Draw unfilled hist()s with the zorder of lines.

anntzer · anntzer · commit 6cb7e8d3fb49 · 2020-04-21T22:32:53.000+02:00
Unfilled hist()s (`histtype="step"`) are technically drawn as Patches
with `fill=False`, but they are effectively lines and should therefore
be drawn above gridlines (like Line2D), not below (like Patch).  Change
their default zorder accordingly.
diff --git a/doc/api/api_changes_3.3/behaviour.rst b/doc/api/api_changes_3.3/behaviour.rst
@@ -181,3 +181,8 @@ wx Timer interval
 ~~~~~~~~~~~~~~~~~
 Setting the timer interval on a not-yet-started ``TimerWx`` won't start it
 anymore.
+
+"step"-type histograms default to the zorder of `.Line2D`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This ensures that they go above gridlines by default.  The old ``zorder`` can
+be kept by passing it as a keyword argument to `.Axes.hist`.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -6769,7 +6769,8 @@ def hist(self, x, bins=None, range=None, density=False, weights=None,
                     closed=True if fill else None,
                     facecolor=c,
                     edgecolor=None if fill else c,
-                    fill=fill if fill else None))
+                    fill=fill if fill else None,
+                    zorder=None if fill else mlines.Line2D.zorder))
             for patch_list in patches:
                 for patch in patch_list:
                     if orientation == 'vertical':
