From dbb7828e75fe2406729265b8c5410546dfcca9ff Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 12 Nov 2020 11:49:53 +0100
Subject: [PATCH] Don't subscribe to inner observable if not active.

When subscribing to a `PropertySetterBindingInstance`, if the owner style is not active then there's no need to subscribe to the inner observable as this can cause resource lookups etc. Part of fixing #5027.
---
 .../Styling/PropertySetterBindingInstance.cs              | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Styling/Styling/PropertySetterBindingInstance.cs b/src/Avalonia.Styling/Styling/PropertySetterBindingInstance.cs
index 929f7142bb5d..a67190c83163 100644
--- a/src/Avalonia.Styling/Styling/PropertySetterBindingInstance.cs
+++ b/src/Avalonia.Styling/Styling/PropertySetterBindingInstance.cs
@@ -92,6 +92,7 @@ public void Activate()
         {
             if (!_isActive)
             {
+                _innerSubscription ??= _binding.Observable.Subscribe(_inner);
                 _isActive = true;
                 PublishNext();
             }
@@ -102,6 +103,8 @@ public void Deactivate()
             if (_isActive)
             {
                 _isActive = false;
+                _innerSubscription?.Dispose();
+                _innerSubscription = null;
                 PublishNext();
             }
         }
@@ -148,7 +151,10 @@ void IObserver<BindingValue<T>>.OnNext(BindingValue<T> value)
 
         protected override void Subscribed()
         {
-            _innerSubscription = _binding.Observable.Subscribe(_inner);
+            if (_isActive)
+            {
+                _innerSubscription = _binding.Observable.Subscribe(_inner);
+            }
         }
 
         protected override void Unsubscribed()