XCLASS to change style of IRRE blocks in FormEngine

ext_localconf.php

<?php
// This is file EXT:your_ext/ext_localconf.php

// snip

// Add support for changing the IRRE div background color
// See https://twitter.com/xperseguers/status/859327351028690944 for result
$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects'][\TYPO3\CMS\Backend\Form\Container\InlineRecordContainer::class] = [
    'className' => \VENDOR\YourExt\Xclass\Backend\Form\Container\InlineRecordContainer::class,
];

InlineRecordContainer.php

<?php
// This is file EXT:your_ext/Classes/Xclass/Backend/Form/Container/InlineRecordContainer.php

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

namespace VENDOR\YourExt\Xclass\Backend\Form\Container;

use TYPO3\CMS\Core\Utility\GeneralUtility;

/**
 * Extends \TYPO3\CMS\Backend\Form\Container\InlineRecordContainer to allow changing the color of the whole inline record
 * block color.
 *
 * @author      Xavier Perseguers <xavier@causal.ch>
 * @license     http://www.gnu.org/licenses/lgpl.html GNU Lesser General Public License, version 3 or later
 */
class InlineRecordContainer extends \TYPO3\CMS\Backend\Form\Container\InlineRecordContainer
{

    /**
     * Entry method
     *
     * @return array As defined in initializeResultArray() of AbstractNode
     * @throws AccessDeniedContentEditException
     */
    public function render()
    {
        $data = $this->data;
        $this->inlineData = $data['inlineData'];

        $inlineStackProcessor = $this->inlineStackProcessor;
        $inlineStackProcessor->initializeByGivenStructure($data['inlineStructure']);

        $record = $data['databaseRow'];
        $inlineConfig = $data['inlineParentConfig'];
        $foreignTable = $inlineConfig['foreign_table'];

        $resultArray = $this->initializeResultArray();

        // Send a mapping information to the browser via JSON:
        // e.g. data[<curTable>][<curId>][<curField>] => data-<pid>-<parentTable>-<parentId>-<parentField>-<curTable>-<curId>-<curField>
        $formPrefix = $inlineStackProcessor->getCurrentStructureFormPrefix();
        $domObjectId = $inlineStackProcessor->getCurrentStructureDomObjectIdPrefix($data['inlineFirstPid']);
        $this->inlineData['map'][$formPrefix] = $domObjectId;

        $resultArray['inlineData'] = $this->inlineData;

        // If there is a selector field, normalize it:
        if (!empty($inlineConfig['foreign_selector'])) {
            $foreign_selector = $inlineConfig['foreign_selector'];
            $valueToNormalize = $record[$foreign_selector];
            if (is_array($record[$foreign_selector])) {
                // @todo: this can be kicked again if always prepared rows are handled here
                $valueToNormalize = implode(',', $record[$foreign_selector]);
            }
            $record[$foreign_selector] = $this->normalizeUid($valueToNormalize);
        }

        // Get the current naming scheme for DOM name/id attributes:
        $appendFormFieldNames = '[' . $foreignTable . '][' . $record['uid'] . ']';
        $objectId = $domObjectId . '-' . $foreignTable . '-' . $record['uid'];
        $class = '';
        $html = '';
        $combinationHtml = '';
        $isNewRecord = $data['command'] === 'new';
        $hiddenField = '';
        if (isset($data['processedTca']['ctrl']['enablecolumns']['disabled'])) {
            $hiddenField = $data['processedTca']['ctrl']['enablecolumns']['disabled'];
        }
        if (!$data['isInlineDefaultLanguageRecordInLocalizedParentContext']) {
            if ($isNewRecord || $data['isInlineChildExpanded']) {
                // Render full content ONLY IF this is an AJAX request, a new record, or the record is not collapsed
                $combinationHtml = '';
                if (isset($data['combinationChild'])) {
                    $combinationChild = $this->renderCombinationChild($data, $appendFormFieldNames);
                    $combinationHtml = $combinationChild['html'];
                    $combinationChild['html'] = '';
                    $resultArray = $this->mergeChildReturnIntoExistingResult($resultArray, $combinationChild);
                }
                $childArray = $this->renderChild($data);
                $html = $childArray['html'];
                $childArray['html'] = '';
                $resultArray = $this->mergeChildReturnIntoExistingResult($resultArray, $childArray);
            } else {
                // This string is the marker for the JS-function to check if the full content has already been loaded
                $html = '<!--notloaded-->';
            }
            if ($isNewRecord) {
                // Add pid of record as hidden field
                $html .= '<input type="hidden" name="data' . htmlspecialchars($appendFormFieldNames)
                    . '[pid]" value="' . htmlspecialchars($record['pid']) . '"/>';
                // Tell DataHandler this record is expanded
                $ucFieldName = 'uc[inlineView]'
                    . '[' . $data['inlineTopMostParentTableName'] . ']'
                    . '[' . $data['inlineTopMostParentUid'] . ']'
                    . $appendFormFieldNames;
                $html .= '<input type="hidden" name="' . htmlspecialchars($ucFieldName)
                    . '" value="' . (int)$data['isInlineChildExpanded'] . '" />';
            } else {
                // Set additional field for processing for saving
                $html .= '<input type="hidden" name="cmd' . htmlspecialchars($appendFormFieldNames)
                    . '[delete]" value="1" disabled="disabled" />';
                if (!$data['isInlineChildExpanded'] && !empty($hiddenField)) {
                    $checked = !empty($record[$hiddenField]) ? ' checked="checked"' : '';
                    $html .= '<input type="checkbox" data-formengine-input-name="data'
                        . htmlspecialchars($appendFormFieldNames)
                        . '[' . htmlspecialchars($hiddenField) . ']" value="1"' . $checked . ' />';
                    $html .= '<input type="input" name="data' . htmlspecialchars($appendFormFieldNames)
                        . '[' . htmlspecialchars($hiddenField) . ']" value="' . htmlspecialchars($record[$hiddenField]) . '" />';
                }
            }
            // If this record should be shown collapsed
            $class = $data['isInlineChildExpanded'] ? 'panel-visible' : 'panel-collapsed';
        }
        if ($inlineConfig['renderFieldsOnly']) {
            // Render "body" part only
            $html = $html . $combinationHtml;
        } else {
            // Render header row and content (if expanded)
            if ($data['isInlineDefaultLanguageRecordInLocalizedParentContext']) {
                $class .= ' t3-form-field-container-inline-placeHolder';
            }
            if (!empty($hiddenField) && isset($record[$hiddenField]) && (int)$record[$hiddenField]) {
                $class .= ' t3-form-field-container-inline-hidden';
            }
            $class .= ($isNewRecord ? ' inlineIsNewRecord' : '');
            // XCLASS [begin]
            $parameters = [
                'tableName' => $data['tableName'],
                'row' => $data['databaseRow'],
                'style' => '',
            ];
            // callUserFunction requires a third parameter, but we don't want to give $this as reference!
            $null = null;
            if (!empty($data['processedTca']['ctrl']['irreHeaderStyle_userFunc'])) {
                GeneralUtility::callUserFunction($data['processedTca']['ctrl']['irreHeaderStyle_userFunc'], $parameters, $null);
            }
            $html = '
				<div class="panel panel-default panel-condensed ' . trim($class) . '" id="' . htmlspecialchars($objectId) . '_div">
					<div class="panel-heading" data-toggle="formengine-inline" id="' . htmlspecialchars($objectId) . '_header" data-expandSingle="' . ($inlineConfig['appearance']['expandSingle'] ? 1 : 0) . '">
						<div class="form-irre-header" style="' . trim($parameters['style']) . '">
							<div class="form-irre-header-cell form-irre-header-icon">
								<span class="caret"></span>
							</div>
							' . $this->renderForeignRecordHeader($data) . '
						</div>
					</div>
					<div class="panel-collapse" id="' . htmlspecialchars($objectId) . '_fields" data-expandSingle="' . ($inlineConfig['appearance']['expandSingle'] ? 1 : 0) . '" data-returnURL="' . htmlspecialchars(GeneralUtility::getIndpEnv('REQUEST_URI')) . '">' . $html . $combinationHtml . '</div>
				</div>';
            // XCLASS [end]
        }

        $resultArray['html'] = $html;
        return $resultArray;
    }

}

SomeTable.php

<?php
// This is file EXT:your_ext/Classes/Tca/SomeTable.php

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

namespace VENDOR\YourExt\Tca;

class SomeTable
{
    /**
     * Returns the styles to be used for an IRRE block.
     *
     * @param array $params
     * @param null $pObj
     * @return void
     */
    public function getIrreHeaderStyle(array &$params, $pObj = null)
    {
        if (true) { // TODO: own business logic of course
            $params['style'] = 'background-color:#ff6265';
        }
    }
}

tx_yourext_sometable.php

<?php
// This is file EXT:your_ext/Configuration/TCA/tx_yourext_sometable.php

return [
    'ctrl' => [
        'title' => 'Whatever',
        'irreHeaderStyle_userFunc' => \VENDOR\YourExt\Tca\SomeTable::class . '->getIrreHeaderStyle',
        /// snip
    ],
    // snip
];