Merge pull request #11407 from anntzer/step-markers

tacaswell · web-flow · commit 0d2c4365e7cc · 2018-06-10T09:59:05.000-05:00
FIX: Properly position markers in step plots.
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -739,16 +739,17 @@ def draw(self, renderer):
             subslice = slice(max(i0 - 1, 0), i1 + 1)
             self.ind_offset = subslice.start
             self._transform_path(subslice)
-
-        transf_path = self._get_transformed_path()
+        else:
+            subslice = None
 
         if self.get_path_effects():
             from matplotlib.patheffects import PathEffectRenderer
             renderer = PathEffectRenderer(self.get_path_effects(), renderer)
 
         renderer.open_group('line2d', self.get_gid())
         if self._lineStyles[self._linestyle] != '_draw_nothing':
-            tpath, affine = transf_path.get_transformed_path_and_affine()
+            tpath, affine = (self._get_transformed_path()
+                             .get_transformed_path_and_affine())
             if len(tpath.vertices):
                 gc = renderer.new_gc()
                 self._set_gc_clip(gc)
@@ -796,7 +797,20 @@ def draw(self, renderer):
             gc.set_foreground(ec_rgba, isRGBA=True)
 
             marker = self._marker
-            tpath, affine = transf_path.get_transformed_points_and_affine()
+
+            # Markers *must* be drawn ignoring the drawstyle (but don't pay the
+            # recaching if drawstyle is already "default").
+            if self.get_drawstyle() != "default":
+                with cbook._setattr_cm(
+                        self, _drawstyle="default", _transformed_path=None):
+                    self.recache()
+                    self._transform_path(subslice)
+                    tpath, affine = (self._get_transformed_path()
+                                    .get_transformed_path_and_affine())
+            else:
+                tpath, affine = (self._get_transformed_path()
+                                 .get_transformed_path_and_affine())
+
             if len(tpath.vertices):
                 # subsample the markers if markevery is not None
                 markevery = self.get_markevery()
diff --git a/lib/matplotlib/tests/test_lines.py b/lib/matplotlib/tests/test_lines.py
@@ -1,6 +1,8 @@
 """
 Tests specific to the lines module.
 """
+
+from io import BytesIO
 import itertools
 import matplotlib.lines as mlines
 import pytest
@@ -195,3 +197,15 @@ def test_nan_is_sorted():
     assert line._is_sorted(np.array([1, 2, 3]))
     assert line._is_sorted(np.array([1, np.nan, 3]))
     assert not line._is_sorted([3, 5] + [np.nan] * 100 + [0, 2])
+
+
+def test_step_markers():
+    fig, ax = plt.subplots()
+    ax.step([0, 1], "-o")
+    buf1 = BytesIO()
+    fig.savefig(buf1)
+    fig, ax = plt.subplots()
+    ax.plot([0, 0, 1], [0, 1, 1], "-o", markevery=[0, 2])
+    buf2 = BytesIO()
+    fig.savefig(buf2)
+    assert buf1.getvalue() == buf2.getvalue()
