main.c

#include <stdio.h>
#include <X11/Xlib.h>
#include <X11/extensions/XInput2.h>
#include <signal.h>
#include <assert.h>

int working = 1;

void signal_callback_handler(int signum) {
    working = 0;
}

int main() {

    /* Connect to the X server */
    signal(SIGINT, signal_callback_handler);
    signal(SIGTSTP, signal_callback_handler);
    signal(SIGTERM, signal_callback_handler);

    Display *dpy = XOpenDisplay(NULL);
    assert(dpy);

    /* XInput Extension available? */
    int opcode, event, error;
    if (!XQueryExtension(dpy, "XInputExtension", &opcode, &event, &error)) {
        printf("X Input extension not available.\n");
        return -1;
    }

    /* Which version of XI2? We support 2.0 */
    int major = 2, minor = 0;
    if (XIQueryVersion(dpy, &major, &minor) == BadRequest) {
        printf("XI2 not available. Server supports %d.%d\n", major, minor);
        return -1;
    }


    XIEventMask eventmask;

    unsigned char mask[1] = { 0 }; /* the actual mask */

    eventmask.deviceid = XIAllDevices;
    eventmask.mask_len = sizeof(mask); /* always in bytes */
    eventmask.mask = mask;

    /* now set the mask */
    XISetMask(mask, XI_RawButtonPress);

    /* select on the window */
    XISelectEvents(dpy, DefaultRootWindow(dpy), &eventmask, 1);

    while(working) {
        XEvent ev;
        XNextEvent(dpy, &ev);
        if (ev.xcookie.type == GenericEvent &&
                ev.xcookie.extension == opcode &&
                XGetEventData(dpy, &ev.xcookie))
        {
            switch(ev.xcookie.evtype)
            {
                case XI_RawButtonPress:
                    printf("RawButtonPress");
                    break;
            }
        }
        XFreeEventData(dpy, &ev.xcookie);
    }
}

X Error of failed request: XI_BadDevice (invalid Device parameter)
Major opcode of failed request: 131 (XInputExtension)
Minor opcode of failed request: 46 ()
Device id in failed request: 0xad
Serial number of failed request: 15
Current serial number in output stream: 15