fn = function() {

                played = Utils.timestamp() - now;
                if ( played >= self._playtime && self._playing ) {
                    self.clearTimer( timer_id );
                    self.next();
                    return;
                }
                if ( self._playing ) {

                    // trigger the PROGRESS event
                    self.trigger({
                        type:         Galleria.PROGRESS,
                        percent:      M.ceil( played / self._playtime * 100 ),
                        seconds:      M.floor( played / 1000 ),
                        milliseconds: played
                    });

                    self.addTimer( timer_id, fn, interval );
                }
            }
Checks if the gallery is currently in fullscreen mode

        @returns {Boolean}