Refactor Studio customization and message dispatch to use decorator-based handlers

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
2026-07-02 09:14:02 -07:00
parent 1ca64b441b
commit 0dfa4b509a
7 changed files with 507 additions and 358 deletions
@@ -0,0 +1,198 @@
+# Copyright 2026 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Viewer handle and event handlers for the simulation side."""
+
+from typing import Any, Callable
+import mujoco
+from mujoco.experimental.studio import endpoints
+from mujoco.experimental.studio import handler_registry
+from mujoco.experimental.studio import messages
+from mujoco.experimental.studio import sim as _sim
+import numpy as np
+
+
+class ViewerHandle:
+  """A handle for interacting with a running Studio application from the sim."""
+
+  def __init__(
+      self,
+      sim_endpoint: endpoints.SimEndpoint,
+      *,
+      handlers: list[Any] | None = None,
+      is_alive_fn: Callable[[], bool] | None = None,
+  ) -> None:
+    """Initializes the ViewerHandle.
+
+    Args:
+      sim_endpoint: The endpoint to use for communication with the viewer.
+      handlers: Optional list of handler instances for sim-side processing,
+        which are classes with methods decorated with ``@handler``.
+      is_alive_fn: Optional function called to check if the viewer is still
+        alive/responsive. If not provided, the viewer is assumed to be running
+        until ``close()`` is called.
+    """
+
+    self._sim_endpoint = sim_endpoint
+    self._is_running = True
+    self._is_alive_fn = is_alive_fn
+    self.model: mujoco.MjModel | None = None
+    self.data: mujoco.MjData | None = None
+    self.step_control: _sim.StepControl | None = None
+
+    # Instantiate handlers from user handlers + framework defaults.
+    all_handlers: list[Any] = list(handlers or [])
+    all_handlers.append(self)
+    self._handlers = handler_registry.HandlerRegistry(all_handlers)
+
+  def close(self) -> None:
+    """Signals the viewer to exit and closes the sim endpoint."""
+    if self._is_running:
+      self._is_running = False
+      try:
+        self.send_to_viewer(messages.ExitEvent())
+      except Exception:  # pylint: disable=broad-exception-caught
+        pass  # Ignore exceptions, the viewer may have already closed.
+    self._sim_endpoint.close()
+
+  def __enter__(self) -> 'ViewerHandle':
+    return self
+
+  def __exit__(
+      self,
+      exc_type: type[BaseException] | None,
+      exc_val: BaseException | None,
+      exc_tb: Any,
+  ) -> None:
+    self.close()
+
+  def is_running(self) -> bool:
+    """Returns True while the viewer is open."""
+    if self._is_alive_fn is not None and not self._is_alive_fn():
+      self.close()
+    return self._is_running
+
+  def send_to_viewer(self, message: messages.Message) -> None:
+    """Sends an event or snapshot message to the viewer process.
+
+    Args:
+      message: The message to send.
+    """
+    self._sim_endpoint.send_to_viewer(message)
+
+  def sync(
+      self,
+      model: mujoco.MjModel | None,
+      data: mujoco.MjData | None,
+      step_control: _sim.StepControl,
+  ) -> tuple[mujoco.MjModel | None, mujoco.MjData | None, _sim.StepControl]:
+    """Syncs the simulation with the viewer and returns the updated sim state.
+
+    This method processes incoming events from the viewer, updates the sim state
+    accordingly, and sends the current simulation state to the viewer as a
+    snapshot.
+
+    Args:
+      model: The current model.
+      data: The current data.
+      step_control: The current step control state.
+
+    Returns:
+      The updated model, data, and step control state.
+    """
+
+    self.model, self.data, self.step_control = model, data, step_control
+
+    # Process incoming events from the viewer.
+    for event in self._sim_endpoint.get_viewer_events():
+      self._handlers.dispatch(event)
+
+    # Process incoming snapshots from the viewer.
+    for snapshot in self._sim_endpoint.get_viewer_snapshots():
+      self._handlers.dispatch(snapshot)
+
+    model, data, step_control = self.model, self.data, self.step_control
+
+    # Send the simulation state to the viewer process as a snapshot.
+    if model is not None:
+      assert data is not None
+      integration_sig = int(mujoco.mjtState.mjSTATE_INTEGRATION)
+      integration_size = mujoco.mj_stateSize(model, integration_sig)
+      integration_state = np.empty(integration_size, np.float64)
+      mujoco.mj_getState(
+          model,
+          data,
+          integration_state,
+          integration_sig,
+      )
+      self._sim_endpoint.send_to_viewer(
+          messages.StateSnapshot(
+              state=integration_state, state_sig=integration_sig
+          ),
+      )
+
+    return model, data, step_control
+
+  @messages.handler(priority=messages.Priority.INTERNAL)
+  def _on_model(self, event: messages.ModelEvent) -> bool:
+    self.model = event.model
+    self.data = mujoco.MjData(event.model)
+    mujoco.mj_forward(self.model, self.data)
+    self.step_control = _sim.StepControl()
+    return True
+
+  @messages.handler(priority=messages.Priority.INTERNAL)
+  def _on_perturb(self, event: messages.PerturbEvent) -> bool:
+    model = self.model
+    data = self.data
+    if model is not None and data is not None:
+      state_size = mujoco.mj_stateSize(model, event.state_sig)
+      if len(event.state) == state_size:
+        mujoco.mj_setState(model, data, event.state, event.state_sig)
+    return True
+
+  @messages.handler(priority=messages.Priority.INTERNAL)
+  def _on_reset(self, _: messages.ResetEvent) -> bool:
+    model = self.model
+    data = self.data
+    if model is not None:
+      assert data is not None
+      mujoco.mj_resetData(model, data)
+      mujoco.mj_forward(model, data)
+    return True
+
+  @messages.handler(priority=messages.Priority.INTERNAL)
+  def _on_exit(self, _: messages.ExitEvent) -> bool:
+    self._is_running = False  # pylint: disable=protected-access
+    return True
+
+  @messages.handler(priority=messages.Priority.INTERNAL)
+  def _on_step_control(self, event: messages.StepControlSnapshot) -> bool:
+    sc = self.step_control
+    if sc is not None:
+      sc.set_pause_state(event.pause_state)
+      sc.set_speed(event.speed)
+      sc.set_noise_parameters(event.noise_scale, event.noise_rate)
+    return True
+
+  @messages.handler(priority=messages.Priority.INTERNAL)
+  def _on_mjoption(self, event: messages.MjOptionSnapshot) -> bool:
+    model = self.model
+    if model is not None:
+      for field in model.opt._all_fields:  # pylint: disable=protected-access
+        val = getattr(event.opt, field)
+        try:
+          getattr(model.opt, field)[:] = val
+        except (TypeError, AttributeError):
+          setattr(model.opt, field, val)
+    return True