dump focused window

$ gcc -lX11 foobar.c -o foobar#include <X11/Xlib.h>#include <stdio.h>int main(int argc, char *argv[]){    char *disp_name = ":0";    Display *disp;    if(!(disp = XOpenDisplay(disp_name))) return 1;    while(1) {        char *name;        int id, ret;        Window wid;        XGetInputFocus(disp, &wid, &id);        ret = XFetchName(disp, wid, &name);        if(ret != 0) printf("Window name: %s\n", name);        XFree(name);        sleep(1);    }    return 0;}