Stop computing glyph_name in mathtext font handling.

None of the MathtextBackends actually accesses the .glyph_name
attribute anymore, and they are the only public API that can interact
with the glyph infos returned by the Fonts classes (and there is no
public API to register new MathtextBackends).

Author: anntzer

lib/matplotlib/_mathtext.py

@@ -245,8 +245,8 @@ def _get_info(self, fontname, font_class, sym, fontsize, dpi, math=True):
         if bunch is not None:
             return bunch
 
-        font, num, glyph_name, fontsize, slanted = \
-            self._get_glyph(fontname, font_class, sym, fontsize, math)
+        font, num, fontsize, slanted = self._get_glyph(
+            fontname, font_class, sym, fontsize, math)
 
         font.set_size(fontsize, dpi)
         glyph = font.load_char(
@@ -273,8 +273,6 @@ def _get_info(self, fontname, font_class, sym, fontsize, dpi, math=True):
             fontsize        = fontsize,
             postscript_name = font.postscript_name,
             metrics         = metrics,
-            glyph_name      = glyph_name,
-            symbol_name     = glyph_name,  # Backcompat alias.
             num             = num,
             glyph           = glyph,
             offset          = offset
@@ -340,7 +338,6 @@ def __init__(self, *args, **kwargs):
     _slanted_symbols = set(r"\int \oint".split())
 
     def _get_glyph(self, fontname, font_class, sym, fontsize, math=True):
-        glyph_name = None
         font = None
         if fontname in self.fontmap and sym in latex_to_bakoma:
             basename, num = latex_to_bakoma[sym]
@@ -351,18 +348,12 @@ def _get_glyph(self, fontname, font_class, sym, fontsize, math=True):
             font = self._get_font(fontname)
             if font is not None:
                 num = ord(sym)
-
-        if font is not None:
-            gid = font.get_char_index(num)
-            if gid != 0:
-                glyph_name = font.get_glyph_name(gid)
-
-        if glyph_name is None:
+        if font is not None and font.get_char_index(num) != 0:
+            return font, num, fontsize, slanted
+        else:
             return self._stix_fallback._get_glyph(
                 fontname, font_class, sym, fontsize, math)
 
-        return font, num, glyph_name, fontsize, slanted
-
     # The Bakoma fonts contain many pre-sized alternatives for the
     # delimiters.  The AutoSizedChar class will use these alternatives
     # and select the best (closest sized) glyph.
@@ -532,14 +523,11 @@ def _get_glyph(self, fontname, font_class, sym, fontsize, math=True):
                 _log.warning("Font {!r} does not have a glyph for {!a} "
                              "[U+{:x}], substituting with a dummy "
                              "symbol.".format(new_fontname, sym, uniindex))
-                fontname = 'rm'
-                font = self._get_font(fontname)
+                font = self._get_font('rm')
                 uniindex = 0xA4  # currency char, for lack of anything better
-                glyphindex = font.get_char_index(uniindex)
                 slanted = False
 
-        glyph_name = font.get_glyph_name(glyphindex)
-        return font, uniindex, glyph_name, fontsize, slanted
+        return font, uniindex, fontsize, slanted
 
     def get_sized_alternatives_for_symbol(self, fontname, sym):
         if self.cm_fallback: