From ed7f6c0af4b80be2b0302cf15ecf6b816819ee2f Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 8 Jun 2020 17:21:29 +0200
Subject: [PATCH] Fix LayoutUpdated subscriptions.

And don't call `OnEffectiveViewportChanged` if viewport unchanged.
---
 src/Avalonia.Controls/Repeater/ViewportManager.cs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Repeater/ViewportManager.cs b/src/Avalonia.Controls/Repeater/ViewportManager.cs
index 6677b8fea7..57ac1cf2a5 100644
--- a/src/Avalonia.Controls/Repeater/ViewportManager.cs
+++ b/src/Avalonia.Controls/Repeater/ViewportManager.cs
@@ -288,6 +288,7 @@ namespace Avalonia.Controls
         private void OnLayoutUpdated(object sender, EventArgs args)
         {
             _owner.LayoutUpdated -= OnLayoutUpdated;
+            _layoutUpdatedSubscribed = false;
             if (_managingViewportDisabled)
             {
                 return;
@@ -424,6 +425,7 @@ namespace Avalonia.Controls
             if (_layoutUpdatedSubscribed)
             {
                 _owner.LayoutUpdated -= OnLayoutUpdated;
+                _layoutUpdatedSubscribed = false;
             }
         }
 
@@ -538,7 +540,12 @@ namespace Avalonia.Controls
         private void ScrollContentPresenterPreArrange(object sender, EventArgs e)
         {
             var scp = (ScrollContentPresenter)sender;
-            OnEffectiveViewportChanged(new Rect((Point)scp.Offset, scp.Viewport));
+            var effectiveViewport = new Rect((Point)scp.Offset, scp.Viewport);
+
+            if (effectiveViewport != _visibleWindow)
+            {
+                OnEffectiveViewportChanged(effectiveViewport);
+            }
         }
 
         private class ScrollerInfo