Don't allow bins lower than 0 if dtype is unisgned

Author: p-j-smith

Diff for: examples/histogram.py

@@ -5,7 +5,7 @@
 import napari
 
 viewer = napari.Viewer()
-viewer.open_sample("napari", "kidney")
+viewer.open_sample("napari", "coins")
 
 viewer.window.add_plugin_dock_widget(
     plugin_name="napari-matplotlib", widget_name="Histogram"

Diff for: src/napari_matplotlib/histogram.py

@@ -46,7 +46,7 @@ def __init__(
         bins_start.setStepType(QAbstractSpinBox.AdaptiveDecimalStepType)
         bins_start.setRange(-1e10, 1e10)
         bins_start.setValue(0)
-        bins_start.setWrapping(True)
+        bins_start.setWrapping(False)
         bins_start.setKeyboardTracking(False)
         bins_start.setDecimals(2)
 
@@ -55,6 +55,7 @@ def __init__(
         bins_stop.setStepType(QAbstractSpinBox.AdaptiveDecimalStepType)
         bins_stop.setRange(-1e10, 1e10)
         bins_stop.setValue(100)
+        bins_start.setWrapping(False)
         bins_stop.setKeyboardTracking(False)
         bins_stop.setDecimals(2)
 
@@ -148,13 +149,17 @@ def on_update_layers(self) -> None:
         self.autoset_widget_bins(data=layer_data)
 
         # Only allow integer bins for integer data
+        # And only allow values greater than 0 for unsigned integers
         n_decimals = 0 if np.issubdtype(layer_data.dtype, np.integer) else 2
-        self.findChild(QDoubleSpinBox, name="bins start").setDecimals(
-            n_decimals
-        )
-        self.findChild(QDoubleSpinBox, name="bins stop").setDecimals(
-            n_decimals
-        )
+        is_unsigned = layer_data.dtype.kind == "u"
+        minimum_value = 0 if is_unsigned else -1e10
+
+        bins_start = self.findChild(QDoubleSpinBox, name="bins start")
+        bins_stop = self.findChild(QDoubleSpinBox, name="bins stop")
+        bins_start.setDecimals(n_decimals)
+        bins_stop.setDecimals(n_decimals)
+        bins_start.setMinimum(minimum_value)
+        bins_stop.setMinimum(minimum_value)
 
     def draw(self) -> None:
         """
@@ -169,7 +174,7 @@ def draw(self) -> None:
             self.bins_start,
             self.bins_stop,
             self.bins_num,
-            dtype=int if np.issubdtype(data.dtype, np.integer) else float,
+            dtype=data.dtype,
         )
 
         if layer.rgb: