Windows - Enable preview events

[bengavin]

This updates the library to support binding to the 'Preview' events on Windows. It also works around a bug where the behavior can be attached multiple times to the same bindable without intervening Detached events [currently a bug in the CommunityToolkit PopupService, see: https://github.com/CommunityToolkit/Maui/issues/1912 ].

Also does some general cleanup:

• Removal of unused classes
• KeyboardKeys is NOT a set of flags, so don't treat it as such
• Naming/etc cleanup, pull things internal that shouldn't be exposed by the library

[Copilot]

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/Plugin.Maui.KeyListener/KeyboardKeysExtensions.cs:41

• [nitpick] The mapping for KeyboardKeys.N returns an uppercase 'N' while most mappings use lowercase letters; it might be more consistent to return 'n' unless the uppercase is intentional.

KeyboardKeys.N => 'N',

[Copilot]

The initialization of _boundIds using [Guid.Empty] is not valid C# syntax; consider changing it to 'new List { Guid.Empty }' if the intention is to start with a default value, or initialize an empty list if no default is required.

Suggested change

	private List<Guid> _boundIds = [Guid.Empty];
	private List<Guid> _boundIds = new List<Guid> { Guid.Empty };

[PureWeen]

@bengavin I realize it's been a bit here

But what's the motivation for wiring into Preview events? What problem are you solving here?

[bengavin]

@bengavin I realize it's been a bit here

But what's the motivation for wiring into Preview events? What problem are you solving here?

In our case we needed to capture input from a barcode scanner without having the user need to have focus on an input field. The preview events seemed to be the only way on windows to accomplish this, and it was still relatively unreliable if the screen was clicked on in an area that also handled keyboard events.