates, but as a quick glance at the
upstream changelog shows , nothing between those two versions changed
anything about output naming. It would be insane to do so; those names
come from the server, so changing them in xrandr would mean xrandr
disagreeing with everything else.
But when I say "come from the server" I really mean the 2D X driver
makes up the name and the server just reports it. And indeed, between
xorg-x11-drv-intel-2.21.15-4 and -9 output naming was changed to include
a dash (if using UXA), which happened because the output setup code was
synced with the version in the generic modesetting driver (which also
happens to match radeon and nouveau). Upstream intel omits the dash for
both sna and uxa still though. And if we were to ever get multi-gpu
randr working the names would destabilize again, since we'd have to move
the %d part of the name up to the core server since you really don't
want two outputs both named VGA-0. And caring about the names is
somewhat futile anyway since what you're usually more concerned with is
the _monitor_, which is why all sane desktops save configurations based
on EDIDs not on output names.
tl;dr it's a mess, sorry about that. Stable output naming isn't
something that any of our desktop environments care about, afaik, so
it's not something I'd ever see as a regression. In a sense, noticing
this level of implementation detail is the price you pay for choosing
not to run something that gets it right for you. 
 - http://cgit.freedesktop.org/xorg/app/xrandr/log/
 - And Linux, as we know, is all about choice.