Rhino panels should be treated as if they might have been used before…

… as Panels.Closed isn't called

Connectors/Rhino/Speckle.Connectors.RhinoShared/HostApp/SpeckleRhinoPanelHost.cs

@@ -21,7 +21,33 @@ public SpeckleRhinoPanelHost(uint docSn)
     _webView = SpeckleConnectorsRhinoPlugin.Instance.Container?.GetRequiredService<DUI3ControlWebView>();
     Panels.Closed += PanelsOnClosed;
   }
-
+
+  /// <summary>
+  /// This is a lot like PanelsOnClosed but called when trying to show the panel to clear out a lingering parent as PanelsOnClosed isn't called
+  /// </summary>
+  /// <param name="webView"></param>
+  public static void Reinitialize(DUI3ControlWebView? webView)
+  {
+    if (webView == null)
+    {
+      return;
+    }
+    // This check comes from behavioral difference on closing Rhino Panels.
+    // IsPanelVisible returns;
+    //  - True, when docked Panel closed from the list on right click on panel tab,
+    // whenever it is closed with this way, Rhino.Panels tries to reinit this object and expect the different UIElement, that's why we disconnect Child.
+    //  - False, when detached Panel is closed by 'X' close button.
+    // whenever it is closed with this way, Rhino.Panels don't create this object, that's why we do not disconnect Child UIElement.
+    if (Panels.IsPanelVisible(typeof(SpeckleRhinoPanelHost).GUID))
+    {
+      return;
+    }
+    // Disconnect UIElement from WpfElementHost. Otherwise, we can't reinit panel with same DUI3ControlWebView
+    if (LogicalTreeHelper.GetParent(webView) is Border border)
+    {
+      border.Child = null;
+    }
+  }
   private void PanelsOnClosed(object? sender, PanelEventArgs e)
   {
     if (e.PanelId == typeof(SpeckleRhinoPanelHost).GUID)

Connectors/Rhino/Speckle.Connectors.RhinoShared/Plugin/Speckle.Connectors.RhinoCommand.cs

@@ -1,9 +1,11 @@
 using System.IO;
 using System.Reflection;
+using Microsoft.Extensions.DependencyInjection;
 using Rhino;
 using Rhino.Commands;
 using Rhino.Input.Custom;
 using Rhino.UI;
+using Speckle.Connectors.DUI.WebView;
 using Speckle.Connectors.Rhino.HostApp;
 
 // using Speckle.Connectorss.Rhino.Properties;
@@ -65,6 +67,7 @@ protected override Result RunCommand(RhinoDoc doc, RunMode mode)
 
     if (mode == RunMode.Interactive)
     {
+      SpeckleRhinoPanelHost.Reinitialize(SpeckleConnectorsRhinoPlugin.Instance.Container?.GetRequiredService<DUI3ControlWebView>());
       Panels.OpenPanel(panelId);
       return Result.Success;
     }