Create TransformThumb.cs

Author: yanjinhuagood

src/WPFDevelopers.Samples.Shared/Controls/ElementAdorner/TransformThumb.cs

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+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Documents;
+
+namespace WPFDevelopers.Samples.Controls
+{
+    public class TransformThumb : ContentControl
+    {
+        static TransformThumb()
+        {
+            DefaultStyleKeyProperty.OverrideMetadata(typeof(TransformThumb), new FrameworkPropertyMetadata(typeof(TransformThumb)));
+        }
+        public override void OnApplyTemplate()
+        {
+            base.OnApplyTemplate();
+            IsVisibleChanged += TransformThumb_IsVisibleChanged;
+            CreateAdorner();
+        }
+        void CreateAdorner()
+        {
+            var adornerLayer = AdornerLayer.GetAdornerLayer(this);
+            if (adornerLayer != null)
+            {
+                var adorner = new ElementAdorner(this);
+                adornerLayer.Add(adorner);
+            }
+        }
+        private void TransformThumb_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
+        {
+            if (e.NewValue is bool isVisible)
+            {
+                if(isVisible)
+                {
+                    CreateAdorner();
+                }
+                
+            }
+        }
+    }
+}