brightness is not saved and restored correctly

[Martin Pool]

Binary package hint: gnome-power-manager

Following on from bug 128452:

When all the options are turned off in the Power control panel, I can
set the brightness using the function keys and it stays set.

If I set "dim display when idle" it also seems to work ok.

If I add a brightness applet things seem to work too.

If I set "reduce backlight brightness" on battery power it's not so
good: when unplugged, the brightness goes to almost the lowest
setting, which is too dim for me, and when re-plugging it stays
somewhat dimmer than it was before. Perhaps that's a separate bug, at
any rate it's a big improvement.

One additional failure mode:

I have 'dim display when idle' turned on for battery, off for AC.

My laptop had been idle on battery for a while, with the display
dimmed. I plugged in the power supply before pressing any keys. The
display remained dim, even after I pressed a key; I had to turn it
back up manually.

What should have happened: plugging in ac should have restored the brightness.

Tomasz writes: yeah, i think it's a different bug. it seems like the brightness settings aren't saved properly. similiar thing happens when you suspend: after unsuspending the brightness is set to the max, even if it was set to the lowest before suspend. not sure if the same is true for hibernation, as it doesn't seem to work for me.

[Steve Zemanek (steve-zemanek)]

I'm having the same problem, I like the laptop to be at full brightness when on AC power

I'm running a ThinkPad T60 w/ an ATI Radeon x1400

when I plug the power back in, i need to manually readjust the brightness settings, i played around with gconf-editor, but even with the AC brightness turned to "100" it's still not full brightness.

I didn't have this problem in 7.10, I recently did a fresh new install of ubuntu 8.04 on this laptop, and now i'm having this problem.

[Steve Zemanek (steve-zemanek)]

and the weird part is, if I use the "brightness applet" to adjust the display brightness, I can still manage to turn up the brightness all the way.

[Tomasz Rzepecki (nub)]

i've found out the same thing happens when you simply close the lid (when it's set to just turn off the screen in such case) or switch to tty by ctrl-alt-f1 and back by ctrl-alt-f7 - the brightness is reset.
a funny thing happens when you do it quickly - you can see the brightness applet showing the brightness dimmed, while the screen is at full brightness.
steps to reproduce:
1. turn down the brightness using the function keys (or otherwise, i guess). all the way or only a bit, it doesn't seem to matter.
2. either:
a) restart computer
b) go to 'switch user' menu, and log back in
c) suspend and unsuspend
d) close the lid (making sure it isn't set to hibernate or suspend) and open it again
e) switch to terminal mode using ctrl-alt-f1, then back to x using ctrl-alt-f7
3. brightness goes to the max instead of staying the way it was. if it's of any importance: in b) and e) the brightness stays at the set level in the login screen (b) ) or terminal (e) ).

[Tomasz Rzepecki (nub)]

found another similar bug, altough it may be an mplayer bug.
steps to reproduce:
1. turn down the brightness.
2. open any video in mplayer. brightness goes to the max (this may be the way it's supposed to work).
3. close mplayer. brightness is still max, while it should go back (or not change at all).

[Ryan Zeigler (rzeigler)]

I can confirm this on a Dell XPS M1330. Fiddling with the battery brightness levels to make them match available levels as shown in /proc/acpi/video/VID/LCD/brightness causes the brightness to get very close to being restored to 100%, but still not all the way.