Fix virtual key to char conversion on Windows

[jeremy-visionaid]

Use MapVirtualKey to convert VirtualKey to char

Fixes: #25

[jeremy-visionaid]

@davidortinau Maybe you'd like to use CsWin32 to provide the bindings, or know some other way of handling it without hitting the Win32 API directly? Either way, I'm happy to clean it up before merge.

[jeremy-visionaid]

I've added CsWin32 as a build dependency on Windows. It's maybe a bit overkill for one function, but it's something others will be reasonably familiar with if more bindings are needed and it saves debate about how to manage p/invokes. I'd understand if it's not wanted though.

[jeremy-visionaid]

Didn't take long to find that we do in fact need more bindings 😆 This is essentially a prerequisite for #27

[Copilot]

Pull Request Overview

This PR adds proper Win32 interop to convert VirtualKey codes into characters and refactors Windows-specific key event handling to use these new extensions.

• Introduce CsWin32 package and config to generate the MapVirtualKey P/Invoke binding
• Add ToChar and ToKeyPressedEventArgs extension methods to centralize key-to-char conversion
• Update KeyboardBehavior.Windows and sample to consume the new helpers

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Plugin.Maui.KeyListener/Plugin.Maui.KeyListener.csproj	Add Microsoft.Windows.CsWin32 package reference for Win32 APIs
src/Plugin.Maui.KeyListener/NativeMethods.txt	List of native method names (MapVirtualKey) for CsWin32 generation
src/Plugin.Maui.KeyListener/NativeMethods.json	CsWin32 configuration (wideCharOnly, emitSingleFile, public=false)
src/Plugin.Maui.KeyListener/KeyboardKeysExtensions.Windows.cs	Implement ToChar and ToKeyPressedEventArgs extensions
src/Plugin.Maui.KeyListener/KeyboardBehavior.Windows.cs	Refactor key event handlers to use ToKeyPressedEventArgs
samples/Plugin.Maui.KeyListener.Sample/MainPage.xaml.cs	Update sample to show KeyChar in output

Comments suppressed due to low confidence (2)

src/Plugin.Maui.KeyListener/KeyboardKeysExtensions.Windows.cs:172

• The new ToKeyPressedEventArgs helper wraps key conversion logic. Consider adding unit tests to verify that Keys and KeyChar are set correctly across a variety of VirtualKey values and modifier states.

internal static KeyPressedEventArgs ToKeyPressedEventArgs(this KeyRoutedEventArgs e)

src/Plugin.Maui.KeyListener/NativeMethods.txt:1

• [nitpick] It's not clear how NativeMethods.txt is consumed. Consider adding a header or comment explaining its purpose or remove it if it's no longer needed.

MapVirtualKey

[Copilot]

Using MapVirtualKey with MAPVK_VK_TO_CHAR ignores modifier keys (Shift, Ctrl) and current keyboard layout/layout-specific dead keys. Consider using ToUnicodeEx to accurately map key codes + modifiers to characters.

[Copilot]

[nitpick] Importing the entire Windows.Win32 namespace is broad. You can narrow this to Windows.Win32.UI.Input.KeyboardAndMouse to limit scope and improve readability.

Suggested change

using Windows.Win32;

[Copilot]

The newly added ToChar extension lacks XML documentation. Adding a <summary> explaining expected behavior, limitations (e.g., no modifiers), and return value would help maintainers and API consumers.