[Sugar-devel] automatic backlight control

[Paul Fox]

forster at ozonline.com.au wrote:
 > Thanks Paul

thanks for testing!

 > 
 > The logic appears to be buggy, see #11487:  XO-1.75 OS12 backlight
 > is off when you come back inside

okay, more testing is needed.  as you noted, it's quite hard to tell
when it's on and off.  i'll see if i can come up with an indicator,
on the display or on the LEDs, which will help during debug.

 > 
 > As it stands, neither the monochrome nor colour modes are OK in
 > full sunlight.  The colour mode causes a significant loss of
 > resolution for reading small black text and even more resolution
 > loss with coloured text.

to clarify -- neither of these issues is caused by the auto-turnoff,
but they might suggest that one or the other modes is a better target
in full sun -- is that what you're saying?

where can i find some colored text on the laptop?

 > 
 > With the monochrome mode, the shadow of your hands as you type is
 > enough to switch mode which is quite distracting

the color/mono selection shouldn't have affect on how much light
causes the mode switch.

 > 
 > The cutin cutout settings are 50 (bright)and 80 (dark).  It does
 > not seem worth raising the 80 figure because there is still visible
 > colour information at 70.  The 50 figure could be lowered, direct
 > sunlight is 5-10, so I tried 15, this still could give mode
 > switching from your hands' shadow in direct sunlight.

how can you tell the switch has occurred, if you're in full sunlight?
i honestly can't tell when it's happened.

 > 
 > What I suggest is that the backlight not switch off unless you have
 > been in the sun for (eg) 5 minutes, but switch back on immediately
 > in the dark.  I don't have the coding skills or I would have tried
 > it out.
 > 
 > For anybody who wants to try it powerd is at /usr/sbin/power
 > 
 > the brightness settings are at line1853 monochrome is commented out
 > at lines 1764 &1793
 > 
 > uncommenting these lines reenables monochrome in response to the
 > sensor but surprisingly not the control keys

i don't follow -- the code in powerd currently has (or should have) no
effect on how the brightness keys work.  they're handled by
olpc-brightness.  so they should continue doing what they were doing
before you modified those lines to reenable "zero brightness gives mono"
behavior.

paul

 > 
 > Tony
 > 
 > > forster at ozonline.com.au wrote:
 > >  > The shift from colour to monochrome is noticable and would be annoying if 
 > it 
 > >  > happened a lot, for example as clouds pass, trees and people move.
 > >  > 
 > >  > If the hysterisis, the difference between cutin and cutout brightness is 
 > large, 
 > >  > the change in mode will happen a lot less frequently and not be annoying.
 > >  > 
 > >  > I would like to try it switching automatically to monochrome but with 
 > large 
 > >  > hysterisis.
 > >  > 
 > >  > I'll wait to try OS12
 > > 
 > > 
 > > you may be in a better position to play with this, geographically
 > > speaking, than i am -- we're running low on sunlight these days.
 > > 
 > > the hysteresis is currently hard-coded in powerd -- you'll find it in
 > > the function ambient_adjust_init().  it only gets set once, though, so
 > > after powerd starts, you can change the limits directly and they
 > > should take effect immediately.
 > > 
 > > additionally, to cause auto-monochrome to happen, uncomment the
 > > obvious lines at the end of set_brightness() and brightness_ramp().
 > > 
 > > paul
 > > 
 > >  > 
 > >  > Tony
 > >  > _______________________________________________
 > >  > Devel mailing list
 > >  > Devel at lists.laptop.org
 > >  > http://lists.laptop.org/listinfo/devel
 > > 
 > > =---------------------
 > >  paul fox, pgf at laptop.org
 > > _______________________________________________
 > > Sugar-devel mailing list
 > > Sugar-devel at lists.sugarlabs.org
 > > http://lists.sugarlabs.org/listinfo/sugar-devel
 > > 
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=---------------------
 paul fox, pgf at laptop.org