Feature: #79196 - Allow reload of topbar

See Issue #79196

Description

A new JavaScript API to reload the backend's topbar has been introduced to the TYPO3 Core.

Impact

The toolbar reloading may be triggered on JavaScript and PHP code-level. To enforce the reloading on PHP side, call \TYPO3\CMS\Backend\Utility\BackendUtility::setUpdateSignal('updateTopbar').

Reloading the topbar via JavaScript requires the following code:

// Either: RequireJS style
define(['TYPO3/CMS/Backend/Viewport'], function(Viewport) {
   Viewport.Topbar.refresh();
});

// Or: old-fashioned JavaScript
if (top && top.TYPO3.Backend && top.TYPO3.Backend.Topbar) {
   top.TYPO3.Backend.Topbar.refresh();
}';

In case a toolbar item registers to the load event of the page, the registration must be changed. Reason is that the event information gets lost, as the whole toolbar is rendered from scratch after a reload.

Example:

define(['jquery', 'TYPO3/CMS/Backend/Viewport'], function($, Viewport) {
   // old registration
   $(MyAwesomeItem.doStuff)

   // new registration
   Viewport.Topbar.Toolbar.registerEvent(MyAwesomeItem.doStuff);
});