function showClientCoords(win, x, y, timeout=1000) {
    let d = win.document.createElement("div");
    d.style.width = "10px";
    d.style.height = "10px";
    d.style.borderRadius = "5px";
    d.style.backgroundColor = "red";
    d.style.position = "fixed";
    d.style.top = (y + 5) + "px";
    d.style.left = (x + 5) + "px";
    win.document.documentElement.appendChild(d);
    win.setTimeout(function() {
      d.remove();
    }, timeout);
  }