feat(MenuFlyout): Add ItemContainerTheme

[workgroupengineering]

What does the pull request do?

Add ItemContainerTheme to MenuFlyout

What is the current behavior?

MenuFlyout has no ItemContainerTheme

What is the updated/expected behavior with this PR?

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/Documentation with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #10010
Depend of #10019 Because it depends on the style fix made in issue #10019

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0028956-beta. (feed url: https://pkgs.dev.azure.com/AvaloniaUI/AvaloniaUI/_packaging/avalonia-all/nuget/v3/index.json) [PRBUILDID]

[maxkatz6]

Not sure if I understand.
When I set <MenuFlyout ItemContainerTheme="" /> I would expect same container theme to be applied on flyout items and subitems.

[workgroupengineering]

I agree with you. But I have decided to respect the same behavior of the menus.

Avalonia/src/Avalonia.Controls/Menu.cs

Lines 97 to 105 in 61916d7

	protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
	{
	base.PrepareContainerForItemOverride(element, item, index);
	// Child menu items should not inherit the menu's ItemContainerTheme as that is specific
	// for top-level menu items.
	if ((element as MenuItem)?.ItemContainerTheme == ItemContainerTheme)
	element.ClearValue(ItemContainerThemeProperty);
	}

I've opened a discussion #10060 about it, but no one has responded yet.

[maxkatz6]

I think it's different in case of Menu control.
As in Menu control you have top level menu items that are always rendered horizontally and flyout/popup menus with a different styles. And there you wouldn't expect same style to be applied everywhere.

[workgroupengineering]

I personally expected the same behavior also for the Menu as it happens in WPF. I'd like to do a PR that changes the behavior of the menus, but I'm waiting for your response first. I don't want invest time unnecessarily.

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0029132-beta. (feed url: https://pkgs.dev.azure.com/AvaloniaUI/AvaloniaUI/_packaging/avalonia-all/nuget/v3/index.json) [PRBUILDID]