XIfEvent(3X11) X Version 11 (Release 5) XIfEvent(3X11)
NAME
XIfEvent, XCheckIfEvent, XPeekIfEvent - check the event
queue with a predicate procedure
SYNTAX
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;
ARGUMENTS
arg Specifies the user-supplied argument that will be
passed to the predicate procedure.
display Specifies the connection to the X server.
event_return
Returns either a copy of or the matched event's
associated structure.
predicate Specifies the procedure that is to be called to
determine if the next event in the queue matches
what you want.
DESCRIPTION
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
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XIfEvent(3X11) X Version 11 (Release 5) XIfEvent(3X11)
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.
SEE ALSO
XAnyEvent(3X11), XNextEvent(3X11), XPutBackEvent(3X11)
XSendEvent(3X11)
Xlib - C Language X Interface
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