UI: cache camera clients (#39166)

openpilot/selfdrive/ui/onroad/cameraview.py

@@ -88,8 +88,9 @@ class CameraView(Widget):
   def __init__(self, name: str, stream_type: VisionStreamType):
     super().__init__()
     self._name = name
-    # Primary stream
-    self.client = VisionIpcClient(name, stream_type, conflate=True)
+    # Reuse subscribers: destroying a VisionIpcClient doesn't reclaim its msgq reader slot.
+    self._clients = {stream: VisionIpcClient(name, stream, conflate=True) for stream in VisionStreamType}
+    self.client = self._clients[stream_type]
     self._stream_type: VisionStreamType = stream_type
     self.available_streams: list[VisionStreamType] = []
 
@@ -130,16 +131,14 @@ class CameraView(Widget):
     ui_state.add_offroad_transition_callback(self._offroad_transition)
 
   def _offroad_transition(self):
-    # Reconnect if not first time going onroad
+    # Discard queued frames from the previous drive without recreating subscribers.
     if ui_state.is_onroad() and self.frame is not None:
-      # Prevent old frames from showing when going onroad. Qt has a separate thread
-      # which drains the VisionIpcClient SubSocket for us. Re-connecting is not enough
-      # and only clears internal buffers, not the message queue.
       self.frame = None
-      self.available_streams.clear()
-      if self.client:
-        del self.client
-      self.client = VisionIpcClient(self._name, self._stream_type, conflate=True)
+      for client in self._clients.values():
+        client.recv(timeout_ms=0)
+      self._target_client = None
+      self._target_stream_type = None
+      self._switching = False
 
   def _set_placeholder_color(self, color: rl.Color):
     """Set a placeholder color to be drawn when no frame is available."""
@@ -154,11 +153,8 @@ class CameraView(Widget):
 
     cloudlog.debug(f'Preparing switch from {self._stream_type} to {stream_type}')
 
-    if self._target_client:
-      del self._target_client
-
     self._target_stream_type = stream_type
-    self._target_client = VisionIpcClient(self._name, stream_type, conflate=True)
+    self._target_client = self._clients[stream_type]
     self._switching = True
 
   @property
@@ -181,6 +177,8 @@ class CameraView(Widget):
     self.frame = None
     self.available_streams.clear()
     self.client = None
+    self._target_client = None
+    self._clients.clear()
 
   def __del__(self):
     self.close()
@@ -350,10 +348,6 @@ class CameraView(Widget):
   def _complete_switch(self) -> None:
     """Instantly switch to target stream."""
     cloudlog.debug(f"Switching to {self._target_stream_type}")
-    # Clean up current resources
-    if self.client:
-      del self.client
-
     # Switch to target
     assert self._target_client is not None and self._target_stream_type is not None
     self.client = self._target_client