Implemented math_fontfamily param in FontProperties

diegopetrola · diegopetrola · commit ccac5e3a54b7 · 2020-08-24T14:20:34.000-03:00
- The parameter can change the family of fonts for each text element instead
  of globally with `rcParams['mathtext.fontset']`
- Added example of usage `/examples/text_labels_and_annotations/mathtext_fontfamily_example.py`
- Added tests
- Added documentation
diff --git a/examples/text_labels_and_annotations/mathtext_fontfamily_example.py b/examples/text_labels_and_annotations/mathtext_fontfamily_example.py
@@ -0,0 +1,37 @@
+"""
+===============
+Math fontfamily
+===============
+
+A simple example showcasing the new *math_fontfamily* parameter that can
+be used to change the family of fonts for each individual text
+element in a plot.
+
+If no parameter is set, the global value
+:rc:`mathtext.fontset` will be used.
+"""
+
+import matplotlib.pyplot as plt
+
+plt.figure(figsize=(6, 5))
+
+# A simple plot for the background.
+plt.plot(range(11), color="0.9")
+
+# A text mixing normal text and math text.
+msg = (r"Normal Text. $Text\ in\ math\ mode:\ "
+       r"\int_{0}^{\infty } x^2 dx$")
+
+# Set the text in the plot.
+plt.text(1, 7, msg, size=12, math_fontfamily='cm')
+
+# Set another font for the next text.
+plt.text(1, 3, msg, size=12, math_fontfamily='dejavuserif')
+
+# *math_fontfamily* can be used in most places where there is text,
+# like in the title:
+plt.title(r"$Title\ in\ math\ mode:\ \int_{0}^{\infty } x^2 dx$",
+          math_fontfamily='stixsans', size=14)
+
+# Note that the normal text is not changed by *math_fontfamily*.
+plt.show()
diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
@@ -41,6 +41,7 @@
 from matplotlib import afm, cbook, ft2font, rcParams
 from matplotlib.fontconfig_pattern import (
     parse_fontconfig_pattern, generate_fontconfig_pattern)
+from matplotlib.rcsetup import _validators
 
 _log = logging.getLogger(__name__)
 
@@ -624,10 +625,10 @@ class FontProperties:
     """
     A class for storing and manipulating font properties.
 
-    The font properties are those described in the `W3C Cascading
-    Style Sheet, Level 1
+    The font properties are the six properties described in the
+    `W3C Cascading Style Sheet, Level 1
     <http://www.w3.org/TR/1998/REC-CSS2-19980512/>`_ font
-    specification.  The six properties are:
+    specification and *math_fontfamily* for math fonts:
 
     - family: A list of font names in decreasing order of priority.
       The items may include a generic font family name, either
@@ -653,6 +654,12 @@ class FontProperties:
       'small', 'medium', 'large', 'x-large', 'xx-large' or an
       absolute font size, e.g., 12.
 
+    - math_fontfamily: The family of fonts used to render math text; overrides
+      :rc:`mathtext.fontset`. Supported values are the same as the ones
+      supported by :rc:`mathtext.fontset` ::
+
+        'dejavusans', 'dejavuserif', 'cm', 'stix', 'stixsans' and 'custom'.
+
     The default font property for TrueType fonts (as specified in the
     default rcParams) is ::
 
@@ -690,6 +697,7 @@ def __init__(self,
                  stretch= None,
                  size   = None,
                  fname  = None,  # if set, it's a hardcoded filename to use
+                 math_fontfamily = None,
                  ):
         self._family = _normalize_font_family(rcParams['font.family'])
         self._slant = rcParams['font.style']
@@ -698,6 +706,7 @@ def __init__(self,
         self._stretch = rcParams['font.stretch']
         self._size = rcParams['font.size']
         self._file = None
+        self._math_fontfamily = None
 
         if isinstance(family, str):
             # Treat family as a fontconfig pattern if it is the only
@@ -714,6 +723,7 @@ def __init__(self,
         self.set_stretch(stretch)
         self.set_file(fname)
         self.set_size(size)
+        self.set_math_fontfamily(math_fontfamily)
 
     @classmethod
     def _from_any(cls, arg):
@@ -745,7 +755,8 @@ def __hash__(self):
              self.get_weight(),
              self.get_stretch(),
              self.get_size_in_points(),
-             self.get_file())
+             self.get_file(),
+             self.get_math_fontfamily())
         return hash(l)
 
     def __eq__(self, other):
@@ -934,6 +945,45 @@ def set_fontconfig_pattern(self, pattern):
             else:
                 getattr(self, "set_" + key)(val)
 
+    def get_math_fontfamily(self):
+        """
+        Return the name of the font family used for math text.
+
+        The default font is :rc:`mathtext.fontset`.
+        """
+        if self._math_fontfamily is None:
+            return rcParams['mathtext.fontset']
+        return self._math_fontfamily
+
+    def set_math_fontfamily(self, fontfamily):
+        """
+        Set the font family for text in math mode.
+
+        If not set explicitly, :rc:`mathtext.fontset` will be used.
+
+        Parameters
+        ----------
+        fontfamily : str
+            The name of the font family.
+
+            Available font families are defined in the
+            matplotlibrc.template file
+            :ref:`here <customizing-with-matplotlibrc-files>`
+
+        See Also
+        --------
+        .text.Text.get_math_fontfamily
+        """
+        if fontfamily is None:
+            self._math_fontfamily = None
+            return
+
+        valid_fonts = _validators['mathtext.fontset'].valid.values()
+        # _check_in_list() Validates the parameter math_fontfamily as
+        # if it were passed to rcParams['mathtext.fontset']
+        cbook._check_in_list(valid_fonts, math_fontfamily=fontfamily)
+        self._math_fontfamily = fontfamily
+
     def copy(self):
         """Return a copy of self."""
         new = type(self)()
diff --git a/lib/matplotlib/mathtext.py b/lib/matplotlib/mathtext.py
@@ -3351,12 +3351,10 @@ def parse(self, s, dpi=72, prop=None, *, _force_standard_ps_fonts=False):
         # lru_cache can't decorate parse() directly because the ps.useafm and
         # mathtext.fontset rcParams also affect the parse (e.g. by affecting
         # the glyph metrics).
-        return self._parse_cached(s, dpi, prop, _force_standard_ps_fonts,
-                                  rcParams['mathtext.fontset'])
+        return self._parse_cached(s, dpi, prop, _force_standard_ps_fonts)
 
     @functools.lru_cache(50)
-    def _parse_cached(self, s, dpi, prop, force_standard_ps_fonts, fontset):
-
+    def _parse_cached(self, s, dpi, prop, force_standard_ps_fonts):
         if prop is None:
             prop = FontProperties()
 
@@ -3365,7 +3363,8 @@ def _parse_cached(self, s, dpi, prop, force_standard_ps_fonts, fontset):
         else:
             backend = self._backend_mapping[self._output]()
             fontset_class = cbook._check_getitem(
-                self._font_type_mapping, fontset=fontset)
+                self._font_type_mapping,
+                fontset=prop.get_math_fontfamily())
             font_output = fontset_class(prop, backend)
 
         fontsize = prop.get_size_in_points()
diff --git a/lib/matplotlib/tests/baseline_images/test_mathtext/mathtext_fontset_image.png b/lib/matplotlib/tests/baseline_images/test_mathtext/mathtext_fontset_image.png
diff --git a/lib/matplotlib/tests/test_mathtext.py b/lib/matplotlib/tests/test_mathtext.py
@@ -364,3 +364,13 @@ def test_mathtext_to_png(tmpdir):
     mt = mathtext.MathTextParser('bitmap')
     mt.to_png(str(tmpdir.join('example.png')), '$x^2$')
     mt.to_png(io.BytesIO(), '$x^2$')
+
+
+@image_comparison(baseline_images=['mathtext_fontset_image.png'],
+                  savefig_kwarg={'dpi': 40})
+def test_math_fontfamily():
+    fig = plt.figure(figsize=(10, 3))
+    fig.text(0.2, 0.7, r"$This\ text\ should\ have\ one\ font$",
+             size=24, math_fontfamily='dejavusans')
+    fig.text(0.2, 0.3, r"$This\ text\ should\ have\ another$",
+             size=24, math_fontfamily='cm')
diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -1061,6 +1061,40 @@ def set_fontsize(self, fontsize):
         self._fontproperties.set_size(fontsize)
         self.stale = True
 
+    def get_math_fontfamily(self):
+        """
+        Return the font family name for math text rendered by Matplotlib.
+
+        The default value is :rc:`mathtext.fontset`.
+
+        See Also
+        --------
+        set_math_fontfamily
+        """
+        return self._fontproperties.get_math_fontfamily()
+
+    def set_math_fontfamily(self, fontfamily):
+        """
+        Set the font family for math text rendered by Matplotlib.
+
+        This does only affect Matplotlib's own math renderer. It has no effect
+        when rendering with TeX (``usetex=True``).
+
+        Parameters
+        ----------
+        fontfamily : str
+            The name of the font family.
+
+            Available font families are defined in the
+            :ref:`matplotlibrc.template file
+            <customizing-with-matplotlibrc-files>`.
+
+        See Also
+        --------
+        get_math_fontfamily
+        """
+        self._fontproperties.set_math_fontfamily(fontfamily)
+
     def set_fontweight(self, weight):
         """
         Set the font weight.
