http://www.newton-inc.com/dev/techinfo/qa/qa.htm
Gestalt
function as follows:// define this somewhere in your project
// until the platform file defines it (not in 1.2d2)
constant kGestalt_BackLight := '[0x02000007, [struct, boolean], 1];
local isBacklight := Gestalt(kGestalt_BackLight);
if isBacklight AND isBacklight[0] then
// has a backlight
else
// has not got one
Status of the backlight BackLightStatus()
return value = nil (backlight is off) or non-nil (backlight is on) BackLight(state)
return value - unspecified