Comment by 90s_dev

This is the entire source:

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

    #define stk(s)    XKeysymToKeycode(d, XStringToKeysym(s))
    #define on(_, x)  if (e.type == _) { x; }
    #define map(k, x) if (e.xkey.keycode == stk(k)) { x; }
    #define grab(...) const char *l[] = { __VA_ARGS__, 0 }; \
                        for (int i = 0; l[i]; i++) XGrabKey(d, stk(l[i]), Mod4Mask, r, 1, 1, 1);

    int main() {
      Display *d = XOpenDisplay(0); Window r = DefaultRootWindow(d); XEvent e;
      XSelectInput(d, r, SubstructureRedirectMask);
      grab("n", "q", "e");

      while (!XNextEvent (d, &e)) {
        on(ConfigureRequest, XMoveResizeWindow(d, e.xconfigure.window, 0, 0, e.xconfigure.width, e.xconfigure.height));
              on(MapRequest, XMapWindow(d, e.xmaprequest.window);
                            XSetInputFocus(d, e.xmaprequest.window, 2, 0));
                on(KeyPress, map("n", XCirculateSubwindowsUp(d, r); XSetInputFocus(d, e.xkey.window, 2, 0))
                            map("q", XKillClient(d, e.xkey.subwindow))
                            map("e", system("dmenu_run &")));
      }
    }

I have to say, I'm not usually a huge fan of C macros, but it works here so well, it feels so elegant and clean somehow.