TYPO3 Core

The API calls are splitted in single requests. They are included as script tags with
<script src="ajax.php?ajaxID=ExtDirect::getAPI&namespace=TYPO3.XYZ" ...

If you load the BE you have 6 single requests of these just to get the API, each request uses ajax.php and so have an own BE authentification using init.php. As they are script tags, they block the other scrupts from continue loading, and this takes a long time.

The patch get rid of this technique completely, you now only have to add the ExtDirect code, and the API is rendered inline in document.

There are 2 possibilities:
a)

$this->pageRenderer->addExtDirectCode();

this includes all necessary javascript including all available namespaces start with TYPO3

b)

$this->pageRenderer->addExtDirectCode(array(
    'TYPO3.EM',
    'TYPO3.EMSOAP',
    'TYPO3.ExtDirectStateProvider'
));

this includes all necessary javascript including all defined namespaces in the array

(issue imported from #M17592)