[FEATURE] Form validation: Scroll to first visible field with an error if submit failed because of validation

Resolves: #754

Author: einpraegsam

Resources/Private/Build/JavaScript/FormValidation.js

@@ -112,7 +112,21 @@ class Form {
    *
    * @type {{name: function(*=, *): boolean}}
    */
-  #submitErrorCallbacks = {};
+  #submitErrorCallbacks = {
+    'scrollToFirstError': () => {
+      try {
+        const fieldsWithError = this.#form.querySelectorAll('.powermail_field_error');
+        fieldsWithError.forEach((field) => {
+          if (Utility.isElementVisible(field)) {
+            field.scrollIntoView({behavior:'smooth'});
+            throw 'StopException';
+          }
+        });
+      } catch (exception) {
+        // stop, do nothing
+      }
+    }
+  };
 
   constructor(form) {
     this.#form = form;

Resources/Private/Build/JavaScript/Utility.js

@@ -92,4 +92,14 @@ export default class Utility {
       element.style.display = 'block';
     }
   }
+
+  /**
+   * Check if an element is really visible (not only check for style visibility)
+   *
+   * @param element
+   * @returns {boolean}
+   */
+  static isElementVisible(element) {
+    return element.offsetParent !== null;
+  }
 }