The WM_TIMER message is posted to the installing thread's message queue or sent to the appropriate TimerProc callback function after each interval specified in the SetTimer function used to install a timer.
WM_TIMER
wTimerID = wParam; // timer identifier
tmprc = (TIMERPROC *) lParam; // address of timer callback
Parameters
wTimerID
Value of wParam. Specifies the timer identifier.
tmprc
Value of lParam. Points to an application-defined callback function that was passed to the SetTimer function when the timer was installed. If the tmprc parameter is not NULL, Windows passes the WM_TIMER message to the specified callback function rather than posting the message to the thread's message queue.
Return Values
An application should return zero if it processes this message.
Remarks
The DispatchMessage function forwards this message when no other messages are in the thread's message queue.
See Also