class WebformSignature in Webform 6.x

Provides a webform element for entering a signature.

Plugin annotation

@FormElement("webform_signature");

Hierarchy

• class \Drupal\Component\Plugin\PluginBase implements DerivativeInspectionInterface, PluginInspectionInterface
  • class \Drupal\Core\Plugin\PluginBase uses DependencySerializationTrait, MessengerTrait, StringTranslationTrait
    • class \Drupal\Core\Render\Element\RenderElement implements ElementInterface
      • class \Drupal\Core\Render\Element\FormElement implements FormElementInterface
        • class \Drupal\webform\Element\WebformSignature

2 files declare their use of WebformSignature

webform.install.update.inc in includes/webform.install.update.inc

Archived Webform update hooks.

WebformSignature.php in src/Plugin/WebformElement/WebformSignature.php

File

src/Element/WebformSignature.php, line 14

Namespace

Drupal\webform\Element

class WebformSignature extends FormElement {

  /**
   * {@inheritdoc}
   */
  public function getInfo() {
    $class = get_class($this);
    return [
      '#input' => TRUE,
      '#process' => [
        [
          $class,
          'processWebformSignature',
        ],
        [
          $class,
          'processAjaxForm',
        ],
        [
          $class,
          'processGroup',
        ],
      ],
      '#pre_render' => [
        [
          $class,
          'preRenderWebformSignature',
        ],
      ],
      '#theme' => 'input__webform_signature',
      '#theme_wrappers' => [
        'form_element',
      ],
      // Add '#markup' property to add an 'id' attribute to the form element.
      // @see template_preprocess_form_element()
      '#markup' => '',
    ];
  }

  /**
   * Processes a signature webform element.
   */
  public static function processWebformSignature(&$element, FormStateInterface $form_state, &$complete_form) {

    // Remove 'for' from the element's label.
    $element['#label_attributes']['webform-remove-for-attribute'] = TRUE;

    // Add validate callback.
    $element += [
      '#element_validate' => [],
    ];
    array_unshift($element['#element_validate'], [
      get_called_class(),
      'validateWebformSignature',
    ]);
    return $element;
  }

  /**
   * Prepares a #type 'webform_signature' render element for input.html.twig.
   *
   * @param array $element
   *   An associative array containing the properties of the element.
   *   Properties used: #title, #value, #description, #min, #max, #attributes,
   *   #step.
   *
   * @return array
   *   The $element with prepared variables ready for input.html.twig.
   */
  public static function preRenderWebformSignature(array $element) {
    $element['#attributes']['type'] = 'hidden';
    Element::setAttributes($element, [
      'name',
      'value',
    ]);
    static::setAttributes($element, [
      'js-webform-signature',
      'form-webform-signature',
    ]);
    $build = [
      '#prefix' => '<div class="js-webform-signature-pad webform-signature-pad">',
      '#suffix' => '</div>',
    ];
    $build['reset'] = [
      '#type' => 'button',
      '#value' => t('Reset'),
    ];
    $build['canvas'] = [
      '#type' => 'html_tag',
      '#tag' => 'canvas',
    ];
    $element['#children'] = $build;
    $element['#attached']['library'][] = 'webform/webform.element.signature';
    return $element;
  }

  /**
   * Webform element validation handler for #type 'signature'.
   */
  public static function validateWebformSignature(&$element, FormStateInterface $form_state, &$complete_form) {
    $value = $element['#value'];
    if (!static::isSignatureValid($value)) {
      $t_args = [
        '@title' => isset($element['#title']) ? $element['#title'] : t('Form'),
      ];
      $form_state
        ->setError($element, t('@title contains an invalid signature.', $t_args));
    }
  }

  /**
   * Determine that signature PNG is valid.
   *
   * @param string $value
   *   Upload base64 png image.
   *
   * @return bool
   *   TRUE if signature PNG is valid.
   */
  public static function isSignatureValid($value) {
    if (empty($value)) {
      return TRUE;
    }

    // Make sure the signature is a png.
    if (strpos($value, 'data:image/png;base64,') !== 0) {
      return FALSE;
    }

    // Make sure signature's image size can be read.

    /** @var \Drupal\Core\File\FileSystemInterface $file_system */
    $file_system = \Drupal::service('file_system');
    $temp_image = $file_system
      ->tempnam('temporary://', 'webform_signature_');
    $encoded_image = explode(',', $value)[1];
    $decoded_image = base64_decode($encoded_image);
    file_put_contents($temp_image, $decoded_image);
    $image_size = getimagesize($temp_image);
    if (!$image_size) {
      return FALSE;
    }

    // Make sure signature is not larger than a 500 kb.
    if (filesize($temp_image) > 500000) {
      return FALSE;
    }

    // Make sure the signature contains no colors.
    $image = imagecreatefrompng($temp_image);
    $number_of_colors = imagecolorstotal($image);
    imagedestroy($image);
    if ($number_of_colors > 0) {
      return FALSE;
    }
    return TRUE;
  }

}

Members

Name	Modifiers	Type	Description	Overrides
DependencySerializationTrait::$_entityStorages	protected	property
DependencySerializationTrait::$_serviceIds	protected	property
DependencySerializationTrait::__sleep	public	function		2
DependencySerializationTrait::__wakeup	public	function		2
FormElement::processAutocomplete	public static	function	Adds autocomplete functionality to elements.
FormElement::processPattern	public static	function	#process callback for #pattern form element property.
FormElement::validatePattern	public static	function	#element_validate callback for #pattern form element property.
FormElement::valueCallback	public static	function	Determines how user input is mapped to an element's #value property. Overrides FormElementInterface::valueCallback	15
MessengerTrait::$messenger	protected	property	The messenger.	27
MessengerTrait::messenger	public	function	Gets the messenger.	27
MessengerTrait::setMessenger	public	function	Sets the messenger.
PluginBase::$configuration	protected	property	Configuration information passed into the plugin.	1
PluginBase::$pluginDefinition	protected	property	The plugin implementation definition.	1
PluginBase::$pluginId	protected	property	The plugin_id.
PluginBase::DERIVATIVE_SEPARATOR		constant	A string which is used to separate base plugin IDs from the derivative ID.
PluginBase::getBaseId	public	function	Gets the base_plugin_id of the plugin instance. Overrides DerivativeInspectionInterface::getBaseId
PluginBase::getDerivativeId	public	function	Gets the derivative_id of the plugin instance. Overrides DerivativeInspectionInterface::getDerivativeId
PluginBase::getPluginDefinition	public	function	Gets the definition of the plugin implementation. Overrides PluginInspectionInterface::getPluginDefinition	2
PluginBase::getPluginId	public	function	Gets the plugin_id of the plugin instance. Overrides PluginInspectionInterface::getPluginId
PluginBase::isConfigurable	public	function	Determines if the plugin is configurable.
PluginBase::__construct	public	function	Constructs a \Drupal\Component\Plugin\PluginBase object.	98
RenderElement::preRenderAjaxForm	public static	function	Adds Ajax information about an element to communicate with JavaScript.
RenderElement::preRenderGroup	public static	function	Adds members of this group as actual elements for rendering.
RenderElement::processAjaxForm	public static	function	Form element processing handler for the #ajax form property.	1
RenderElement::processGroup	public static	function	Arranges elements into groups.
RenderElement::setAttributes	public static	function	Sets a form element's class attribute. Overrides ElementInterface::setAttributes
StringTranslationTrait::$stringTranslation	protected	property	The string translation service.	4
StringTranslationTrait::formatPlural	protected	function	Formats a string containing a count of items.
StringTranslationTrait::getNumberOfPlurals	protected	function	Returns the number of plurals supported by a given language.
StringTranslationTrait::getStringTranslation	protected	function	Gets the string translation service.
StringTranslationTrait::setStringTranslation	public	function	Sets the string translation service to use.	2
StringTranslationTrait::t	protected	function	Translates a string to the current language or to a given language.
WebformSignature::getInfo	public	function	Returns the element properties for this element. Overrides ElementInterface::getInfo
WebformSignature::isSignatureValid	public static	function	Determine that signature PNG is valid.
WebformSignature::preRenderWebformSignature	public static	function	Prepares a #type 'webform_signature' render element for input.html.twig.
WebformSignature::processWebformSignature	public static	function	Processes a signature webform element.
WebformSignature::validateWebformSignature	public static	function	Webform element validation handler for #type 'signature'.