better default value for clabel zorder

pharshalp · pharshalp · commit bae7d207fa71 · 2020-01-26T17:01:33.000-05:00
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -127,7 +127,9 @@ def clabel(self, levels=None, *,
         zorder : float or None, optional
             zorder of the contour labels.
 
-            If not specified, the default zorder of `.Text` class is used.
+            If not specified, the zorder of contour labels is set to either
+            (2 + zorder of contours) or (1 + zorder of contours) depending on
+            whether the contours are filled or not filled.
 
         Returns
         -------
@@ -149,7 +151,14 @@ def clabel(self, levels=None, *,
         # Detect if manual selection is desired and remove from argument list.
         self.labelManual = manual
         self.rightside_up = rightside_up
-        self._zorder = zorder
+        if zorder is None:
+            if self.filled:
+                self._clabel_zorder = 2+self._contour_zorder
+            else:
+                self._clabel_zorder = 1+self._contour_zorder
+        else:
+            self._clabel_zorder = zorder
+
 
         if levels is None:
             levels = self.levels
@@ -403,7 +412,7 @@ def _get_label_text(self, x, y, rotation):
         dx, dy = self.ax.transData.inverted().transform((x, y))
         t = text.Text(dx, dy, rotation=rotation,
                       horizontalalignment='center',
-                      verticalalignment='center', zorder=self._zorder)
+                      verticalalignment='center', zorder=self._clabel_zorder)
         return t
 
     def _get_label_clabeltext(self, x, y, rotation):
@@ -417,7 +426,7 @@ def _get_label_clabeltext(self, x, y, rotation):
                                                   np.array([[x, y]]))
         t = ClabelText(dx, dy, rotation=drotation[0],
                        horizontalalignment='center',
-                       verticalalignment='center', zorder=self._zorder)
+                       verticalalignment='center', zorder=self._clabel_zorder)
 
         return t
 
@@ -875,7 +884,7 @@ def __init__(self, ax, *args,
                 self.allkinds = [None] * len(self.allsegs)
 
             # Default zorder taken from Collection
-            zorder = kwargs.pop('zorder', 1)
+            self._contour_zorder = kwargs.pop('zorder', 1)
             for level, level_upper, segs, kinds in \
                     zip(lowers, uppers, self.allsegs, self.allkinds):
                 paths = self._make_paths(segs, kinds)
@@ -886,7 +895,7 @@ def __init__(self, ax, *args,
                     edgecolors='none',
                     alpha=self.alpha,
                     transform=self.get_transform(),
-                    zorder=zorder)
+                    zorder=self._contour_zorder)
                 self.ax.add_collection(col, autolim=False)
                 self.collections.append(col)
         else:
@@ -897,7 +906,7 @@ def __init__(self, ax, *args,
             if aa is not None:
                 aa = (self.antialiased,)
             # Default zorder taken from LineCollection
-            zorder = kwargs.pop('zorder', 2)
+            self._contour_zorder = kwargs.pop('zorder', 2)
             for level, width, lstyle, segs in \
                     zip(self.levels, tlinewidths, tlinestyles, self.allsegs):
                 col = mcoll.LineCollection(
@@ -907,7 +916,7 @@ def __init__(self, ax, *args,
                     linestyles=[lstyle],
                     alpha=self.alpha,
                     transform=self.get_transform(),
-                    zorder=zorder)
+                    zorder=self._contour_zorder)
                 col.set_label('_nolegend_')
                 self.ax.add_collection(col, autolim=False)
                 self.collections.append(col)
diff --git a/lib/matplotlib/tests/test_contour.py b/lib/matplotlib/tests/test_contour.py
@@ -290,20 +290,31 @@ def test_circular_contour_warning():
     assert len(record) == 0
 
 
-@pytest.mark.parametrize("use_clabeltext", [True, False])
-def test_clabel_zorder(use_clabeltext):
+@pytest.mark.parametrize("use_clabeltext, contour_zorder, clabel_zorder",
+                         [(True, 123, 1234), (False, 123, 1234),
+                          (True, 123, None), (False, 123, None)])
+def test_clabel_zorder(use_clabeltext, contour_zorder, clabel_zorder):
     x, y = np.meshgrid(np.arange(0, 10), np.arange(0, 10))
     z = np.max(np.dstack([abs(x), abs(y)]), 2)
 
     fig, (ax1, ax2) = plt.subplots(ncols=2)
-    cs1 = ax1.contour(x, y, z)
-    cs2 = ax2.contourf(x, y, z)
-    clabels1 = cs1.clabel(zorder=1234, use_clabeltext=use_clabeltext)
-    clabels2 = cs2.clabel(zorder=12345, use_clabeltext=use_clabeltext)
+    cs = ax1.contour(x, y, z, zorder=contour_zorder)
+    cs_filled = ax2.contourf(x, y, z, zorder=contour_zorder)
+    clabels1 = cs.clabel(zorder=clabel_zorder, use_clabeltext=use_clabeltext)
+    clabels2 = cs_filled.clabel(zorder=clabel_zorder,
+                                use_clabeltext=use_clabeltext)
+
+    if clabel_zorder is None:
+        expected_clabel_zorder = 1+contour_zorder
+        expected_filled_clabel_zorder = 2+contour_zorder
+    else:
+        expected_clabel_zorder = clabel_zorder
+        expected_filled_clabel_zorder = clabel_zorder
+
     for clabel in clabels1:
-        assert clabel.get_zorder() == 1234
+        assert clabel.get_zorder() == expected_clabel_zorder
     for clabel in clabels2:
-        assert clabel.get_zorder() == 12345
+        assert clabel.get_zorder() == expected_filled_clabel_zorder
 
 
 @image_comparison(['contour_log_extension.png'],
