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

1.1     ! root        1: #include "copyright.h"
        !             2: 
        !             3: /* $Header: XIfEvent.c,v 11.8 87/09/11 08:09:02 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 matching the
        !            13:  * predicate in the queue.
        !            14:  */
        !            15: 
        !            16: XIfEvent (dpy, event, predicate, arg)
        !            17:        register Display *dpy;
        !            18:        Bool (*predicate)();            /* function to call */
        !            19:        register XEvent *event;
        !            20:        char *arg;
        !            21: {
        !            22:        register _XQEvent *qelt, *prev;
        !            23:        
        !            24:        LockDisplay(dpy);
        !            25:        _XFlush (dpy);
        !            26:        /*
        !            27:         * first must search queue to find if any events match.
        !            28:         * If so, then remove from queue.
        !            29:         */
        !            30:        prev = NULL;
        !            31:        qelt = dpy->head;
        !            32:        while (qelt) {
        !            33:            if ((*predicate)(dpy, &qelt->event, arg)) {
        !            34:                *event = qelt->event;
        !            35:                if (prev) {
        !            36:                    if ((prev->next = qelt->next) == NULL)
        !            37:                        dpy->tail = prev;
        !            38:                } else {
        !            39:                    if ((dpy->head = qelt->next) == NULL)
        !            40:                     dpy->tail = NULL;
        !            41:                 }
        !            42:                qelt->next = _qfree;
        !            43:                _qfree = qelt;
        !            44:                dpy->qlen--;
        !            45:                UnlockDisplay(dpy);
        !            46:                return;
        !            47:                }
        !            48:                qelt = (prev = qelt)->next;
        !            49:        }
        !            50: 
        !            51:        
        !            52:        /* if the queue is empty, read as many events as possible
        !            53:           and enqueue them */
        !            54:        while (1) {
        !            55:            char buf[BUFSIZE];
        !            56:            long pend_not_register; /* because can't "&" a register variable */
        !            57:            register long pend;
        !            58:            register xEvent *ev;
        !            59:            XEvent scratch;
        !            60: 
        !            61:            /* find out how much data can be read */
        !            62:            if (BytesReadable(dpy->fd, (char *)&pend_not_register) < 0)
        !            63:                (*_XIOErrorFunction)(dpy);
        !            64:            pend = pend_not_register;
        !            65: 
        !            66:            /* must read at least one xEvent; if none is pending, then
        !            67:               we'll just block waiting for it */
        !            68:            if (pend < sizeof(xEvent))
        !            69:                pend = sizeof (xEvent);
        !            70:                
        !            71:            /* but we won't read more than the max buffer size */
        !            72:            if (pend > BUFSIZE)
        !            73:                pend = BUFSIZE;
        !            74: 
        !            75:            /* round down to an integral number of XReps */
        !            76:            pend = (pend / sizeof (xEvent)) * sizeof (xEvent);
        !            77: 
        !            78:            _XRead (dpy, buf, pend);
        !            79:            for (ev = (xEvent *) buf; pend > 0; ev++, pend -= sizeof(xEvent))
        !            80:                if (ev->u.u.type == X_Error)
        !            81:                    _XError (dpy, (xError *) ev);
        !            82:                else  { 
        !            83:                    /* it's an event packet; enqueue it if not predicate */
        !            84:                    (*dpy->event_vec[ev->u.u.type & 0177])(dpy, &scratch, ev);
        !            85:                    if ((*predicate)(dpy, &scratch, arg)) {
        !            86:                        ev++;                   /* Enqueue remaining events */
        !            87:                        pend -= sizeof(xEvent);
        !            88:                        for (; pend > 0; ev++, pend -= sizeof(xEvent))
        !            89:                            if (ev->u.u.type == X_Error)
        !            90:                                _XError (dpy, (xError *) ev);
        !            91:                            else
        !            92:                                _XEnq (dpy, ev);
        !            93:                        *event = scratch;
        !            94:                        UnlockDisplay(dpy);
        !            95:                        return;
        !            96:                        }
        !            97:                    _XEnq (dpy, ev);
        !            98:            }
        !            99:        }
        !           100: }
        !           101: 

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