Merge pull request #4123 from MahApps/fix/4117

Fix getting the wrong Ancestor (ScrollViewer) at CustomValidationPopup

Author: punker76

src/MahApps.Metro/Controls/CustomValidationPopup.cs

@@ -144,7 +144,7 @@ private void CustomValidationPopup_Loaded(object? sender, RoutedEventArgs e)
                 this.scrollViewer.ScrollChanged -= this.ScrollViewer_ScrollChanged;
             }
 
-            this.scrollViewer = adornedElement.TryFindParent<ScrollViewer>();
+            this.scrollViewer = adornedElement.GetVisualAncestor<ScrollViewer>();
             if (this.scrollViewer != null)
             {
                 this.scrollViewer.ScrollChanged += this.ScrollViewer_ScrollChanged;

src/MahApps.Metro/Controls/TreeHelper.cs

@@ -63,8 +63,7 @@ public static IEnumerable<DependencyObject> GetAncestors(this DependencyObject c
 
         /// <summary>
         /// Returns full visual ancestry, starting at the leaf.
-        /// <para>If element is not of <see cref="Visual"/> or <see cref="Visual3D"/> the
-        /// logical ancestry is used.</para>
+        /// <para>If element is not of <see cref="Visual"/> or <see cref="Visual3D"/> the logical ancestry is used.</para>
         /// </summary>
         /// <param name="leaf">The starting object.</param>
         /// <returns></returns>
@@ -79,6 +78,30 @@ public static IEnumerable<DependencyObject> GetVisualAncestry(this DependencyObj
             }
         }
 
+        /// <summary>
+        /// Tries to find and returns a visual ancestor, starting at the leaf.
+        /// <para>If element is not of <see cref="Visual"/> or <see cref="Visual3D"/> the logical ancestry is used.</para>
+        /// </summary>
+        /// <param name="leaf">The starting object.</param>
+        /// <returns></returns>
+        public static T? GetVisualAncestor<T>(this DependencyObject? leaf)
+            where T : DependencyObject
+        {
+            while (leaf is not null)
+            {
+                if (leaf is T ancestor)
+                {
+                    return ancestor;
+                }
+
+                leaf = leaf is Visual or Visual3D
+                    ? VisualTreeHelper.GetParent(leaf)
+                    : LogicalTreeHelper.GetParent(leaf);
+            }
+
+            return default(T);
+        }
+
         /// <summary>
         /// Finds a Child of a given item in the visual tree. 
         /// </summary>