Prevent computer from going to sleep but _not_ disable dimming

FROM : Manfred Schwind
DATE : Mon May 26 22:17:21 2008

Hi,

I want preventing the computer from going to sleep while doing lengthy 
calculations - but I still want to allow the display to dimm.
I tried UpdateSystemActivity() with all available constants, but all 
of them also prevent the display from dimming.
Is this a bug? Or is it a feature? (Maybe to give the user some 
"feedback" that the computer will not go to sleep?!?)

In the header file I can find:

  OverallAct                    = 0,    /* Delays idle sleep by small 
amount                */
  UsrActivity                  = 1,    /* Delays idle sleep and 
dimming by timeout time          */
  NetActivity                  = 2,    /* Delays idle sleep and 
power cycling by small amount        */
  HDActivity                    = 3,    /* Delays hard drive spindown 
and idle sleep by small amount  */
  IdleActivity                  = 4    /* Delays idle sleep by 
timeout time                */

In my understanding, using e.g. OverallAct, NetActivity or  HDActivity 
should not prevent the display from dimming, but UsrActivity should.
But I tried them all and it doesn't matter which one I use, the 
display always did never dimm.

Any ideas?
Mani
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