Merge pull request #10471 from jp2masa/issue-10226

Fixed templated parent theme changed loop

src/Avalonia.Base/Visual.cs

@@ -732,6 +732,23 @@ namespace Avalonia
             }
         }
 
+        internal override void OnTemplatedParentControlThemeChanged()
+        {
+            base.OnTemplatedParentControlThemeChanged();
+
+            var count = VisualChildren.Count;
+            var templatedParent = TemplatedParent;
+
+            for (var i = 0; i < count; ++i)
+            {
+                if (VisualChildren[i] is StyledElement child &&
+                    child.TemplatedParent == templatedParent)
+                {
+                    child.OnTemplatedParentControlThemeChanged();
+                }
+            }
+        }
+
         /// <summary>
         /// Computes the <see cref="HasMirrorTransform"/> value according to the 
         /// <see cref="FlowDirection"/> and <see cref="BypassFlowDirectionPolicies"/>

src/Avalonia.Controls/Primitives/TemplatedControl.cs

@@ -405,22 +405,5 @@ namespace Avalonia.Controls.Primitives
                 }
             }
         }
-
-        internal override void OnTemplatedParentControlThemeChanged()
-        {
-            base.OnTemplatedParentControlThemeChanged();
-
-            var count = VisualChildren.Count;
-            var templatedParent = TemplatedParent;
-
-            for (var i = 0; i < count; ++i)
-            {
-                if (VisualChildren[i] is TemplatedControl child &&
-                    child.TemplatedParent == templatedParent)
-                {
-                    child.OnTemplatedParentControlThemeChanged();
-                }
-            }
-        }
     }
 }

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

@@ -569,6 +569,46 @@ public class StyledElementTests_Theming
             Assert.Equal(Brushes.Green, border.Background);
         }
 
+        [Fact]
+        public void TemplatedParent_Theme_Change_Applies_Recursively_To_VisualChildren()
+        {
+            var theme = CreateDerivedTheme();
+            var target = CreateTarget();
+
+            Assert.Null(target.Theme);
+            Assert.Null(target.Template);
+
+            var root = CreateRoot(target, theme.BasedOn);
+
+            Assert.NotNull(target.Theme);
+            Assert.NotNull(target.Template);
+
+            root.Styles.Add(new Style(x => x.OfType<ThemedControl>().Class("foo"))
+            {
+                Setters = { new Setter(StyledElement.ThemeProperty, theme) }
+            });
+
+            root.LayoutManager.ExecuteLayoutPass();
+
+            var border = Assert.IsType<Border>(target.VisualChild);
+            var inner = Assert.IsType<Border>(border.Child);
+
+            Assert.Equal(Brushes.Red, border.Background);
+            Assert.Equal(Brushes.Red, inner.Background);
+
+            Assert.Equal(null, inner.BorderBrush);
+            Assert.Equal(null, inner.BorderBrush);
+
+            target.Classes.Add("foo");
+            root.LayoutManager.ExecuteLayoutPass();
+
+            Assert.Equal(Brushes.Green, border.Background);
+            Assert.Equal(Brushes.Green, inner.Background);
+
+            Assert.Equal(Brushes.Cyan, inner.BorderBrush);
+            Assert.Equal(Brushes.Cyan, inner.BorderBrush);
+        }
+
         private static ThemedControl CreateTarget()
         {
             return new ThemedControl();
@@ -595,7 +635,8 @@ public class StyledElementTests_Theming
 
     private static ControlTheme CreateTheme(string tag = "theme")
     {
-        var template = new FuncControlTemplate<ThemedControl>((o, n) => new Border());
+        var template = new FuncControlTemplate<ThemedControl>(
+            (o, n) => new Border() { Child = new Border() });
 
         return new ControlTheme
         {