fix(waveform): Ignore callbacks for on_async_readback from QtSender objects that are already destroyed; closes #497

bec_widgets/utils/bec_dispatcher.py

@@ -27,8 +27,9 @@ if TYPE_CHECKING:  # pragma: no cover
 class QtThreadSafeCallback(QObject):
     cb_signal = pyqtSignal(dict, dict)
 
-    def __init__(self, cb):
+    def __init__(self, cb: Callable, cb_info: dict | None = None):
         super().__init__()
+        self.cb_info = cb_info
 
         self.cb = cb
         self.cb_signal.connect(self.cb)
@@ -37,7 +38,7 @@ class QtThreadSafeCallback(QObject):
         # make 2 differents QtThreadSafeCallback to look
         # identical when used as dictionary keys, if the
         # callback is the same
-        return id(self.cb)
+        return f"{id(self.cb)}{self.cb_info}".__hash__()
 
     def __call__(self, msg_content, metadata):
         self.cb_signal.emit(msg_content, metadata)
@@ -141,6 +142,7 @@ class BECDispatcher:
         self,
         slot: Callable,
         topics: Union[EndpointInfo, str, list[Union[EndpointInfo, str]]],
+        cb_info: dict | None = None,
         **kwargs,
     ) -> None:
         """Connect widget's qt slot, so that it is called on new pub/sub topic message.
@@ -150,7 +152,7 @@ class BECDispatcher:
                 the corresponding pub/sub message
             topics (EndpointInfo | str | list): A topic or list of topics that can typically be acquired via bec_lib.MessageEndpoints
         """
-        slot = QtThreadSafeCallback(slot)
+        slot = QtThreadSafeCallback(cb=slot, cb_info=cb_info)
         self.client.connector.register(topics, cb=slot, **kwargs)
         topics_str, _ = self.client.connector._convert_endpointinfo(topics)
         self._slots[slot].update(set(topics_str))

bec_widgets/widgets/plots/waveform/waveform.py

@@ -1182,10 +1182,11 @@ class Waveform(PlotBase):
             self.on_async_readback,
             MessageEndpoints.device_async_readback(self.scan_id, name),
             from_start=True,
+            cb_info={"scan_id": self.scan_id},
         )
         logger.info(f"Setup async curve {name}")
 
-    @SafeSlot(dict, dict)
+    @SafeSlot(dict, dict, verify_sender=True)
     def on_async_readback(self, msg, metadata):
         """
         Get async data readback. This code needs to be fast, therefor we try
@@ -1204,6 +1205,14 @@ class Waveform(PlotBase):
             msg(dict): Message with the async data.
             metadata(dict): Metadata of the message.
         """
+        sender = self.sender()
+        if not hasattr(sender, "cb_info"):
+            logger.info(f"Sender {sender} has no cb_info.")
+            return
+        scan_id = sender.cb_info.get("scan_id", None)
+        if scan_id != self.scan_id:
+            logger.info("Scan ID mismatch, ignoring async readback.")
+
         instruction = metadata.get("async_update", {}).get("type")
         if instruction not in ["add", "add_slice", "replace"]:
             logger.warning(f"Invalid async update instruction: {instruction}")
@@ -1212,6 +1221,7 @@ class Waveform(PlotBase):
         plot_mode = self.x_axis_mode["name"]
         for curve in self._async_curves:
             x_data = None  # Reset x_data
+            y_data = None  # Reset y_data
             # Get the curve data
             async_data = msg["signals"].get(curve.config.signal.entry, None)
             if async_data is None: