RealmUI Limitations and Fallbacks

Accessibility

• CmdUiAccessKitActionRequest is currently fallback-only with a diagnostic error.
• The command does not execute native AccessKit action in the current runtime.

Multi-Viewport

• When backend does not support native viewport, the core emits fallback:
  • UiViewportFallbackEmbedded
  • UiViewportCommand so the host can decide integration.

Host-Dependent Resources

• Real clipboard support depends on host <-> OS bridge.
• Screenshot depends on explicit host response:
  • request: UiScreenshotRequest
  • reply: CmdUiScreenshotReply

Platform Behaviors

• Cursor/IME/focus may vary by backend (desktop vs wasm).
• Async decode tries to avoid loop blocking; latency depends on environment.