How to get the rootpage Id in a itemproc function? - typo3

Question

I got an extension which uses itemproc functions to configure the plugins.
/Configuration/FlexForms/Config.xml:
<T3DataStructure>
<meta type="array">
<langChildren>0</langChildren>
<langDisable>1</langDisable>
</meta>
<sheets>
<sDEF>
<ROOT>
<TCEforms>
<sheetTitle>Allgemein</sheetTitle>
</TCEforms>
<type>array</type>
<el>
:
<settings.auswahlKategorie>
<TCEforms>
<label>Anzuzeigende Kategorie wählen:</label>
<config>
<type>select</type>
<itemsProcFunc>Company\myextension\UserFunc\ItemsProcFunc->getCategoryList</itemsProcFunc>
</config>
</TCEforms>
</settings.auswahlKategorie>
:
</el>
</ROOT>
</sDEF>
</sheets>
</T3DataStructure>
in function definition
/**
* Generiert die Liste der Kategorien.
*
* Wird für den Aufbau der "FlexForm" benötigt.
*
* #param string_array $config TYPO3 config array.
* #return string_array Angepasstes TYPO3 - Config array.
*/
public function getCategoryList($config) {
:
they assume the root page could be accessed with:
$pageId = $config['flexParentDatabaseRow']['pid'];
to access the typoscript configuration:
$conf = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('Company\\myextension\\Services\\Config');
$conf->setConfFromTsSetup($pageId);
but there is no value $config['flexParentDatabaseRow']['pid'] and so the typoscript from page 0 is fetched, where no typoscript exist.
how can I provide a correct root-page Id (without modifying the sources from the external company)?

Answer 1

I'm pretty sure what they meant is that you have to add the configuration to your flexform config.
Should be something like this:
<config>
<type>select</type>
<itemsProcFunc>Company\myextension\UserFunc\ItemsProcFunc->getCategoryList</itemsProcFunc>
<flexParentDatabaseRow>
<pid>1</pid>
</flexParentDatabaseRow>
</config>
Not sure this is the correct way, but I'm pretty sure that $config refers to that very config section of the flexform or TCA setup if TCA is used.

Answer 2

The problem was the installed compatibility6 extension.
This issue gave the hint:
The breaking change no 70132 ("FormEngine custom functions") in the
TYPO3 core 7.6 suggests using 'flexParentDatabaseRow' instead of 'row'
for retrieving the full parent database row in a userFunc /
itemsProcFunc.
There is no setting I need to do. The values are set when the data is received.