ToolTips no longer use ViewLocator after updating to 11.1

[airbreather]

Describe the bug

I have an Avalonia application on 11.0 that uses the ViewLocator pattern. Sometimes, I set a ToolTip.Tip to something that's supposed to get its template that way.

When I upgraded to 11.1.2, these ToolTips stopped displaying at all.

To Reproduce

I managed to get a somewhat slim repro project and pushed it to: https://github.com/airbreather/AvaloniaRepro

When running this as-is using dotnet run (on my Linux desktop, which is all I have readily accessible at the moment), I get a big red rectangle with a ToolTip that reads "Testing 123 (in a tooltip!)".

If I replace all the 11.0.13 to 11.1.2 in AvaloniaRepro.csproj and run it again using dotnet run, I get that same big red rectangle but with a blank ToolTip.

Expected behavior

11.1 should behave the same as 11.0: the ToolTip should display "Testing 123 (in a tooltip!)".

Avalonia version

11.1.2

OS

Linux

Additional context

No response

[airbreather]

Some progress in narrowing this down: this issue does not reproduce with the pared-down XAML-free version from this branch of that repository, and the relevant files are small enough for me to embed here:

AvaloniaRepro.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <Nullable>enable</Nullable>
    <BuiltInComInteropSupport>true</BuiltInComInteropSupport>
    <ApplicationManifest>app.manifest</ApplicationManifest>
    <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Avalonia" Version="11.1.2" />
    <PackageReference Include="Avalonia.Desktop" Version="11.1.2" />
  </ItemGroup>
</Project>

Program.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Presenters;
using Avalonia.Controls.Shapes;
using Avalonia.Controls.Templates;
using Avalonia.Data;
using Avalonia.Media;

Application app = AppBuilder.Configure<Application>()
    .UsePlatformDetect()
    .SetupWithClassicDesktopLifetime(args)
    .Instance!;

app.DataTemplates.Add(new ViewLocator());
Window window = new()
{
    Content = new Rectangle
    {
        Fill = Brushes.Red,
        [ToolTip.TipProperty] = new { Tip = "Testing 123" },
    },
};
window.Show();
app.Run(window);

public sealed class ViewLocator : IDataTemplate
{
    public bool Match(object? data) => data?.GetType().GetProperty("Tip") is not null;
    public Control Build(object? param) => new ContentPresenter
    {
        [!ContentPresenter.ContentProperty] = new Binding
        {
            Source = param,
            Path = "Tip",
            StringFormat = "{0} (from tooltip!)",
        },
    };
}

So it has something to do with the stuff that happens in the slightly fuller version that does not also happen here.

[airbreather]

And here's another branch on 11.1 that also works around it, which confuses me. The change looks like:

 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:avaloniaRepro="clr-namespace:AvaloniaRepro"
              x:DataType="avaloniaRepro:ToolTipViewModel"
-             x:Class="AvaloniaRepro.ToolTipView">
+             x:Class="AvaloniaRepro.ToolTipView"
+             x:Name="ThisControl">
-    <ContentPresenter Content="{Binding Tip, StringFormat='{}{0} (in a tooltip!)'}" />
+    <ContentPresenter Content="{ReflectionBinding DataContext.Tip, ElementName=ThisControl, StringFormat='{}{0} (in a tooltip!)'}" />
 </UserControl>

[TomEdwardsEnscape]

This isn't related to tooltips, but is because your ToolTipView control is using ContentPresenter. That type is only for templates. The control's content should be ContentControl. and making this change fixes the issue.

The default template for UserControl generates its own ContentPresenter, the content of which is bound to UserControl.Content (i.e. the ContentPresenter of your ToolTipView, see screenshot below). This double presenter layer is presumably what breaks things. I don't know why it worked before.

[timunie]

Good catch @TomEdwardsEnscape . Yes, this is by design.