source: liacs/mms/project/uinput.c@ 157

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <signal.h>
#include <X11/Xlib.h>

static int fd;

struct coords {
        int x;
        int y; 
};

void close_pointer() {
    ioctl(fd, UI_DEV_DESTROY);
    close(fd);
}

// Close stuff nicely in case of issues
void ex_program(int sig) {
    close_pointer();
    printf("Terminated signal: %d\n", sig);
    (void) signal(SIGINT, SIG_DFL);
    exit(-1);
}

// Wrapper to send cool stuff over the wire
int send_event(int fd, __u16 type, __u16 code, __s32 value)
{
    struct input_event event;

    memset(&event, 0, sizeof(event));
    event.type = type;
    event.code = code;
    event.value = value;
    gettimeofday(&event.time, NULL);

    if (write(fd, &event, sizeof(event)) != sizeof(event)) {
        fprintf(stderr, "Error on send_event");
        return -1;
    }

    return 0;
}

//XXX: Make me more effient
struct coords 
get_coords() {
        Display *dsp = XOpenDisplay( NULL );
        
        struct coords xy_current = { -1, -1 };
        if( !dsp ){ return xy_current; }
        
        int screenNumber = DefaultScreen(dsp);
        
        XEvent event;
        
        /* get info about current pointer position */
        XQueryPointer(dsp, RootWindow(dsp, screenNumber),
        &event.xbutton.root, &event.xbutton.window,
        &event.xbutton.x_root, &event.xbutton.y_root,
        &event.xbutton.x, &event.xbutton.y,
        &event.xbutton.state);
        
        printf("Mouse Coordinates: %d %d\n", event.xbutton.x, event.xbutton.y);
        XCloseDisplay( dsp );
        xy_current.x = event.xbutton.x;
        xy_current.y = event.xbutton.y;
        return(xy_current);
}


// Set the pointer to a certain location
int
init_pointer()
{
    int i;
    struct uinput_user_dev device;
    memset(&device, 0, sizeof device);

    fd=open("/dev/uinput",O_WRONLY | O_NDELAY);
    strcpy(device.name,"test mouse");

    device.id.bustype=BUS_USB;
    device.id.vendor= 0x0001;
    device.id.product=0x0001;
    device.id.version=UINPUT_VERSION;

    //for (i=0; i < ABS_MAX; i++) {
    //    device.absmax[i] = -1;
    //    device.absmin[i] = -1;
    //    device.absfuzz[i] = -1;
    //    device.absflat[i] = -1;
    //}

    if (write(fd,&device,sizeof(device)) != sizeof(device))
    {
        fprintf(stderr, "error setup\n");
        return -1;
    }

    (void) signal(SIGINT, ex_program);

    /* mousedev only recognize our device as a mouse
     * if it has at least two axis and one left button.
     * Also, mouse buttons have to send sync events. 
     */
    //ioctl(fd, UI_SET_EVBIT, EV_KEY);
    ioctl(fd, UI_SET_EVBIT, EV_REL);
    ioctl(fd, UI_SET_EVBIT, EV_SYN);

    ioctl(fd, UI_SET_RELBIT, REL_X);
    ioctl(fd, UI_SET_RELBIT, REL_Y);
    //ioctl(fd, UI_SET_RELBIT, REL_WHEEL);

    ioctl(fd, UI_SET_KEYBIT, BTN_LEFT);
    //ioctl(fd, UI_SET_KEYBIT, BTN_RIGHT);
    //ioctl(fd, UI_SET_KEYBIT, BTN_MIDDLE);

    //for (i=0; i < 256; i++) {
        //    ioctl(fd, UI_SET_KEYBIT, i);
    //}

    ioctl(fd, UI_DEV_CREATE, NULL);

}

int set_pointer(const struct coords xy_target) {
    struct coords xy_diff, xy_prev;
    struct coords xy_current = { -1 , -1 }; // Bogus inital value
    char c;
    // Force pointer to absolute location on the screen
    while ( 1 ) {
        //XXX: Screen pointer get updated really slow
        xy_prev.x = xy_current.x;
        xy_prev.y = xy_current.y;
        while ( 1 ) {
            xy_current = get_coords();
            // Found ourself an update
            printf("old->new coordinates %ix%i -> %ix%i\n",
                xy_prev.x,xy_prev.y,
                xy_current.x,xy_current.y); 
            if (xy_prev.x != xy_current.x || xy_prev.y != xy_current.y) {
                //ex_program(1);
                break;
            }
            usleep(200000);
        }

        xy_diff.x = (xy_target.x - xy_current.x);
        xy_diff.y = (xy_target.y - xy_current.y);
        if (xy_diff.x == 0 && xy_diff.y == 0) {
            printf("Location %ix%i\n", xy_current.x, xy_current.y);
            break;
        } else {
            printf("Trying to sync current:%ix%i target:%ix%i diff:%ix%i\n",
                xy_current.x, xy_current.y,
                xy_target.x, xy_target.y,
                xy_diff.x, xy_diff.y);
            send_event(fd, EV_REL, REL_X, xy_diff.x);
            send_event(fd, EV_REL, REL_Y, xy_diff.y);
            send_event(fd, EV_SYN, SYN_REPORT, 0);
            // Wait some small period of time to get it populated (and the screen get updated)
            usleep(200000);
        }
    }
}

int 
main() {
    struct coords xy_target = { 200,200 };
    init_pointer();
        set_pointer(xy_target); 
    xy_target.x = 500;
    xy_target.y = 500;
        set_pointer(xy_target); 
    close_pointer();
        return(0);
}