Fix unicode_minus + usetex.

anntzer · anntzer · commit a973b75f650b · 2019-06-18T11:54:00.000+02:00
... by telling TeX to treat \u2212 (unicode minus) as a minus sign.

This also uncovered a bug in _parse_enc (basically, there can be
multiple character entries per line, so one needs to use `.split()`
instead of `.split("\n")`.
diff --git a/lib/matplotlib/dviread.py b/lib/matplotlib/dviread.py
@@ -989,7 +989,7 @@ def _parse_enc(path):
     with open(path, encoding="ascii") as file:
         no_comments = "\n".join(line.split("%")[0].rstrip() for line in file)
     array = re.search(r"(?s)\[(.*)\]", no_comments).group(1)
-    lines = [line for line in array.split("\n") if line]
+    lines = [line for line in array.split() if line]
     if all(line.startswith("/") for line in lines):
         return [line[1:] for line in lines]
     else:
diff --git a/lib/matplotlib/tests/test_usetex.py b/lib/matplotlib/tests/test_usetex.py
@@ -1,26 +1,22 @@
-import warnings
-
 import pytest
 
-import matplotlib
-from matplotlib.testing.decorators import image_comparison
+import matplotlib as mpl
+from matplotlib.testing.decorators import check_figures_equal, image_comparison
 import matplotlib.pyplot as plt
 from matplotlib.ticker import EngFormatter
 
 
-with warnings.catch_warnings():
-    warnings.simplefilter('ignore')
-    needs_usetex = pytest.mark.skipif(
-        not matplotlib.checkdep_usetex(True),
-        reason='Missing TeX of Ghostscript or dvipng')
+@pytest.fixture(autouse=True)  # All tests in this module use usetex.
+def usetex():
+    if not mpl.checkdep_usetex(True):
+        pytest.skip('Missing TeX of Ghostscript or dvipng')
+    mpl.rcParams['text.usetex'] = True
 
 
-@needs_usetex
 @image_comparison(baseline_images=['test_usetex'],
                   extensions=['pdf', 'png'],
                   tol=0.3)
 def test_usetex():
-    matplotlib.rcParams['text.usetex'] = True
     fig = plt.figure()
     ax = fig.add_subplot(111)
     ax.text(0.1, 0.2,
@@ -32,3 +28,9 @@ def test_usetex():
             fontsize=24)
     ax.set_xticks([])
     ax.set_yticks([])
+
+
+@check_figures_equal()
+def test_unicode_minus(fig_test, fig_ref):
+    fig_test.text(.5, .5, "$-$")
+    fig_ref.text(.5, .5, "\N{MINUS SIGN}")
diff --git a/lib/matplotlib/texmanager.py b/lib/matplotlib/texmanager.py
@@ -206,11 +206,10 @@ def make_tex(self, tex, fontsize):
                                                        r'{\rmfamily %s}')
         tex = fontcmd % tex
 
-        if rcParams['text.latex.unicode']:
-            unicode_preamble = r"""
-\usepackage[utf8]{inputenc}"""
-        else:
-            unicode_preamble = ''
+        unicode_preamble = "\n".join([
+            r"\usepackage[utf8]{inputenc}",
+            r"\DeclareUnicodeCharacter{2212}{\ensuremath{-}}",
+        ]) if rcParams["text.latex.unicode"] else ""
 
         s = r"""
 \documentclass{article}
@@ -257,11 +256,10 @@ def make_tex_preview(self, tex, fontsize):
                                                        r'{\rmfamily %s}')
         tex = fontcmd % tex
 
-        if rcParams['text.latex.unicode']:
-            unicode_preamble = r"""
-\usepackage[utf8]{inputenc}"""
-        else:
-            unicode_preamble = ''
+        unicode_preamble = "\n".join([
+            r"\usepackage[utf8]{inputenc}",
+            r"\DeclareUnicodeCharacter{2212}{\ensuremath{-}}",
+        ]) if rcParams["text.latex.unicode"] else ""
 
         # newbox, setbox, immediate, etc. are used to find the box
         # extent of the rendered text.
