Make dynamic resources work in more situations.

Fixes #492 in a fashion: `DynamicResource` now works for this scenario.

src/Avalonia.Controls/Application.cs

@@ -128,6 +128,9 @@ namespace Avalonia
         /// <inheritdoc/>
         bool IResourceProvider.HasResources => _resources?.Count > 0;
 
+        /// <inheritdoc/>
+        IResourceProvider IResourceProvider.ResourceParent => null;
+
         /// <summary>
         /// Initializes the application by loading XAML etc.
         /// </summary>

src/Avalonia.Controls/Control.cs

@@ -283,10 +283,17 @@ namespace Avalonia.Controls
                 {
                     if (_styles != null)
                     {
+                        (_styles as ISetStyleParent)?.SetParent(null);
                         _styles.ResourcesChanged -= StyleResourcesChanged;
                     }
 
                     _styles = value;
+
+                    if (value is ISetStyleParent setParent && setParent.ResourceParent == null)
+                    {
+                        setParent.SetParent(this);
+                    }
+
                     _styles.ResourcesChanged += StyleResourcesChanged;
                 }
             }
@@ -385,6 +392,9 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         bool IResourceProvider.HasResources => _resources?.Count > 0 || Styles.HasResources;
 
+        /// <inheritdoc/>
+        IResourceProvider IResourceProvider.ResourceParent => ((IStyleHost)this).StylingParent as IResourceProvider;
+
         /// <inheritdoc/>
         IAvaloniaReadOnlyList<string> IStyleable.Classes => Classes;
 

src/Avalonia.Controls/ControlExtensions.cs

@@ -81,35 +81,6 @@ namespace Avalonia.Controls
                 .FirstOrDefault(x => x != null);
         }
 
-        /// <summary>
-        /// Finds the specified resource by searching up the logical tree and then global styles.
-        /// </summary>
-        /// <param name="control">The control.</param>
-        /// <param name="key">The resource key.</param>
-        /// <returns>The resource, or <see cref="AvaloniaProperty.UnsetValue"/> if not found.</returns>
-        public static object FindResource(this IControl control, string key)
-        {
-            Contract.Requires<ArgumentNullException>(control != null);
-            Contract.Requires<ArgumentNullException>(key != null);
-
-            var current = control as IStyleHost;
-
-            while (current != null)
-            {
-                if (current is IResourceProvider host)
-                {
-                    if (host.TryGetResource(key, out var value))
-                    {
-                        return value;
-                    }
-                }
-
-                current = current.StylingParent;
-            }
-
-            return AvaloniaProperty.UnsetValue;
-        }
-
         /// <summary>
         /// Adds or removes a pseudoclass depending on a boolean value.
         /// </summary>

src/Avalonia.Styling/Controls/IResourceProvider.cs

@@ -17,6 +17,11 @@ namespace Avalonia.Controls
         /// </summary>
         bool HasResources { get; }
 
+        /// <summary>
+        /// Gets the parent resource provider, if any.
+        /// </summary>
+        IResourceProvider ResourceParent { get; }
+
         /// <summary>
         /// Tries to find a resource within the element.
         /// </summary>

src/Avalonia.Styling/Controls/ResourceProviderExtensions.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Reactive;
+using System.Reactive.Linq;
+using System.Text;
+
+namespace Avalonia.Controls
+{
+    public static class ResourceProviderExtensions
+    {
+        /// <summary>
+        /// Finds the specified resource by searching up the logical tree and then global styles.
+        /// </summary>
+        /// <param name="control">The control.</param>
+        /// <param name="key">The resource key.</param>
+        /// <returns>The resource, or <see cref="AvaloniaProperty.UnsetValue"/> if not found.</returns>
+        public static object FindResource(this IResourceProvider control, string key)
+        {
+            Contract.Requires<ArgumentNullException>(control != null);
+            Contract.Requires<ArgumentNullException>(key != null);
+
+            var current = control;
+
+            while (current != null)
+            {
+                if (current is IResourceProvider host)
+                {
+                    if (host.TryGetResource(key, out var value))
+                    {
+                        return value;
+                    }
+                }
+
+                current = current.ResourceParent;
+            }
+
+            return AvaloniaProperty.UnsetValue;
+        }
+
+        public static IObservable<object> GetResourceObservable(this IResourceProvider target, string key)
+        {
+            return Observable.FromEventPattern<ResourcesChangedEventArgs>(
+                x => target.ResourcesChanged += x,
+                x => target.ResourcesChanged -= x)
+                .StartWith((EventPattern<ResourcesChangedEventArgs>)null)
+                .Select(x => target.FindResource(key));
+        }
+    }
+}

src/Avalonia.Styling/LogicalTree/ILogical.cs

@@ -58,7 +58,7 @@ namespace Avalonia.LogicalTree
         void NotifyDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e);
 
         /// <summary>
-        /// Notifies the control that a change has been made to its resources.
+        /// Notifies the control that a change has been made to resources that apply to it.
         /// </summary>
         /// <param name="e">The event args.</param>
         /// <remarks>

src/Avalonia.Styling/Styling/ISetStyleParent.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Avalonia.Controls;
+
+namespace Avalonia.Styling
+{
+    /// <summary>
+    /// Defines an interface through which a <see cref="Style"/>'s parent can be set.
+    /// </summary>
+    /// <remarks>
+    /// You should not usually need to use this interface - it is for internal use only.
+    /// </remarks>
+    public interface ISetStyleParent : IStyle
+    {
+        /// <summary>
+        /// Sets the style parent.
+        /// </summary>
+        /// <param name="parent">The parent.</param>
+        void SetParent(IResourceProvider parent);
+
+        /// <summary>
+        /// Notifies the style that a change has been made to resources that apply to it.
+        /// </summary>
+        /// <param name="e">The event args.</param>
+        /// <remarks>
+        /// This method will be called automatically by the framework, you should not need to call
+        /// this method yourself.
+        /// </remarks>
+        void NotifyResourcesChanged(ResourcesChangedEventArgs e);
+    }
+}

src/Avalonia.Styling/Styling/Style.cs

@@ -13,10 +13,11 @@ namespace Avalonia.Styling
     /// <summary>
     /// Defines a style.
     /// </summary>
-    public class Style : IStyle
+    public class Style : IStyle, ISetStyleParent
     {
         private static Dictionary<IStyleable, List<IDisposable>> _applied =
             new Dictionary<IStyleable, List<IDisposable>>();
+        private IResourceProvider _parent;
         private ResourceDictionary _resources;
 
         /// <summary>
@@ -69,6 +70,9 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         bool IResourceProvider.HasResources => _resources?.Count > 0;
 
+        /// <inheritdoc/>
+        IResourceProvider IResourceProvider.ResourceParent => _parent;
+
         /// <summary>
         /// Attaches the style to a control if the style's selector matches.
         /// </summary>
@@ -128,6 +132,23 @@ namespace Avalonia.Styling
             }
         }
 
+        /// <inheritdoc/>
+        void ISetStyleParent.NotifyResourcesChanged(ResourcesChangedEventArgs e)
+        {
+            ResourcesChanged?.Invoke(this, e);
+        }
+
+        /// <inheritdoc/>
+        void ISetStyleParent.SetParent(IResourceProvider parent)
+        {
+            if (_parent != null && parent != null)
+            {
+                throw new InvalidOperationException("The Style already has a parent.");
+            }
+
+            _parent = parent;
+        }
+
         private static List<IDisposable> GetSubscriptions(IStyleable control)
         {
             List<IDisposable> subscriptions;

src/Avalonia.Styling/Styling/Styles.cs

@@ -12,8 +12,9 @@ namespace Avalonia.Styling
     /// <summary>
     /// A style that consists of a number of child styles.
     /// </summary>
-    public class Styles : AvaloniaList<IStyle>, IStyle
+    public class Styles : AvaloniaList<IStyle>, IStyle, ISetStyleParent
     {
+        private IResourceProvider _parent;
         private ResourceDictionary _resources;
 
         public Styles()
@@ -22,6 +23,12 @@ namespace Avalonia.Styling
             this.ForEachItem(
                 x =>
                 {
+                    if (x.ResourceParent == null && x is ISetStyleParent setParent)
+                    {
+                        setParent.SetParent(this);
+                        setParent.NotifyResourcesChanged(new ResourcesChangedEventArgs());
+                    }
+
                     if (x.HasResources)
                     {
                         ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
@@ -31,6 +38,12 @@ namespace Avalonia.Styling
                 },
                 x =>
                 {
+                    if (x.ResourceParent == this && x is ISetStyleParent setParent)
+                    {
+                        setParent.SetParent(null);
+                        setParent.NotifyResourcesChanged(new ResourcesChangedEventArgs());
+                    }
+
                     if (x.HasResources)
                     {
                         ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
@@ -64,6 +77,9 @@ namespace Avalonia.Styling
             }
         }
 
+        /// <inheritdoc/>
+        IResourceProvider IResourceProvider.ResourceParent => _parent;
+
         /// <summary>
         /// Attaches the style to a control if the style's selector matches.
         /// </summary>
@@ -99,13 +115,49 @@ namespace Avalonia.Styling
             return false;
         }
 
+        /// <inheritdoc/>
+        void ISetStyleParent.SetParent(IResourceProvider parent)
+        {
+            if (_parent != null && parent != null)
+            {
+                throw new InvalidOperationException("The Style already has a parent.");
+            }
+
+            _parent = parent;
+        }
+
+        /// <inheritdoc/>
+        void ISetStyleParent.NotifyResourcesChanged(ResourcesChangedEventArgs e)
+        {
+            ResourcesChanged?.Invoke(this, e);
+        }
+
         private void ResourceDictionaryChanged(object sender, NotifyCollectionChangedEventArgs e)
         {
-            ResourcesChanged?.Invoke(this, new ResourcesChangedEventArgs());
+            var ev = new ResourcesChangedEventArgs();
+
+            foreach (var child in this)
+            {
+                (child as ISetStyleParent)?.NotifyResourcesChanged(ev);
+            }
+
+            ResourcesChanged?.Invoke(this, ev);
         }
 
         private void SubResourceChanged(object sender, ResourcesChangedEventArgs e)
         {
+            var foundSource = false;
+
+            foreach (var child in this)
+            {
+                if (foundSource)
+                {
+                    (child as ISetStyleParent)?.NotifyResourcesChanged(e);
+                }
+
+                foundSource |= child == sender;
+            }
+
             ResourcesChanged?.Invoke(this, e);
         }
     }

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs

@@ -15,7 +15,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
 {
     public class DynamicResourceExtension : MarkupExtension, IBinding
     {
-        private IControl _anchor;
+        private IResourceProvider _anchor;
 
         public DynamicResourceExtension()
         {
@@ -33,9 +33,9 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
             var context = (ITypeDescriptorContext)serviceProvider;
             var provideTarget = context.GetService<IProvideValueTarget>();
 
-            if (!(provideTarget.TargetObject is IControl))
+            if (!(provideTarget.TargetObject is IResourceProvider))
             {
-                _anchor = GetAnchor<IControl>(context);
+                _anchor = GetAnchor<IResourceProvider>(context);
             }
 
             return this;
@@ -47,17 +47,11 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
             object anchor,
             bool enableDataValidation)
         {
-            var control = target as IControl ?? _anchor as IControl;
+            var control = target as IResourceProvider ?? _anchor;
 
             if (control != null)
             {
-                var o = Observable.FromEventPattern<ResourcesChangedEventArgs>(
+                return new InstancedBinding(control.GetResourceObservable(ResourceKey));
-                    x => control.ResourcesChanged += x,
-                    x => control.ResourcesChanged -= x)
-                    .StartWith((EventPattern<ResourcesChangedEventArgs>)null)
-                    .Select(x => control.FindResource(ResourceKey));
-
-                return new InstancedBinding(o);
             }
 
             return null;

src/Markup/Avalonia.Markup.Xaml/Styling/StyleInclude.cs

@@ -10,16 +10,16 @@ namespace Avalonia.Markup.Xaml.Styling
     /// <summary>
     /// Includes a style from a URL.
     /// </summary>
-    public class StyleInclude : IStyle
+    public class StyleInclude : IStyle, ISetStyleParent
     {
         private Uri _baseUri;
         private IStyle _loaded;
+        private IResourceProvider _parent;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="StyleInclude"/> class.
         /// </summary>
         /// <param name="baseUri"></param>
-
         public StyleInclude(Uri baseUri)
         {
             _baseUri = baseUri;
@@ -44,6 +44,7 @@ namespace Avalonia.Markup.Xaml.Styling
                 {
                     var loader = new AvaloniaXamlLoader();
                     _loaded = (IStyle)loader.Load(Source, _baseUri);
+                    (_loaded as ISetStyleParent)?.SetParent(this);
                 }
 
                 return _loaded;
@@ -53,6 +54,9 @@ namespace Avalonia.Markup.Xaml.Styling
         /// <inheritdoc/>
         bool IResourceProvider.HasResources => Loaded.HasResources;
 
+        /// <inheritdoc/>
+        IResourceProvider IResourceProvider.ResourceParent => _parent;
+
         /// <inheritdoc/>
         public void Attach(IStyleable control, IStyleHost container)
         {
@@ -64,5 +68,22 @@ namespace Avalonia.Markup.Xaml.Styling
 
         /// <inheritdoc/>
         public bool TryGetResource(string key, out object value) => Loaded.TryGetResource(key, out value);
+
+        /// <inheritdoc/>
+        void ISetStyleParent.NotifyResourcesChanged(ResourcesChangedEventArgs e)
+        {
+            (Loaded as ISetStyleParent)?.NotifyResourcesChanged(e);
+        }
+
+        /// <inheritdoc/>
+        void ISetStyleParent.SetParent(IResourceProvider parent)
+        {
+            if (_parent != null && parent != null)
+            {
+                throw new InvalidOperationException("The Style already has a parent.");
+            }
+
+            _parent = parent;
+        }
     }
 }

tests/Avalonia.Controls.UnitTests/ControlTests_Resources.cs

@@ -204,44 +204,6 @@ namespace Avalonia.Controls.UnitTests
             Assert.True(raised);
         }
 
-        [Fact]
-        public void Adding_Style_With_Resource_Should_Raise_ResourceChanged()
-        {
-            Style style = new Style
-            {
-                Resources = { { "foo", "bar" } },
-            };
-
-            var target = new Decorator();
-            var raised = false;
-
-            target.ResourcesChanged += (_, __) => raised = true;
-            target.Styles.Add(style);
-
-            Assert.True(raised);
-        }
-
-        [Fact]
-        public void Removing_Style_With_Resource_Should_Raise_ResourceChanged()
-        {
-            var target = new Decorator
-            {
-                Styles =
-                {
-                    new Style
-                    {
-                        Resources = { { "foo", "bar" } },
-                    }
-                }
-            };
-            var raised = false;
-
-            target.ResourcesChanged += (_, __) => raised = true;
-            target.Styles.Clear();
-
-            Assert.True(raised);
-        }
-
         private IControlTemplate ContentControlTemplate()
         {
             return new FuncControlTemplate<ContentControl>(x =>

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/DynamicResourceExtensionTests.cs

@@ -360,8 +360,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
   <Style.Resources>
     <Color x:Key='Red'>Red</Color>
-    <Color x:Key='Green'>Green</Color>
-    <Color x:Key='Blue'>Blue</Color>
   </Style.Resources>
 </Style>";
             var style2Xaml = @"
@@ -369,8 +367,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
   <Style.Resources>
     <SolidColorBrush x:Key='RedBrush' Color='{DynamicResource Red}'/>
-    <SolidColorBrush x:Key='GreenBrush' Color='{DynamicResource Green}'/>
-    <SolidColorBrush x:Key='BlueBrush' Color='{DynamicResource Blue}'/>
   </Style.Resources>
 </Style>";
             using (StyledWindow(

tests/Avalonia.Styling.UnitTests/SelectorTests_Child.cs

@@ -154,6 +154,11 @@ namespace Avalonia.Styling.UnitTests
             {
                 throw new NotImplementedException();
             }
+
+            public void NotifyResourcesChanged(ResourcesChangedEventArgs e)
+            {
+                throw new NotImplementedException();
+            }
         }
 
         public class TestLogical1 : TestLogical

tests/Avalonia.Styling.UnitTests/SelectorTests_Descendent.cs

@@ -184,6 +184,11 @@ namespace Avalonia.Styling.UnitTests
             {
                 throw new NotImplementedException();
             }
+
+            public void NotifyResourcesChanged(ResourcesChangedEventArgs e)
+            {
+                throw new NotImplementedException();
+            }
         }
 
         public class TestLogical1 : TestLogical

tests/Avalonia.Styling.UnitTests/StylesTests.cs

@@ -0,0 +1,115 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using Xunit;
+
+namespace Avalonia.Styling.UnitTests
+{
+    public class StylesTests
+    {
+        [Fact]
+        public void Adding_Style_With_Resources_Should_Raise_ResourceChanged()
+        {
+            var style = new Style
+            {
+                Resources = { { "foo", "bar" } },
+            };
+
+            var target = new Styles();
+            var raised = false;
+
+            target.ResourcesChanged += (_, __) => raised = true;
+            target.Add(style);
+
+            Assert.True(raised);
+        }
+
+        [Fact]
+        public void Removing_Style_With_Resources_Should_Raise_ResourceChanged()
+        {
+            var target = new Styles
+            {
+                new Style
+                {
+                    Resources = { { "foo", "bar" } },
+                }
+            };
+
+            var raised = false;
+
+            target.ResourcesChanged += (_, __) => raised = true;
+            target.Clear();
+
+            Assert.True(raised);
+        }
+
+        [Fact]
+        public void Adding_Style_Without_Resources_Should_Not_Raise_ResourceChanged()
+        {
+            var style = new Style();
+            var target = new Styles();
+            var raised = false;
+
+            target.ResourcesChanged += (_, __) => raised = true;
+            target.Add(style);
+
+            Assert.False(raised);
+        }
+
+        [Fact]
+        public void Adding_Resource_Should_Raise_Child_ResourceChanged()
+        {
+            Style child;
+            var target = new Styles
+            {
+                (child = new Style()),
+            };
+
+            var raised = false;
+
+            child.ResourcesChanged += (_, __) => raised = true;
+            target.Resources.Add("foo", "bar");
+
+            Assert.True(raised);
+        }
+
+        [Fact]
+        public void Adding_Resource_To_Younger_Sibling_Style_Should_Raise_ResourceChanged()
+        {
+            Style style1;
+            Style style2;
+            var target = new Styles
+            {
+                (style1 = new Style()),
+                (style2 = new Style()),
+            };
+
+            var raised = false;
+
+            style2.ResourcesChanged += (_, __) => raised = true;
+            style1.Resources.Add("foo", "bar");
+
+            Assert.True(raised);
+        }
+
+        [Fact]
+        public void Adding_Resource_To_Older_Sibling_Style_Should_Raise_ResourceChanged()
+        {
+            Style style1;
+            Style style2;
+            var target = new Styles
+            {
+                (style1 = new Style()),
+                (style2 = new Style()),
+            };
+
+            var raised = false;
+
+            style1.ResourcesChanged += (_, __) => raised = true;
+            style2.Resources.Add("foo", "bar");
+
+            Assert.False(raised);
+        }
+    }
+}