From 7a325af366cfe1c91d905ae41ef617415edb6d45 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 12 Aug 2020 20:52:08 +0200
Subject: [PATCH] Fix auto-sizing on secondary monitors on win32.

- Allow nested calls to `BeginAutoSizing` - previously it was called twice when showing a window on a secondary monitor and when the second `using` block exited it cleared the autosizing state despite the outer block not completing
- Call `SetWindowStartupLocation` within the auto-sizing block. Moving to a secondary monitor causes a resize message.
---
 src/Avalonia.Controls/Window.cs     |  2 +-
 src/Avalonia.Controls/WindowBase.cs | 11 ++++-------
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/src/Avalonia.Controls/Window.cs b/src/Avalonia.Controls/Window.cs
index d8e7f3a387..317b6d3f2e 100644
--- a/src/Avalonia.Controls/Window.cs
+++ b/src/Avalonia.Controls/Window.cs
@@ -652,8 +652,8 @@ namespace Avalonia.Controls
 
                 PlatformImpl?.Show();
                 Renderer?.Start();
+                SetWindowStartupLocation(Owner?.PlatformImpl);
             }
-            SetWindowStartupLocation(Owner?.PlatformImpl);
             OnOpened(EventArgs.Empty);
         }
 
diff --git a/src/Avalonia.Controls/WindowBase.cs b/src/Avalonia.Controls/WindowBase.cs
index eb6e7319f5..1efd6c8c1d 100644
--- a/src/Avalonia.Controls/WindowBase.cs
+++ b/src/Avalonia.Controls/WindowBase.cs
@@ -39,6 +39,7 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<bool> TopmostProperty =
             AvaloniaProperty.Register<WindowBase, bool>(nameof(Topmost));
 
+        private int _autoSizing;
         private bool _hasExecutedInitialLayoutPass;
         private bool _isActive;
         private bool _ignoreVisibilityChange;
@@ -97,11 +98,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Whether an auto-size operation is in progress.
         /// </summary>
-        protected bool AutoSizing
-        {
-            get;
-            private set;
-        }
+        protected bool AutoSizing => _autoSizing > 0;
 
         /// <summary>
         /// Gets or sets the owner of the window.
@@ -186,8 +183,8 @@ namespace Avalonia.Controls
         /// </remarks>
         protected IDisposable BeginAutoSizing()
         {
-            AutoSizing = true;
-            return Disposable.Create(() => AutoSizing = false);
+            ++_autoSizing;
+            return Disposable.Create(() => --_autoSizing);
         }
 
         /// <summary>