ext_tables.php

<?php
if (!defined('TYPO3_MODE')) {
    die('Access denied.');
}

\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile(
    $_EXTKEY,
    'Configuration/TypoScript',
    'PhotoSwipe'
);

\TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin(
    $_EXTKEY,
    'Pi1',
    'PhotoSwipe'
);

// Add flexform for frontend plugin
$extensionName = \TYPO3\CMS\Core\Utility\GeneralUtility::underscoredToUpperCamelCase($_EXTKEY);
$pluginSignature = strtolower($extensionName) . '_pi1';
$TCA['tt_content']['types']['list']['subtypes_addlist'][$pluginSignature] = 'pi_flexform';
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPiFlexFormValue(
    $pluginSignature,
    'FILE:EXT:' . $_EXTKEY . '/Configuration/FlexForms/pi1.xml'
);

// Removed unused fields
$GLOBALS['TCA']['tt_content']['types']['list']['subtypes_excludelist'][$pluginSignature] = 'layout,select_key,pages,recursive';

// Add special mfp palette
$GLOBALS['TCA']['sys_file_reference']['palettes']['jhPhotoswipePalette'] = array(
    'showitem' => 'title, author;;;;3-3-3,--linebreak--, description',
    'canNotCollapse' => true
);

/** @var \TYPO3\CMS\Core\Imaging\IconRegistry $iconRegistry */
$iconRegistry = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Imaging\IconRegistry::class);
$iconRegistry->registerIcon(
    'jh-photoswipe-contentelement',
    \TYPO3\CMS\Core\Imaging\IconProvider\SvgIconProvider::class,
    ['source' => 'EXT:' . $_EXTKEY . '/Resources/Public/Icons/' . 'ceWizard.svg']
);