ColorFieldWidgetBase.php

<?php

declare (strict_types=1);
namespace Drupal\color_field\Plugin\Field\FieldWidget;

use Drupal\Component\Utility\Html;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\WidgetBase;
use Drupal\Core\Form\FormStateInterface;

/**
 * Base class for color_field widgets.
 */
abstract class ColorFieldWidgetBase extends WidgetBase {
    
    /**
     * {@inheritdoc}
     */
    public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) : array {
        $element['#uid'] = Html::getUniqueId('color-field-' . $this->fieldDefinition
            ->getName());
        // Prepare color.
        $color = NULL;
        if (isset($items[$delta]->color)) {
            $color = $items[$delta]->color;
            if (!str_starts_with($color, '#')) {
                $color = '#' . $color;
            }
        }
        $input = [
            '#type' => 'textfield',
            '#maxlength' => 7,
            '#size' => 7,
            '#required' => $element['#required'],
            '#default_value' => $color,
        ];
        if ($this->getFieldSetting('opacity')) {
            $element['color'] = $input;
            $element['color']['#title'] = $element['#title'];
            $element['color']['#description'] = $element['#description'];
            $element['color']['#error_no_message'] = TRUE;
            $element['#type'] = 'container';
            $element['opacity'] = [
                '#title' => $this->t('Opacity'),
                '#type' => 'number',
                '#min' => 0,
                '#max' => 1,
                '#step' => 0.01,
                '#required' => $element['#required'],
                '#default_value' => $items[$delta]->opacity ?? NULL,
                '#placeholder' => $this->getSetting('placeholder_opacity'),
                '#error_no_message' => TRUE,
            ];
        }
        else {
            $element['color'] = $element + $input;
            $element['#type'] = 'container';
            // Add a null field for opacity. Ths is required to accurately/detect
            // changes in translations under some circumstances.
            $element['opacity'] = [
                '#type' => 'value',
                '#value' => NULL,
            ];
        }
        return $element;
    }

}