Linux mendapatkan pemberitahuan tentang perubahan jendela gui terfokus

Contoh dalam JavaScript menggunakan node-x11:

var x11 = require('x11');
x11.createClient(function(err, display) {
  var X = display.client;
  X.ChangeWindowAttributes(display.screen[0].root, { eventMask: x11.eventMask.PropertyChange });
  X.on('event', function(ev) {
    if(ev.name == 'PropertyNotify') {
      X.GetAtomName(ev.atom, function(err, name) {
        if (name == '_NET_ACTIVE_WINDOW') {
          X.GetProperty(0, ev.window, ev.atom, X.atoms.WINDOW, 0, 4, function(err, prop) {
            console.log('New active window:' + prop.data.readUInt32LE(0));
          });
        }
      });
    }
  });
});