Improve font spec for SVG font referencing.

anntzer · anntzer · commit 4345d23fcdc6 · 2020-12-31T19:54:36.000+01:00
This replaces e.g.
`"font-family:DejaVu Sans;font-size:12px;font-style:book;font-weight:book;"`
by `"font: 400 12px 'DejaVu Sans'"`.
Note that the previous font weight was plain wrong...
diff --git a/lib/matplotlib/backends/backend_svg.py b/lib/matplotlib/backends/backend_svg.py
@@ -21,7 +21,7 @@
 from matplotlib.backends.backend_mixed import MixedModeRenderer
 from matplotlib.colors import rgb2hex
 from matplotlib.dates import UTC
-from matplotlib.font_manager import findfont, get_font
+from matplotlib.font_manager import findfont, get_font, ttfFontProperty
 from matplotlib.ft2font import LOAD_NO_HINTING
 from matplotlib.mathtext import MathTextParser
 from matplotlib.path import Path
@@ -94,6 +94,12 @@ def escape_attrib(s):
     return s
 
 
+def _quote_escape_attrib(s):
+    return ('"' + escape_cdata(s) + '"' if '"' not in s else
+            "'" + escape_cdata(s) + "'" if "'" not in s else
+            '"' + escape_attrib(s) + '"')
+
+
 def short_float_fmt(x):
     """
     Create a short string representation of a float, which is %f
@@ -159,8 +165,8 @@ def start(self, tag, attrib={}, **extra):
         for k, v in sorted({**attrib, **extra}.items()):
             if v:
                 k = escape_cdata(k)
-                v = escape_attrib(v)
-                self.__write(' %s="%s"' % (k, v))
+                v = _quote_escape_attrib(v)
+                self.__write(' %s=%s' % (k, v))
         self.__open = 1
         return len(self.__tags) - 1
 
@@ -1197,11 +1203,20 @@ def _draw_text_as_text(self, gc, x, y, s, prop, angle, ismath, mtext=None):
             # Sort the characters by font, and output one tspan for each.
             spans = OrderedDict()
             for font, fontsize, thetext, new_x, new_y in glyphs:
-                style = generate_css({
-                    'font-size': short_float_fmt(fontsize) + 'px',
-                    'font-family': font.family_name,
-                    'font-style': font.style_name.lower(),
-                    'font-weight': font.style_name.lower()})
+                entry = ttfFontProperty(font)
+                font_parts = ['font:']
+                if entry.style != 'normal':
+                    font_parts.append(entry.style)
+                if entry.variant != 'normal':
+                    font_parts.append(entry.variant)
+                font_parts.extend([
+                    f'{entry.weight}',
+                    f'{short_float_fmt(fontsize)}px',
+                    f'{entry.name!r}',  # ensure quoting
+                ])
+                if entry.stretch != 'normal':
+                    font_parts.extend(['; font-stretch:', entry.stretch])
+                style = ' '.join(font_parts)
                 if thetext == 32:
                     thetext = 0xa0  # non-breaking space
                 spans.setdefault(style, []).append((new_x, -new_y, thetext))
diff --git a/lib/matplotlib/tests/test_mathtext.py b/lib/matplotlib/tests/test_mathtext.py
@@ -1,6 +1,8 @@
 import io
-import os
+from pathlib import Path
 import re
+import shlex
+from xml.etree import ElementTree as ET
 
 import numpy as np
 import pytest
@@ -328,7 +330,7 @@ def test_mathtext_fallback_to_cm_invalid():
      ("stix", ['DejaVu Sans', 'mpltest', 'STIXGeneral'])])
 def test_mathtext_fallback(fallback, fontlist):
     mpl.font_manager.fontManager.addfont(
-        os.path.join((os.path.dirname(os.path.realpath(__file__))), 'mpltest.ttf'))
+        str(Path(__file__).resolve().parent / 'mpltest.ttf'))
     mpl.rcParams["svg.fonttype"] = 'none'
     mpl.rcParams['mathtext.fontset'] = 'custom'
     mpl.rcParams['mathtext.rm'] = 'mpltest'
@@ -342,12 +344,13 @@ def test_mathtext_fallback(fallback, fontlist):
     fig, ax = plt.subplots()
     fig.text(.5, .5, test_str, fontsize=40, ha='center')
     fig.savefig(buff, format="svg")
-    char_fonts = [
-        line.split("font-family:")[-1].split(";")[0]
-        for line in str(buff.getvalue()).split(r"\n") if "tspan" in line
-    ]
+    tspans = (ET.fromstring(buff.getvalue())
+              .findall(".//{http://www.w3.org/2000/svg}tspan[@style]"))
+    # Getting the last element of the style attrib is a close enough
+    # approximation for parsing the font property.
+    char_fonts = [shlex.split(tspan.attrib["style"])[-1] for tspan in tspans]
     assert char_fonts == fontlist
-    mpl.font_manager.fontManager.ttflist = mpl.font_manager.fontManager.ttflist[:-1]
+    mpl.font_manager.fontManager.ttflist.pop()
 
 
 def test_math_to_image(tmpdir):
