[support-gang] XO brightness key operation

Nicholas Doiron ndoiron at mapmeld.com
Mon Apr 9 12:20:19 EDT 2012

Is there a way to read the current value of the 1.75's ambient light
sensor? It'd be neat if that could be displayed by an activity.

Nick Doiron
Code for America
On Apr 9, 2012 9:16 AM, "Paul Fox" <pgf at laptop.org> wrote:

> i just sent this to the folks working on the current doc sprint, and
> then realized it probably deserves a wider audience.  operation of the
> brightness keys was enhanced a bit in 11.3.1, based on discussion on
> the devel list, but i don't recall that i ever sent out a summary mail.
> for convenience, i'm going to refer to the brightness keys as BrUp and
> BrDown here.
> on all laptops, in all sofware releases to date:
>    - the unmodified BrUp and BrDown keys adjust the brightness in 15
>        steps.  when turning the backlight all the way off (i.e.,
>        the lowest setting) the display will switch into the higher
>        resolution monochrome mode.
>    - using the Alt-BrUp and Alt-BrDown combinations will immediately
>        change the backlight to its maximum and off values (including the
>        change to monochrome when off).
> in release 11.3.1 and later, on all laptops:
>    - the Ctrl-BrUp and Ctrl-BrDown combinations don't actually change
>        the backlight level, but rather will toggle the screen between
>        "normal" mode and the higher resolution monochrome mode.  this
>        monochrome mode will be sticky, so further normal use of the
>        keys will adjust the brightness but won't restore color.  this
>        can be useful if you want the higher resolution, and don't
>        currently need to have color displayed.  unfortunately, there
>        is currently no way to enter this "semi-permanent monochrome
>        mode" via the Sugar user interface -- only Ctrl-BrDown will do it.
> and finally, on XO-1.75 only:
>    - the backlight may automatically turn off when the laptop is in
>        bright sunlight.  when this happens, it is _not_ put into the
>        hi-res monochrome mode.  when the light level returns to
>        "normal" -- i.e., indoor or shady light -- the backlight will
>        be restored to its previous value.
>        the ambient light sensor shares the opening in the plastic
>        with the LED that looks like "(o)" near the lower left corner
>        of the screen, so covering that location when outside, or
>        shining a bright light on it when inside, may cause the
>        backlight level to change.
> it's also worth noting that the F9 and F10 keys are, by default, the
> brightness keys, and are intercepted by system software before a
> running program can receive them.  if the Fn key is pressed at the
> same time as F9 or F10, then the keys instead generate the true F9 and
> F10 codes, and are available to the current application (or perhaps
> the window manager).  this is also true of the volume keys on F11 and
> F12 -- on any of our keyboards, holding Fn will force the top row of
> keys to generate F1 through F12.
> finally:  all of the above functionality is available from the
> shell commandline:
>    $ olpc-brightness -h
>    usage: olpc-brightness [up|down|max|min|<0-15>|color|mono]
> paul
> =---------------------
>  paul fox, pgf at laptop.org
> _______________________________________________
> support-gang mailing list
> support-gang at lists.laptop.org
> http://lists.laptop.org/listinfo/support-gang
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