From d5fc004df0d149452e873040102f1e98cb929a2d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 11 Feb 2020 21:59:51 +0100
Subject: [PATCH] Prevent reentrancy in ExecuteInitialLayoutPass.

Fixes #3550.
---
 src/Avalonia.Layout/LayoutManager.cs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Layout/LayoutManager.cs b/src/Avalonia.Layout/LayoutManager.cs
index 1792655a13..69a4406828 100644
--- a/src/Avalonia.Layout/LayoutManager.cs
+++ b/src/Avalonia.Layout/LayoutManager.cs
@@ -132,8 +132,16 @@ namespace Avalonia.Layout
         /// <inheritdoc/>
         public void ExecuteInitialLayoutPass(ILayoutRoot root)
         {
-            Measure(root);
-            Arrange(root);
+            try
+            {
+                _running = true;
+                Measure(root);
+                Arrange(root);
+            }
+            finally
+            {
+                _running = false;
+            }
 
             // Running the initial layout pass may have caused some control to be invalidated
             // so run a full layout pass now (this usually due to scrollbars; its not known