Fix colors for scatter() with unfilled markers

timhoffm · timhoffm · commit d86cc2bab818 · 2020-06-04T22:07:16.000+02:00
Previously, markers with fillstyle='none' still were drawn with a facecolor.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -4393,8 +4393,9 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
             - 'none': No patch boundary will be drawn.
             - A color or sequence of colors.
 
-            For non-filled markers, the *edgecolors* kwarg is ignored and
-            forced to 'face' internally.
+            For non-filled markers, *edgecolors* is ignored. Instead, the color
+            is determined like with 'face', i.e. from *c*, *colors*, or
+            *facecolors*.
 
         plotnonfinite : bool, default: False
             Set to plot points with nonfinite *c*, in conjunction with
@@ -4476,7 +4477,6 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
         path = marker_obj.get_path().transformed(
             marker_obj.get_transform())
         if not marker_obj.is_filled():
-            edgecolors = 'face'
             if linewidths is None:
                 linewidths = rcParams['lines.linewidth']
             elif np.iterable(linewidths):
@@ -4488,8 +4488,8 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
 
         collection = mcoll.PathCollection(
                 (path,), scales,
-                facecolors=colors,
-                edgecolors=edgecolors,
+                facecolors=colors if marker_obj.is_filled() else 'none',
+                edgecolors=edgecolors if marker_obj.is_filled() else colors,
                 linewidths=linewidths,
                 offsets=offsets,
                 transOffset=kwargs.pop('transform', self.transData),
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -1837,6 +1837,16 @@ def test_scatter_color(self):
         with pytest.raises(ValueError):
             plt.scatter([1, 2, 3], [1, 2, 3], color=[1, 2, 3])
 
+    def test_scatter_unfilled(self):
+        coll = plt.scatter([0, 1, 2], [1, 3, 2], c=['0.1', '0.3', '0.5'],
+                           marker=mmarkers.MarkerStyle('o', fillstyle='none'),
+                           linewidths=[1.1, 1.2, 1.3])
+        assert coll.get_facecolors().shape == (0, 4)  # no facecolors
+        assert_array_equal(coll.get_edgecolors(), [[0.1, 0.1, 0.1, 1],
+                                                   [0.3, 0.3, 0.3, 1],
+                                                   [0.5, 0.5, 0.5, 1]])
+        assert_array_equal(coll.get_linewidths(), [1.1, 1.2, 1.3])
+
     def test_scatter_size_arg_size(self):
         x = np.arange(4)
         with pytest.raises(ValueError):
