From 972b815c596792c0f40a3a368f44e5b8eada3b26 Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Fri, 15 Jul 2022 16:47:55 +0200
Subject: [PATCH 1/3] Directly support ^% in pgf.

Support for `^` is inspired from the support for `_` as implemented
in underscore.sty, but much simpler because 1) we don't care about
hyphenation, 2) we don't care about substituting a real underscore by
a rule box when the current font lacks an underscore (there's no real
way out if the font has no caret, anyways), and 3) we don't care about
the active character ending up in tex `\commands` because the character
is only made active in the context of matplotlib-provided strings, not
globally.
---
 lib/matplotlib/backends/backend_pgf.py   | 29 ++++++++++++++----------
 lib/matplotlib/tests/test_backend_pgf.py | 11 +++++----
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
index a5c93136829d..94ab547f3b47 100644
--- a/lib/matplotlib/backends/backend_pgf.py
+++ b/lib/matplotlib/backends/backend_pgf.py
@@ -85,9 +85,6 @@ def _get_preamble():
 
 _NO_ESCAPE = r"(?<!\\)(?:\\\\)*"
 _split_math = re.compile(_NO_ESCAPE + r"\$").split
-_replace_escapetext = functools.partial(
-    # When the next character is an unescaped % or ^, insert a backslash.
-    re.compile(_NO_ESCAPE + "(?=[%^])").sub, "\\\\")
 _replace_mathdefault = functools.partial(
     # Replace \mathdefault (when not preceded by an escape) by empty string.
     re.compile(_NO_ESCAPE + r"(\\mathdefault)").sub, "")
@@ -106,8 +103,6 @@ def _tex_escape(text):
     This distinguishes text-mode and math-mode by replacing the math separator
     ``$`` with ``\(\displaystyle %s\)``. Escaped math separators (``\$``)
     are ignored.
-
-    The following characters are escaped in text segments: ``^%``
     """
     # Sometimes, matplotlib adds the unknown command \mathdefault.
     # Not using \mathnormal instead since this looks odd for the latex cm font.
@@ -116,11 +111,7 @@ def _tex_escape(text):
     # split text into normaltext and inline math parts
     parts = _split_math(text)
     for i, s in enumerate(parts):
-        if not i % 2:
-            # textmode replacements
-            s = _replace_escapetext(s)
-        else:
-            # mathmode replacements
+        if i % 2:  # mathmode replacements
             s = r"\(\displaystyle %s\)" % s
         parts[i] = s
     return "".join(parts)
@@ -168,7 +159,17 @@ def _escape_and_apply_props(s, prop):
         commands.append(r"\bfseries")
 
     commands.append(r"\selectfont")
-    return "".join(commands) + " " + _tex_escape(s)
+    return (
+        "{"
+        + "".join(commands)
+        + r"\catcode`\^=\active\def^{\ifmmode\sp\else\^{}\fi}"
+        # It should normally be enough to set the catcode of % to 12 ("normal
+        # character"); this works on TeXLive 2021 but not on 2018, so we just
+        # make it active too.
+        + r"\catcode`\%=\active\def%{\%}"
+        + _tex_escape(s)
+        + "}"
+    )
 
 
 def _metadata_to_str(key, value):
@@ -357,7 +358,11 @@ def _get_box_metrics(self, tex):
         """
         # This method gets wrapped in __init__ for per-instance caching.
         self._stdin_writeln(  # Send textbox to TeX & request metrics typeout.
-            r"\sbox0{%s}\typeout{\the\wd0,\the\ht0,\the\dp0}" % tex)
+            # \sbox doesn't handle catcode assignments inside its argument,
+            # so repeat the assignment of the catcode of "^" and "%" outside.
+            r"{\catcode`\^=\active\catcode`\%%=\active\sbox0{%s}"
+            r"\typeout{\the\wd0,\the\ht0,\the\dp0}}"
+            % tex)
         try:
             answer = self._expect_prompt()
         except LatexError as err:
diff --git a/lib/matplotlib/tests/test_backend_pgf.py b/lib/matplotlib/tests/test_backend_pgf.py
index 482bc073a766..26a7124b7cbb 100644
--- a/lib/matplotlib/tests/test_backend_pgf.py
+++ b/lib/matplotlib/tests/test_backend_pgf.py
@@ -35,19 +35,22 @@ def compare_figure(fname, savefig_kwargs={}, tol=0):
 
 @pytest.mark.parametrize('plain_text, escaped_text', [
     (r'quad_sum: $\sum x_i^2$', r'quad_sum: \(\displaystyle \sum x_i^2\)'),
-    ('% not a comment', r'\% not a comment'),
-    ('^not', r'\^not'),
 ])
 def test_tex_escape(plain_text, escaped_text):
     assert _tex_escape(plain_text) == escaped_text
 
 
 @needs_pgf_xelatex
+@needs_ghostscript
 @pytest.mark.backend('pgf')
 def test_tex_special_chars(tmp_path):
     fig = plt.figure()
-    fig.text(.5, .5, "_^ $a_b^c$")
-    fig.savefig(tmp_path / "test.pdf")  # Should not error.
+    fig.text(.5, .5, "%_^ $a_b^c$")
+    buf = BytesIO()
+    fig.savefig(buf, format="png", backend="pgf")
+    buf.seek(0)
+    t = plt.imread(buf)
+    assert not (t == 1).all()  # The leading "%" didn't eat up everything.
 
 
 def create_figure():

From 1936c948476b7d58d10f2c50003a0b9c38f30477 Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Fri, 15 Jul 2022 17:23:44 +0200
Subject: [PATCH 2/3] Also handle `\displaystyle` and `\mathdefault` at the TeX
 level.

Note that tex_escape is still being tested by
test_minus_signs_with_tex, which explicitly checks support for unicode
minus.
---
 lib/matplotlib/backends/backend_pgf.py   | 37 ++++++++----------------
 lib/matplotlib/tests/test_backend_pgf.py |  9 +-----
 2 files changed, 13 insertions(+), 33 deletions(-)

diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
index 94ab547f3b47..77cbc899c16b 100644
--- a/lib/matplotlib/backends/backend_pgf.py
+++ b/lib/matplotlib/backends/backend_pgf.py
@@ -38,9 +38,9 @@
 @_api.caching_module_getattr
 class __getattr__:
     NO_ESCAPE = _api.deprecated("3.6", obj_type="")(
-        property(lambda self: _NO_ESCAPE))
+        property(lambda self: r"(?<!\\)(?:\\\\)*"))
     re_mathsep = _api.deprecated("3.6", obj_type="")(
-        property(lambda self: _split_math.__self__))
+        property(lambda self: r"(?<!\\)(?:\\\\)*\$"))
 
 
 @_api.deprecated("3.6")
@@ -58,7 +58,15 @@ def get_preamble():
 
 def _get_preamble():
     """Prepare a LaTeX preamble based on the rcParams configuration."""
-    preamble = [mpl.rcParams["pgf.preamble"]]
+    preamble = [
+        # Remove Matplotlib's custom command \mathdefault.  (Not using
+        # \mathnormal instead since this looks odd with Computer Modern.)
+        r"\def\mathdefault#1{#1}",
+        # Use displaystyle for all math.
+        r"\everymath=\expandafter{\the\everymath\displaystyle}",
+        # Allow pgf.preamble to override the above definitions.
+        mpl.rcParams["pgf.preamble"],
+    ]
     if mpl.rcParams["pgf.texsystem"] != "pdflatex":
         preamble.append("\\usepackage{fontspec}")
         if mpl.rcParams["pgf.rcfonts"]:
@@ -83,13 +91,6 @@ def _get_preamble():
 mpl_in_to_pt = 1. / mpl_pt_to_in
 
 
-_NO_ESCAPE = r"(?<!\\)(?:\\\\)*"
-_split_math = re.compile(_NO_ESCAPE + r"\$").split
-_replace_mathdefault = functools.partial(
-    # Replace \mathdefault (when not preceded by an escape) by empty string.
-    re.compile(_NO_ESCAPE + r"(\\mathdefault)").sub, "")
-
-
 @_api.deprecated("3.6")
 def common_texification(text):
     return _tex_escape(text)
@@ -99,22 +100,8 @@ def _tex_escape(text):
     r"""
     Do some necessary and/or useful substitutions for texts to be included in
     LaTeX documents.
-
-    This distinguishes text-mode and math-mode by replacing the math separator
-    ``$`` with ``\(\displaystyle %s\)``. Escaped math separators (``\$``)
-    are ignored.
     """
-    # Sometimes, matplotlib adds the unknown command \mathdefault.
-    # Not using \mathnormal instead since this looks odd for the latex cm font.
-    text = _replace_mathdefault(text)
-    text = text.replace("\N{MINUS SIGN}", r"\ensuremath{-}")
-    # split text into normaltext and inline math parts
-    parts = _split_math(text)
-    for i, s in enumerate(parts):
-        if i % 2:  # mathmode replacements
-            s = r"\(\displaystyle %s\)" % s
-        parts[i] = s
-    return "".join(parts)
+    return text.replace("\N{MINUS SIGN}", r"\ensuremath{-}")
 
 
 @_api.deprecated("3.6")
diff --git a/lib/matplotlib/tests/test_backend_pgf.py b/lib/matplotlib/tests/test_backend_pgf.py
index 26a7124b7cbb..5cd58963e4cf 100644
--- a/lib/matplotlib/tests/test_backend_pgf.py
+++ b/lib/matplotlib/tests/test_backend_pgf.py
@@ -11,7 +11,7 @@
 import matplotlib.pyplot as plt
 from matplotlib.testing import _has_tex_package, _check_for_pgf
 from matplotlib.testing.compare import compare_images, ImageComparisonFailure
-from matplotlib.backends.backend_pgf import PdfPages, _tex_escape
+from matplotlib.backends.backend_pgf import PdfPages
 from matplotlib.testing.decorators import (
     _image_directories, check_figures_equal, image_comparison)
 from matplotlib.testing._markers import (
@@ -33,13 +33,6 @@ def compare_figure(fname, savefig_kwargs={}, tol=0):
         raise ImageComparisonFailure(err)
 
 
-@pytest.mark.parametrize('plain_text, escaped_text', [
-    (r'quad_sum: $\sum x_i^2$', r'quad_sum: \(\displaystyle \sum x_i^2\)'),
-])
-def test_tex_escape(plain_text, escaped_text):
-    assert _tex_escape(plain_text) == escaped_text
-
-
 @needs_pgf_xelatex
 @needs_ghostscript
 @pytest.mark.backend('pgf')

From e56ff716f7831d0becae1f8b1ef05a979f17030a Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Tue, 19 Jul 2022 22:23:15 +0200
Subject: [PATCH 3/3] Bump test tolerance by 1-per-thousand on old
 ghostscripts.

---
 lib/matplotlib/tests/test_backend_pgf.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/matplotlib/tests/test_backend_pgf.py b/lib/matplotlib/tests/test_backend_pgf.py
index 5cd58963e4cf..5b2f1a5c43fa 100644
--- a/lib/matplotlib/tests/test_backend_pgf.py
+++ b/lib/matplotlib/tests/test_backend_pgf.py
@@ -95,7 +95,7 @@ def test_xelatex():
 @pytest.mark.skipif(not _has_tex_package('ucs'), reason='needs ucs.sty')
 @pytest.mark.backend('pgf')
 @image_comparison(['pgf_pdflatex.pdf'], style='default',
-                  tol=11.7 if _old_gs_version else 0)
+                  tol=11.71 if _old_gs_version else 0)
 def test_pdflatex():
     if os.environ.get('APPVEYOR'):
         pytest.xfail("pdflatex test does not work on appveyor due to missing "