From 586e96cd072562af74d0c182ad57853af0002260 Mon Sep 17 00:00:00 2001
From: Dan Walmsley <dan@walms.co.uk>
Date: Tue, 10 Dec 2019 13:58:09 -0300
Subject: [PATCH] synchronise acces to lockFocusIfCanDraw.

---
 native/Avalonia.Native/src/OSX/window.mm | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/native/Avalonia.Native/src/OSX/window.mm b/native/Avalonia.Native/src/OSX/window.mm
index 08d4515d88..500bdf8148 100644
--- a/native/Avalonia.Native/src/OSX/window.mm
+++ b/native/Avalonia.Native/src/OSX/window.mm
@@ -735,7 +735,23 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
 
 - (void)onClosed
 {
-    _parent = NULL;
+    @synchronized (self)
+    {
+        _parent = nullptr;
+    }
+}
+
+- (BOOL)lockFocusIfCanDraw
+{
+    @synchronized (self)
+    {
+        if(_parent == nullptr)
+        {
+            return NO;
+        }
+    }
+    
+    return [super lockFocusIfCanDraw];
 }
 
 -(AvnPixelSize) getPixelSize