public function setHeaderPopup($popup, $icon = 'caret square down')
    {
        $this->hasHeaderAction = true;
        $id = $this->name.'_ac';

        $this->headerActionTag = ['div',  ['class'=>'atk-table-dropdown'],
            [
                ['i', ['id' => $id, 'class' => $icon.' icon']],
            ],
        ];
        $popup->triggerBy = '#'.$id;
        $popup->popOptions = array_merge($popup->popOptions, ['on' =>'click', 'position' => 'bottom right', 'movePopup' => false]);
        $popup->stopClickEvent = true;

        if (@$_GET['__atk_reload']) {
            //This is part of a reload, need to reactivate popup.
            $this->table->js(true, $popup->jsPopup());
        }
    }