Oct 30, 2025 · Oct 29, 2025
diff --git a/src/napari_matplotlib/histogram.py b/src/napari_matplotlib/histogram.py
        Called when the selected layers are updated.
        """
        super().on_update_layers()
        if self._valid_layer_selection:
        if self._valid_layer_selection and self.layers:
            self.layers[0].events.contrast_limits.connect(self._update_contrast_lims)

        if not self.layers:
            return

        # Reset the num bins based on new layer data
        layer_data = self._get_layer_data(self.layers[0])
        self._set_widget_nums_bins(data=layer_data)
            # Reset the num bins based on new layer data
            layer_data = self._get_layer_data(self.layers[0])
            self._set_widget_nums_bins(data=layer_data)

    def _update_contrast_lims(self) -> None:
        for lim, line in zip(
diff --git a/src/napari_matplotlib/tests/test_histogram.py b/src/napari_matplotlib/tests/test_histogram.py
    # update contrast limits of image layer, and check no errors are thrown
    image_layer = viewer.layers[0]
    image_layer.contrast_limits = [2, 50]


 def test_select_labels_layer(make_napari_viewer):
    """Test that no errors are thrown when the Histogram widget
    is opened with a labels layer selected."""
    viewer = make_napari_viewer()
    viewer.add_labels(np.ones(shape=(5, 5, 5), dtype="uint8"))

    widget = HistogramWidget(viewer)
    viewer.window.add_dock_widget(widget)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -99,15 +99,12 @@ def on_update_layers(self) -> None:
		Called when the selected layers are updated.
		"""
		super().on_update_layers()
		if self._valid_layer_selection:
		if self._valid_layer_selection and self.layers:
		self.layers[0].events.contrast_limits.connect(self._update_contrast_lims)

		if not self.layers:
		return

		# Reset the num bins based on new layer data
		layer_data = self._get_layer_data(self.layers[0])
		self._set_widget_nums_bins(data=layer_data)
		# Reset the num bins based on new layer data
		layer_data = self._get_layer_data(self.layers[0])
		self._set_widget_nums_bins(data=layer_data)

		def _update_contrast_lims(self) -> None:
		for lim, line in zip(
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -164,3 +164,13 @@ def test_change_contrast(make_napari_viewer, astronaut_data):
		# update contrast limits of image layer, and check no errors are thrown
		image_layer = viewer.layers[0]
		image_layer.contrast_limits = [2, 50]


		def test_select_labels_layer(make_napari_viewer):
		"""Test that no errors are thrown when the Histogram widget
		is opened with a labels layer selected."""
		viewer = make_napari_viewer()
		viewer.add_labels(np.ones(shape=(5, 5, 5), dtype="uint8"))

		widget = HistogramWidget(viewer)
		viewer.window.add_dock_widget(widget)