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<HTML><HEAD><TITLE>Xlib Programming Manual: XCheckIfEvent</TITLE></HEAD><BODY><H1 ALIGN=center>XCheckIfEvent</H1><H2>Syntax</H2><!.IN "XCheckIfEvent" "" "@DEF@"><CODE><PRE>Bool XCheckIfEvent(<B>display</B>, <B>event_return</B>, <B>predicate</B>, <B>arg</B>)      <A HREF="../../display/opening.html#Display">Display</A> *<B>display</B>;      <A HREF="../../events/structures.html#XEvent">XEvent</A> *<B>event_return</B>;      Bool (*<B><A HREF="selecting-using-predicate.html#predicate">predicate</A></B>)();      XPointer <B>arg</B>;</PRE></CODE><H2>Arguments</H2><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>event_return</B><TD> Returns a copy of the matched event's associated structure.<TR><TD> <B>predicate</B><TD> Specifies the procedure that is to be called to determineif the next event in the queue matches what you want.<TR><TD> <B>arg</B><TD> Specifies the user-supplied argument that will be passed to the predicate procedure.</TABLE><H2>Description</H2>When the predicate procedure finds a match,<B>XCheckIfEvent()</B>copies the matched event into the client-supplied<A HREF="../../events/structures.html#XEvent">XEvent</A>structure and returns <B>True</B>.(This event is removed from the queue.)If the predicate procedure finds no match,<B>XCheckIfEvent()</B>returns<B>False</B>,and the output buffer will have been flushed.All earlier events stored in the queue are not discarded.<H2>See also</H2><B><A HREF="XIfEvent.html">XIfEvent()</A></B>,<B><A HREF="XNextEvent.html">XNextEvent()</A></B>,<B><A HREF="XPeekIfEvent.html">XPeekIfEvent()</A></B>,<B><A HREF="../XPutBackEvent.html">XPutBackEvent()</A></B>,<B><A HREF="../XSendEvent.html">XSendEvent()</A></B>,"<A HREF="selecting-using-predicate.html">Selecting Events Using a Predicate Procedure</A>".<HR><ADDRESS><A HREF="http://tronche.com/">Christophe Tronche</A>, <A HREF="mailto:ch.tronche@computer.org">ch.tronche@computer.org</A></ADDRESS></BODY></HTML>

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