From 4ee9700f08d61625ebc1615129b27d462c3e053a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 30 Apr 2020 16:45:53 +0200
Subject: [PATCH] Set initial size when showing Window as dialog.

Fixes #3843.
---
 src/Avalonia.Controls/Window.cs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/Avalonia.Controls/Window.cs b/src/Avalonia.Controls/Window.cs
index dd00b850fe..75f32c862e 100644
--- a/src/Avalonia.Controls/Window.cs
+++ b/src/Avalonia.Controls/Window.cs
@@ -500,6 +500,19 @@ namespace Avalonia.Controls
 
             EnsureInitialized();
             IsVisible = true;
+
+            var initialSize = new Size(
+                double.IsNaN(Width) ? ClientSize.Width : Width,
+                double.IsNaN(Height) ? ClientSize.Height : Height);
+
+            if (initialSize != ClientSize)
+            {
+                using (BeginAutoSizing())
+                {
+                    PlatformImpl?.Resize(initialSize);
+                }
+            }
+
             LayoutManager.ExecuteInitialLayoutPass(this);
 
             var result = new TaskCompletionSource<TResult>();