Using static styles in templated control works incorrectly

[MartinZikmund]

Discussed in #2349

^{Originally posted by kucint June 13, 2024}
This issue is a continuation of #2316.

Repro steps:
Create a simple control with two predefined static styles: MyStyleA and MyStyleB
Assign MyStyleA to your control's style.

---

Issue 1:

this issue can be observed on windows:
TargetFramework: net8.0-desktop;

Expected behavior: MyStyleA is used,
Actual behavior: MyStyleB is used,

internal sealed class MyControl : Control
{
    public static readonly Style<MyControl> _styleA = new MyStyleA();   // red
    public static readonly Style<MyControl> _styleB = new MyStyleB();   // blue

    public MyControl()
    {
        DefaultStyleKey = typeof(MyControl);

        Style = _styleA;              // uses style B: error, expected style A
        //Style = _styleB;            // uses style B
        //Style = new MyStyleA();     // uses style A
        //Style = new MyStyleB();     // uses style B
    }
}

internal class MyStyleA : Style<MyControl>
{
    public MyStyleA() => Setters(s => s
        .Template(ctrl =>
            new Frame()
            .Background(Colors.LightCoral)
        ));
}

internal class MyStyleB : Style<MyControl>
{
    public MyStyleB() => Setters(s => s
        .Template(ctrl =>
            new Frame()
            .Background(Colors.LightSkyBlue)
        ));
}

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this
            .Background(ThemeResource.Get<Brush>("ApplicationPageBackgroundThemeBrush"))
            .Content(new StackPanel()
            .VerticalAlignment(VerticalAlignment.Center)
            .HorizontalAlignment(HorizontalAlignment.Center)
            .Children(
                new TextBlock()
                .Text("Hello Uno Platform!"),
                new MyControl()
                .Width(200)
                .Height(200)
            ));
    }
}

---

Issue 2:

this issue can be observed on windows:
TargetFramework: net8.0-windows10.0.19041

Application is unstable:
One of following may happen:

• app starts without errors but MyControl is not presented, terminates with error code = 0
• app starts without errors but MyControl is not presented, terminates with error code = 0xc0000374
• app fail to start throwing Exception = {"No installed components were detected.\r\n\r\nCannot apply a Style with TargetType 'Microsoft.UI.Xaml.Controls.ControlTemplate' to an object of type 'UnoChangingControlStyleApp.Controls.MyControl'."}

See #2311 for similar behavior

---

"Uno.Sdk": "5.2.161"
repro: UnoChangingControlStyleApp.zip

[Youssef1313]

C# Markup wasn't setting TargetType correctly, this is fixed in 5.4.0-dev.27. Once a package is released, I'll re-test the behavior on WinUI, and also check the other issues.

[Youssef1313]

For the wrong style issue, the remaining issue is also a C# Markup bug which we will track.

As a workaround, create extra empty classes:

public partial class FrameA : Frame { }
public partial class FrameB : Frame { }

And use them in the template of the styles. So, instead of new Frame(), do new FrameA() in StyleA and new FrameB() in StyleB.

And yes, I know it doesn't make any sense that my suggestion can have an impact on behavior, but it does due to some implementation details of C# Markup.

Alternative workaround: In only one of the templates, cast the Frame to Control

[Youssef1313]

Re-opening to validate the recent fixes and investigate more

[Youssef1313]

This is now fixed in C# Markup 5.4.0-dev.30.

[kucint]

I tested it with the newest branch "Uno.Sdk": "5.4.0-dev.145" and it does not work

[Youssef1313]

@kucint Can you verify you are not overriding UnoCSharpMarkupVersion with an old version?

If you have <UnoCSharpMarkupVersion>SomeVersion</UnoCSharpMarkupVersion> somewhere (e.g, Directory.Build.props), remove that line

[kucint]

you are right, I forgot that this section is no longer necessary starting from "Uno.Sdk": "5.4.0"

  <PropertyGroup>
    <UnoExtensionsVersion>4.1.24</UnoExtensionsVersion>
    <UnoToolkitVersion>6.0.24</UnoToolkitVersion>
    <UnoThemesVersion>5.0.13</UnoThemesVersion>
    <UnoCSharpMarkupVersion>5.2.14</UnoCSharpMarkupVersion>
  </PropertyGroup>

My bad, sorry!