class ColorFieldDefaultWidget

class ColorFieldDefaultWidget extends WidgetBase {
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return array(
            'placeholder_color' => '',
            'placeholder_opacity' => '',
        ) + parent::defaultSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $element['placeholder_color'] = array(
            '#type' => 'textfield',
            '#title' => t('Color placeholder'),
            '#default_value' => $this->getSetting('placeholder_color'),
            '#description' => t('Text that will be shown inside the field until a value is entered. This hint is usually a sample value or a brief description of the expected format.'),
        );
        $element['placeholder_opacity'] = array(
            '#type' => 'textfield',
            '#title' => t('Opacity placeholder'),
            '#default_value' => $this->getSetting('placeholder_opacity'),
            '#description' => t('Text that will be shown inside the field until a value is entered. This hint is usually a sample value or a brief description of the expected format.'),
        );
        return $element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $summary = array();
        $placeholder_color = $this->getSetting('placeholder_color');
        $placeholder_opacity = $this->getSetting('placeholder_opacity');
        if (!empty($placeholder_color)) {
            $summary[] = t('Color placeholder: @placeholder_color', array(
                '@placeholder_color' => $placeholder_color,
            ));
        }
        if (!empty($placeholder_opacity)) {
            $summary[] = t('Opacity placeholder: @placeholder_opacity', array(
                '@placeholder_opacity' => $placeholder_opacity,
            ));
        }
        if (empty($summary)) {
            $summary[] = t('No placeholder');
        }
        return $summary;
    }
    
    /**
     * {@inheritdoc}
     */
    public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
        $element['color'] = array(
            '#title' => t('Color'),
            '#type' => 'textfield',
            '#maxlength' => 6,
            '#size' => 6,
            '#required' => $element['#required'],
            '#default_value' => isset($items[$delta]->color) ? $items[$delta]->color : NULL,
        );
        if ($this->getFieldSetting('opacity')) {
            $element['color']['#prefix'] = '<div class="container-inline">';
            $element['opacity'] = array(
                '#title' => t('Opacity'),
                '#type' => 'textfield',
                '#maxlength' => 3,
                '#size' => 3,
                '#required' => $element['#required'],
                '#default_value' => isset($items[$delta]->opacity) ? $items[$delta]->opacity : NULL,
                '#suffix' => '</div>',
            );
        }
        return $element;
    }

}