Expose activation state via a method.

Previously, the `IsActive` property caused the activator state to be re-evaluated, which meant that when the _debugger_ read it, it was re-evaluated, making debugging difficult.

src/Avalonia.Base/Styling/Activators/AndActivator.cs

@@ -33,7 +33,7 @@ namespace Avalonia.Styling.Activators
 
             for (var i = 0; i < count; ++i)
             {
-                if (_sources[i].IsActive)
+                if (_sources[i].GetIsActive())
                     flags |= 1ul << i;
             }
 

src/Avalonia.Base/Styling/Activators/IStyleActivator.cs

@@ -19,20 +19,20 @@ namespace Avalonia.Styling.Activators
     public interface IStyleActivator : IDisposable
     {
         /// <summary>
-        /// Gets a value indicating whether the style is activated.
+        /// Gets a value indicating whether the style is subscribed.
+        /// </summary>
+        bool IsSubscribed { get; }
+
+        /// <summary>
+        /// Gets the current activation state.
         /// </summary>
         /// <remarks>
-        /// This property should read directly from its inputs and not rely on any subscriptions 
+        /// This method should read directly from its inputs and not rely on any subscriptions 
         /// to fire in order to be up-to-date. If a change in active state occurs when reading
-        /// this property then any subscribed <see cref="IStyleActivatorSink"/> should not be
+        /// this method then any subscribed <see cref="IStyleActivatorSink"/> should not be
         /// notified of the change.
         /// </remarks>
-        bool IsActive { get; }
-
-        /// <summary>
-        /// Gets a value indicating whether the style is subscribed.
-        /// </summary>
-        bool IsSubscribed { get; }
+        bool GetIsActive();
 
         /// <summary>
         /// Subscribes to the activator.

src/Avalonia.Base/Styling/Activators/NotActivator.cs

@@ -8,7 +8,7 @@
         private readonly IStyleActivator _source;
         public NotActivator(IStyleActivator source) => _source = source;
         void IStyleActivatorSink.OnNext(bool value, int tag) => ReevaluateIsActive();
-        protected override bool EvaluateIsActive() => !_source.IsActive;
+        protected override bool EvaluateIsActive() => !_source.GetIsActive();
         protected override void Initialize() => _source.Subscribe(this, 0);
         protected override void Deinitialize() => _source.Unsubscribe(this);
     }

src/Avalonia.Base/Styling/Activators/OrActivator.cs

@@ -27,7 +27,7 @@ namespace Avalonia.Styling.Activators
 
             foreach (var source in _sources)
             {
-                if (source.IsActive)
+                if (source.GetIsActive())
                     return true;
             }
 

src/Avalonia.Base/Styling/Activators/StyleActivatorBase.cs

@@ -9,7 +9,7 @@ namespace Avalonia.Styling.Activators
         private int _tag;
         private bool _value;
 
-        public bool IsActive => _value = EvaluateIsActive();
+        public bool GetIsActive() => _value = EvaluateIsActive();
 
         public bool IsSubscribed => _sink is not null;
 
@@ -48,7 +48,7 @@ namespace Avalonia.Styling.Activators
         }
 
         /// <summary>
-        /// Evaluates the <see cref="IsActive"/> value.
+        /// Evaluates the activation state.
         /// </summary>
         /// <remarks>
         /// This method should read directly from its inputs and not rely on any subscriptions to
@@ -57,8 +57,8 @@ namespace Avalonia.Styling.Activators
         protected abstract bool EvaluateIsActive();
 
         /// <summary>
-        /// Called from a derived class when the <see cref="IsActive"/> state should be re-evaluated
-        /// and the subscriber notified of any change.
+        /// Called from a derived class when the activation state should be re-evaluated and the 
+        /// subscriber notified of any change.
         /// </summary>
         /// <returns>
         /// The evaluated active state;

src/Avalonia.Base/Styling/StyleInstance.cs

@@ -92,10 +92,10 @@ namespace Avalonia.Styling
             if (_activator?.IsSubscribed == false)
             {
                 _activator.Subscribe(this);
-                _animationTrigger?.OnNext(_activator.IsActive);
+                _animationTrigger?.OnNext(_activator.GetIsActive());
             }
 
-            _isActive = _activator?.IsActive ?? true;
+            _isActive = _activator?.GetIsActive() ?? true;
             hasChanged = _isActive != previous;
             return _isActive;
         }

tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs

@@ -295,7 +295,7 @@ namespace Avalonia.Base.UnitTests.Styling
             public ActivatorSink(IStyleActivator source)
             {
                 source.Subscribe(this);
-                Active = source.IsActive;
+                Active = source.GetIsActive();
             }
 
 

tests/Avalonia.Base.UnitTests/Styling/StyleActivatorExtensions.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Base.UnitTests.Styling
             
             protected override void Subscribed(IObserver<bool> observer, bool first)
             {
-                observer.OnNext(_source.IsActive);
+                observer.OnNext(_source.GetIsActive());
             }
 
             void IStyleActivatorSink.OnNext(bool value, int tag)