var form = new qx.ui.form.Form();

/* Add some input fields here */

var controller = new qx.data.controller.Form(null, form);
var model = controller.createModel();


/* If everything ok with form, go on. */
loginbutton.addListener("execute", function() {
      if (form.validate()) {
        var loginData = {
          username : controller.getModel().getUsername(),
          password : controller.getModel().getPassword()
        };

    //THERE! :D
        this.fireDataEvent("changeLoginData", loginData);
        this.close();
      }
    }, this);