Avoid recursive XAML view update churn

CSharpMath.Avalonia/CSharpMath.Avalonia.csproj

@@ -6,6 +6,7 @@
     <PackageTags>$(PackageTags) avalonia</PackageTags>
     <DefineConstants>$(DefineConstants) Avalonia</DefineConstants>
   </PropertyGroup>
+  <ItemGroup><InternalsVisibleTo Include="CSharpMath.Xaml.Tests" /></ItemGroup>
 
   <ItemGroup>
 	<Compile Include="..\CSharpMath.Xaml\**\*.cs" Link="%(RecursiveDir)%(Filename)%(Extension)" />

CSharpMath.Maui/CSharpMath.Maui.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-	<PropertyGroup>
+  <PropertyGroup>
 		<TargetFrameworks>net10.0;net10.0-android</TargetFrameworks>
 		<TargetFrameworks Condition="!$([System.OperatingSystem]::IsLinux())">$(TargetFrameworks);net10.0-ios;net10.0-maccatalyst</TargetFrameworks>
 		<TargetFrameworks Condition="$([System.OperatingSystem]::IsWindows())">$(TargetFrameworks);net10.0-windows10.0.19041.0</TargetFrameworks>
@@ -18,7 +18,8 @@
 		<PackageTags>$(PackageTags) maui</PackageTags>
 		<DefineConstants>$(DefineConstants) Maui</DefineConstants>
 
-	</PropertyGroup>
+  </PropertyGroup>
+  <ItemGroup><InternalsVisibleTo Include="CSharpMath.Xaml.Tests" /></ItemGroup>
 
 	<ItemGroup>
 		<AdditionalFiles Include="PublicAPI\$(TargetFramework)\PublicAPI.Shipped.txt" />

CSharpMath.Rendering.Benchmarks/CSharpMath.Rendering.Benchmarks.csproj

@@ -9,6 +9,9 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="BenchmarkDotNet" Version="0.15.8" />
+    <PackageReference Include="Avalonia" Version="$(AvaloniaVersion)" />
+    <PackageReference Include="Avalonia.Headless" Version="$(AvaloniaVersion)" />
     <ProjectReference Include="../CSharpMath.SkiaSharp/CSharpMath.SkiaSharp.csproj" />
+    <ProjectReference Include="../CSharpMath.Avalonia/CSharpMath.Avalonia.csproj" />
   </ItemGroup>
-</Project>
+</Project>

CSharpMath.Rendering.Benchmarks/Program.cs

@@ -1,4 +1,8 @@
+using Avalonia;
+using Avalonia.Headless;
 using BenchmarkDotNet.Attributes;
+using CSharpMath.Atom;
+using CSharpMath.SkiaSharp;
 namespace CSharpMath.Rendering.Benchmarks {
   using SkiaSharp;
   using Data = Tests.TestRenderingMathData;
@@ -41,4 +45,73 @@ static void Main(string[] args) {
 #endif
     }
   }
-}
+
+  [MemoryDiagnoser]
+  public class ViewUpdateChurnBenchmarks {
+    const string Sample = @"x_1 = 1.234e50";
+    [Params(100, 1000)] public int Iterations;
+    readonly MathPainter painter = new();
+    readonly MathList content = new MathPainter { LaTeX = Sample }.Content!;
+
+    [Benchmark]
+    public void LaTeXAssignment() {
+      for (var i = 0; i < Iterations; i++) {
+        painter.LaTeX = Sample;
+        painter.Measure(1000);
+      }
+    }
+
+    [Benchmark]
+    public void ContentAssignment() {
+      for (var i = 0; i < Iterations; i++) {
+        painter.Content = content;
+        painter.Measure(1000);
+      }
+    }
+
+    [Benchmark]
+    public void DirectPainterReuse() {
+      painter.LaTeX = Sample;
+      for (var i = 0; i < Iterations; i++) painter.Measure(1000);
+    }
+  }
+
+  [MemoryDiagnoser]
+  public class AvaloniaViewUpdateChurnBenchmarks {
+    const string FirstSample = @"x_1 = 1.234e50";
+    const string SecondSample = @"x_2 = 5.678e90";
+    [Params(100, 1000)] public int Iterations;
+    static AvaloniaViewUpdateChurnBenchmarks() {
+      _ = CSharpMath.Rendering.BackEnd.Fonts.GlobalTypefaces.ToString();
+      AppBuilder.Configure<BenchmarkApplication>()
+        .UseHeadless(new AvaloniaHeadlessPlatformOptions())
+        .SetupWithoutStarting();
+    }
+    sealed class BenchmarkApplication : Application { }
+    readonly CSharpMath.Avalonia.MathView view = new();
+    readonly MathList firstContent = new MathPainter { LaTeX = FirstSample }.Content!;
+    readonly MathList secondContent = new MathPainter { LaTeX = SecondSample }.Content!;
+
+    [Benchmark]
+    public void ViewLaTeXAssignment() {
+      for (var i = 0; i < Iterations; i++) {
+        view.LaTeX = i % 2 == 0 ? FirstSample : SecondSample;
+        view.Measure(new Size(1000, 1000));
+      }
+    }
+
+    [Benchmark]
+    public void ViewContentAssignment() {
+      for (var i = 0; i < Iterations; i++) {
+        view.Content = i % 2 == 0 ? firstContent : secondContent;
+        view.Measure(new Size(1000, 1000));
+      }
+    }
+
+    [Benchmark]
+    public void DirectPainterReuse() {
+      view.Painter.LaTeX = FirstSample;
+      for (var i = 0; i < Iterations; i++) view.Painter.Measure(1000);
+    }
+  }
+}

CSharpMath.Rendering/FrontEnd/Painter.cs

@@ -50,7 +50,7 @@ public Painter() {
     Atom.LineStyle __style = Atom.LineStyle.Display;
     public Atom.LineStyle LineStyle { get => __style; set { __style = value; SetRedisplay(); } }
     TContent? __content;
-    public TContent? Content { get => __content; set { __content = value; SetRedisplay(); } }
+    public TContent? Content { get => __content; set { __content = value; ErrorMessage = null; SetRedisplay(); } }
     public string? LaTeX { get => Content is null ? "" : ContentToLaTeX(Content); set => (Content, ErrorMessage) = LaTeXToContent(value ?? ""); }
     #endregion Redisplaying properties
 
@@ -132,4 +132,4 @@ GlyphBoxColor is var (glyph, textRun) ? Nullable((WrapColor(glyph), WrapColor(te
     public Painter<TCanvas, TContent, TColor> ShallowClone() => (Painter<TCanvas, TContent, TColor>)MemberwiseClone();
     #endregion Methods
   }
-}
+}

CSharpMath.Uno/CSharpMath.Uno.csproj

@@ -10,6 +10,7 @@
     <DefineConstants>$(DefineConstants) Uno</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
+    <InternalsVisibleTo Include="CSharpMath.Xaml.Tests" />
     <AdditionalFiles Include="PublicAPI\$(TargetFramework)\PublicAPI.Shipped.txt" />
     <AdditionalFiles Include="PublicAPI\$(TargetFramework)\PublicAPI.Unshipped.txt" />
     <Compile Include="..\CSharpMath.Xaml\**\*.cs" Link="%(RecursiveDir)%(Filename)%(Extension)" />

CSharpMath.Xaml.Tests/CSharpMath.Xaml.Tests.csproj

@@ -4,5 +4,6 @@
     <PackageReference Include="Avalonia.Markup.Xaml.Loader" Version="$(AvaloniaVersion)" />
     <ProjectReference Include="..\CSharpMath.Avalonia\CSharpMath.Avalonia.csproj" />
     <ProjectReference Include="..\CSharpMath.Maui\CSharpMath.Maui.csproj" />
+    <ProjectReference Include="..\CSharpMath.Uno\CSharpMath.Uno.csproj" AdditionalProperties="TargetFramework=net10.0" />
   </ItemGroup>
-</Project>
+</Project>

CSharpMath.Xaml.Tests/Test.cs

@@ -11,6 +11,10 @@ namespace CSharpMath.Xaml.Tests {
   using Rendering.BackEnd;
   using Rendering.FrontEnd;
   using Rendering.Text;
+  interface ITestDiagnostics {
+    void Reset();
+    int Count(string name);
+  }
   public abstract class Test<TColor, TBindingMode, TProperty, TBaseView, TMathView, TTextView>
     where TBindingMode : struct, Enum
     where TMathView : TBaseView, ICSharpMathAPI<MathList, TColor>, new()
@@ -32,8 +36,18 @@ void SetAndRaise<T>(ref T field, T value, [System.Runtime.CompilerServices.Calle
     protected abstract TBindingMode OneWayToSource { get; }
     protected abstract TBindingMode TwoWay { get; }
     protected abstract TView ParseFromXaml<TView>(string xaml) where TView : TBaseView, new();
+    protected abstract TBaseView CreateInstrumentedMathView();
     protected abstract void SetBindingContext(TBaseView view, object viewModel);
     protected abstract IDisposable SetBinding(TBaseView view, TProperty property, string viewModelProperty, TBindingMode bindingMode);
+    static void AssertUpdateCounts(TBaseView view, bool contentSource, Action update) {
+      var diagnostics = Assert.IsAssignableFrom<ITestDiagnostics>(view);
+      diagnostics.Reset();
+      update();
+      Assert.Equal(contentSource ? 1 : 0, diagnostics.Count("ContentToLaTeX"));
+      Assert.Equal(contentSource ? 0 : 1, diagnostics.Count("LaTeXToContent"));
+      Assert.Equal(1, diagnostics.Count("MeasureInvalidation"));
+      Assert.Equal(1, diagnostics.Count("VisualInvalidation"));
+    }
     IDisposable SetBinding<TView>(TView view, string propertyName, TBindingMode? bindingMode = null) where TView : TBaseView =>
       SetBinding(view,
         (TProperty)typeof(TView)
@@ -52,6 +66,9 @@ static void Test<TView, TContent>(TView view, TContent content)
       }
       Test(new TMathView(), new MathList(new Atom.Atoms.Number("1")));
       Test(new TTextView(), (TextAtom)new TextAtom.Text("1"));
+      var countedView = CreateInstrumentedMathView();
+      var counted = Assert.IsAssignableFrom<ICSharpMathAPI<MathList, TColor>>(countedView);
+      AssertUpdateCounts(countedView, false, () => counted.LaTeX = "1");
     }
     [Fact]
     public void ContentUpdatesLaTeX() {
@@ -64,6 +81,33 @@ static void Test<TView, TContent>(TView view, TContent content)
       }
       Test(new TMathView(), new MathList(new Atom.Atoms.Number("1")));
       Test(new TTextView(), (TextAtom)new TextAtom.Text("1"));
+      var countedView = CreateInstrumentedMathView();
+      var counted = Assert.IsAssignableFrom<ICSharpMathAPI<MathList, TColor>>(countedView);
+      AssertUpdateCounts(countedView, true, () => counted.Content = new MathList(new Atom.Atoms.Number("1")));
+    }
+    [Fact]
+    public void RepeatedContentUpdatesRemainNormalized() {
+      var view = new TMathView();
+      for (var i = 0; i < 8; i++) {
+        view.Content = new MathList(new Atom.Atoms.Number((i + 1).ToString()));
+        Assert.Equal((i + 1).ToString(), view.LaTeX);
+        Assert.Null(view.ErrorMessage);
+      }
+      var text = new TTextView();
+      for (var i = 0; i < 8; i++) {
+        text.LaTeX = "a b";
+        Assert.NotNull(text.Content);
+        Assert.Null(text.ErrorMessage);
+      }
+    }
+    [Fact]
+    public void ValidContentClearsPreviousError() {
+      var view = new TMathView();
+      view.LaTeX = @"\missingcommand";
+      Assert.NotNull(view.ErrorMessage);
+      view.Content = new MathList(new Atom.Atoms.Number("1"));
+      Assert.Null(view.ErrorMessage);
+      Assert.Equal("1", view.LaTeX);
     }
     [Fact]
     public void ContentIsBindable() {
@@ -259,4 +303,4 @@ public void LaTeXIsContent() {
       Assert.Equal(new TextAtom.List(new TextAtom[] { new TextAtom.Text("a"), new TextAtom.ControlSpace(), new TextAtom.Text("b") }), text.Content);
     }
   }
-}
+}

CSharpMath.Xaml.Tests/TestAvalonia.cs

@@ -9,6 +9,12 @@
 
 namespace CSharpMath.Xaml.Tests {
   using Avalonia;
+  public class InstrumentedMathView : MathView, ITestDiagnostics {
+    readonly Dictionary<string, int> counts = new();
+    internal override void OnDiagnostic(string name) => counts[name] = counts.GetValueOrDefault(name) + 1;
+    public void Reset() => counts.Clear();
+    public int Count(string name) => counts.GetValueOrDefault(name);
+  }
   public class TestAvalonia
     : Test<Color, BindingMode, AvaloniaProperty, Control, MathView, TextView> {
     protected override Display.IDisplay<Rendering.BackEnd.Fonts, Rendering.BackEnd.Glyph> GetDisplay(Control control) {
@@ -27,10 +33,11 @@ public class TestAvalonia
     protected override BindingMode Default => BindingMode.Default;
     protected override BindingMode OneWayToSource => BindingMode.OneWayToSource;
     protected override BindingMode TwoWay => BindingMode.TwoWay;
+    protected override Control CreateInstrumentedMathView() => new InstrumentedMathView();
     protected override TView ParseFromXaml<TView>(string xaml) => AvaloniaRuntimeXamlLoader.Parse<TView>(xaml);
     protected override IDisposable SetBinding(Control view, AvaloniaProperty property, string viewModelProperty, BindingMode bindingMode) =>
       view.Bind(property, new Binding(viewModelProperty) { Mode = bindingMode });
     protected override void SetBindingContext(Control view, object viewModel) =>
       view.DataContext = viewModel;
   }
-}
+}

CSharpMath.Xaml.Tests/TestMaui.cs

@@ -9,6 +9,13 @@ namespace CSharpMath.Xaml.Tests {
   using Maui;
   using Microsoft.Maui.Controls.Xaml;
 
+  public class InstrumentedMauiMathView : MathView, ITestDiagnostics {
+    readonly Dictionary<string, int> counts = new();
+    internal override void OnDiagnostic(string name) => counts[name] = counts.GetValueOrDefault(name) + 1;
+    public void Reset() => counts.Clear();
+    public int Count(string name) => counts.GetValueOrDefault(name);
+  }
+
   public class TestMaui
     : Test<Color, BindingMode, BindableProperty, GraphicsView, MathView, TextView> {
 
@@ -57,6 +64,7 @@ public bool DispatchDelayed(TimeSpan delay, Action action) {
     protected override BindingMode Default => BindingMode.Default;
     protected override BindingMode OneWayToSource => BindingMode.OneWayToSource;
     protected override BindingMode TwoWay => BindingMode.TwoWay;
+    protected override GraphicsView CreateInstrumentedMathView() => new InstrumentedMauiMathView();
     protected override TView ParseFromXaml<TView>(string xaml) {
       var view = new TView();
       view.LoadFromXaml(xaml);
@@ -74,4 +82,4 @@ protected override IDisposable SetBinding(GraphicsView view, BindableProperty pr
     protected override void SetBindingContext(GraphicsView view, object viewModel) =>
       view.BindingContext = viewModel;
   }
-}
+}

CSharpMath.Xaml.Tests/TestUno.cs

@@ -0,0 +1,15 @@
+using System.Runtime.CompilerServices;
+using Microsoft.UI.Xaml.Data;
+using Xunit;
+
+namespace CSharpMath.Xaml.Tests {
+  public class TestUno {
+    [Fact]
+    public void BindingExpressionMarkerPreventsCounterpartAssignment() {
+      var binding = RuntimeHelpers.GetUninitializedObject(typeof(BindingExpression));
+      Assert.False(Uno.UnoPropertySynchronization.ShouldAssignCounterpart(binding));
+      Assert.True(Uno.UnoPropertySynchronization.ShouldAssignCounterpart(null));
+      Assert.True(Uno.UnoPropertySynchronization.ShouldAssignCounterpart(new object()));
+    }
+  }
+}