Refactor Popup handling across UI frameworks

Introduce `popupUI` alias for `Primitives` namespace to streamline `Popup` control references across Windows.UI.Xaml, Avalonia, Microsoft.UI.Xaml, and System.Windows. Fix a bug in `PopupRoot` handling by correcting a variable name and updating logic for setting `pElement`. Remove unused code for cleaner implementation. Ensure consistency and adaptability with conditional compilation.

Author: vb2ae

src/Caliburn.Micro.Platform/ActionMessage.cs

@@ -14,6 +14,7 @@
     using Microsoft.Xaml.Interactivity;
     using TriggerBase = Microsoft.Xaml.Interactivity.IBehavior;
     using EventTrigger = Microsoft.Xaml.Interactions.Core.EventTriggerBehavior;
+    using popupUI = Windows.UI.Xaml.Controls.Primitives;
 #elif AVALONIA
     using Avalonia;
     using Avalonia.Data;
@@ -30,6 +31,7 @@
     using EventTrigger = Avalonia.Xaml.Interactions.Core.EventTriggerBehavior;
     using FrameworkElement = Avalonia.Controls.Control;
     using Avalonia.Input;
+    using popupUI = Avalonia.Controls.Primitives;
 #elif WinUI3
     using Microsoft.UI.Xaml;
     using Microsoft.UI.Xaml.Data;
@@ -40,13 +42,15 @@
     using Microsoft.Xaml.Interactivity;
     using TriggerBase = Microsoft.Xaml.Interactivity.IBehavior;
     using EventTrigger = Microsoft.Xaml.Interactions.Core.EventTriggerBehavior;
+    using popupUI = Microsoft.UI.Xaml.Controls.Primitives;
 #else
     using System.Windows;
     using System.Windows.Controls.Primitives;
     using System.Windows.Data;
     using System.Windows.Markup;
     using Microsoft.Xaml.Behaviors;
     using EventTrigger = Microsoft.Xaml.Behaviors.EventTrigger;
+    using popupUI = System.Windows.Controls.Primitives;
 #endif
 
 #if NET5_0_WINDOWS || NET6_0_WINDOWS
@@ -597,16 +601,20 @@ public override string ToString()
                     }
                 }
 
-                //currentElement = BindingScope.GetVisualParent(currentElement);
                 var pElement = BindingScope.GetVisualParent(currentElement);
-                if(pElemenet != null && currentElement.GetType().Name.Equals("PopupRoot", StringComparison.OrdinalIgnoreCase))
+                if (pElement != null && currentElement.GetType().Name.Equals("PopupRoot", StringComparison.OrdinalIgnoreCase))
                 {
-                  if(currentElement is PopupRoot popupRoot && popupRoot.Parent is Popup popup)
-                  {
-                      pElement = popup.PlacementTarget;
-                  }
+                    if (currentElement is popupUI.Popup popupRoot && popupRoot.Parent is popupUI.Popup popup)
+                    {
+#if WINDOWS_UWP
+                        pElement = popup.Parent;
+#else
+                        pElement = popup.PlacementTarget;
+#endif
+                    }
                 }
                 currentElement = pElement;
+
             }
 #if AVALONIA
             Log.Info("SetMethodBinding avalonia");