Method handleKeyDown

lib/input-handler.ts:300–482

* Handle keydown event * @param event - KeyboardEvent

(event: KeyboardEvent)

   * @param event - KeyboardEvent
   */
  private handleKeyDown(event: KeyboardEvent): void {
    if (this.isDisposed) return;

    // Ignore keydown events during composition
    // Note: Some browsers send keyCode 229 for all keys during composition
    if (this.isComposing || event.isComposing || event.keyCode === 229) {
      return;
    }

    // Emit onKey event first (before any processing)
    if (this.onKeyCallback) {
      this.onKeyCallback({ key: event.key, domEvent: event });
    }

    // Check custom key event handler
    if (this.customKeyEventHandler) {
      const handled = this.customKeyEventHandler(event);
      if (handled) {
        // Custom handler consumed the event
        event.preventDefault();
        return;
      }
    }

    // Allow Ctrl+V and Cmd+V to trigger paste event (don't preventDefault)
    if ((event.ctrlKey || event.metaKey) && event.code === 'KeyV') {
      // Let the browser's native paste event fire
      return;
    }

    // Allow Cmd+C for copy (on Mac, Cmd+C should copy, not send interrupt)
    // SelectionManager handles the actual copying
    // Note: Ctrl+C on all platforms sends interrupt signal (0x03)
    if (event.metaKey && event.code === 'KeyC') {
      // Let browser/SelectionManager handle copy
      return;
    }

    // For printable characters without modifiers, send the character directly
    // This handles: a-z, A-Z (with shift), 0-9, punctuation, etc.
    if (this.isPrintableCharacter(event)) {
      event.preventDefault();
      this.onDataCallback(event.key);
      return;
    }

    // Map the physical key code
    const key = this.mapKeyCode(event.code);
    if (key === null) {
      // Unknown key - ignore it
      return;
    }

    // Extract modifiers
    const mods = this.extractModifiers(event);

    // Handle simple special keys that produce standard sequences
    if (mods === Mods.NONE || mods === Mods.SHIFT) {