Public bug reported:
I'm running Ubuntu 11.04, and I have a hp dm3z laptop with an external
22" monitor.
I have it set to extended desktop, with the external screen to the left
of the laptop. The external screen has a resolution of 1680x1050, and
the laptop has a resolution of 1366x800.
I noticed daily that it would reset my desktop to mirrored display, with
a resolution of 800x600. I tracked down the cause to be the mlocate
script within cron.daily (rant: really annoying), where the underlying
cause was on_ac_power, and specifically the command
cat /sys/class/power_supply/AC/online
starts going through the cycle of different desktop layouts.
When in the layout of external to left of laptop screen, with each successive
call to 'cat /sys/class/power_supply/AC/online',
it goes to the following layouts, in this order:
mirrored (800x600)
laptop screen on left side of extended desktop, external on right (both at
correct resolutions)
laptop screen only (correct resolution)
external monitor only (correct resolution)
external monitor on left, laptop screen on right (both at correct resolution)
I've also noticed that if I unplug my AC power while the external
monitor is plugged in, and unplug the external monitor (because I move
my laptop), it seems to go through at least one full cycle before it
finally settles on laptop only, but it takes a good few seconds (and
it's very, very noticeable).
This happens when the external monitor is plugged into the HDMI port or
the VGA port.
Additionally, this also happens if I run 'cat <
/sys/class/power_supply/AC/online'
When on battery power, it outputs '0', when on AC power, it outputs '1'.
I've run Ubuntu 11.10 (but decided to downgrade for other reasons) and
this problem still persists there.
Please let me know if there's any other information I can provide.
If it wasn't obvious, I don't expect my monitors to cycle through the
different possible output modes because of a daily cron script.
Instead, it does happen. It's really annoying. Now that I've found it,
I can disable the cron script, but it was really annoying to track down.
brian@nevada:/etc/cron.daily$ lsb_release -rd
Description: Ubuntu 11.04
Release: 11.04
brian@nevada:/etc/cron.daily$ uname -a
Linux nevada 2.6.38-13-generic #52-Ubuntu SMP Tue Nov 8 16:53:51 UTC 2011
x86_64 x86_64 x86_64 GNU/Linux
brian@nevada:/etc/cron.daily$ lspci | grep -i radeon
01:05.0 VGA compatible controller: ATI Technologies Inc RS780M/RS780MN [Radeon
HD 3200 Graphics]
** Affects: ubuntu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/893854
Title:
cat /sys/class/power_supply/AC/online cycles through monitor display
layouts
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