From d6ea0778a7da7765b187f8db2bb4c261fc25532b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 1 Nov 2022 10:51:08 +0100
Subject: [PATCH] Make IsEvaluating re-entrancy friendly.

---
 src/Avalonia.Base/PropertyStore/ValueStore.cs | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Base/PropertyStore/ValueStore.cs b/src/Avalonia.Base/PropertyStore/ValueStore.cs
index 88ed0d73d5..4da24c1414 100644
--- a/src/Avalonia.Base/PropertyStore/ValueStore.cs
+++ b/src/Avalonia.Base/PropertyStore/ValueStore.cs
@@ -15,6 +15,7 @@ namespace Avalonia.PropertyStore
         private Dictionary<int, IDisposable>? _localValueBindings;
         private AvaloniaPropertyDictionary<EffectiveValue> _effectiveValues;
         private int _inheritedValueCount;
+        private int _isEvaluating;
         private int _frameGeneration;
         private int _styling;
 
@@ -22,7 +23,7 @@ namespace Avalonia.PropertyStore
 
         public AvaloniaObject Owner { get; }
         public ValueStore? InheritanceAncestor { get; private set; }
-        public bool IsEvaluating { get; private set; }
+        public bool IsEvaluating => _isEvaluating > 0;
         public IReadOnlyList<ValueFrame> Frames => _frames;
 
         public void BeginStyling() => ++_styling;
@@ -745,7 +746,7 @@ namespace Avalonia.PropertyStore
             EffectiveValue? current,
             bool ignoreLocalValue = false)
         {
-            IsEvaluating = true;
+            ++_isEvaluating;
 
             try
             {
@@ -824,13 +825,13 @@ namespace Avalonia.PropertyStore
             }
             finally
             {
-                IsEvaluating = false;
+                --_isEvaluating;
             }
         }
 
         private void ReevaluateEffectiveValues()
         {
-            IsEvaluating = true;
+            ++_isEvaluating;
 
             try
             {
@@ -903,7 +904,7 @@ namespace Avalonia.PropertyStore
             }
             finally
             {
-                IsEvaluating = false;
+                --_isEvaluating;
             }
         }