Fluent2 Menu/MenuItem Resource Keys Misnamed

[robert-abeo]

Description

Every Fluent2 control template I've looked at has some very serious issues with resource keys. They don't follow upstream Fluent at all. The original author of this theme just did what they thought best but came up with a far inferior design. I have major concerns launching the Fluent2 theme like this. I think it needs to be re-written following upstream resources...

A good example of this is the Menu/MenuItem resource keys:

wpf/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.Dark.xaml

Lines 513 to 518 in e16222f

	<!-- Menu -->
	<SolidColorBrush x:Key="MenuBarBackground" Color="{StaticResource SubtleFillColorTransparent}" />
	<SolidColorBrush x:Key="MenuBarForeground" Color="{StaticResource TextFillColorPrimary}" />
	<SolidColorBrush x:Key="MenuBarItemBackgroundSelected" Color="{StaticResource SubtleFillColorTertiary}" />
	<SolidColorBrush x:Key="MenuBarItemBorderBrush" Color="{StaticResource ControlAltFillColorTertiary}" />
	<SolidColorBrush x:Key="MenuBarItemBackgroundMousePointer" Color="{StaticResource SubtleFillColorTertiary}" />

What is MenuBarItemBackgroundMousePointer. I think this should be MenuBarItemBackgroundPointerOver matching everywhere else. But there are so many resources missing here based on upstream. It forces re-templating most of the time. It is also incompatible with existing Fluent themes that define these resources.

https://github.com/microsoft/microsoft-ui-xaml/blob/d74a0332cf0d5e58f12eddce1070fa7a79b4c2db/src/controls/dev/MenuBar/MenuBar_themeresources.xaml#L5-L15

If you notice the MenuBarItemBackgroundMousePointer is also flat wrong as it should be pointing to the secondary instead of tertiary brush...

Reproduction Steps

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Expected behavior

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Actual behavior

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Regression?

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Known Workarounds

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Configuration

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