Merge pull request matplotlib#30328 from lukashergt/fix-legend-labelcolor-linecolor

Fix legend `labelcolor=‘linecolor’` to handle various corner cases, e.g. step histograms and transparent markers

Author: QuLogic

lib/matplotlib/legend.py

@@ -576,7 +576,11 @@ def __init__(
         # set the text color
 
         color_getters = {  # getter function depends on line or patch
-            'linecolor':       ['get_color',           'get_facecolor'],
+            'linecolor':       ['get_markerfacecolor',
+                                'get_facecolor',
+                                'get_markeredgecolor',
+                                'get_edgecolor',
+                                'get_color'],
             'markerfacecolor': ['get_markerfacecolor', 'get_facecolor'],
             'mfc':             ['get_markerfacecolor', 'get_facecolor'],
             'markeredgecolor': ['get_markeredgecolor', 'get_edgecolor'],
@@ -595,19 +599,22 @@ def __init__(
                 for getter_name in getter_names:
                     try:
                         color = getattr(handle, getter_name)()
-                        if isinstance(color, np.ndarray):
-                            if (
-                                    color.shape[0] == 1
-                                    or np.isclose(color, color[0]).all()
-                            ):
-                                text.set_color(color[0])
-                            else:
-                                pass
-                        else:
-                            text.set_color(color)
-                        break
                     except AttributeError:
-                        pass
+                        continue
+                    if isinstance(color, np.ndarray):
+                        if color.size == 0:
+                            continue
+                        elif (color.shape[0] == 1 or np.isclose(color, color[0]).all()):
+                            text.set_color(color[0])
+                        else:
+                            pass
+                    elif cbook._str_lower_equal(color, 'none'):
+                        continue
+                    elif mpl.colors.to_rgba(color)[3] == 0:
+                        continue
+                    else:
+                        text.set_color(color)
+                    break
         elif cbook._str_equal(labelcolor, 'none'):
             for text in self.texts:
                 text.set_color(labelcolor)

lib/matplotlib/tests/test_legend.py

@@ -1068,6 +1068,201 @@ def test_legend_labelcolor_rcparam_markerfacecolor_short():
         assert mpl.colors.same_color(text.get_color(), color)
 
 
+def assert_last_legend_patch_color(histogram, leg, expected_color,
+                                   facecolor=False, edgecolor=False):
+    """
+    Check that histogram color, legend handle color, and legend label color all
+    match the expected input. Provide facecolor and edgecolor flags to clarify
+    which feature to match.
+    """
+    label_color = leg.texts[-1].get_color()
+    patch = leg.get_patches()[-1]
+    histogram = histogram[-1][0]
+    assert mpl.colors.same_color(label_color, expected_color)
+    if facecolor:
+        assert mpl.colors.same_color(label_color, patch.get_facecolor())
+        assert mpl.colors.same_color(label_color, histogram.get_facecolor())
+    if edgecolor:
+        assert mpl.colors.same_color(label_color, patch.get_edgecolor())
+        assert mpl.colors.same_color(label_color, histogram.get_edgecolor())
+
+
+def test_legend_labelcolor_linecolor_histograms():
+    x = np.arange(10)
+
+    # testing c kwarg for bar, step, and stepfilled histograms
+    fig, ax = plt.subplots()
+    h = ax.hist(x, histtype='bar', color='r', label="red bar hist with a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'r', facecolor=True)
+
+    h = ax.hist(x, histtype='step', color='g', label="green step hist, green label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'g', edgecolor=True)
+
+    h = ax.hist(x, histtype='stepfilled', color='b',
+                label="blue stepfilled hist with a blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'b', facecolor=True)
+
+    # testing c, fc, and ec combinations for bar histograms
+    h = ax.hist(x, histtype='bar', color='r', ec='b',
+                label="red bar hist with blue edges and a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'r', facecolor=True)
+
+    h = ax.hist(x, histtype='bar', fc='r', ec='b',
+                label="red bar hist with blue edges and a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'r', facecolor=True)
+
+    h = ax.hist(x, histtype='bar', fc='none', ec='b',
+                label="unfilled blue bar hist with a blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)
+
+    # testing c, and ec combinations for step histograms
+    h = ax.hist(x, histtype='step', color='r', ec='b',
+                label="blue step hist with a blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)
+
+    h = ax.hist(x, histtype='step', ec='b',
+                label="blue step hist with a blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)
+
+    # testing c, fc, and ec combinations for stepfilled histograms
+    h = ax.hist(x, histtype='stepfilled', color='r', ec='b',
+                label="red stepfilled hist, blue edges, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'r', facecolor=True)
+
+    h = ax.hist(x, histtype='stepfilled', fc='r', ec='b',
+                label="red stepfilled hist, blue edges, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'r', facecolor=True)
+
+    h = ax.hist(x, histtype='stepfilled', fc='none', ec='b',
+                label="unfilled blue stepfilled hist, blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)
+
+    h = ax.hist(x, histtype='stepfilled', fc='r', ec='none',
+                label="edgeless red stepfilled hist with a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_patch_color(h, leg, 'r', facecolor=True)
+
+
+def assert_last_legend_linemarker_color(line_marker, leg, expected_color, color=False,
+                                        facecolor=False, edgecolor=False):
+    """
+    Check that line marker color, legend handle color, and legend label color all
+    match the expected input. Provide color, facecolor and edgecolor flags to clarify
+    which feature to match.
+    """
+    label_color = leg.texts[-1].get_color()
+    leg_marker = leg.get_lines()[-1]
+    assert mpl.colors.same_color(label_color, expected_color)
+    if color:
+        assert mpl.colors.same_color(label_color, leg_marker.get_color())
+        assert mpl.colors.same_color(label_color, line_marker.get_color())
+    if facecolor:
+        assert mpl.colors.same_color(label_color, leg_marker.get_markerfacecolor())
+        assert mpl.colors.same_color(label_color, line_marker.get_markerfacecolor())
+    if edgecolor:
+        assert mpl.colors.same_color(label_color, leg_marker.get_markeredgecolor())
+        assert mpl.colors.same_color(label_color, line_marker.get_markeredgecolor())
+
+
+def test_legend_labelcolor_linecolor_plot():
+    x = np.arange(5)
+
+    # testing line plot
+    fig, ax = plt.subplots()
+    l, = ax.plot(x, c='r', label="red line with a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'r', color=True)
+
+    # testing c, fc, and ec combinations for maker plots
+    l, = ax.plot(x, 'o', c='r', label="red circles with a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'r', color=True)
+
+    l, = ax.plot(x, 'o', c='r', mec='b', label="red circles, blue edges, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'r', color=True)
+
+    l, = ax.plot(x, 'o', mfc='r', mec='b', label="red circles, blue edges, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'r', facecolor=True)
+
+    # 'none' cases
+    l, = ax.plot(x, 'o', mfc='none', mec='b',
+                 label="blue unfilled circles, blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'b', edgecolor=True)
+
+    l, = ax.plot(x, 'o', mfc='r', mec='none', label="red edgeless circles, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'r', facecolor=True)
+
+    l, = ax.plot(x, 'o', c='none', mec='none',
+                 label="black label despite invisible circles for dummy entries")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_linemarker_color(l, leg, 'k')
+
+
+def assert_last_legend_scattermarker_color(scatter_marker, leg, expected_color,
+                                           facecolor=False, edgecolor=False):
+    """
+    Check that scatter marker color, legend handle color, and legend label color all
+    match the expected input. Provide facecolor and edgecolor flags to clarify
+    which feature to match.
+    """
+    label_color = leg.texts[-1].get_color()
+    leg_handle = leg.legend_handles[-1]
+    assert mpl.colors.same_color(label_color, expected_color)
+    if facecolor:
+        assert mpl.colors.same_color(label_color, leg_handle.get_facecolor())
+        assert mpl.colors.same_color(label_color, scatter_marker.get_facecolor())
+    if edgecolor:
+        assert mpl.colors.same_color(label_color, leg_handle.get_edgecolor())
+        assert mpl.colors.same_color(label_color, scatter_marker.get_edgecolor())
+
+
+def test_legend_labelcolor_linecolor_scatter():
+    x = np.arange(5)
+
+    # testing c, fc, and ec combinations for scatter plots
+    fig, ax = plt.subplots()
+    s = ax.scatter(x, x, c='r', label="red circles with a red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)
+
+    s = ax.scatter(x, x, c='r', ec='b', label="red circles, blue edges, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)
+
+    s = ax.scatter(x, x, fc='r', ec='b', label="red circles, blue edges, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)
+
+    # 'none' cases
+    s = ax.scatter(x, x, fc='none', ec='b', label="blue unfilled circles, blue label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_scattermarker_color(s, leg, 'b', edgecolor=True)
+
+    s = ax.scatter(x, x, fc='r', ec='none', label="red edgeless circles, red label")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)
+
+    s = ax.scatter(x, x, c='none', ec='none',
+                   label="black label despite invisible circles for dummy entries")
+    leg = ax.legend(labelcolor='linecolor')
+    assert_last_legend_scattermarker_color(s, leg, 'k')
+
+
 @pytest.mark.filterwarnings("ignore:No artists with labels found to put in legend")
 def test_get_set_draggable():
     legend = plt.legend()