class StyleTest

class StyleTest extends StylePluginBase {
    
    /**
     * A string which will be output when the view is rendered.
     *
     * @var string
     */
    public $output;
    
    /**
     * {@inheritdoc}
     */
    protected $usesRowPlugin = TRUE;
    
    /**
     * {@inheritdoc}
     */
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['test_option'] = [
            'default' => '',
        ];
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        $form['test_option'] = [
            '#title' => $this->t('Test option'),
            '#type' => 'textfield',
            '#description' => $this->t('This is a textfield for test_option.'),
            '#default_value' => $this->options['test_option'],
        ];
    }
    
    /**
     * Sets the usesRowPlugin property.
     *
     * @param bool $status
     *   TRUE if this style plugin should use rows.
     */
    public function setUsesRowPlugin($status) {
        $this->usesRowPlugin = $status;
    }
    
    /**
     * Sets the output property.
     *
     * @param string $output
     *   The string to output by this plugin.
     */
    public function setOutput($output) {
        $this->output = $output;
    }
    
    /**
     * Returns the output property.
     *
     * @return string
     */
    public function getOutput() {
        return $this->output;
    }
    
    /**
     * {@inheritdoc}
     */
    public function render() {
        $output = '';
        if (!$this->usesRowPlugin()) {
            $output = $this->getOutput();
        }
        else {
            foreach ($this->view->result as $index => $row) {
                $this->view->row_index = $index;
                $output .= $this->view->rowPlugin
                    ->render($row) . "\n";
            }
        }
        return $output;
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        return [
            'content' => [
                'StyleTest',
            ],
        ];
    }

}