Correctly get weight & style hints from certain newer Microsoft fonts (matplotlib#12945)

Author: Stephen-Chilcote

lib/matplotlib/font_manager.py

@@ -321,9 +321,13 @@ def ttfFontProperty(font):
     sfnt = font.get_sfnt()
     # These tables are actually mac_roman-encoded, but mac_roman support may be
     # missing in some alternative Python implementations and we are only going
-    # to look for ASCII substrings, where any ASCII-compatible encoding works.
-    sfnt2 = sfnt.get((1, 0, 0, 2), b'').decode('latin-1').lower()
-    sfnt4 = sfnt.get((1, 0, 0, 4), b'').decode('latin-1').lower()
+    # to look for ASCII substrings, where any ASCII-compatible encoding works
+    # - or big-endian UTF-16, since important Microsoft fonts use that.
+    sfnt2 = (sfnt.get((1, 0,      0, 2), b'').decode('latin-1').lower() or
+             sfnt.get((3, 1, 0x0409, 2), b'').decode('utf_16_be').lower())
+    sfnt4 = (sfnt.get((1, 0,      0, 4), b'').decode('latin-1').lower() or
+             sfnt.get((3, 1, 0x0409, 4), b'').decode('utf_16_be').lower())
+
     if sfnt4.find('oblique') >= 0:
         style = 'oblique'
     elif sfnt4.find('italic') >= 0:

lib/matplotlib/tests/test_font_manager.py

@@ -1,5 +1,6 @@
 from pathlib import Path
 import shutil
+import sys
 import warnings
 
 import numpy as np
@@ -87,3 +88,20 @@ def test_hinting_factor(factor):
     # Check that hinting only changes text layout by a small (10%) amount.
     np.testing.assert_allclose(hinted_font.get_width_height(), expected,
                                rtol=0.1)
+
+
+@pytest.mark.skipif(sys.platform != "win32",
+                   reason="Need Windows font to test against")
+def test_utf16m_sfnt():
+    segoe_ui_semibold = None
+    for f in fontManager.ttflist:
+        # seguisbi = Microsoft Segoe UI Semibold
+        if f.fname[-12:] == "seguisbi.ttf":
+            segoe_ui_semibold = f
+            break
+    else:
+        pytest.xfail(reason="Couldn't find font to test against.")
+
+    # Check that we successfully read the "semibold" from the font's
+    # sfnt table and set its weight accordingly
+    assert segoe_ui_semibold.weight == "semibold"