Fix InlineDictionary Behavior for Single Item Reassignment

[lindexi]

What does the pull request do?

This PR addresses an issue with the InlineDictionary when handling reassignment of a single item.

What is the current behavior?

Current Behavior:

• When the Set method was called, it ignored the overwrite parameter if the dictionary contained only one item.
• This caused the Set method to behave like the Add method, leading to unexpected behavior in composition animations.
• Specifically, the second composition animation would not play because it could not replace the first animation. Instead, it was added after the first animation, preventing it from being executed.

See

Avalonia/src/Avalonia.Base/Rendering/Composition/Server/ServerObjectAnimations.cs

Lines 109 to 120 in 68a626f

	public void OnSetAnimatedValue<T>(CompositionProperty<T> prop, ref T field, TimeSpan committedAt, IAnimationInstance animation) where T : struct
	{
	if (_owner.IsActive && _animations.TryGetValue(prop, out var oldAnimation))
	oldAnimation.Animation.Deactivate();
	_animations[prop] = new ServerObjectAnimationInstance<T>(this, animation, prop);
	animation.Initialize(committedAt, ExpressionVariant.Create(field), prop);
	if(_owner.IsActive)
	animation.Activate();
	OnSetDirectValue(prop);
	}

What is the updated/expected behavior with this PR?

Updated Behavior:

• The InlineDictionary now respects the overwrite parameter even when it contains only one item.
• This ensures that the second composition animation can overwrite the first one, allowing it to play correctly.

How was the solution implemented (if it's not obvious)?

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #17368

[MrJul]

Thank you! Could you please add a matching unit test to the InlineDictionaryTests? There isn't a lot of test coverage for this class currently, but we should at least cover fixed bugs :)

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0052850-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0052852-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[MrJul]

Thanks for adding the test! A couple of minor points and it should be good to go.

[lindexi]

@MrJul Thank you for your review. And I updated my code.

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0052893-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]