From 82835ef95708edaf80a4ac2406179192d2db3d59 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 21 Apr 2022 09:53:28 +0200
Subject: [PATCH] Use nested styles in Button template.

And related fixes to make this work.
---
 src/Avalonia.Base/Styling/NestingSelector.cs  |  2 +-
 src/Avalonia.Base/Styling/Style.cs            |  8 +-
 .../Controls/Button.xaml                      | 80 ++++++++++---------
 .../Styling/SelectorTests_Nesting.cs          | 68 +++++++++++++++-
 4 files changed, 116 insertions(+), 42 deletions(-)

diff --git a/src/Avalonia.Base/Styling/NestingSelector.cs b/src/Avalonia.Base/Styling/NestingSelector.cs
index 1be54dea3c..741eb7e9ca 100644
--- a/src/Avalonia.Base/Styling/NestingSelector.cs
+++ b/src/Avalonia.Base/Styling/NestingSelector.cs
@@ -17,7 +17,7 @@ namespace Avalonia.Styling
         {
             if (parent is Style s && s.Selector is Selector selector)
             {
-                return selector.Match(control, null, subscribe);
+                return selector.Match(control, (parent as Style)?.Parent, subscribe);
             }
 
             throw new InvalidOperationException(
diff --git a/src/Avalonia.Base/Styling/Style.cs b/src/Avalonia.Base/Styling/Style.cs
index 6020dfe25f..7a83322355 100644
--- a/src/Avalonia.Base/Styling/Style.cs
+++ b/src/Avalonia.Base/Styling/Style.cs
@@ -120,15 +120,19 @@ namespace Avalonia.Styling
                 instance.Start();
             }
 
+            var result = match.Result;
+
             if (_children is not null)
             {
                 foreach (var child in _children)
                 {
-                    child.TryAttach(target, host);
+                    var childResult = child.TryAttach(target, host);
+                    if (childResult > result)
+                        result = childResult;
                 }
             }
 
-            return match.Result;
+            return result;
         }
 
         public bool TryGetResource(object key, out object? result)
diff --git a/src/Avalonia.Themes.Fluent/Controls/Button.xaml b/src/Avalonia.Themes.Fluent/Controls/Button.xaml
index f545206a2f..282f575605 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Button.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Button.xaml
@@ -7,9 +7,11 @@
       </StackPanel>
     </Border>
   </Design.PreviewWith>
+
   <Styles.Resources>
     <Thickness x:Key="ButtonPadding">8,5,8,6</Thickness>
   </Styles.Resources>
+  
   <Style Selector="Button">
     <Setter Property="Background" Value="{DynamicResource ButtonBackground}" />
     <!--<Setter Property="BackgroundSizing" Value="OuterBorderEdge" />-->
@@ -37,43 +39,54 @@
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" />
       </ControlTemplate>
     </Setter>
-  </Style>
 
-  <!-- PointerOverState -->  
-  <Style Selector="Button:pointerover /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPointerOver}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPointerOver}" />
-    <Setter Property="Foreground" Value="{DynamicResource ButtonForegroundPointerOver}" />
-  </Style>
+    <Style.Children>
+      <Style Selector="&amp;:pointerover /template/ ContentPresenter#PART_ContentPresenter">
+        <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPointerOver}" />
+        <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPointerOver}" />
+        <Setter Property="Foreground" Value="{DynamicResource ButtonForegroundPointerOver}" />
+      </Style>
 
-  <Style Selector="Button:pressed  /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPressed}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPressed}" />
-    <Setter Property="Foreground" Value="{DynamicResource ButtonForegroundPressed}" />
-  </Style>
+      <Style Selector="&amp;:pressed  /template/ ContentPresenter#PART_ContentPresenter">
+        <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPressed}" />
+        <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPressed}" />
+        <Setter Property="Foreground" Value="{DynamicResource ButtonForegroundPressed}" />
+      </Style>
 
-  <Style Selector="Button:disabled /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource ButtonBackgroundDisabled}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushDisabled}" />
-    <Setter Property="Foreground" Value="{DynamicResource ButtonForegroundDisabled}" />
-  </Style>
+      <Style Selector="&amp;:disabled /template/ ContentPresenter#PART_ContentPresenter">
+        <Setter Property="Background" Value="{DynamicResource ButtonBackgroundDisabled}" />
+        <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushDisabled}" />
+        <Setter Property="Foreground" Value="{DynamicResource ButtonForegroundDisabled}" />
+      </Style>
 
-  <Style Selector="Button.accent /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource AccentButtonBackground}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrush}" />
-    <Setter Property="Foreground" Value="{DynamicResource AccentButtonForeground}" />
-  </Style>
+      <Style Selector="&amp;.accent">
+        <Style.Children>
+          <Style Selector="&amp; /template/ ContentPresenter#PART_ContentPresenter">
+            <Setter Property="Background" Value="{DynamicResource AccentButtonBackground}" />
+            <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrush}" />
+            <Setter Property="Foreground" Value="{DynamicResource AccentButtonForeground}" />
+          </Style>
 
-  <Style Selector="Button.accent:pointerover /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundPointerOver}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushPointerOver}" />
-    <Setter Property="Foreground" Value="{DynamicResource AccentButtonForegroundPointerOver}" />
-  </Style>
+          <Style Selector="&amp;:pointerover /template/ ContentPresenter#PART_ContentPresenter">
+            <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundPointerOver}" />
+            <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushPointerOver}" />
+            <Setter Property="Foreground" Value="{DynamicResource AccentButtonForegroundPointerOver}" />
+          </Style>
 
-  <Style Selector="Button.accent:pressed  /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundPressed}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushPressed}" />
-    <Setter Property="Foreground" Value="{DynamicResource AccentButtonForegroundPressed}" />
+          <Style Selector="&amp;:pressed  /template/ ContentPresenter#PART_ContentPresenter">
+            <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundPressed}" />
+            <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushPressed}" />
+            <Setter Property="Foreground" Value="{DynamicResource AccentButtonForegroundPressed}" />
+          </Style>
+
+          <Style Selector="&amp;:disabled /template/ ContentPresenter#PART_ContentPresenter">
+            <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundDisabled}" />
+            <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushDisabled}" />
+            <Setter Property="Foreground" Value="{DynamicResource AccentButtonForegroundDisabled}" />
+          </Style>
+        </Style.Children>
+      </Style>
+    </Style.Children>
   </Style>
 
   <Style Selector="Button, RepeatButton, ToggleButton, DropDownButton">
@@ -89,9 +102,4 @@
     <Setter Property="RenderTransform" Value="scale(0.98)" />    
   </Style>
 
-  <Style Selector="Button.accent:disabled /template/ ContentPresenter#PART_ContentPresenter">
-    <Setter Property="Background" Value="{DynamicResource AccentButtonBackgroundDisabled}" />
-    <Setter Property="BorderBrush" Value="{DynamicResource AccentButtonBorderBrushDisabled}" />
-    <Setter Property="Foreground" Value="{DynamicResource AccentButtonForegroundDisabled}" />
-  </Style>
 </Styles>
diff --git a/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs b/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs
index eeb2fad996..f7e8793ede 100644
--- a/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs
+++ b/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs
@@ -9,7 +9,7 @@ namespace Avalonia.Base.UnitTests.Styling
     public class SelectorTests_Nesting
     {
         [Fact]
-        public void Nesting_Class_Doesnt_Match_Parent_Selector()
+        public void Nesting_Class_Doesnt_Match_Parent_OfType_Selector()
         {
             var control = new Control2();
             Style nested;
@@ -26,7 +26,7 @@ namespace Avalonia.Base.UnitTests.Styling
         }
 
         [Fact]
-        public void Or_Nesting_Class_Doesnt_Match_Parent_Selector()
+        public void Or_Nesting_Class_Doesnt_Match_Parent_OfType_Selector()
         {
             var control = new Control2();
             Style nested;
@@ -45,7 +45,7 @@ namespace Avalonia.Base.UnitTests.Styling
         }
 
         [Fact]
-        public void Or_Nesting_Child_OfType_Does_Not_Match_Parent_Selector()
+        public void Or_Nesting_Child_OfType_Doesnt_Match_Parent_OfType_Selector()
         {
             var control = new Control1();
             var panel = new DockPanel { Children = { control } };
@@ -64,6 +64,34 @@ namespace Avalonia.Base.UnitTests.Styling
             Assert.Equal(SelectorMatchResult.NeverThisInstance, match.Result);
         }
 
+        [Fact]
+        public void Double_Nesting_Class_Doesnt_Match_Grandparent_OfType_Selector()
+        {
+            var control = new Control2
+            {
+                Classes = { "foo", "bar" },
+            };
+
+            Style parent;
+            Style nested;
+            var grandparent = new Style(x => x.OfType<Control1>())
+            {
+                Children =
+                {
+                    (parent = new Style(x => x.Nesting().Class("foo"))
+                    {
+                        Children =
+                        {
+                            (nested = new Style(x => x.Nesting().Class("bar")))
+                        }
+                    })
+                }
+            };
+
+            var match = nested.Selector.Match(control, parent);
+            Assert.Equal(SelectorMatchResult.NeverThisType, match.Result);
+        }
+
         [Fact]
         public void Nesting_Class_Matches()
         {
@@ -87,6 +115,40 @@ namespace Avalonia.Base.UnitTests.Styling
             Assert.False(sink.Active);
         }
 
+        [Fact]
+        public void Double_Nesting_Class_Matches()
+        {
+            var control = new Control1
+            {
+                Classes = { "foo", "bar" },
+            };
+
+            Style parent;
+            Style nested;
+            var grandparent = new Style(x => x.OfType<Control1>())
+            {
+                Children =
+                {
+                    (parent = new Style(x => x.Nesting().Class("foo"))
+                    {
+                        Children =
+                        {
+                            (nested = new Style(x => x.Nesting().Class("bar")))
+                        }
+                    })
+                }
+            };
+
+            var match = nested.Selector.Match(control, parent);
+            Assert.Equal(SelectorMatchResult.Sometimes, match.Result);
+
+            var sink = new ActivatorSink(match.Activator);
+
+            Assert.True(sink.Active);
+            control.Classes.Remove("foo");
+            Assert.False(sink.Active);
+        }
+
         [Fact]
         public void Or_Nesting_Class_Matches()
         {