matplotlib · QuLogic · Mar 1, 2025
diff --git a/doc/users/next_whats_new/font_features.rst b/doc/users/next_whats_new/font_features.rst
@@ -0,0 +1,40 @@
+Specifying font feature tags
+----------------------------
+
+OpenType fonts may support feature tags that specify alternate glyph shapes or
+substitutions to be made optionally. The text API now supports setting a list of feature
+tags to be used with the associated font. Feature tags can be set/get with:
+
+- `matplotlib.text.Text.set_fontfeatures` / `matplotlib.text.Text.get_fontfeatures`
+- Any API that creates a `.Text` object by passing the *fontfeatures* argument (e.g.,
+  ``plt.xlabel(..., fontfeatures=...)``)
+
+Font feature strings are eventually passed to HarfBuzz, and so all `string formats
+supported by hb_feature_from_string()
+<https://harfbuzz.github.io/harfbuzz-hb-common.html#hb-feature-from-string>`__ are
+supported.
+
+For example, the default font ``DejaVu Sans`` enables Standard Ligatures (the ``'liga'``
+tag) by default, and also provides optional Discretionary Ligatures (the ``dlig`` tag.)
+These may be toggled with ``+`` or ``-``.
+
+.. plot::
+    :include-source:
+
+    fig = plt.figure(figsize=(7, 3))
+
+    fig.text(0.5, 0.85, 'Ligatures', fontsize=40, horizontalalignment='center')
+
+    # Default has Standard Ligatures (liga).
+    fig.text(0, 0.6, 'Default: fi ffi fl st', fontsize=40)
+
+    # Disable Standard Ligatures with -liga.
+    fig.text(0, 0.35, 'Disabled: fi ffi fl st', fontsize=40,
+             fontfeatures=['-liga'])
+
+    # Enable Discretionary Ligatures with dlig.
+    fig.text(0, 0.1, 'Discretionary: fi ffi fl st', fontsize=40,
+             fontfeatures=['dlig'])
+
+Available font feature tags may be found at
+https://learn.microsoft.com/en-us/typography/opentype/spec/featurelist
diff --git a/lib/matplotlib/_text_helpers.py b/lib/matplotlib/_text_helpers.py
@@ -43,7 +43,7 @@ def warn_on_missing_glyph(codepoint, fontnames):
             f"Matplotlib currently does not support {block} natively.")
 
 
-def layout(string, font, *, kern_mode=Kerning.DEFAULT):
+def layout(string, font, *, features=None, kern_mode=Kerning.DEFAULT):
     """
     Render *string* with *font*.
 
@@ -56,6 +56,8 @@ def layout(string, font, *, kern_mode=Kerning.DEFAULT):
         The string to be rendered.
     font : FT2Font
         The font.
+    features : tuple of str, optional
+        The font features to apply to the text.
     kern_mode : Kerning
         A FreeType kerning mode.
 
@@ -65,7 +67,7 @@ def layout(string, font, *, kern_mode=Kerning.DEFAULT):
     """
     x = 0
     prev_glyph_idx = None
-    char_to_font = font._get_fontmap(string)
+    char_to_font = font._get_fontmap(string)  # TODO: Pass in features.
     base_font = font
     for char in string:
         # This has done the fallback logic

diff --git a/lib/matplotlib/backends/backend_agg.py b/lib/matplotlib/backends/backend_agg.py
@@ -189,7 +189,8 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
         font = self._prepare_font(prop)
         # We pass '0' for angle here, since it will be rotated (in raster
         # space) in the following call to draw_text_image).
-        font.set_text(s, 0, flags=get_hinting_flag())
+        font.set_text(s, 0, flags=get_hinting_flag(),
+                      features=mtext.get_fontfeatures() if mtext is not None else None)
         font.draw_glyphs_to_bitmap(
             antialiased=gc.get_antialiased())
         d = font.get_descent() / 64.0

diff --git a/lib/matplotlib/backends/backend_pdf.py b/lib/matplotlib/backends/backend_pdf.py
@@ -2338,6 +2338,7 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
             return self.draw_mathtext(gc, x, y, s, prop, angle)
 
         fontsize = prop.get_size_in_points()
+        features = mtext.get_fontfeatures() if mtext is not None else None
 
         if mpl.rcParams['pdf.use14corefonts']:
             font = self._get_font_afm(prop)
@@ -2348,7 +2349,7 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
             fonttype = mpl.rcParams['pdf.fonttype']
 
         if gc.get_url() is not None:
-            font.set_text(s)
+            font.set_text(s, features=features)
             width, height = font.get_width_height()
             self.file._annotations[-1][1].append(_get_link_annotation(
                 gc, x, y, width / 64, height / 64, angle))
@@ -2382,7 +2383,8 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
             multibyte_glyphs = []
             prev_was_multibyte = True
             prev_font = font
-            for item in _text_helpers.layout(s, font, kern_mode=Kerning.UNFITTED):
+            for item in _text_helpers.layout(s, font, features=features,
+                                             kern_mode=Kerning.UNFITTED):
                 if _font_supports_glyph(fonttype, ord(item.char)):
                     if prev_was_multibyte or item.ft_object != prev_font:
                         singlebyte_chunks.append((item.ft_object, item.x, []))

diff --git a/lib/matplotlib/backends/backend_ps.py b/lib/matplotlib/backends/backend_ps.py
@@ -795,9 +795,10 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
                 thisx += width * scale
 
         else:
+            features = mtext.get_fontfeatures() if mtext is not None else None
             font = self._get_font_ttf(prop)
             self._character_tracker.track(font, s)
-            for item in _text_helpers.layout(s, font):
+            for item in _text_helpers.layout(s, font, features=features):
                 ps_name = (item.ft_object.postscript_name
                            .encode("ascii", "replace").decode("ascii"))
                 glyph_name = item.ft_object.get_glyph_name(item.glyph_idx)

diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
@@ -536,7 +536,7 @@ def afmFontProperty(fontpath, font):
 
 def _cleanup_fontproperties_init(init_method):
     """
-    A decorator to limit the call signature to single a positional argument
+    A decorator to limit the call signature to a single positional argument
     or alternatively only keyword arguments.
 
     We still accept but deprecate all other call signatures.

diff --git a/lib/matplotlib/ft2font.pyi b/lib/matplotlib/ft2font.pyi
@@ -236,7 +236,12 @@ class FT2Font(Buffer):
     def set_charmap(self, i: int) -> None: ...
     def set_size(self, ptsize: float, dpi: float) -> None: ...
     def set_text(
-        self, string: str, angle: float = ..., flags: LoadFlags = ...
+        self,
+        string: str,
+        angle: float = ...,
+        flags: LoadFlags = ...,
+        *,
+        features: tuple[str] | None = ...,
     ) -> NDArray[np.float64]: ...
     @property
     def ascender(self) -> int: ...

diff --git a/lib/matplotlib/tests/test_ft2font.py b/lib/matplotlib/tests/test_ft2font.py
@@ -199,6 +199,19 @@ def test_ft2font_set_size():
     assert font.get_width_height() == tuple(pytest.approx(2 * x, 1e-1) for x in orig)
 
 
+def test_ft2font_features():
+    # Smoke test that these are accepted as intended.
+    file = fm.findfont('DejaVu Sans')
+    font = ft2font.FT2Font(file)
+    font.set_text('foo', features=None)  # unset
+    font.set_text('foo', features=['calt', 'dlig'])  # list
+    font.set_text('foo', features=('calt', 'dlig'))  # tuple
+    with pytest.raises(TypeError):
+        font.set_text('foo', features=123)
+    with pytest.raises(TypeError):
+        font.set_text('foo', features=[123, 456])
+
+
 def test_ft2font_charmaps():
     def enc(name):
         # We don't expose the encoding enum from FreeType, but can generate it here.

diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -136,6 +136,7 @@
         super().__init__()
         self._x, self._y = x, y
         self._text = ''
+        self._features = None
         self._reset_visual_defaults(
             text=text,
             color=color,
@@ -847,6 +848,12 @@
         """
         return self._fontproperties.get_family()
 
+    def get_fontfeatures(self):
+        """
+        Return a tuple of font feature tags to enable.
+        """
+        return self._features
+
     def get_fontname(self):
         """
         Return the font name as a string.
@@ -1094,6 +1101,38 @@
         self._fontproperties.set_family(fontname)
         self.stale = True
 
+    def set_fontfeatures(self, features):
+        """
+        Set the feature tags to enable on the font.
+
+        Parameters
+        ----------
+        features : list[str]
+            A list of feature tags to be used with the associated font. These strings
+            are eventually passed to HarfBuzz, and so all `string formats supported by
+            hb_feature_from_string()
+            <https://harfbuzz.github.io/harfbuzz-hb-common.html#hb-feature-from-string>`__
+            are supported.
+
+            For example, if your desired font includes Stylistic Sets which enable
+            various typographic alternates including one that you do not wish to use
+            (e.g., Contextual Ligatures), then you can pass the following to enable one
+            and not the other::
+
+                fp.set_features([
+                    'ss01',  # Use Stylistic Set 1.
+                    '-clig',  # But disable Contextural Ligatures.
+                ])
+
+            Available font feature tags may be found at
+            https://learn.microsoft.com/en-us/typography/opentype/spec/featurelist
+        """
+        _api.check_isinstance((list, tuple, None), features=features)
+        if features is not None:
+            features = tuple(features)
+        self._features = features
+        self.stale = True
+
     def set_fontvariant(self, variant):
         """
         Set the font variant.

diff --git a/lib/matplotlib/text.pyi b/lib/matplotlib/text.pyi
@@ -56,6 +56,7 @@ class Text(Artist):
     def get_color(self) -> ColorType: ...
     def get_fontproperties(self) -> FontProperties: ...
     def get_fontfamily(self) -> list[str]: ...
+    def get_fontfeatures(self) -> tuple[str, ...] | None: ...
     def get_fontname(self) -> str: ...
     def get_fontstyle(self) -> Literal["normal", "italic", "oblique"]: ...
     def get_fontsize(self) -> float | str: ...
@@ -80,6 +81,7 @@ class Text(Artist):
     def set_multialignment(self, align: Literal["left", "center", "right"]) -> None: ...
     def set_linespacing(self, spacing: float) -> None: ...
     def set_fontfamily(self, fontname: str | Iterable[str]) -> None: ...
+    def set_fontfeatures(self, features: list[str] | tuple[str, ...] | None) -> None: ...
     def set_fontvariant(self, variant: Literal["normal", "small-caps"]) -> None: ...
     def set_fontstyle(
         self, fontstyle: Literal["normal", "italic", "oblique"]

diff --git a/lib/matplotlib/textpath.py b/lib/matplotlib/textpath.py
@@ -69,7 +69,7 @@ def get_text_width_height_descent(self, s, prop, ismath):
         d /= 64.0
         return w * scale, h * scale, d * scale
 
-    def get_text_path(self, prop, s, ismath=False):
+    def get_text_path(self, prop, s, ismath=False, *, features=None):
         """
         Convert text *s* to path (a tuple of vertices and codes for
         matplotlib.path.Path).
@@ -109,7 +109,8 @@ def get_text_path(self, prop, s, ismath=False):
             glyph_info, glyph_map, rects = self.get_glyphs_tex(prop, s)
         elif not ismath:
             font = self._get_font(prop)
-            glyph_info, glyph_map, rects = self.get_glyphs_with_font(font, s)
+            glyph_info, glyph_map, rects = self.get_glyphs_with_font(
+                font, s, features=features)
         else:
             glyph_info, glyph_map, rects = self.get_glyphs_mathtext(prop, s)
 
@@ -130,7 +131,7 @@ def get_text_path(self, prop, s, ismath=False):
         return verts, codes
 
     def get_glyphs_with_font(self, font, s, glyph_map=None,
-                             return_new_glyphs_only=False):
+                             return_new_glyphs_only=False, *, features=None):
         """
         Convert string *s* to vertices and codes using the provided ttf font.
         """
@@ -145,7 +146,7 @@ def get_glyphs_with_font(self, font, s, glyph_map=None,
 
         xpositions = []
         glyph_ids = []
-        for item in _text_helpers.layout(s, font):
+        for item in _text_helpers.layout(s, font, features=features):
             char_id = self._get_char_id(item.ft_object, ord(item.char))
             glyph_ids.append(char_id)
             xpositions.append(item.x)

diff --git a/lib/matplotlib/textpath.pyi b/lib/matplotlib/textpath.pyi
@@ -16,14 +16,21 @@ class TextToPath:
         self, s: str, prop: FontProperties, ismath: bool | Literal["TeX"]
     ) -> tuple[float, float, float]: ...
     def get_text_path(
-        self, prop: FontProperties, s: str, ismath: bool | Literal["TeX"] = ...
+        self,
+        prop: FontProperties,
+        s: str,
+        ismath: bool | Literal["TeX"] = ...,
+        *,
+        features: tuple[str] | None = ...,
     ) -> list[np.ndarray]: ...
     def get_glyphs_with_font(
         self,
         font: FT2Font,
         s: str,
         glyph_map: dict[str, tuple[np.ndarray, np.ndarray]] | None = ...,
         return_new_glyphs_only: bool = ...,
+        *,
+        features: tuple[str] | None = ...,
     ) -> tuple[
            list[tuple[str, float, float, float]],
         dict[str, tuple[np.ndarray, np.ndarray]],

diff --git a/src/ft2font.cpp b/src/ft2font.cpp
@@ -397,7 +397,8 @@ void FT2Font::set_kerning_factor(int factor)
 }
 
 void FT2Font::set_text(
-    std::u32string_view text, double angle, FT_Int32 flags, std::vector<double> &xys)
+    std::u32string_view text, double angle, FT_Int32 flags,
+    std::optional<std::vector<std::string>> features, std::vector<double> &xys)
 {
     FT_Matrix matrix; /* transformation matrix */
 

diff --git a/src/ft2font.h b/src/ft2font.h
@@ -6,6 +6,7 @@
 #ifndef MPL_FT2FONT_H
 #define MPL_FT2FONT_H
 
+#include <optional>
 #include <set>
 #include <string>
 #include <string_view>
@@ -79,6 +80,7 @@ class FT2Font
     void set_charmap(int i);
     void select_charmap(unsigned long i);
     void set_text(std::u32string_view codepoints, double angle, FT_Int32 flags,
+                  std::optional<std::vector<std::string>> features,
                   std::vector<double> &xys);
     int get_kerning(FT_UInt left, FT_UInt right, FT_Kerning_Mode mode, bool fallback);
     int get_kerning(FT_UInt left, FT_UInt right, FT_Kerning_Mode mode, FT_Vector &delta);

diff --git a/src/ft2font_wrapper.cpp b/src/ft2font_wrapper.cpp
@@ -703,6 +703,11 @@ const char *PyFT2Font_set_text__doc__ = R"""(
 
         .. versionchanged:: 3.10
             This now takes an `.ft2font.LoadFlags` instead of an int.
+    features : tuple[str, ...]
+        The font feature tags to use for the font.
+
+        Available font feature tags may be found at
+        https://learn.microsoft.com/en-us/typography/opentype/spec/featurelist
 
     Returns
     -------
@@ -712,7 +717,8 @@ const char *PyFT2Font_set_text__doc__ = R"""(
 
 static py::array_t<double>
 PyFT2Font_set_text(PyFT2Font *self, std::u32string_view text, double angle = 0.0,
-                   std::variant<LoadFlags, FT_Int32> flags_or_int = LoadFlags::FORCE_AUTOHINT)
+                   std::variant<LoadFlags, FT_Int32> flags_or_int = LoadFlags::FORCE_AUTOHINT,
+                   std::optional<std::vector<std::string>> features = std::nullopt)
 {
     std::vector<double> xys;
     LoadFlags flags;
@@ -732,7 +738,7 @@ PyFT2Font_set_text(PyFT2Font *self, std::u32string_view text, double angle = 0.0
         throw py::type_error("flags must be LoadFlags or int");
     }
 
-    self->x->set_text(text, angle, static_cast<FT_Int32>(flags), xys);
+    self->x->set_text(text, angle, static_cast<FT_Int32>(flags), features, xys);
 
     py::ssize_t dims[] = { static_cast<py::ssize_t>(xys.size()) / 2, 2 };
     py::array_t<double> result(dims);
@@ -1621,7 +1627,8 @@ PYBIND11_MODULE(ft2font, m, py::mod_gil_not_used())
         .def("get_kerning", &PyFT2Font_get_kerning, "left"_a, "right"_a, "mode"_a,
              PyFT2Font_get_kerning__doc__)
         .def("set_text", &PyFT2Font_set_text,
-             "string"_a, "angle"_a=0.0, "flags"_a=LoadFlags::FORCE_AUTOHINT,
+             "string"_a, "angle"_a=0.0, "flags"_a=LoadFlags::FORCE_AUTOHINT, py::kw_only(),
+             "features"_a=nullptr,
              PyFT2Font_set_text__doc__)
         .def("_get_fontmap", &PyFT2Font_get_fontmap, "string"_a,
              PyFT2Font_get_fontmap__doc__)