code: public function setMultiSrcFlags($varValue, Contao\DataContainer $dc)
  	{
  		if ($dc->activeRecord)
  		{
  			switch ($dc->activeRecord->type)
  			{
  				case 'gallery':
  					$GLOBALS['TL_DCA'][$dc->table]['fields'][$dc->field]['eval']['isGallery'] = true;
  					$GLOBALS['TL_DCA'][$dc->table]['fields'][$dc->field]['eval']['extensions'] = Contao\Config::get('validImageTypes');
  					break;
  
  				case 'downloads':
  					$GLOBALS['TL_DCA'][$dc->table]['fields'][$dc->field]['eval']['isDownloads'] = true;
  					$GLOBALS['TL_DCA'][$dc->table]['fields'][$dc->field]['eval']['extensions'] = Contao\Config::get('allowedDownload');
  					break;
  			}
  		}
  
  		return $varValue;
  	}
docs: Dynamically add flags to the "multiSRC" field
  
  @param mixed                $varValue
  @param Contao\DataContainer $dc
  
  @return mixed