Resources/contao/classes/TextField.php
public function generateLabel()
    {
        if (($this->require_input) && ($this->value == '')) {
            $this->required = true;
        }
        return parent::generateLabel();
    }
public function generateLabel()
    {
        if (($this->require_input) && ($this->value == '')) {
            $this->required = true;
        }
        return parent::generateLabel();
    }
public function generateLabel ( ) { if ( ( $ this -> require_input ) && ( $ this -> value == '' ) ) { $ this -> required = true ; } return parent :: generateLabel ( ) ; }
Check custom setting 'require_input', which implements custom mandatory handling possibility
@return string
Check custom setting require_input which implements custom mandatory handling possibility