How to add a width property to the listvalue to control the width

var CBIListValue = CBIValue.extend({
name: 'CBI.ListValue',
init: function() {
this.super('init', arguments);
this.widget = 'select';
this.orientation = 'horizontal';
this.deplist = ;
},
renderWidget: function(section_id, option_index, cfgvalue) {
var choices = this.transformChoices();
var widget = new ui.Select((cfgvalue != null) ? cfgvalue : this.default, choices, {
id: this.cbid(section_id),
size: this.size,
sort: this.keylist,
widget: this.widget,
optional: this.optional,
orientation: this.orientation,
placeholder: this.placeholder,
validate: L.bind(this.validate, this, section_id),
disabled: (this.readonly != null) ? this.readonly : this.map.readonly
});
return widget.render();
},
});