Intermec 6100 Reference Guide

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plications to run if they have messages, which keeps your application WindowsĆ

friendly.  But if there are no pending message for anyone, PeekMessage()

immediately returns to its caller and does not allow the Windows kernel to beĆ

come idle.  The result is an application that calls PeekMessage() more or less conĆ

tinuously with short breaks while other applications process their messages.  In

other words, a cooperative busy loop" is the result.  The powerĆfriendly way to

implement a PeekMessage() loop is to implement the following:

Call PeekMessage()

if no messages, perform background processing
if there is no background processing to do, then

 

call GetMessage()

or

call WaitMessage()

"

If an application is busy with communication or processing, for extended periods

of time with no user interaction, the system might time out into suspend during

processing.  In order to prevent this, the application should fail SUSPENDREĆ

QUEST broadcasts while performing CPUĆbound tasks.  As mentioned above,

USERSUSPEND requests can also be failed, but the application should inform

the user about this type of action, otherwise the user may think that the system

is locked up (since the Suspend/Resume button does not work) and might reset

the system or take some other drastic measure.

The APM BIOS specification defines event codes for various power management

events.  NORWINPM.DRV collects these events from the APM BIOS and either

handles them directly or broadcasts them to the system components (Windows

drivers, applications and DOS TSRs).  System components can use the events to

monitor system power state changes.  Some APM events have responses which

can implement cooperative power management.

NORWINPM.DRV broadcasts APM events to Windows applications, system drivĆ

ers, installable drivers, VxDs, DOS drivers, and DOS TSRs loaded installed in

the System VM.  Each device has a different broadcast API.  The most common

APIs are documented below.

Windows applications receive APM event broadcasts via the message procedures

of any topĆlevel windows that they own.  The message format is:

Msg:

WM_POWER (defined in WINDOWS.H)

wParam:

PWR_* event code defined in APMCODES.H or WINDOWS.H.

lParam:

Undefined

Returns:

Application should return PWR_FAIL (from WINDOWS.H) if it wishes to
reject an event. Otherwise, PWR_OK should be returned.