From 083b381f1306f9cd6f89f021218d151fbcfabda8 Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Thu, 9 Sep 2021 22:44:30 +0200
Subject: [PATCH] Backport PR #21017: FIX: Don't subslice lines if non-standard
 transform

---
 lib/matplotlib/lines.py            |  3 ++-
 lib/matplotlib/tests/test_lines.py | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
index 1203862a3f50..658900da9e91 100644
--- a/lib/matplotlib/lines.py
+++ b/lib/matplotlib/lines.py
@@ -677,7 +677,8 @@ def recache(self, always=False):
                 self.axes.name == 'rectilinear' and
                 self.axes.get_xscale() == 'linear' and
                 self._markevery is None and
-                self.get_clip_on()):
+                self.get_clip_on() and
+                self.get_transform() == self.axes.transData):
             self._subslice = True
             nanmask = np.isnan(x)
             if nanmask.any():
diff --git a/lib/matplotlib/tests/test_lines.py b/lib/matplotlib/tests/test_lines.py
index def26456bb36..a9e52ed26850 100644
--- a/lib/matplotlib/tests/test_lines.py
+++ b/lib/matplotlib/tests/test_lines.py
@@ -16,6 +16,7 @@
 from matplotlib.markers import MarkerStyle
 from matplotlib.path import Path
 import matplotlib.pyplot as plt
+import matplotlib.transforms as mtransforms
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
 
 
@@ -131,6 +132,17 @@ def test_drawstyle_variants():
         ax.set(xlim=(0, 2), ylim=(0, 2))
 
 
+@check_figures_equal(extensions=('png',))
+def test_no_subslice_with_transform(fig_ref, fig_test):
+    ax = fig_ref.add_subplot()
+    x = np.arange(2000)
+    ax.plot(x + 2000, x)
+
+    ax = fig_test.add_subplot()
+    t = mtransforms.Affine2D().translate(2000.0, 0.0)
+    ax.plot(x, x, transform=t+ax.transData)
+
+
 def test_valid_drawstyles():
     line = mlines.Line2D([], [])
     with pytest.raises(ValueError):