Move towards making texmanager stateless.

Previously, TexManager needed to call get_font_config at a specific
place in the middle of processing to update some internal attributes
before proceeding with TeX source generation.  Instead, move towards
making TexManager stateless (except for caching), i.e. the user facing
API should be thought of as a bunch of independently callable functions
`make_tex()`, `make_dvi()`, etc. (they will probably stay as methods on
a "empty" TexManager object for a long time for backcompat, in fact).

doc/api/next_api_changes/deprecations/22725-AL.rst

@@ -0,0 +1,4 @@
+``TexManager.get_font_config``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is deprecated with no replacement.  (It previously returned an internal
+hashed key for used for caching purposes.)

lib/matplotlib/tests/test_texmanager.py

@@ -7,17 +7,14 @@
 
 
 def test_fontconfig_preamble():
-    """Test that the preamble is included in _fontconfig."""
+    """Test that the preamble is included in the source."""
     plt.rcParams['text.usetex'] = True
 
-    tm1 = TexManager()
-    font_config1 = tm1.get_font_config()
-
+    src1 = TexManager()._get_tex_source("", fontsize=12)
     plt.rcParams['text.latex.preamble'] = '\\usepackage{txfonts}'
-    tm2 = TexManager()
-    font_config2 = tm2.get_font_config()
+    src2 = TexManager()._get_tex_source("", fontsize=12)
 
-    assert font_config1 != font_config2
+    assert src1 != src2
 
 
 @pytest.mark.parametrize(

lib/matplotlib/texmanager.py

@@ -61,37 +61,44 @@ class TexManager:
     """
 
     texcache = os.path.join(mpl.get_cachedir(), 'tex.cache')
-
     _grey_arrayd = {}
-    _font_family = 'serif'
+
     _font_families = ('serif', 'sans-serif', 'cursive', 'monospace')
-    _font_info = {
-        'new century schoolbook': ('pnc', r'\renewcommand{\rmdefault}{pnc}'),
-        'bookman': ('pbk', r'\renewcommand{\rmdefault}{pbk}'),
-        'times': ('ptm', r'\usepackage{mathptmx}'),
-        'palatino': ('ppl', r'\usepackage{mathpazo}'),
-        'zapf chancery': ('pzc', r'\usepackage{chancery}'),
-        'cursive': ('pzc', r'\usepackage{chancery}'),
-        'charter': ('pch', r'\usepackage{charter}'),
-        'serif': ('cmr', ''),
-        'sans-serif': ('cmss', ''),
-        'helvetica': ('phv', r'\usepackage{helvet}'),
-        'avant garde': ('pag', r'\usepackage{avant}'),
-        'courier': ('pcr', r'\usepackage{courier}'),
+    _font_preambles = {
+        'new century schoolbook': r'\renewcommand{\rmdefault}{pnc}',
+        'bookman': r'\renewcommand{\rmdefault}{pbk}',
+        'times': r'\usepackage{mathptmx}',
+        'palatino': r'\usepackage{mathpazo}',
+        'zapf chancery': r'\usepackage{chancery}',
+        'cursive': r'\usepackage{chancery}',
+        'charter': r'\usepackage{charter}',
+        'serif': '',
+        'sans-serif': '',
+        'helvetica': r'\usepackage{helvet}',
+        'avant garde': r'\usepackage{avant}',
+        'courier': r'\usepackage{courier}',
         # Loading the type1ec package ensures that cm-super is installed, which
         # is necessary for Unicode computer modern.  (It also allows the use of
         # computer modern at arbitrary sizes, but that's just a side effect.)
-        'monospace': ('cmtt', r'\usepackage{type1ec}'),
-        'computer modern roman': ('cmr', r'\usepackage{type1ec}'),
-        'computer modern sans serif': ('cmss', r'\usepackage{type1ec}'),
-        'computer modern typewriter': ('cmtt', r'\usepackage{type1ec}')}
+        'monospace': r'\usepackage{type1ec}',
+        'computer modern roman': r'\usepackage{type1ec}',
+        'computer modern sans serif': r'\usepackage{type1ec}',
+        'computer modern typewriter': r'\usepackage{type1ec}',
+    }
     _font_types = {
-        'new century schoolbook': 'serif', 'bookman': 'serif',
-        'times': 'serif', 'palatino': 'serif', 'charter': 'serif',
-        'computer modern roman': 'serif', 'zapf chancery': 'cursive',
-        'helvetica': 'sans-serif', 'avant garde': 'sans-serif',
+        'new century schoolbook': 'serif',
+        'bookman': 'serif',
+        'times': 'serif',
+        'palatino': 'serif',
+        'zapf chancery': 'cursive',
+        'charter': 'serif',
+        'helvetica': 'sans-serif',
+        'avant garde': 'sans-serif',
+        'courier': 'monospace',
+        'computer modern roman': 'serif',
         'computer modern sans serif': 'sans-serif',
-        'courier': 'monospace', 'computer modern typewriter': 'monospace'}
+        'computer modern typewriter': 'monospace',
+    }
 
     grey_arrayd = _api.deprecate_privatize_attribute("3.5")
     font_family = _api.deprecate_privatize_attribute("3.5")
@@ -103,33 +110,48 @@ def __new__(cls):
         Path(cls.texcache).mkdir(parents=True, exist_ok=True)
         return object.__new__(cls)
 
+    @_api.deprecated("3.6")
     def get_font_config(self):
+        preamble, font_cmd = self._get_font_preamble_and_command()
+        # Add a hash of the latex preamble to fontconfig so that the
+        # correct png is selected for strings rendered with same font and dpi
+        # even if the latex preamble changes within the session
+        preambles = preamble + font_cmd + self.get_custom_preamble()
+        return hashlib.md5(preambles.encode('utf-8')).hexdigest()
+
+    @classmethod
+    def _get_font_family_and_reduced(cls):
         ff = rcParams['font.family']
         ff_val = ff[0].lower() if len(ff) == 1 else None
         reduced_notation = False
-        if len(ff) == 1 and ff_val in self._font_families:
-            self._font_family = ff_val
-        elif len(ff) == 1 and ff_val in self._font_info:
-            reduced_notation = True
-            self._font_family = self._font_types[ff_val]
+        if len(ff) == 1 and ff_val in cls._font_families:
+            return ff_val, False
+        elif len(ff) == 1 and ff_val in cls._font_preambles:
+            return cls._font_types[ff_val], True
         else:
             _log.info('font.family must be one of (%s) when text.usetex is '
                       'True. serif will be used by default.',
-                      ', '.join(self._font_families))
-            self._font_family = 'serif'
-
-        fontconfig = [self._font_family]
-        fonts = {}
-        for font_family in self._font_families:
-            if reduced_notation and self._font_family == font_family:
-                fonts[font_family] = self._font_info[ff_val]
+                      ', '.join(cls._font_families))
+            return 'serif', False
+
+    @classmethod
+    def _get_font_preamble_and_command(cls):
+        requested_family, is_reduced_font = cls._get_font_family_and_reduced()
+
+        preambles = {}
+        for font_family in cls._font_families:
+            if is_reduced_font and font_family == requested_family:
+                preambles[font_family] = cls._font_preambles[
+                    rcParams['font.family'][0].lower()]
             else:
                 for font in rcParams['font.' + font_family]:
-                    if font.lower() in self._font_info:
-                        fonts[font_family] = self._font_info[font.lower()]
+                    if font.lower() in cls._font_preambles:
+                        preambles[font_family] = \
+                            cls._font_preambles[font.lower()]
                         _log.debug(
                             'family: %s, font: %s, info: %s',
-                            font_family, font, self._font_info[font.lower()])
+                            font_family, font,
+                            cls._font_preambles[font.lower()])
                         break
                     else:
                         _log.debug('%s font is not compatible with usetex.',
@@ -138,64 +160,62 @@ def get_font_config(self):
                     _log.info('No LaTeX-compatible font found for the %s font'
                               'family in rcParams. Using default.',
                               font_family)
-                    fonts[font_family] = self._font_info[font_family]
-            fontconfig.append(fonts[font_family][0])
-        # Add a hash of the latex preamble to fontconfig so that the
-        # correct png is selected for strings rendered with same font and dpi
-        # even if the latex preamble changes within the session
-        preamble_bytes = self.get_custom_preamble().encode('utf-8')
-        fontconfig.append(hashlib.md5(preamble_bytes).hexdigest())
+                    preambles[font_family] = cls._font_preambles[font_family]
 
         # The following packages and commands need to be included in the latex
         # file's preamble:
-        cmd = {fonts[family][1]
+        cmd = {preambles[family]
                for family in ['serif', 'sans-serif', 'monospace']}
-        if self._font_family == 'cursive':
-            cmd.add(fonts['cursive'][1])
+        if requested_family == 'cursive':
+            cmd.add(preambles['cursive'])
         cmd.add(r'\usepackage{type1cm}')
-        self._font_preamble = '\n'.join(sorted(cmd))
-
-        return ''.join(fontconfig)
+        preamble = '\n'.join(sorted(cmd))
+        fontcmd = (r'\sffamily' if requested_family == 'sans-serif' else
+                   r'\ttfamily' if requested_family == 'monospace' else
+                   r'\rmfamily')
+        return preamble, fontcmd
 
-    def get_basefile(self, tex, fontsize, dpi=None):
+    @classmethod
+    def get_basefile(cls, tex, fontsize, dpi=None):
         """
         Return a filename based on a hash of the string, fontsize, and dpi.
         """
-        src = self._get_tex_source(tex, fontsize) + str(dpi)
+        src = cls._get_tex_source(tex, fontsize) + str(dpi)
         return os.path.join(
-            self.texcache, hashlib.md5(src.encode('utf-8')).hexdigest())
+            cls.texcache, hashlib.md5(src.encode('utf-8')).hexdigest())
 
-    def get_font_preamble(self):
+    @classmethod
+    def get_font_preamble(cls):
         """
         Return a string containing font configuration for the tex preamble.
         """
-        return self._font_preamble
+        font_preamble, command = cls._get_font_preamble_and_command()
+        return font_preamble
 
-    def get_custom_preamble(self):
+    @classmethod
+    def get_custom_preamble(cls):
         """Return a string containing user additions to the tex preamble."""
         return rcParams['text.latex.preamble']
 
-    def _get_tex_source(self, tex, fontsize):
+    @classmethod
+    def _get_tex_source(cls, tex, fontsize):
         """Return the complete TeX source for processing a TeX string."""
-        self.get_font_config()  # Updates self._font_preamble.
+        font_preamble, fontcmd = cls._get_font_preamble_and_command()
         baselineskip = 1.25 * fontsize
-        fontcmd = (r'\sffamily' if self._font_family == 'sans-serif' else
-                   r'\ttfamily' if self._font_family == 'monospace' else
-                   r'\rmfamily')
         return "\n".join([
             r"\documentclass{article}",
             r"% Pass-through \mathdefault, which is used in non-usetex mode",
             r"% to use the default text font but was historically suppressed",
             r"% in usetex mode.",
             r"\newcommand{\mathdefault}[1]{#1}",
-            self._font_preamble,
+            font_preamble,
             r"\usepackage[utf8]{inputenc}",
             r"\DeclareUnicodeCharacter{2212}{\ensuremath{-}}",
             r"% geometry is loaded before the custom preamble as ",
             r"% convert_psfrags relies on a custom preamble to change the ",
             r"% geometry.",
             r"\usepackage[papersize=72in, margin=1in]{geometry}",
-            self.get_custom_preamble(),
+            cls.get_custom_preamble(),
             r"% Use `underscore` package to take care of underscores in text.",
             r"% The [strings] option allows to use underscores in file names.",
             _usepackage_if_not_loaded("underscore", option="strings"),
@@ -215,21 +235,23 @@ def _get_tex_source(self, tex, fontsize):
             r"\end{document}",
         ])
 
-    def make_tex(self, tex, fontsize):
+    @classmethod
+    def make_tex(cls, tex, fontsize):
         """
         Generate a tex file to render the tex string at a specific font size.
 
         Return the file name.
         """
-        texfile = self.get_basefile(tex, fontsize) + ".tex"
-        Path(texfile).write_text(self._get_tex_source(tex, fontsize))
+        texfile = cls.get_basefile(tex, fontsize) + ".tex"
+        Path(texfile).write_text(cls._get_tex_source(tex, fontsize))
         return texfile
 
-    def _run_checked_subprocess(self, command, tex, *, cwd=None):
+    @classmethod
+    def _run_checked_subprocess(cls, command, tex, *, cwd=None):
         _log.debug(cbook._pformat_subprocess(command))
         try:
             report = subprocess.check_output(
-                command, cwd=cwd if cwd is not None else self.texcache,
+                command, cwd=cwd if cwd is not None else cls.texcache,
                 stderr=subprocess.STDOUT)
         except FileNotFoundError as exc:
             raise RuntimeError(
@@ -247,16 +269,17 @@ def _run_checked_subprocess(self, command, tex, *, cwd=None):
         _log.debug(report)
         return report
 
-    def make_dvi(self, tex, fontsize):
+    @classmethod
+    def make_dvi(cls, tex, fontsize):
         """
         Generate a dvi file containing latex's layout of tex string.
 
         Return the file name.
         """
-        basefile = self.get_basefile(tex, fontsize)
+        basefile = cls.get_basefile(tex, fontsize)
         dvifile = '%s.dvi' % basefile
         if not os.path.exists(dvifile):
-            texfile = Path(self.make_tex(tex, fontsize))
+            texfile = Path(cls.make_tex(tex, fontsize))
             # Generate the dvi in a temporary directory to avoid race
             # conditions e.g. if multiple processes try to process the same tex
             # string at the same time.  Having tmpdir be a subdirectory of the
@@ -266,23 +289,24 @@ def make_dvi(self, tex, fontsize):
             # the absolute path may contain characters (e.g. ~) that TeX does
             # not support.)
             with TemporaryDirectory(dir=Path(dvifile).parent) as tmpdir:
-                self._run_checked_subprocess(
+                cls._run_checked_subprocess(
                     ["latex", "-interaction=nonstopmode", "--halt-on-error",
                      f"../{texfile.name}"], tex, cwd=tmpdir)
                 (Path(tmpdir) / Path(dvifile).name).replace(dvifile)
         return dvifile
 
-    def make_png(self, tex, fontsize, dpi):
+    @classmethod
+    def make_png(cls, tex, fontsize, dpi):
         """
         Generate a png file containing latex's rendering of tex string.
 
         Return the file name.
         """
-        basefile = self.get_basefile(tex, fontsize, dpi)
+        basefile = cls.get_basefile(tex, fontsize, dpi)
         pngfile = '%s.png' % basefile
         # see get_rgba for a discussion of the background
         if not os.path.exists(pngfile):
-            dvifile = self.make_dvi(tex, fontsize)
+            dvifile = cls.make_dvi(tex, fontsize)
             cmd = ["dvipng", "-bg", "Transparent", "-D", str(dpi),
                    "-T", "tight", "-o", pngfile, dvifile]
             # When testing, disable FreeType rendering for reproducibility; but
@@ -292,24 +316,26 @@ def make_png(self, tex, fontsize, dpi):
             if (getattr(mpl, "_called_from_pytest", False) and
                     mpl._get_executable_info("dvipng").raw_version != "1.16"):
                 cmd.insert(1, "--freetype0")
-            self._run_checked_subprocess(cmd, tex)
+            cls._run_checked_subprocess(cmd, tex)
         return pngfile
 
-    def get_grey(self, tex, fontsize=None, dpi=None):
+    @classmethod
+    def get_grey(cls, tex, fontsize=None, dpi=None):
         """Return the alpha channel."""
         if not fontsize:
             fontsize = rcParams['font.size']
         if not dpi:
             dpi = rcParams['savefig.dpi']
-        key = tex, self.get_font_config(), fontsize, dpi
-        alpha = self._grey_arrayd.get(key)
+        key = cls._get_tex_source(tex, fontsize), dpi
+        alpha = cls._grey_arrayd.get(key)
         if alpha is None:
-            pngfile = self.make_png(tex, fontsize, dpi)
-            rgba = mpl.image.imread(os.path.join(self.texcache, pngfile))
-            self._grey_arrayd[key] = alpha = rgba[:, :, -1]
+            pngfile = cls.make_png(tex, fontsize, dpi)
+            rgba = mpl.image.imread(os.path.join(cls.texcache, pngfile))
+            cls._grey_arrayd[key] = alpha = rgba[:, :, -1]
         return alpha
 
-    def get_rgba(self, tex, fontsize=None, dpi=None, rgb=(0, 0, 0)):
+    @classmethod
+    def get_rgba(cls, tex, fontsize=None, dpi=None, rgb=(0, 0, 0)):
         r"""
         Return latex's rendering of the tex string as an rgba array.
 
@@ -319,17 +345,18 @@ def get_rgba(self, tex, fontsize=None, dpi=None, rgb=(0, 0, 0)):
         >>> s = r"\TeX\ is $\displaystyle\sum_n\frac{-e^{i\pi}}{2^n}$!"
         >>> Z = texmanager.get_rgba(s, fontsize=12, dpi=80, rgb=(1, 0, 0))
         """
-        alpha = self.get_grey(tex, fontsize, dpi)
+        alpha = cls.get_grey(tex, fontsize, dpi)
         rgba = np.empty((*alpha.shape, 4))
         rgba[..., :3] = mpl.colors.to_rgb(rgb)
         rgba[..., -1] = alpha
         return rgba
 
-    def get_text_width_height_descent(self, tex, fontsize, renderer=None):
+    @classmethod
+    def get_text_width_height_descent(cls, tex, fontsize, renderer=None):
         """Return width, height and descent of the text."""
         if tex.strip() == '':
             return 0, 0, 0
-        dvifile = self.make_dvi(tex, fontsize)
+        dvifile = cls.make_dvi(tex, fontsize)
         dpi_fraction = renderer.points_to_pixels(1.) if renderer else 1
         with dviread.Dvi(dvifile, 72 * dpi_fraction) as dvi:
             page, = dvi