From 81fc978d642884141f0f48a2d860d9f15769bea0 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 8 Apr 2021 12:36:32 +0200
Subject: [PATCH] Use hidden window when clearing parent...

...if `ShowInTaskbar == false`.
---
 src/Windows/Avalonia.Win32/WindowImpl.cs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index 0fbd58eeb9..d1dfb4a675 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -581,8 +581,15 @@ namespace Avalonia.Win32
 
         public void SetParent(IWindowImpl parent)
         {
-            _parent = (WindowImpl)parent;
-            SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, _parent?._hwnd ?? IntPtr.Zero);
+            var parentHwnd = ((WindowImpl)parent)?._hwnd ?? IntPtr.Zero;
+
+            if (parentHwnd == IntPtr.Zero && !_windowProperties.ShowInTaskbar)
+            {
+                parentHwnd = OffscreenParentWindow.Handle;
+                _hiddenWindowIsParent = true;
+            }
+
+            SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, parentHwnd);
         }
 
         public void SetEnabled(bool enable) => EnableWindow(_hwnd, enable);
@@ -1108,6 +1115,7 @@ namespace Avalonia.Win32
                         if (shown)
                             Hide();
 
+                        _hiddenWindowIsParent = false;
                         SetParent(null);
 
                         if (shown)