chore: separated System.Windows.Interactivity code

src/Shared/System.Windows.Interactivity/Interaction.cs

@@ -0,0 +1,76 @@
+using System;
+using System.Windows;
+
+namespace HandyControl.Interactivity;
+
+public static class Interaction
+{
+    private static readonly DependencyProperty TriggersProperty =
+        DependencyProperty.RegisterAttached("ShadowTriggers", typeof(TriggerCollection), typeof(Interaction),
+            new FrameworkPropertyMetadata(OnTriggersChanged));
+
+    private static readonly DependencyProperty BehaviorsProperty =
+        DependencyProperty.RegisterAttached("ShadowBehaviors", typeof(BehaviorCollection), typeof(Interaction),
+            new FrameworkPropertyMetadata(OnBehaviorsChanged));
+
+    internal static bool ShouldRunInDesignMode { get; set; }
+
+    public static TriggerCollection GetTriggers(DependencyObject obj)
+    {
+        var triggerCollection = (TriggerCollection) obj.GetValue(TriggersProperty);
+        if (triggerCollection == null)
+        {
+            triggerCollection = new TriggerCollection();
+            obj.SetValue(TriggersProperty, triggerCollection);
+        }
+        return triggerCollection;
+    }
+
+    public static BehaviorCollection GetBehaviors(DependencyObject obj)
+    {
+        var behaviorCollection = (BehaviorCollection) obj.GetValue(BehaviorsProperty);
+        if (behaviorCollection == null)
+        {
+            behaviorCollection = new BehaviorCollection();
+            obj.SetValue(BehaviorsProperty, behaviorCollection);
+        }
+        return behaviorCollection;
+    }
+
+    private static void OnBehaviorsChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
+    {
+        var oldValue = (BehaviorCollection) args.OldValue;
+        var newValue = (BehaviorCollection) args.NewValue;
+        if (Equals(oldValue, newValue))
+            return;
+        if (oldValue?.AssociatedObject != null)
+            oldValue.Detach();
+        if (newValue == null || obj == null)
+            return;
+        if (newValue.AssociatedObject != null)
+            throw new InvalidOperationException(ExceptionStringTable
+                .CannotHostBehaviorCollectionMultipleTimesExceptionMessage);
+        newValue.Attach(obj);
+    }
+
+    private static void OnTriggersChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
+    {
+        var oldValue = args.OldValue as TriggerCollection;
+        var newValue = args.NewValue as TriggerCollection;
+        if (Equals(oldValue, newValue))
+            return;
+        if (oldValue?.AssociatedObject != null)
+            oldValue.Detach();
+        if (newValue == null || obj == null)
+            return;
+        if (newValue.AssociatedObject != null)
+            throw new InvalidOperationException(ExceptionStringTable
+                .CannotHostTriggerCollectionMultipleTimesExceptionMessage);
+        newValue.Attach(obj);
+    }
+
+    internal static bool IsElementLoaded(FrameworkElement element)
+    {
+        return element.IsLoaded;
+    }
+}