waitfor(3,100,WAIT_INFINITE,WAIT_KEEP+WAIT_EXACT+WAIT_GID) 

1. This procedure suspends the execution of the caller until an event of a particular class is available. The second form specifies a time limit: the processing is suspended for at most dur seconds, the special value WAIT_INFINITE is interpreted as an infinite duration.

2. If the time limit is 0 the execution is not suspended but the queue of events is processed once and a subsequent call to waitexpired will return true if no valid event was found.

3. The parameter dur may also take a negative value: in this case it is interpreted as the opposite of a timer identifier (see settimer) and the function will wait until this timer expires if no valid event arrives. When the routine interrupts its monitoring due to the expiration of a timer the first event in the queue is the event EVENT_TIMER associated to this timer. Note that if no timer corresponds to the given value the routine will terminate only when an expected event is available as if WAIT_INFINITE had been used.

4. By default, the parameter mask is interpreted as a bit mask to select the expected events: all events sent to the model are automatically dropped until an event ev satisfies the following condition:

bittest(getclass(ev),mask)<>0

5. If the parameter opt includes option WAIT_EXACT, the parameter mask becomes the target event class: the wait will end when an event of a class equal to mask is found.

6. If the parameter opt includes option WAIT_KEEP, unexpected events are not dropped but the first event satisfying the condition is moved to the top of the queue such that it is returned by the next call to getnextevent.

7. With the last form of the function an ID is specified: it characterises events coming from a particular model or a group of models. By default the argument id is interpreted as the unique model ID (see getid), if option WAIT_UID is used, the ID is interpreted as a user ID (see getuid) and with option WAIT_GID the argument is a group ID (see getgid).