Intermec 6200 Reference Guide

R

Fills a 

tagPOWER_STATUS

 structure with current power status values.

Determines whether ac is on line to detect docking and to check battery status.

This structure transfers power information.  The structure is six bytes long,

although, as documented earlier, some APM event broadcasts return the first or

last four bytes of the structure in the 32Ćbit optional parameter.

Returns APM state for particular APM or OEMĆdefined devices.

Sets APM power state of a particular APM or OEMĆdefined device.  If the

SYSTEM device is set to 

, SetPowerState treats the request the same

as a suspend timeout and broadcasts the suspend request to the system, then

suspend the system.  If an application or driver fails the suspend request,

SetPowerState returns 

PWR_FAIL

.

Call this function to indicate that system or user activity has occurred.  This

keeps the system from timing out into standby (backlight off) or suspend.  This

function is typically called by drivers that control communications (serial,

Ethernet) or user input (scanner) peripherals.  Applications can also call this

function to indicate that they are busy during long periods of processing;

however, it is preferable that applications receive and process the

SUSPENDREQUEST message.

A Windows application can benefit system power management by allowing the

CPU to idle, by closing unused devices, and by suspending the system when the

application knows that the user is idle.

To maintain good system response in a multiĆtasking system like Windows, you

should minimize the use of busy loops.  Busy loops, moreover, waste system

power.  Applications should be careful to never busyĆwait when implementing

timeouts or polling routines.  Instead, a system timer should be used, thereby

allowing the system to continue to idle during periods of inactivity.
Another practice to avoid is the use of 

PeekMessage

 loops instead of 

GetMessage

loops.  Calling 

PeekMessage

 to see whether a message is waiting for you does

allow other Windows applications to run if they have messages, which keeps

your application friendly.  But if there are no messages pending, 

PeekMessage