[X] CSS specificity

src/Controls/src/Core/StyleSheets/Selector.cs

@@ -1,5 +1,6 @@
 #nullable disable
 using System;
+using System.Diagnostics;
 
 namespace Microsoft.Maui.Controls.StyleSheets
 {
@@ -313,5 +314,65 @@ public override bool Matches(IStyleSelectable styleable)
 				//return siblingIndex != -1;
 			}
 		}
+
+		[DebuggerDisplay("{id} - {class} = {type}")]
+		public struct SelectorSpecificity
+		{
+			int id;
+			int @class;
+			int type;
+
+			public int Id { get => id;  }
+			public int Class { get => @class;  }
+			public int Type { get => type; }
+
+			public static SelectorSpecificity FromSelector(Selector selector)
+			{
+				switch(selector)
+				{
+					case Selector.Class c:
+						return new SelectorSpecificity { @class = 1 };
+					case Selector.Id i:
+						return new SelectorSpecificity { id = 1 };
+					case Selector.Element e:
+						return new SelectorSpecificity { type = 1 };
+					case Selector.Base b:
+						return new SelectorSpecificity { type = 1 };
+					case Selector.And a:
+						return FromSelector(a.Left) + FromSelector(a.Right);
+					case Selector.Or o:
+						return FromSelector(o.Left) + FromSelector(o.Right);
+					case Selector.Child c:
+						return FromSelector(c.Left) + FromSelector(c.Right);
+					case Selector.Descendent d:
+						return FromSelector(d.Left) + FromSelector(d.Right);
+					case Selector.Adjacent a:
+						return FromSelector(a.Left) + FromSelector(a.Right);
+					case Selector.Sibling s:
+						return FromSelector(s.Left) + FromSelector(s.Right);
+					default:
+						return default;
+				}
+			}
+
+			public static SelectorSpecificity operator +(SelectorSpecificity left, SelectorSpecificity right)
+			{
+				return new SelectorSpecificity
+				{
+					id = left.id + right.id,
+					@class = left.@class + right.@class,
+					type = left.type + right.type
+				};
+			}
+			public SelectorSpecificity Add(SelectorSpecificity other)
+			{
+				return new SelectorSpecificity
+				{
+					id = id + other.id,
+					@class = @class + other.@class,
+					type = type + other.type
+				};
+			}
+		}
 	}
 }

src/Controls/src/Core/StyleSheets/Style.cs

@@ -60,7 +60,7 @@ public static Style Parse(CssReader reader, char stopChar = '\0')
 			return style;
 		}
 
-		public void Apply(VisualElement styleable, bool inheriting = false)
+		public void Apply(VisualElement styleable, Selector.SelectorSpecificity selectorSpecificity = default, bool inheriting = false)
 		{
 			if (styleable == null)
 				throw new ArgumentNullException(nameof(styleable));
@@ -71,15 +71,14 @@ public void Apply(VisualElement styleable, bool inheriting = false)
 				if (property == null)
 					continue;
 				if (string.Equals(decl.Value, "initial", StringComparison.OrdinalIgnoreCase))
-					//FIXME
-					styleable.ClearValue(property, new SetterSpecificity(SetterSpecificity.StyleImplicit, 0, 0, 0));
+					styleable.SetValue(property, property.DefaultValue, new SetterSpecificity(SetterSpecificity.StyleImplicit, (byte)selectorSpecificity.Id, (byte)selectorSpecificity.Class, (byte)selectorSpecificity.Type));					
 				else
 				{
 					object value;
 					if (!convertedValues.TryGetValue(decl, out value))
 						convertedValues[decl] = (value = Convert(styleable, decl.Value, property));
 					//FIXME: compute distance
-					styleable.SetValue(property, value, new SetterSpecificity(SetterSpecificity.StyleImplicit, 0, 0, 0));
+					styleable.SetValue(property, value, new SetterSpecificity(SetterSpecificity.StyleImplicit, (byte)selectorSpecificity.Id, (byte)selectorSpecificity.Class, (byte)selectorSpecificity.Type));
 				}
 			}
 

src/Controls/src/Core/StyleSheets/StyleSheet.cs

@@ -111,7 +111,8 @@ void Apply(Element styleable)
 				var style = kvp.Value;
 				if (!selector.Matches(styleable))
 					continue;
-				style.Apply(visualStylable);
+
+				style.Apply(visualStylable, Selector.SelectorSpecificity.FromSelector(selector));
 			}
 		}
 

src/Controls/tests/Xaml.UnitTests/Issues/Maui18980.xaml

@@ -0,0 +1,11 @@
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:local="clr-namespace:Microsoft.Maui.Controls.Xaml.UnitTests"
+             x:Class="Microsoft.Maui.Controls.Xaml.UnitTests.Maui18980">
+    <ContentPage.Resources>
+        <ResourceDictionary>
+            <StyleSheet Source="Maui18980Style.css"/>
+        </ResourceDictionary>
+    </ContentPage.Resources>
+    <Button x:Name="button" Text="Hello, World!" StyleClass="buttonClass" />
+</ContentPage>

src/Controls/tests/Xaml.UnitTests/Issues/Maui18980.xaml.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Linq;
+using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Controls.Core.UnitTests;
+using Microsoft.Maui.Controls.Shapes;
+using Microsoft.Maui.Devices;
+using Microsoft.Maui.Dispatching;
+
+using Microsoft.Maui.Graphics;
+using Microsoft.Maui.UnitTests;
+using NUnit.Framework;
+
+namespace Microsoft.Maui.Controls.Xaml.UnitTests
+{
+    public partial class Maui18980 : ContentPage
+    {
+        public Maui18980()
+        {
+            InitializeComponent();
+        }
+        	public Maui18980(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture]
+		class Test
+		{
+			[SetUp]
+			public void Setup()
+			{
+				Application.SetCurrentApplication(new MockApplication());
+				DispatcherProvider.SetCurrent(new DispatcherProviderStub());
+			}
+
+
+			[TearDown] public void TearDown() => AppInfo.SetCurrent(null);
+
+			[Test]
+			public void CSSnotOverridenbyImplicitStyle([Values(false, true)] bool useCompiledXaml)
+			{			
+				// var app = new MockApplication();
+				// app.Resources.Add(new Maui18980Style(useCompiledXaml));
+				// Application.SetCurrentApplication(app);
+
+				var page = new Maui18980(useCompiledXaml);
+				Assert.That(page.button.BackgroundColor, Is.EqualTo(Colors.Red));
+			}
+		}
+	}
+}

src/Controls/tests/Xaml.UnitTests/Issues/Maui18980Style.css

@@ -0,0 +1 @@
+.buttonClass{ background-color: red;}

src/Controls/tests/Xaml.UnitTests/Issues/Maui18980Style.xaml

@@ -0,0 +1,10 @@
+
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Microsoft.Maui.Controls.Xaml.UnitTests.Maui18980Style">
+
+    <Style TargetType="Button">
+        <Setter Property="BackgroundColor" Value="Blue" />
+    </Style>
+
+</ResourceDictionary>

src/Controls/tests/Xaml.UnitTests/Issues/Maui18980Style.xaml.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Linq;
+using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Controls.Core.UnitTests;
+using Microsoft.Maui.Controls.Shapes;
+using Microsoft.Maui.Devices;
+using Microsoft.Maui.Dispatching;
+
+using Microsoft.Maui.Graphics;
+using Microsoft.Maui.UnitTests;
+using NUnit.Framework;
+
+namespace Microsoft.Maui.Controls.Xaml.UnitTests
+{
+    public partial class Maui18980Style : ResourceDictionary
+    {
+        public Maui18980Style()
+        {
+            InitializeComponent();
+        }
+
+        public Maui18980Style(bool useCompiledXaml)
+        {
+            //this stub will be replaced at compile time
+        }
+    }
+}