FIX: Make sure we do not over-write eps short cuts

This tests that we have not re-defined a short-cut by checking that we do not
have two `/name` lines in the output file.

closes matplotlib#21509

Co-authored-by: Antony Lee <[email protected]>

Author: tacaswell

lib/matplotlib/backends/backend_ps.py

@@ -429,7 +429,7 @@ def _get_clip_cmd(self, gc):
             key = (path, id(trf))
             custom_clip_cmd = self._clip_paths.get(key)
             if custom_clip_cmd is None:
-                custom_clip_cmd = "c%x" % len(self._clip_paths)
+                custom_clip_cmd = "c%d" % len(self._clip_paths)
                 self._pswriter.write(f"""\
 /{custom_clip_cmd} {{
 {self._convert_path(path, trf, simplify=False)}
@@ -570,7 +570,7 @@ def draw_path_collection(self, gc, master_transform, paths, all_transforms,
         path_codes = []
         for i, (path, transform) in enumerate(self._iter_collection_raw_paths(
                 master_transform, paths, all_transforms)):
-            name = 'p%x_%x' % (self._path_collection_id, i)
+            name = 'p%d_%d' % (self._path_collection_id, i)
             path_bytes = self._convert_path(path, transform, simplify=False)
             self._pswriter.write(f"""\
 /{name} {{

lib/matplotlib/tests/test_backend_ps.py

@@ -1,16 +1,17 @@
-import io
+from collections import Counter
 from pathlib import Path
+import io
 import re
 import tempfile
 
 import pytest
 
-import matplotlib as mpl
-import matplotlib.pyplot as plt
 from matplotlib import cbook, patheffects
-from matplotlib.testing.decorators import check_figures_equal, image_comparison
 from matplotlib.cbook import MatplotlibDeprecationWarning
-
+from matplotlib.figure import Figure
+from matplotlib.testing.decorators import check_figures_equal, image_comparison
+import matplotlib as mpl
+import matplotlib.pyplot as plt
 
 needs_ghostscript = pytest.mark.skipif(
     "eps" not in mpl.testing.compare.converter,
@@ -244,3 +245,23 @@ def test_linedash():
     fig.savefig(buf, format="ps")
 
     assert buf.tell() > 0
+
+
+def test_no_definintion():
+
+    fig = Figure()
+    axs = fig.subplots(4, 4, subplot_kw=dict(projection="polar"))
+    for ax in axs.flat:
+        ax.set(xticks=[], yticks=[])
+        ax.plot([1, 2])
+    fig.suptitle("hello, world")
+
+    buf = io.StringIO()
+    fig.savefig(buf, format='eps')
+    buf.seek(0)
+
+    wds = [ln.partition(' ')[0] for
+           ln in buf.readlines()
+           if ln.startswith('/')]
+
+    assert max(Counter(wds).values()) == 1