From b73d8055523e0fe23b5f8368e7a08c20fb30e6f2 Mon Sep 17 00:00:00 2001
From: ImportanceOfBeingErnest <elch.rz@ruetz-online.de>
Date: Thu, 30 Apr 2020 16:22:15 +0200
Subject: [PATCH] allow numpy arrays in markevery

---
 lib/matplotlib/lines.py            |  7 ++++---
 lib/matplotlib/tests/test_lines.py | 24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
index f5581476498b..6b67566103b6 100644
--- a/lib/matplotlib/lines.py
+++ b/lib/matplotlib/lines.py
@@ -537,7 +537,7 @@ def set_markevery(self, every):
         Parameters
         ----------
         every : None or int or (int, int) or slice or List[int] or float or \
-(float, float)
+(float, float) or List[bool]
             Which markers to plot.
 
             - every=None, every point will be plotted.
@@ -549,6 +549,8 @@ def set_markevery(self, every):
               point start, up to but not including point end, will be plotted.
             - every=[i, j, m, n], only markers at points i, j, m, and n
               will be plotted.
+            - every=[True, False, True], positions that are True will be
+              plotted.
             - every=0.1, (i.e. a float) then markers will be spaced at
               approximately equal distances along the line; the distance
               along the line between markers is determined by multiplying the
@@ -580,9 +582,8 @@ def set_markevery(self, every):
         axes-bounding-box-diagonal regardless of the actual axes data limits.
 
         """
-        if self._markevery != every:
-            self.stale = True
         self._markevery = every
+        self.stale = True
 
     def get_markevery(self):
         """
diff --git a/lib/matplotlib/tests/test_lines.py b/lib/matplotlib/tests/test_lines.py
index d66509b0ee78..8d8a4dc30dcd 100644
--- a/lib/matplotlib/tests/test_lines.py
+++ b/lib/matplotlib/tests/test_lines.py
@@ -199,6 +199,30 @@ def test_step_markers(fig_test, fig_ref):
     fig_ref.subplots().plot([0, 0, 1], [0, 1, 1], "-o", markevery=[0, 2])
 
 
+@check_figures_equal(extensions=('png',))
+def test_markevery(fig_test, fig_ref):
+    np.random.seed(42)
+    t = np.linspace(0, 3, 14)
+    y = np.random.rand(len(t))
+
+    casesA = [None, 4, (2, 5), [1, 5, 11],
+              [0, -1], slice(5, 10, 2), 0.3, (0.3, 0.4),
+              np.arange(len(t))[y > 0.5]]
+    casesB = ["11111111111111", "10001000100010", "00100001000010",
+              "01000100000100", "10000000000001", "00000101010000",
+              "11011011011110", "01010011011101", "01110001110110"]
+
+    axsA = fig_ref.subplots(3, 3)
+    axsB = fig_test.subplots(3, 3)
+
+    for ax, case in zip(axsA.flat, casesA):
+        ax.plot(t, y, "-gD", markevery=case)
+
+    for ax, case in zip(axsB.flat, casesB):
+        me = np.array(list(case)).astype(int).astype(bool)
+        ax.plot(t, y, "-gD", markevery=me)
+
+
 def test_marker_as_markerstyle():
     fig, ax = plt.subplots()
     line, = ax.plot([2, 4, 3], marker=MarkerStyle("D"))