brightness drops to minimum on lifting finger

[malcolm bennett]

While the slider retains the appropriate position, lifting my FINGER from the slider causes the tablet's brightness to fall back to minimum. Same problem on stopping finger mouvement.
Having no mouse, I cannot get any brighter than the minimum.

[NoSpam Jackson (pleasedontsendmespamplease)]

I am also seeing this bug (using Ubuntu in fallback gnome mode).
Despite the bug-- wonderful work on this, congratulations to the crew.

[Grant Bowman (grantbow)]

Hard to test if you can not see the screen well. I am so glad it was easy to get running! Thanks for your efforts :-)

[Pete (pete-s)]

TL;DR: Possible workaround:

sudo killall luxd

...then again try setting your brightness via the normal control center.

Detailed explanation:

I was having much the same symptoms as described above, though I was using:

/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness

...to check the brightness, which was always 1. Then when I used:

sudo /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 255

...to *set* the brightness, it'd update and I'd get an extremely bright screen for a fraction of a second - then it'd revert back to the low brightness (value 1).

After some lengthy debugging attempts, I tracked it down to a script /usr/bin/luxd running as root (part of the ubuntu-defaults-nexus7 package). If you look at this 12-line shell script, you'll see it *literally* does nothing other than reverting the brightness via "echo 1 >/sys/class/backlight/pwm-backlight/brightness" every bloody second.

So I killed luxd with:

sudo killall luxd

...then again tried setting my brightness like so - this time it stayed bright:

sudo /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 50

50 seems a reasonably sane brightness level (I find the max 255 is *way* too high :)).

Regarding /usr/bin/luxd, I'm not sure what purpose it's *meant* to serve, but it doesn't appear to be working correctly.

[Oliver Grawert (ogra)]

the luxd script divides the collected value from the brightness sensor by 100 and echoes it into the backlight control, put the nexus7 under a lamp or into bright sunlight and you will see it adjusting to a higher level ...

patches to teh script are appreciated to make it more sensitive, it is currently used as a proof of concept to gather data for teh final implementation in gnome-settings-daemon (indeed a proper implementation patch there that disables manual backlight control if automated backlight control is set would even be more appreciated)