refactor: Remove reflection usage in Brush

[dr1rrb]

Refactoring (no functional changes, no api changes)

Remove reflection usage in Brush

What is the current behavior?

We use reflection to invoke event handler

What is the new behavior?

No reflection!

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
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[unodevops]

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[Youssef1313]

Quite scary class to touch, but I don't see leak concerns with the new impl. Just few comments.

I'd also love us to have this well-tested.

e.g (either runtime test or unit test should be fine, though my preference is always runtime test if no platform-specifics are involved):

using System;
using System.Collections.Generic;
using Uno.UI.Helpers;

namespace Uno.UI.RuntimeTests.Tests.Uno_UI;

[TestClass]
public class Given_WeakEventManager
{
	private sealed class EventPublisher
	{
		private readonly WeakEventManager _manager = new();

		internal event Action Event
		{
			add => _manager.AddEventHandler(value);
			remove => _manager.RemoveEventHandler(value);
		}
	}

	private sealed class EventSubscriber
	{
		public void M() { }
	}

	[TestMethod]
	public void When_Many_Subscriptions_Should_Not_Leak()
	{
		var publisher = new EventPublisher();
		var weakRefs = new List<WeakReference<EventSubscriber>>();
		Subscribe(publisher, weakRefs);

		for (int i = 0; i < 10; i++)
		{
			GC.Collect();
			GC.WaitForPendingFinalizers();
		}

		foreach (var x in weakRefs)
		{
			Assert.IsFalse(x.TryGetTarget(out _));
		}
	}

	private void Subscribe(EventPublisher publisher, List<WeakReference<EventSubscriber>> weakRefs)
	{
		for (int i = 0; i < 1000; i++)
		{
			var subscriber = new EventSubscriber();
			publisher.Event += subscriber.M;
			weakRefs.Add(new WeakReference<EventSubscriber>(subscriber));
		}
	}
}

Maybe also have additional tests around a handler that tries to subscribe/unsubscribe, re-entrancy, etc

[Youssef1313]

FYI there are some tests from MAUI here. I haven't looked at them, but just in case there is any interesting test scenario there. This comment isn't necessarily to port them as-is, but just looking if there is anything interesting :)

[unodevops]

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[unodevops]

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[unodevops]

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[unodevops]

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[unodevops]

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[jeromelaban]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[unodevops]

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[jeromelaban]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-16741/index.html

[jeromelaban]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-16741/index.html

[Youssef1313]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[unodevops]

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[unodevops]

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[MartinZikmund]

The failures here don't seem related to the changes, maybe just CI being funky

[Youssef1313]

This is failing on iOS @dr1rrb

[jeromelaban]

Superseeded by #18899