From 591ecc4ded6e5fdaeb1a8d46e6559596f09c3f50 Mon Sep 17 00:00:00 2001
From: Nikita Tsukanov <keks9n@gmail.com>
Date: Fri, 18 Jan 2019 22:27:20 +0300
Subject: [PATCH] [RENDER] Don't crash on Paint call when renderer is already
 disposed

---
 src/Avalonia.Visuals/Rendering/DeferredRenderer.cs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Visuals/Rendering/DeferredRenderer.cs b/src/Avalonia.Visuals/Rendering/DeferredRenderer.cs
index 084b14ea97..60e624948e 100644
--- a/src/Avalonia.Visuals/Rendering/DeferredRenderer.cs
+++ b/src/Avalonia.Visuals/Rendering/DeferredRenderer.cs
@@ -29,6 +29,7 @@ namespace Avalonia.Rendering
         private readonly ISceneBuilder _sceneBuilder;
 
         private bool _running;
+        private bool _disposed;
         private volatile IRef<Scene> _scene;
         private DirtyVisuals _dirty;
         private IRef<IRenderTargetBitmapImpl> _overlay;
@@ -125,6 +126,9 @@ namespace Avalonia.Rendering
         {
             lock (_sceneLock)
             {
+                if (_disposed)
+                    return;
+                _disposed = true;
                 var scene = _scene;
                 _scene = null;
                 scene?.Dispose();
@@ -171,7 +175,7 @@ namespace Avalonia.Rendering
             var t = (IRenderLoopTask)this;
             if(t.NeedsUpdate)
                 UpdateScene();
-            if(_scene.Item != null)
+            if(_scene?.Item != null)
                 Render(true);
         }
 
@@ -481,6 +485,8 @@ namespace Avalonia.Rendering
             Dispatcher.UIThread.VerifyAccess();
             lock (_sceneLock)
             {
+                if (_disposed)
+                    return;
                 if (_scene?.Item.Generation > _lastSceneId)
                     return;
             }