fix(image): preview signals can be used in Image widget; update logic adjusted; closes #683

bec_widgets/cli/client.py

@@ -1459,12 +1459,12 @@ class Image(RPCBase):
     @rpc_call
     def image(
         self,
-        monitor: "str | None" = None,
+        monitor: "str | tuple | None" = None,
         monitor_type: "Literal['auto', '1d', '2d']" = "auto",
         color_map: "str | None" = None,
         color_bar: "Literal['simple', 'full'] | None" = None,
         vrange: "tuple[int, int] | None" = None,
-    ) -> "ImageItem":
+    ) -> "ImageItem | None":
         """
         Set the image source and update the image.
 

bec_widgets/widgets/plots/image/image.py

@@ -35,7 +35,7 @@ class ImageConfig(ConnectionConfig):
 
 
 class ImageLayerConfig(BaseModel):
-    monitor: str | None = Field(None, description="The name of the monitor.")
+    monitor: str | tuple | None = Field(None, description="The name of the monitor.")
     monitor_type: Literal["1d", "2d", "auto"] = Field("auto", description="The type of monitor.")
     source: Literal["device_monitor_1d", "device_monitor_2d", "auto"] = Field(
         "auto", description="The source of the image data."
@@ -179,12 +179,12 @@ class Image(ImageBase):
     @SafeSlot(popup_error=True)
     def image(
         self,
-        monitor: str | None = None,
+        monitor: str | tuple | None = None,
         monitor_type: Literal["auto", "1d", "2d"] = "auto",
         color_map: str | None = None,
         color_bar: Literal["simple", "full"] | None = None,
         vrange: tuple[int, int] | None = None,
-    ) -> ImageItem:
+    ) -> ImageItem | None:
         """
         Set the image source and update the image.
 
@@ -201,21 +201,13 @@ class Image(ImageBase):
 
         if self.subscriptions["main"].monitor:
             self.disconnect_monitor(self.subscriptions["main"].monitor)
-        self.entry_validator.validate_monitor(monitor)
+        if monitor is None or monitor == "":
-        self.subscriptions["main"].monitor = monitor
+            logger.warning(f"No monitor specified, cannot set image, old monitor is unsubscribed")
-
+            return None
-        if monitor_type == "1d":
+        if isinstance(monitor, tuple):
-            self.subscriptions["main"].source = "device_monitor_1d"
+            self.entry_validator.validate_monitor(monitor[0])
-            self.subscriptions["main"].monitor_type = "1d"
+        else:
-        elif monitor_type == "2d":
+            self.entry_validator.validate_monitor(monitor)
-            self.subscriptions["main"].source = "device_monitor_2d"
-            self.subscriptions["main"].monitor_type = "2d"
-        elif monitor_type == "auto":
-            self.subscriptions["main"].source = "auto"
-            logger.warning(
-                f"Updates for '{monitor}' will be fetch from both 1D and 2D monitor endpoints."
-            )
-            self.subscriptions["main"].monitor_type = "auto"
 
         self.set_image_update(monitor=monitor, type=monitor_type)
         if color_map is not None:
@@ -240,7 +232,12 @@ class Image(ImageBase):
                 self.selection_bundle.dim_combo_box,
             ):
                 combo.blockSignals(True)
-            self.selection_bundle.device_combo_box.set_device(config.monitor)
+            if isinstance(config.monitor, tuple):
+                self.selection_bundle.device_combo_box.setCurrentText(
+                    f"{config.monitor[0]}_{config.monitor[1]}"
+                )
+            else:
+                self.selection_bundle.device_combo_box.setCurrentText(config.monitor)
             self.selection_bundle.dim_combo_box.setCurrentText(config.monitor_type)
             for combo in (
                 self.selection_bundle.device_combo_box,
@@ -340,7 +337,8 @@ class Image(ImageBase):
     ########################################
     # Connections
 
-    def set_image_update(self, monitor: str, type: Literal["1d", "2d", "auto"]):
+    @SafeSlot()
+    def set_image_update(self, monitor: str | tuple, type: Literal["1d", "2d", "auto"]):
         """
         Set the image update method for the given monitor.
 
@@ -350,37 +348,95 @@ class Image(ImageBase):
         """
 
         # TODO consider moving connecting and disconnecting logic to Image itself if multiple images
-        if type == "1d":
+        if isinstance(monitor, tuple):
-            self.bec_dispatcher.connect_slot(
+            device = self.dev[monitor[0]]
-                self.on_image_update_1d, MessageEndpoints.device_monitor_1d(monitor)
+            signal = monitor[1]
-            )
+            if len(monitor) == 3:
-        elif type == "2d":
+                signal_config = monitor[2]
-            self.bec_dispatcher.connect_slot(
+            else:
-                self.on_image_update_2d, MessageEndpoints.device_monitor_2d(monitor)
+                signal_config = device._info["signals"][signal]
-            )
+            signal_class = signal_config.get("signal_class", None)
-        elif type == "auto":
+            if signal_class != "PreviewSignal":
-            self.bec_dispatcher.connect_slot(
+                logger.warning(f"Signal '{monitor}' is not a PreviewSignal.")
-                self.on_image_update_1d, MessageEndpoints.device_monitor_1d(monitor)
+                return
-            )
+
-            self.bec_dispatcher.connect_slot(
+            ndim = signal_config.get("describe", None).get("signal_info", None).get("ndim", None)
-                self.on_image_update_2d, MessageEndpoints.device_monitor_2d(monitor)
+            if ndim is None:
-            )
+                logger.warning(
+                    f"Signal '{monitor}' does not have a valid 'ndim' in its signal_info."
+                )
+                return
+
+            if ndim == 1:
+                self.bec_dispatcher.connect_slot(
+                    self.on_image_update_1d, MessageEndpoints.device_preview(device.name, signal)
+                )
+                self.subscriptions["main"].source = "device_monitor_1d"
+                self.subscriptions["main"].monitor_type = "1d"
+            elif ndim == 2:
+                self.bec_dispatcher.connect_slot(
+                    self.on_image_update_2d, MessageEndpoints.device_preview(device.name, signal)
+                )
+                self.subscriptions["main"].source = "device_monitor_2d"
+                self.subscriptions["main"].monitor_type = "2d"
+
+        else:  # FIXME old monitor 1d/2d endpoint handling, present for backwards compatibility, will be removed in future versions
+            if type == "1d":
+                self.bec_dispatcher.connect_slot(
+                    self.on_image_update_1d, MessageEndpoints.device_monitor_1d(monitor)
+                )
+                self.subscriptions["main"].source = "device_monitor_1d"
+                self.subscriptions["main"].monitor_type = "1d"
+            elif type == "2d":
+                self.bec_dispatcher.connect_slot(
+                    self.on_image_update_2d, MessageEndpoints.device_monitor_2d(monitor)
+                )
+                self.subscriptions["main"].source = "device_monitor_2d"
+                self.subscriptions["main"].monitor_type = "2d"
+            elif type == "auto":
+                self.bec_dispatcher.connect_slot(
+                    self.on_image_update_1d, MessageEndpoints.device_monitor_1d(monitor)
+                )
+                self.bec_dispatcher.connect_slot(
+                    self.on_image_update_2d, MessageEndpoints.device_monitor_2d(monitor)
+                )
+                self.subscriptions["main"].source = "auto"
+                logger.warning(
+                    f"Updates for '{monitor}' will be fetch from both 1D and 2D monitor endpoints."
+                )
+                self.subscriptions["main"].monitor_type = "auto"
+
         logger.info(f"Connected to {monitor} with type {type}")
         self.subscriptions["main"].monitor = monitor
 
-    def disconnect_monitor(self, monitor: str):
+    def disconnect_monitor(self, monitor: str | tuple):
         """
         Disconnect the monitor from the image update signals, both 1D and 2D.
 
         Args:
-            monitor(str): The name of the monitor to disconnect.
+            monitor(str|tuple): The name of the monitor to disconnect, or a tuple of (device, signal) for preview signals.
         """
-        self.bec_dispatcher.disconnect_slot(
+        if isinstance(monitor, tuple):
-            self.on_image_update_1d, MessageEndpoints.device_monitor_1d(monitor)
+            if self.subscriptions["main"].source == "device_monitor_1d":
-        )
+                self.bec_dispatcher.disconnect_slot(
-        self.bec_dispatcher.disconnect_slot(
+                    self.on_image_update_1d, MessageEndpoints.device_preview(monitor[0], monitor[1])
-            self.on_image_update_2d, MessageEndpoints.device_monitor_2d(monitor)
+                )
-        )
+            elif self.subscriptions["main"].source == "device_monitor_2d":
+                self.bec_dispatcher.disconnect_slot(
+                    self.on_image_update_2d, MessageEndpoints.device_preview(monitor[0], monitor[1])
+                )
+            else:
+                logger.warning(
+                    f"Cannot disconnect monitor {monitor} with source {self.subscriptions['main'].source}"
+                )
+                return
+        else:  # FIXME old monitor 1d/2d endpoint handling, present for backwards compatibility, will be removed in future versions
+            self.bec_dispatcher.disconnect_slot(
+                self.on_image_update_1d, MessageEndpoints.device_monitor_1d(monitor)
+            )
+            self.bec_dispatcher.disconnect_slot(
+                self.on_image_update_2d, MessageEndpoints.device_monitor_2d(monitor)
+            )
         self.subscriptions["main"].monitor = None
         self._sync_device_selection()
 

bec_widgets/widgets/plots/image/toolbar_bundles/image_selection.py

@@ -1,5 +1,5 @@
 from bec_lib.device import ReadoutPriority
-from qtpy.QtCore import Qt
+from qtpy.QtCore import Qt, QTimer
 from qtpy.QtWidgets import QComboBox, QStyledItemDelegate
 
 from bec_widgets.utils.error_popups import SafeSlot
@@ -50,11 +50,58 @@ class MonitorSelectionToolbarBundle(ToolbarBundle):
 
         self.add_action("dim_combo", WidgetAction(widget=self.dim_combo_box, adjust_size=False))
 
-        # Connect slots, a device will be connected upon change of any combobox
+        self.device_combo_box.currentTextChanged.connect(self.connect_monitor)
-        self.device_combo_box.currentTextChanged.connect(lambda: self.connect_monitor())
+        self.dim_combo_box.currentTextChanged.connect(self.connect_monitor)
-        self.dim_combo_box.currentTextChanged.connect(lambda: self.connect_monitor())
+
+        QTimer.singleShot(0, self._adjust_and_connect)
+
+    def _adjust_and_connect(self):
+        """
+        Adjust the size of the device combo box and populate it with preview signals.
+        Has to be done with QTimer.singleShot to ensure the UI is fully initialized, needed for testing.
+        """
+        self._populate_preview_signals()
+        self._reverse_device_items()
+        self.device_combo_box.setCurrentText("")  # set again default to empty string
+
+    def _populate_preview_signals(self) -> None:
+        """
+        Populate the device combo box with preview‑signal devices in the
+        format '<device>_<signal>' and store the tuple(device, signal) in
+        the item's userData for later use.
+        """
+        preview_signals = self.target_widget.client.device_manager.get_bec_signals("PreviewSignal")
+        for device, signal, signal_config in preview_signals:
+            label = signal_config.get("obj_name", f"{device}_{signal}")
+            self.device_combo_box.addItem(label, (device, signal, signal_config))
+
+    def _reverse_device_items(self) -> None:
+        """
+        Reverse the current order of items in the device combo box while
+        keeping their userData and restoring the previous selection.
+        """
+        current_text = self.device_combo_box.currentText()
+        items = [
+            (self.device_combo_box.itemText(i), self.device_combo_box.itemData(i))
+            for i in range(self.device_combo_box.count())
+        ]
+        self.device_combo_box.clear()
+        for text, data in reversed(items):
+            self.device_combo_box.addItem(text, data)
+        if current_text:
+            self.device_combo_box.setCurrentText(current_text)
 
     @SafeSlot()
-    def connect_monitor(self):
+    def connect_monitor(self, *args, **kwargs):
+        """
+        Connect the target widget to the selected monitor based on the current device and dimension.
+
+        If the selected device is a preview-signal device, it will use the tuple (device, signal) as the monitor.
+        """
         dim = self.dim_combo_box.currentText()
-        self.target_widget.image(monitor=self.device_combo_box.currentText(), monitor_type=dim)
+        data = self.device_combo_box.currentData()
+
+        if isinstance(data, tuple):
+            self.target_widget.image(monitor=data, monitor_type="auto")
+        else:
+            self.target_widget.image(monitor=self.device_combo_box.currentText(), monitor_type=dim)

tests/unit_tests/test_image_view_next_gen.py

@@ -113,6 +113,75 @@ def test_enable_colorbar_with_vrange(qtbot, mocked_client, colorbar_type):
     assert bec_image_view._color_bar is not None
 
 
+##############################################
+# Preview‑signal update mechanism
+
+
+def test_image_setup_preview_signal_1d(qtbot, mocked_client, monkeypatch):
+    """
+    Ensure that calling .image() with a (device, signal, config) tuple representing
+    a 1‑D PreviewSignal connects using the 1‑D path and updates correctly.
+    """
+    import numpy as np
+
+    view = create_widget(qtbot, Image, client=mocked_client)
+
+    signal_config = {
+        "obj_name": "waveform1d_img",
+        "signal_class": "PreviewSignal",
+        "describe": {"signal_info": {"ndim": 1}},
+    }
+
+    # Set the image monitor to the preview signal
+    view.image(monitor=("waveform1d", "img", signal_config))
+
+    # Subscriptions should indicate 1‑D preview connection
+    sub = view.subscriptions["main"]
+    assert sub.source == "device_monitor_1d"
+    assert sub.monitor_type == "1d"
+    assert sub.monitor == ("waveform1d", "img", signal_config)
+
+    # Simulate a waveform update from the dispatcher
+    waveform = np.arange(25, dtype=float)
+    view.on_image_update_1d({"data": waveform}, {"scan_id": "scan_test"})
+    assert view.main_image.raw_data.shape == (1, 25)
+    np.testing.assert_array_equal(view.main_image.raw_data[0], waveform)
+
+
+def test_image_setup_preview_signal_2d(qtbot, mocked_client, monkeypatch):
+    """
+    Ensure that calling .image() with a (device, signal, config) tuple representing
+    a 2‑D PreviewSignal connects using the 2‑D path and updates correctly.
+    """
+    import numpy as np
+
+    view = create_widget(qtbot, Image, client=mocked_client)
+
+    signal_config = {
+        "obj_name": "eiger_img2d",
+        "signal_class": "PreviewSignal",
+        "describe": {"signal_info": {"ndim": 2}},
+    }
+
+    # Set the image monitor to the preview signal
+    view.image(monitor=("eiger", "img2d", signal_config))
+
+    # Subscriptions should indicate 2‑D preview connection
+    sub = view.subscriptions["main"]
+    assert sub.source == "device_monitor_2d"
+    assert sub.monitor_type == "2d"
+    assert sub.monitor == ("eiger", "img2d", signal_config)
+
+    # Simulate a 2‑D image update
+    test_data = np.arange(16, dtype=float).reshape(4, 4)
+    view.on_image_update_2d({"data": test_data}, {})
+    np.testing.assert_array_equal(view.main_image.image, test_data)
+
+
+##############################################
+# Device monitor endpoint update mechanism
+
+
 def test_image_setup_image_2d(qtbot, mocked_client):
     bec_image_view = create_widget(qtbot, Image, client=mocked_client)
     bec_image_view.image(monitor="eiger", monitor_type="2d")
@@ -167,6 +236,10 @@ def test_image_data_update_1d(qtbot, mocked_client):
     assert bec_image_view.main_image.raw_data.shape == (2, 60)
 
 
+##############################################
+# Toolbar and Actions Tests
+
+
 def test_toolbar_actions_presence(qtbot, mocked_client):
     bec_image_view = create_widget(qtbot, Image, client=mocked_client)
     assert "autorange_image" in bec_image_view.toolbar.widgets
@@ -484,3 +557,96 @@ def test_roi_plot_data_from_image(qtbot, mocked_client):
     # Horizontal slice (row)
     h_slice, _ = y_items[0].getData()
     np.testing.assert_array_equal(h_slice, test_data[2])
+
+
+##############################################
+# MonitorSelectionToolbarBundle specific tests
+##############################################
+
+
+def test_monitor_selection_reverse_device_items(qtbot, mocked_client):
+    """
+    Verify that _reverse_device_items correctly reverses the order of items in the
+    device combo‑box while preserving the current selection.
+    """
+    view = create_widget(qtbot, Image, client=mocked_client)
+    bundle = view.selection_bundle
+    combo = bundle.device_combo_box
+
+    # Replace existing items with a deterministic list
+    combo.clear()
+    combo.addItem("samx", 1)
+    combo.addItem("samy", 2)
+    combo.addItem("samz", 3)
+    combo.setCurrentText("samy")
+
+    # Reverse the items
+    bundle._reverse_device_items()
+
+    # Order should be reversed and selection preserved
+    assert [combo.itemText(i) for i in range(combo.count())] == ["samz", "samy", "samx"]
+    assert combo.currentText() == "samy"
+
+
+def test_monitor_selection_populate_preview_signals(qtbot, mocked_client, monkeypatch):
+    """
+    Verify that _populate_preview_signals adds preview‑signal devices to the combo‑box
+    with the correct userData.
+    """
+    view = create_widget(qtbot, Image, client=mocked_client)
+    bundle = view.selection_bundle
+
+    # Provide a deterministic fake device_manager with get_bec_signals
+    class _FakeDM:
+        def get_bec_signals(self, _filter):
+            return [
+                ("eiger", "img", {"obj_name": "eiger_img"}),
+                ("async_device", "img2", {"obj_name": "async_device_img2"}),
+            ]
+
+    monkeypatch.setattr(view.client, "device_manager", _FakeDM())
+
+    initial_count = bundle.device_combo_box.count()
+
+    bundle._populate_preview_signals()
+
+    # Two new entries should have been added
+    assert bundle.device_combo_box.count() == initial_count + 2
+
+    # The first newly added item should carry tuple userData describing the device/signal
+    data = bundle.device_combo_box.itemData(initial_count)
+    assert isinstance(data, tuple) and data[0] == "eiger"
+
+
+def test_monitor_selection_adjust_and_connect(qtbot, mocked_client, monkeypatch):
+    """
+    Verify that _adjust_and_connect performs the full set‑up:
+    ‑ fills the combo‑box with preview signals,
+    ‑ reverses their order,
+    ‑ and resets the currentText to an empty string.
+    """
+    view = create_widget(qtbot, Image, client=mocked_client)
+    bundle = view.selection_bundle
+
+    # Deterministic fake device_manager
+    class _FakeDM:
+        def get_bec_signals(self, _filter):
+            return [("eiger", "img", {"obj_name": "eiger_img"})]
+
+    monkeypatch.setattr(view.client, "device_manager", _FakeDM())
+
+    combo = bundle.device_combo_box
+    # Start from a clean state
+    combo.clear()
+    combo.addItem("", None)
+    combo.setCurrentText("")
+
+    # Execute the method under test
+    bundle._adjust_and_connect()
+
+    # Expect exactly two items: preview label followed by the empty default
+    assert combo.count() == 2
+    # Because of the reversal, the preview label comes first
+    assert combo.itemText(0) == "eiger_img"
+    # Current selection remains empty
+    assert combo.currentText() == ""