error messages on grab failure - slock - simple X display locker utility
 (HTM) git clone git://git.suckless.org/slock
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       ---
 (DIR) commit 9dfe0ce531023bf63c0e518b07ee97cf0cac742a
 (DIR) parent 55e827af0fb94f6c2b9e76a7bfe7e98cf697dc7b
 (HTM) Author: Markus Teich <markus.teich@stusta.mhn.de>
       Date:   Mon, 18 Jan 2016 16:49:15 +0100
       
       error messages on grab failure
       
       Diffstat:
         M slock.c                             |      30 ++++++++++++++++--------------
       
       1 file changed, 16 insertions(+), 14 deletions(-)
       ---
 (DIR) diff --git a/slock.c b/slock.c
       @@ -230,7 +230,7 @@ lockscreen(Display *dpy, int screen)
                XSetWindowAttributes wa;
                Cursor invisible;
        
       -        if (dpy == NULL || screen < 0 || !(lock = malloc(sizeof(Lock))))
       +        if (!running || dpy == NULL || screen < 0 || !(lock = malloc(sizeof(Lock))))
                        return NULL;
        
                lock->screen = screen;
       @@ -253,29 +253,31 @@ lockscreen(Display *dpy, int screen)
                XMapRaised(dpy, lock->win);
                if (rr)
                        XRRSelectInput(dpy, lock->win, RRScreenChangeNotifyMask);
       +
       +        /* Try to grab mouse pointer *and* keyboard, else fail the lock */
                for (len = 1000; len; len--) {
                        if (XGrabPointer(dpy, lock->root, False, ButtonPressMask | ButtonReleaseMask | PointerMotionMask,
                            GrabModeAsync, GrabModeAsync, None, invisible, CurrentTime) == GrabSuccess)
                                break;
                        usleep(1000);
                }
       -        if (running && len) {
       +        if (!len) {
       +                fprintf(stderr, "slock: unable to grab mouse pointer for screen %d\n", screen);
       +        } else {
                        for (len = 1000; len; len--) {
       -                        if (XGrabKeyboard(dpy, lock->root, True, GrabModeAsync, GrabModeAsync, CurrentTime) == GrabSuccess)
       -                                break;
       +                        if (XGrabKeyboard(dpy, lock->root, True, GrabModeAsync, GrabModeAsync, CurrentTime) == GrabSuccess) {
       +                                /* everything fine, we grabbed both inputs */
       +                                XSelectInput(dpy, lock->root, SubstructureNotifyMask);
       +                                return lock;
       +                        }
                                usleep(1000);
                        }
       +                fprintf(stderr, "slock: unable to grab keyboard for screen %d\n", screen);
                }
       -
       -        running &= (len > 0);
       -        if (!running) {
       -                unlockscreen(dpy, lock);
       -                lock = NULL;
       -        } else {
       -                XSelectInput(dpy, lock->root, SubstructureNotifyMask);
       -        }
       -
       -        return lock;
       +        /* grabbing one of the inputs failed */
       +        running = 0;
       +        unlockscreen(dpy, lock);
       +        return NULL;
        }
        
        static void