This change replaces fixed callback protocols (e.g., ViewerGuiHook, ViewerUpdateHook, SimEventHandler) with a general-purpose, priority-based message and event handling mechanism.
Key changes:
- Handler decorator and registry: Introduced the `@messages.handler(priority=...)` decorator and `HandlerRegistry` (`handler_registry.py`). Methods marked as handlers are automatically discovered and dispatched by priority (CRITICAL, USER, LIBRARY, INTERNAL) or method resolution order.
- Local lifecycle events: Added `ViewerAppInitEvent`, `BuildGuiEvent`, and `UpdateEvent` to `messages.py`. Custom GUI rendering and per-frame update logic can now be implemented as standard event handlers without needing separate interface protocols.
- Streamlined launch and app APIs: Replaced individual hook and handler arguments in `launch_passive`, `ViewerApp`, and `ViewerHandle` with unified `viewer_handlers` and `sim_handlers` lists.
- Module restructuring: Extracted simulation-side message handling and `ViewerHandle` from `sim_app.py` into a dedicated `viewer_handle.py` module, removing `sim_app.py`.
- Sample updates: Migrated existing examples (such as `implot.py`) to use the new handler pattern and lifecycle events.
PiperOrigin-RevId: 941729322
Change-Id: I93e7c0edf0a13a8dc854f9e2083451f7c25a1825
Matija Kecman
0dfa4b509a