All non-modal layers currently on the screen. Layers appearing later in the array have higher keyboard priority.
All modal layers currently on the screen. Keyboard and mouse events for modal layers always take precedence over those for pages and ordinary layers.
The screen path to transmit; used by the keyboard system to identify the current page.
State snapshot pushed by the host framework on every engine sync.
The keyboard engine uses it to keep the screen path, layers, and modal layers in sync with the host's navigation state.