Custom Template - Group List filtered by state

Hi Folks,

i’m an openhab noob and i run into a Problem writing a custom Template Widget.
I want to have a widget that lists all items in a group with the itemstate “offline”
So far i have a Template that lists me all members of the group, but i see no way how to filter to show only the offline items:

<div class="row" ng-repeat="item in itemsInGroup('gr_on_offline_HT')">
  <div class="col-xs-8 text-right">{{item.label}}</div>
  <div class="col-xs-4 text-left" ng-style="{ color: itemValue('online' ? 'red':'green' }">