Retrieves an event from the Operating System event queue without removing it.

Boolean OSEventAvail (
    EventMask mask, 
    EventRecord *theEvent
);

mask

A value that indicates which kinds of events are to be returned; this parameter is interpreted as a sum of event mask constants. You specify the event mask using one or more values defined by the “EventMask Constant”. OSEventAvail returns only low-level events stored in the Operating System event queue; it does not return activate, update, operating-system, or high-level events. If no low-level event of any of the designated types is available, OSEventAvail returns a null event.

theEvent

A pointer to an event structure for the next available event of the specified type or types. The OSEventAvail function does not remove the returned event from the Operating System event queue but does return information about the event in an event structure. The event structure includes the type of event received and other information.

DISCUSSION

In most cases your application does not need to use this function. The OSEventAvail function retrieves an event from the Operating System event queue without removing it from the queue. The OSEventAvail function returns false as its function result if the event being returned is a null event; otherwise, OSEventAvail returns true.

OSEventAvail does not intercept or respond to the event in any way. It also does not process Command–Shift–number key combinations or process any alarms set by the user through the Alarm Clock desk accessory.

SPECIAL CONSIDERATIONS

If the OSEventAvail function returns a low-level event from the Operating System event queue, the event will not be accessible later if, in the meantime, the event queue becomes full and the event is discarded from it; however, this is not a common occurrence.

AVAILABILITY

Not supported in Carbon. Not available in Carbon.

CARBON NOTES

OSEventAvail is not supported in Carbon. Use the EventAvail function instead.

© 2000 Apple Computer, Inc. — (Last Updated 5/8/2000)