[Sugar-devel] [FEATURES] Display Device

[Simon Schampijer]

El 21/11/11 17:16, Paul Fox escribió:
> peter wrote:
>   >  On Mon, Nov 21, 2011 at 3:33 PM, Simon Schampijer<simon at schampijer.de>  wrote:
>   >  >  El 21/11/11 15:18, Paul Fox escribió:
>   >  >>
>   >  >>  simon wrote:
>   >  >>   >   Hi,
>   >  >>   >
>   >  >>   >   I would like to propose the following Feature to enhance the Sugar
>   >  >>   >   learning environment:
>   >  >>   >
>   >  >>   >   "Add a frame device to control the display. The idea is to add their
>   >  >>  an
>   >  >>   >   option to change the brightness and to take a screenshot. Both actions
>   >  >>   >   are only available via the keyboard as of today." [1]
>   >  >>
>   >  >>  oh, good idea.  in fact, i have another job for it to do.  :-)
>   >  >>  it would be great if it could switch the display from color to
>   >  >>  monochrome, as well.  see my email on automatic backlight control,
>   >  >>  which i've composed but haven't sent yet.  i'll do so right now.
>   >  >>
>   >  >>  paul
>   >  >
>   >  >  Hi Paul,
>   >  >
>   >  >  I just looked at olpc-kbdshim the olpc-brightness for how we adjust the
>   >  >  brightness on the XO. Looks like we simply echo the values to the files like
>   >  >  '/sys/class/backlight/dcon-bl/brightness'. I wonder what the generic
>   >  >  solution is for that (Sugar on other devices).
>   >  >
>   >  >   From a quick test, I have the following files on my T61:
>   >  >  /sys/class/backlight/intel_backlight/max_brightness and
>   >  >  /sys/class/backlight/intel_backlight/actual_brightness which change
>   >  >  accordingly when adjusting the brightness. But I guess there is a generic
>   >  >  tool for doing that...?
>   >  >
>   >  >  /me should probably have a look what GNOME is doing...
>   >
>   >  There's recently been introduced a generic backlight class so I think
>   >  its all being converted over to that. Its like the IBM one in
>   >  /sys/class/backlight but I'm not sure the full details for
>   >  manipulating it programaticly but I'm sure its documented somewhere.
>   >
>   >  Some details are:
>   >  https://lwn.net/Articles/423170/
>   >  https://wiki.kubuntu.org/Kernel/Debugging/Backlight
>
> we seem to implement anything mentioned in those two links.  i wouldn't
> be surprised if there was a more recent higher level interface that
> might be useful.
>
> paul
> =---------------------
>   paul fox, pgf at laptop.org

I have been checking what gnome is doing (gnome-settings-daemon (the 
functionality was in gnome-power-manager before)):

- they use xbacklight [1] if possible to get/set the brightness [2], 
doing this through the gnome-desktop library [3]

- there is fallback code to deal with hardware where xbacklight is not 
available [4] using the content of "/sys/class/backlight"

Regards,
    Simon

[1] http://linux.die.net/man/1/xbacklight
[2] 
http://git.gnome.org/browse/gnome-settings-daemon/tree/plugins/power/gsd-power-manager.c#n2405
[3] 
http://git.gnome.org/browse/gnome-desktop/tree/libgnome-desktop/gnome-rr.c#n1682
[4] 
http://git.gnome.org/browse/gnome-settings-daemon/tree/plugins/power/gsd-backlight-helper.c