Pass ResourceChanged messages to child styles.

Fixes #3590.

src/Avalonia.Styling/StyledElement.cs

@@ -67,6 +67,7 @@ namespace Avalonia
         private Subject<IStyleable> _styleDetach = new Subject<IStyleable>();
         private ITemplatedControl _templatedParent;
         private bool _dataContextUpdating;
+        private bool _notifyingResourcesChanged;
 
         /// <summary>
         /// Initializes static members of the <see cref="StyledElement"/> class.
@@ -235,6 +236,7 @@ namespace Avalonia
                     }
 
                     _styles.ResourcesChanged += ThisResourcesChanged;
+                    NotifyResourcesChanged(new ResourcesChangedEventArgs());
                 }
             }
         }
@@ -253,6 +255,7 @@ namespace Avalonia
 
                 if (_resources != null)
                 {
+                    (_resources as ISetResourceParent)?.SetParent(null);
                     hadResources = _resources.Count > 0;
                     _resources.ResourcesChanged -= ThisResourcesChanged;
                 }
@@ -260,9 +263,14 @@ namespace Avalonia
                 _resources = value;
                 _resources.ResourcesChanged += ThisResourcesChanged;
 
+                if (value is ISetResourceParent setParent && setParent.ResourceParent == null)
+                {
+                    setParent.SetParent(this);
+                }
+
                 if (hadResources || _resources.Count > 0)
                 {
-                    ((ILogical)this).NotifyResourcesChanged(new ResourcesChangedEventArgs());
+                    NotifyResourcesChanged(new ResourcesChangedEventArgs());
                 }
             }
         }
@@ -407,10 +415,7 @@ namespace Avalonia
         }
 
         /// <inheritdoc/>
-        void ILogical.NotifyResourcesChanged(ResourcesChangedEventArgs e)
-        {
-            ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
-        }
+        void ILogical.NotifyResourcesChanged(ResourcesChangedEventArgs e) => NotifyResourcesChanged(e);
 
         /// <inheritdoc/>
         bool IResourceProvider.TryGetResource(object key, out object value)
@@ -456,7 +461,8 @@ namespace Avalonia
                 {
                     Parent.ResourcesChanged += ThisResourcesChanged;
                 }
-                ((ILogical)this).NotifyResourcesChanged(new ResourcesChangedEventArgs());
+                
+                NotifyResourcesChanged(new ResourcesChangedEventArgs());
 
                 if (Parent is ILogicalRoot || Parent?.IsAttachedToLogicalTree == true || this is ILogicalRoot)
                 {
@@ -721,9 +727,29 @@ namespace Avalonia
             }
         }
 
+        private void NotifyResourcesChanged(ResourcesChangedEventArgs e)
+        {
+            if (_notifyingResourcesChanged)
+            {
+                return;
+            }
+
+            try
+            {
+                _notifyingResourcesChanged = true;
+                (_resources as ISetResourceParent)?.ParentResourcesChanged(e);
+                (_styles as ISetResourceParent)?.ParentResourcesChanged(e);
+                ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
+            }
+            finally
+            {
+                _notifyingResourcesChanged = false;
+            }
+        }
+
         private void ThisResourcesChanged(object sender, ResourcesChangedEventArgs e)
         {
-            ((ILogical)this).NotifyResourcesChanged(e);
+            NotifyResourcesChanged(e);
         }
     }
 }

src/Avalonia.Styling/Styling/Styles.cs

@@ -20,6 +20,7 @@ namespace Avalonia.Styling
         private IResourceDictionary _resources;
         private AvaloniaList<IStyle> _styles = new AvaloniaList<IStyle>();
         private Dictionary<Type, List<IStyle>> _cache;
+        private bool _notifyingResourcesChanged;
 
         public Styles()
         {
@@ -38,7 +39,7 @@ namespace Avalonia.Styling
                         ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
                     }
 
-                    x.ResourcesChanged += SubResourceChanged;
+                    x.ResourcesChanged += NotifyResourcesChanged;
                     _cache = null;
                 },
                 x =>
@@ -54,7 +55,7 @@ namespace Avalonia.Styling
                         ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
                     }
 
-                    x.ResourcesChanged -= SubResourceChanged;
+                    x.ResourcesChanged -= NotifyResourcesChanged;
                     _cache = null;
                 },
                 () => { });
@@ -90,11 +91,11 @@ namespace Avalonia.Styling
                 if (_resources != null)
                 {
                     hadResources = _resources.Count > 0;
-                    _resources.ResourcesChanged -= ResourceDictionaryChanged;
+                    _resources.ResourcesChanged -= NotifyResourcesChanged;
                 }
 
                 _resources = value;
-                _resources.ResourcesChanged += ResourceDictionaryChanged;
+                _resources.ResourcesChanged += NotifyResourcesChanged;
 
                 if (hadResources || _resources.Count > 0)
                 {
@@ -261,34 +262,35 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         void ISetResourceParent.ParentResourcesChanged(ResourcesChangedEventArgs e)
         {
-            ResourcesChanged?.Invoke(this, e);
+            NotifyResourcesChanged(e);
         }
 
-        private void ResourceDictionaryChanged(object sender, ResourcesChangedEventArgs e)
+        private void NotifyResourcesChanged(object sender, ResourcesChangedEventArgs e)
         {
-            foreach (var child in this)
-            {
-                (child as ISetResourceParent)?.ParentResourcesChanged(e);
-            }
-
-            ResourcesChanged?.Invoke(this, e);
+            NotifyResourcesChanged(e);
         }
 
-        private void SubResourceChanged(object sender, ResourcesChangedEventArgs e)
+        private void NotifyResourcesChanged(ResourcesChangedEventArgs e)
         {
-            var foundSource = false;
+            if (_notifyingResourcesChanged)
+            {
+                return;
+            }
 
-            foreach (var child in this)
+            try
             {
-                if (foundSource)
+                _notifyingResourcesChanged = true;
+                foreach (var child in this)
                 {
                     (child as ISetResourceParent)?.ParentResourcesChanged(e);
                 }
 
-                foundSource |= child == sender;
+                ResourcesChanged?.Invoke(this, e);
+            }
+            finally
+            {
+                _notifyingResourcesChanged = false;
             }
-
-            ResourcesChanged?.Invoke(this, e);
         }
     }
 }

tests/Avalonia.Styling.UnitTests/StyledElementTests.cs

@@ -489,6 +489,36 @@ namespace Avalonia.Styling.UnitTests
                 called);
         }
 
+        [Fact]
+        public void Resources_Parent_Is_Set()
+        {
+            var target = new TestControl();
+
+            Assert.Same(target, ((IResourceNode)target.Resources).ResourceParent);
+        }
+
+        [Fact]
+        public void Assigned_Resources_Parent_Is_Set()
+        {
+            var resources = new ResourceDictionary();
+            var target = new TestControl { Resources = resources };
+
+            Assert.Same(target, ((IResourceNode)resources).ResourceParent);
+        }
+
+        [Fact]
+        public void Assigning_Resources_Raises_ResourcesChanged()
+        {
+            var resources = new ResourceDictionary { { "foo", "bar" } };
+            var target = new TestControl();
+            var raised = 0;
+
+            target.ResourcesChanged += (s, e) => ++raised;
+            target.Resources = resources;
+
+            Assert.Equal(1, raised);
+        }
+
         [Fact]
         public void Changing_Parent_Notifies_Resources_ParentResourcesChanged()
         {
@@ -505,6 +535,36 @@ namespace Avalonia.Styling.UnitTests
                 Times.Once);
         }
 
+        [Fact]
+        public void Styles_Parent_Is_Set()
+        {
+            var target = new TestControl();
+
+            Assert.Same(target, ((IResourceNode)target.Styles).ResourceParent);
+        }
+
+        [Fact]
+        public void Assigned_Styles_Parent_Is_Set()
+        {
+            var styles = new Styles();
+            var target = new TestControl { Styles = styles };
+
+            Assert.Same(target, ((IResourceNode)styles).ResourceParent);
+        }
+
+        [Fact]
+        public void Assigning_Styles_Raises_ResourcesChanged()
+        {
+            var styles = new Styles { Resources = { { "foo", "bar" } } };
+            var target = new TestControl();
+            var raised = 0;
+
+            target.ResourcesChanged += (s, e) => ++raised;
+            target.Styles = styles;
+
+            Assert.Equal(1, raised);
+        }
+
         [Fact]
         public void Changing_Parent_Notifies_Styles_ParentResourcesChanged()
         {

tests/Avalonia.Styling.UnitTests/StylesTests.cs

@@ -3,6 +3,7 @@
 
 using System;
 using Avalonia.Controls;
+using Moq;
 using Xunit;
 
 namespace Avalonia.Styling.UnitTests
@@ -76,7 +77,7 @@ namespace Avalonia.Styling.UnitTests
         }
 
         [Fact]
-        public void Adding_Resource_To_Younger_Sibling_Style_Should_Raise_ResourceChanged()
+        public void Adding_Resource_To_Sibling_Style_Should_Raise_ResourceChanged()
         {
             Style style1;
             Style style2;
@@ -95,25 +96,20 @@ namespace Avalonia.Styling.UnitTests
         }
 
         [Fact]
-        public void Adding_Resource_To_Older_Sibling_Style_Should_Raise_ResourceChanged()
+        public void ParentResourcesChanged_Should_Be_Propagated_To_Children()
         {
-            Style style1;
-            Style style2;
-            var target = new Styles
-            {
-                (style1 = new Style()),
-                (style2 = new Style()),
-            };
-
-            var raised = false;
+            var childStyle = new Mock<IStyle>();
+            var setResourceParent = childStyle.As<ISetResourceParent>();
+            var target = new Styles { childStyle.Object };
 
-            style1.ResourcesChanged += (_, __) => raised = true;
-            style2.Resources.Add("foo", "bar");
+            setResourceParent.ResetCalls();
+            ((ISetResourceParent)target).ParentResourcesChanged(new ResourcesChangedEventArgs());
 
-            Assert.False(raised);
+            setResourceParent.Verify(x => x.ParentResourcesChanged(
+                It.IsAny<ResourcesChangedEventArgs>()),
+                Times.Once);
         }
 
-
         [Fact]
         public void Finds_Resource_In_Merged_Dictionary()
         {