Feature: A frontend icon registry and an icon view helper 

Description 

EXT:academic_base now keeps a registry of its own for the icons a visitor sees, separate from the icon registry of TYPO3. That registry is built for the backend: it loads every core icon, the record icons and the flags with it, and a site could only replace a frontend icon by registering it for the backend as well.

• Every active extension and site package can ship Configuration/FrontendIcons.php, in the format of Configuration/Icons.php. The files are read in the loading order of the packages, and a package loaded later replaces an identifier.
• An extension contributes icons from code through the new event \FGTCLB\AcademicBase\Event\CollectFrontendIconsEvent , see CollectFrontendIconsEvent. An entry of a Configuration/FrontendIcons.php with the same identifier wins over a contributed icon.
• The new view helper icon, in the namespace http://typo3.org/ns/FGTCLB/AcademicBase/ViewHelpers, renders an icon of this registry with the arguments of <core:icon> and the same markup. It does not read the icon registry of TYPO3.
• An identifier the frontend registry does not know renders the default-not-found drawing of TYPO3, which EXT:academic_base registers in its own Configuration/FrontendIcons.php, so a site package can replace it.
• The registry is kept with the system caches, per set of active packages, and typo3 cache:warmup builds it. A change to a file takes effect after the system caches are flushed.

return [
    'my-sitepackage-download' => [
        'provider' => \FGTCLB\AcademicBase\Imaging\IconProvider\CurrentColorSvgIconProvider::class,
        'source' => 'EXT:my_sitepackage/Resources/Public/Icons/download.svg',
    ],
];

<html xmlns:ab="http://typo3.org/ns/FGTCLB/AcademicBase/ViewHelpers"
      data-namespace-typo3-fluid="true">

<ab:icon identifier="my-sitepackage-download" alternativeMarkupIdentifier="inline" />

</html>

Impact 

Nothing changes for an existing site through this extension alone. EXT:academic_jobs and EXT:academic_programs register their frontend icons in the new registry, and EXT:academic_persons, EXT:academic_persons_edit and EXT:academic_study_plan render the shared icon set of this extension (see Feature: Icon set shared by the extensions), all of them with the new view helper and each with a Breaking entry in its own changelog. EXT:academic_partners and EXT:academic_projects render the category type icons with it, with an Important entry each. No frontend template of the academic extensions renders an icon with <core:icon> any more. Each changelog entry says what a site package has to move.

A site package may ship Configuration/FrontendIcons.php already. It takes effect for every template that renders an icon with the new view helper. See Frontend icons.