Fix errors in categorical selection

CHANGES.md

@@ -18,6 +18,9 @@ v0.9.0 (unreleased)
   ``glue.external.qt`` package is now deprecated. The ``get_qapp`` and
   ``load_ui`` functions are now available in ``glue.utils.qt``.
 
+* Avoid raising a (harmless) error when selecting a region in between two
+  categorical components.
+
 v0.8.3 (unreleased)
 -------------------
 

glue/core/qt/roi.py

@@ -3,7 +3,7 @@
 import numpy as np
 
 from qtpy.QtCore import Qt
-from qtpy import QtCore, QtWidgets
+from qtpy import QtCore, QtGui, QtWidgets
 from glue.core import roi
 from glue.utils.qt import mpl_to_qt4_color
 
@@ -46,7 +46,7 @@ def paint(self, canvas):
 
     def draw_polygon(self, canvas, x, y):
         x, y = self._transform(x, y)
-        poly = QtWidgets.QPolygon()
+        poly = QtGui.QPolygon()
         points = [QtCore.QPoint(xx, yy) for xx, yy in zip(x, y)]
         for p in points:
             poly.append(p)
@@ -70,7 +70,7 @@ def get_painter(self, canvas):
         edgecolor = mpl_to_qt4_color(self.plot_opts['edgecolor'],
                                      self.plot_opts['alpha'])
 
-        pen = QtWidgets.QPen(edgecolor)
+        pen = QtGui.QPen(edgecolor)
         pen.setWidth(self.plot_opts.get('edgewidth', 0))
         p.setPen(pen)
 

glue/core/roi.py

@@ -1219,14 +1219,15 @@ def contains(self, x, y):
            within the ROI
 
         """
-
-        check = self._categorical_helper(x)
-        index = np.minimum(np.searchsorted(self.categories, check),
-                           len(self.categories) - 1)
-        return self.categories[index] == check
+        if self.categories is None or len(self.categories) == 0:
+            return np.zeros(x.shape, dtype=bool)
+        else:
+            check = self._categorical_helper(x)
+            index = np.minimum(np.searchsorted(self.categories, check),
+                               len(self.categories) - 1)
+            return self.categories[index] == check
 
     def update_categories(self, categories):
-
         self.categories = np.unique(self._categorical_helper(categories))
 
     def defined(self):

glue/core/tests/test_roi.py

@@ -417,6 +417,11 @@ def test_from_range(self):
         np.testing.assert_array_equal(roi.categories,
                                       np.array(list('ghij')))
 
+    def test_empty_categories(self):
+        roi = CategoricalROI()
+        contains = roi.contains(np.array(['a','b','c']), None)
+        np.testing.assert_array_equal(contains, [0, 0, 0])
+
 
 class DummyEvent(object):
     def __init__(self, x, y, inaxes=True, key=None):