Unicode text input

[haefele]

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[haefele]

@greptile

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Greptile Summary

This PR adds Unicode text input support to enable cross-layout keyboard compatibility by introducing a separate text input path that handles printable characters using Avalonia's TextInput event and KeySymbol property, while special keys continue through the existing key event system.

• Added TextInputMessage protocol message and full end-to-end routing from viewer to presenter
• Simplified key detection using ShouldDeferToTextInput() helper that checks KeySymbol for printable characters
• Implemented DoS protection with 100-char limit on viewer side and 1000-char limit on presenter side
• Text injection uses Keyboard.TextEntry() API which properly handles Unicode characters
• All changes follow existing patterns: error handling, input suppression checks, and session recorder integration

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The implementation follows established patterns throughout the codebase, includes appropriate validation and DoS protection at multiple layers, and cleanly separates text input from special key handling. The changes are well-structured across the protocol, service, and UI layers without introducing breaking changes.
• No files require special attention

Important Files Changed

Filename	Overview
src/RemoteViewer.Shared/Protocol/KeyMessage.cs	Added TextInputMessage record to carry Unicode text strings between viewer and presenter
src/RemoteViewer.Client/Views/Viewer/ViewerView.axaml.cs	Simplified key detection using KeySymbol, added TextInput handler with DoS protection (100 char limit)
src/RemoteViewer.Client/Services/HubClient/PresenterConnectionService.cs	Implemented text input handler with validation (1000 char limit), input suppression checks, and injection
src/RemoteViewer.Client/Services/InputInjection/WindowsInputInjectionService.cs	Implemented text injection using TextEntry API with stuck modifier check and action queue

Sequence Diagram

sequenceDiagram
    participant User
    participant ViewerView as ViewerView.axaml.cs
    participant ViewerService as ViewerConnectionService
    participant SignalR as SignalR Hub
    participant Connection as Connection (Presenter)
    participant PresenterService as PresenterConnectionService
    participant InputInjection as WindowsInputInjectionService
    participant OS as Windows OS

    User->>ViewerView: Type character (e.g., "é")
    
    alt Printable character (KeySymbol check)
        ViewerView->>ViewerView: KeyDown event → ShouldDeferToTextInput() = true
        ViewerView->>ViewerView: Defer to TextInput event
        ViewerView->>ViewerView: TextInput event fires
        ViewerView->>ViewerView: Validate: IsInputEnabled && length ≤ 100
        ViewerView->>ViewerService: SendTextInputAsync(text)
        ViewerService->>ViewerService: Serialize TextInputMessage
        ViewerService->>SignalR: Send message (MessageTypes.Input.TextInput)
        SignalR->>Connection: Route input message
        Connection->>Connection: Deserialize TextInputMessage
        Connection->>PresenterService: HandleTextInput(senderClientId, text)
        PresenterService->>PresenterService: Validate: length ≤ 1000, check input blocking
        PresenterService->>InputInjection: InjectText(text, connectionId, ct)
        InputInjection->>InputInjection: CheckAndReleaseStuckModifiers()
        InputInjection->>OS: Keyboard.TextEntry(text)
        OS->>OS: Unicode text injected
    else Special key (Escape, F11, Arrow, etc.)
        ViewerView->>ViewerView: KeyDown event → ShouldDeferToTextInput() = false
        ViewerView->>ViewerService: SendKeyDownAsync(keyCode, modifiers)
        Note over ViewerService,OS: Traditional key event flow (existing)
    end

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