Merge pull request AvaloniaUI#7803 from AvaloniaUI/contextMenu-ignore…

…s-styles-on-first-open

Fix "ContextMenu ignores styles on first open"

src/Avalonia.Controls/ContextMenu.cs

@@ -349,6 +349,11 @@ private void Open(Control control, Control placementTarget, bool requestedByPoin
                 ? PlacementMode.Bottom
                 : PlacementMode;
 
+            //Position of the line below is really important. 
+            //All styles are being applied only when control has logical parent.
+            //Line below will add ContextMenu as child to the Popup and this will trigger styles and they would be applied.
+            //If you will move line below somewhere else it may cause that ContextMenu will behave differently from what you are expecting.
+            _popup.Child = this;
             _popup.PlacementTarget = placementTarget;
             _popup.HorizontalOffset = HorizontalOffset;
             _popup.VerticalOffset = VerticalOffset;
@@ -357,7 +362,6 @@ private void Open(Control control, Control placementTarget, bool requestedByPoin
             _popup.PlacementGravity = PlacementGravity;
             _popup.PlacementRect = PlacementRect;
             _popup.WindowManagerAddShadowHint = WindowManagerAddShadowHint;
-            _popup.Child = this;
             IsOpen = true;
             _popup.IsOpen = true;