#include <iostream>

#include <X11/Xlib.h>
#include <X11/Xutil.h>

int main (int argc, char *argv[]) {
    Display *display = XOpenDisplay(NULL);
    Window win, root, parent, *children;
    int revert = RevertToParent;
    int screen = DefaultScreen(display);
    unsigned int nchild;
    XGetInputFocus(display, &win, &revert);

    if (win != RootWindow(display, screen)) {
        parent = win;
        do {
            win = parent;
            XQueryTree(display, win, &root, &parent, &children, &nchild);
            XFree(children);
        } while(parent != RootWindow(display, screen));
    }

    char *name;
    int status = XFetchName(display, win, &name);
    std::cout << "Returned status:" << status << std::endl
              << "Active window name: " << name << std::endl;

    return 0;
}