code: function(visible, force) {
  			if (this._overviewRulerVisible === visible && !force) { return; }
  			this._overviewRulerVisible = visible;
  			if (!this._overviewRuler) { return; }
  			var textView = this._textView;
  			if (visible) {
  				textView.addRuler(this._overviewRuler);
  			} else {
  				textView.removeRuler(this._overviewRuler);
  			}
  		}
docs: Sets whether the overview ruler is visible.
  
  @param {Boolean} visible <code>true</code> to show ruler, <code>false</code> otherwise