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FearlessSpiff

Member

Registered: 2015-04-17

Posts: 6

[Solved] Brightness control failes with xfce4-power-manager

Hi

I'm new here but old fan of XFCE since 20 years or so. :-)  I'm now getting back to XFCE on my "old" MacBook.

My problem is exactly the same as in [1] with Mate, so I won't describe it again.
I also checked the XFCE code in [2] which looks identical. It prefers the nv_backlight which is of no use on my system. I can change brightness through gmux­_backlight. Can't I configure the power manager to use the gmux_backlight? Did I miss something obvious?

Thanks Spiff!

[1] https://github.com/mate-desktop/mate-po … issues/135
[2] http://git.xfce.org/xfce/xfce4-power-ma … t-helper.c

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 11,481

Re: [Solved] Brightness control failes with xfce4-power-manager

To answer your question, the code in xfce4-power-manager works in a similar manner as mate. A priority list is used to look for backlight interfaces. Unfortunately, in your case, the incorrect one is higher in the priority list.

As per the mate bug report you linked, you can manually change the code to list the gmux_backlight interface higher in the priority list and re-build xfce4-power-manager. Alternatively, you can create a bug report and ask the developer to consider using either the gnome3 method, or to create some other mechanism where one can override the interface.

Or finally, you can try to address the issue directly. Have you tried removing one of the two active backlight interfaces? I don't have any experience with or access to MAC hardware so I don't know for sure if this is possible in your case. Alternatively, you can create a script that watches the values in one file and on any change to the contents, a change is made in the other file. Something like (run as root or change the permissions of /sys/class/backlight/gmux_backlight/brightness to be world-readable):

while inotifywait -e modify /sys/class/backlight/nv_backlight/brightness do echo $(cat /sys/class/backlight/nv_backlight/brightness) > /sys/class/backlight/gmux_backlight/brightness; done

...you'll need to have inotifywait (or inotify-tools depending on distro) installed. This assumes that backlight changes are normally written to the nv_backlight/brightness file - which have no effect.

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FearlessSpiff

Member

Registered: 2015-04-17

Posts: 6

Re: [Solved] Brightness control failes with xfce4-power-manager

Thanks! What a great answer! :-D I'll use your script to accomplish the task. It works. :-D I just have to multiply the value, because max value for both interfaces are different, but that's easy!
Thanks again!

MagnusBerg

Member

Registered: 2004-12-17

Posts: 46

Re: [Solved] Brightness control failes with xfce4-power-manager

Depend on that you want to do with your backlight...

I have color managed my screens. On the laptop I can't set the brightness in hardware and the brightness controlls in Xfce4 is not as precis as I need. To solve that I use Xbacklight. I set is as on of the autostarted applications in Xfce4. In the nice gui i write "xbacklight -set 54" as the command to run. This sets my screen to 54 percent of the maxmal brightness level. With "xbacklight -get" I can se that it works.

FearlessSpiff

Member

Registered: 2015-04-17

Posts: 6

Re: [Solved] Brightness control failes with xfce4-power-manager

Thanks. Unfortuntley xbacklight doesn't work either out of the box. maybe there would be a similar workaround.