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Annotation of researchv9/X11/src/X.V11R1/lib/X/XPeekIfEv.c, revision 1.1

1.1     ! root        1: #include "copyright.h"
        !             2: 
        !             3: /* $Header: XPeekIfEv.c,v 11.9 87/09/11 08:09:07 toddb Exp $ */
        !             4: /* Copyright    Massachusetts Institute of Technology    1986  */
        !             5: 
        !             6: #define NEED_EVENTS
        !             7: #include "Xlibint.h"
        !             8: 
        !             9: extern _XQEvent *_qfree;
        !            10: 
        !            11: /*
        !            12:  * Flush output and (wait for and) return the next event in the queue
        !            13:  * that satisfies the predicate.
        !            14:  * BUT do not remove it from the queue.
        !            15:  */
        !            16: 
        !            17: XPeekIfEvent (dpy, event, predicate, arg)
        !            18:        register Display *dpy;
        !            19:        register XEvent *event;
        !            20:        Bool (*predicate)();
        !            21:        char *arg;
        !            22: {
        !            23:        register _XQEvent *qelt;
        !            24:        xEvent ev;
        !            25: 
        !            26:        LockDisplay(dpy);
        !            27:        _XFlush (dpy);
        !            28: 
        !            29:        qelt = dpy->head;
        !            30:        while (qelt) {
        !            31:            if ((*predicate)(dpy, &qelt->event, arg)) {
        !            32:                *event = qelt->event;
        !            33:                UnlockDisplay(dpy);
        !            34:                return;
        !            35:                }
        !            36:                qelt = qelt->next;
        !            37:        }
        !            38: 
        !            39:        /* 
        !            40:         * if no match in queue, then block waiting for event, enqueing
        !            41:         * other events all the while.
        !            42:         */
        !            43:        while (1) {
        !            44:            _XRead (dpy, (char *)&ev, (long)sizeof(xEvent));
        !            45:            if (ev.u.u.type == X_Error)
        !            46:                _XError (dpy, (xError *) &ev);
        !            47:            else {  /* it's an event packet */
        !            48:                _XEnq (dpy, &ev);
        !            49:                if ((*predicate)(dpy, &dpy->tail->event, arg)) {
        !            50:                        *event = dpy->tail->event;
        !            51:                        UnlockDisplay(dpy);
        !            52:                        return;
        !            53:                        }
        !            54:                }
        !            55:        }
        !            56: }
        !            57: 

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