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XIfEvent, XCheckIfEvent, XPeekIfEvent - check the event queue with a predicate procedure
XIfEvent(display, event_return, predicate, arg)
Display *display;
XEvent *event_return;
Bool (*predicate)();
XPointer arg;
Bool
XCheckIfEvent(display, event_return, predicate, arg)
Display *display;
XEvent *event_return;
Bool (*predicate)();
XPointer arg;
XPeekIfEvent(display, event_return, predicate, arg)
Display *display;
XEvent *event_return;
Bool (*predicate)();
XPointer arg;
Specifies the user-supplied argument that will be passed to
the predicate procedure.
Specifies the connection to the X server.
Returns either a copy of or the matched event's associated
structure.
Specifies the procedure that is to be called to determine
if the next event in the queue matches what you want.
The XIfEvent function completes only when the specified predicate procedure returns True for an event, which indicates an event in the queue matches. XIfEvent flushes the output buffer if it blocks waiting for additional events. XIfEvent removes the matching event from the queue and copies the structure into the client-supplied XEvent structure.
When the predicate procedure finds a match, XCheckIfEvent copies the matched event into the client-supplied XEvent structure and returns True. (This event is removed from the queue.) If the predicate procedure finds no match, XCheckIfEvent returns False, and the output buffer will have been flushed. All earlier events stored in the queue are not discarded.
The
XPeekIfEvent
function returns only when the specified
predicate procedure returns
True
for an event. After the
predicate procedure finds a match,
XPeekIfEvent
copies
the matched event into the client-supplied
XEvent
structure without removing the event from the queue.
XPeekIfEvent
flushes the output buffer if it blocks waiting for additional events.
XAnyEvent(3X11), XNextEvent(3X11), XPutBackEvent(3X11), XSendEvent(3X11)
Xlib -- C Language X Interface