Fixed bugs on Marquee loaded and in updating a marquee animation on the fly

Author: Avid29

components/Marquee/src/Marquee.Events.cs

@@ -55,6 +55,15 @@ private void Marquee_Loaded(object sender, RoutedEventArgs e)
         {
             _marqueeStoryboard.Completed += StoryBoard_Completed;
         }
+
+        // Setup the animation
+        UpdateMarquee(false);
+
+        // The marquee should run when loaded if auto play is enabled
+        if (AutoPlay)
+        {
+            StartMarquee();
+        }
     }
 
     private void Marquee_Unloaded(object sender, RoutedEventArgs e)

components/Marquee/src/Marquee.cs

@@ -53,6 +53,12 @@ public partial class Marquee : ContentControl
     private bool _isActive = false;
     private bool _isPaused = false;
 
+    // This is used to track the position when stopped.
+    // If the animation update happens while running, this position
+    // is lost and must be set when the animation stops.
+    private double _stoppedPosition;
+    private DependencyProperty? _animationProperty;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="Marquee"/> class.
     /// </summary>
@@ -180,6 +186,12 @@ public void StopMarquee()
         _isActive = false;
         _isPaused = false;
 
+        // Set the transform to the stopped position if provided.
+        if (_animationProperty is not null)
+        {
+            _marqueeTransform?.SetValue(_animationProperty, _stoppedPosition);
+        }
+
         if (!wasStopped)
         {
             // Apply state transitions
@@ -380,6 +392,11 @@ private bool UpdateAnimation(out TimeSpan seekPoint)
             _marqueeTransform.SetValue(dp, start);
         }
 
+        // Set stopped position and animation property regardless of the active state.
+        // This will be used when the animation stops.
+        _stoppedPosition = start;
+        _animationProperty = dp;
+
         return true;
     }