[Sugar-devel] automatic backlight control

[forster at ozonline.com.au]

> 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.

Its not too hard to write a TurtleArt program which continuously prints the brightness sensor and the screen brightness, there is a block for the brightness sensor and sample python code 'sensor.py' for the screen bightness

> 
>  > 
>  > 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?

The loss of resolution in full sunlight results from disabling the monochrome mode, disabled for both manual and automatic triggering in OS12

> 
> where can i find some colored text on the laptop?

I am not sure what you are asking, links in webpages is one example, you can create coloured text in Write

> 
>  > 
>  > 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.

no it doesn't, what are you saying?

> 
>  > 
>  > 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.

I am running a Turtleart program to interrogate the sensor and screen brightness

> 
>  > 
>  > 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.

The brightness keys no longer give monochrome at zero brightness. You must have coded that somewhere in powerd? Line 1793 looked like it was going to be the culprit.

> 
> 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
>  > > _______________________________________________
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>  > > Sugar-devel at lists.sugarlabs.org
>  > > http://lists.sugarlabs.org/listinfo/sugar-devel
>  > > 
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> =---------------------
>  paul fox, pgf at laptop.org
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