Make edgecolors and facecolors the same when using stepfilled histogram.

Closes matplotlib#6493

Expand the test to try the 6 histype/fill combinations, and in
particular change yaxis min limit to see if the paths are closed or not.

lib/matplotlib/axes/_axes.py

@@ -6281,17 +6281,18 @@ def _normalize_input(inp, ename='input'):
                     xvals.append(x.copy())
                     yvals.append(y.copy())
 
+            #stepfill is closed, step is not
+            split = -1 if fill else 2 * len(bins)
             # add patches in reverse order so that when stacking,
             # items lower in the stack are plottted on top of
             # items higher in the stack
-            split = -1 if fill else 2 * len(bins)
             for x, y, c in reversed(list(zip(xvals, yvals, color))):
                 patches.append(self.fill(
                     x[:split], y[:split],
-                    closed=not fill,
-                    fill=fill,
-                    edgecolor=None if fill else c,
+                    closed=True if fill else None,
                     facecolor=c,
+                    edgecolor=None if fill else c,
+                    fill=fill if fill else None,
                     margins=margins))
 
             # we return patches, so put it back in the expected order

lib/matplotlib/tests/test_axes.py

@@ -1153,14 +1153,23 @@ def test_hist_steplog():
 
 @image_comparison(baseline_images=['hist_step_filled'], extensions=['png'])
 def test_hist_step_filled():
-    np.random.seed(0)    
-    n_bins = 10
+    np.random.seed(0)
     x = np.random.randn(1000, 3)
-    fig, ax = plt.subplots()
-    ax.hist(x, n_bins,  histtype='step', fill=True, stacked=True)
-    #display anything that would be hidden by X Axis, like closed/unclosed edge path.
-    ax.set_ylim(ymin=-50)
-    patches= ax.patches
+    n_bins=10
+
+    kwargs = [{'fill':True}, {'fill':False},{'fill':None},{}]*2
+    types = ['step']*4+['stepfilled']*4
+    fig, axes = plt.subplots(nrows=2, ncols=4)
+    axes = axes.flatten()
+
+
+    for kg,_type,ax in zip(kwargs, types, axes):
+        ax.hist(x, n_bins, histtype=_type, stacked=True,**kg)
+        ax.set_title('%s/%s' % (kg, _type) )
+        ax.set_ylim(ymin=-50)
+
+    patches= axes[0].patches
+    all([p.get_facecolor() == p.get_edgecolor() for p in patches])
     all([p.get_facecolor() == p.get_edgecolor() for p in patches])