From 5b78b6fcfb485dd7abeed8603afcd41f0b4c9a9a Mon Sep 17 00:00:00 2001
From: Antony Lee <anntzer.lee@gmail.com>
Date: Thu, 11 Feb 2021 19:18:14 +0100
Subject: [PATCH] Fully fold overset/underset into _genset.

No need to repeat the tokens expansion twice, and it seems reasonable
enough to check the string itself instead of inventing a separate
parameter just to pass the information of whether an overset or an
underset is being handled.
---
 lib/matplotlib/_mathtext.py | 33 ++++++++-------------------------
 1 file changed, 8 insertions(+), 25 deletions(-)

diff --git a/lib/matplotlib/_mathtext.py b/lib/matplotlib/_mathtext.py
index 6f0e47b239e6..2d9df8f34be4 100644
--- a/lib/matplotlib/_mathtext.py
+++ b/lib/matplotlib/_mathtext.py
@@ -2859,12 +2859,13 @@ def binom(self, s, loc, toks):
         return self._genfrac('(', ')', 0.0, self._MathStyle.TEXTSTYLE,
                              num, den)
 
-    def _genset(self, state, annotation, body, overunder):
+    def _genset(self, s, loc, toks):
+        (annotation, body), = toks
+        state = self.get_state()
         thickness = state.font_output.get_underline_thickness(
             state.font, state.fontsize, state.dpi)
 
         annotation.shrink()
-
         cannotation = HCentered([annotation])
         cbody = HCentered([body])
         width = max(cannotation.width, cbody.width)
@@ -2872,16 +2873,14 @@ def _genset(self, state, annotation, body, overunder):
         cbody.hpack(width, 'exactly')
 
         vgap = thickness * 3
-        if overunder == "under":
+        if s[loc + 1] == "u":  # \underset
             vlist = Vlist([cbody,                       # body
                            Vbox(0, vgap),               # space
                            cannotation                  # annotation
                            ])
             # Shift so the body sits in the same vertical position
-            shift_amount = cbody.depth + cannotation.height + vgap
-
-            vlist.shift_amount = shift_amount
-        else:
+            vlist.shift_amount = cbody.depth + cannotation.height + vgap
+        else:  # \overset
             vlist = Vlist([cannotation,                 # annotation
                            Vbox(0, vgap),               # space
                            cbody                        # body
@@ -2891,6 +2890,8 @@ def _genset(self, state, annotation, body, overunder):
         # an Hlist and extend it with an Hbox(0, horizontal_gap)
         return vlist
 
+    overset = underset = _genset
+
     def sqrt(self, s, loc, toks):
         (root, body), = toks
         state = self.get_state()
@@ -2951,24 +2952,6 @@ def overline(self, s, loc, toks):
         hlist = Hlist([rightside])
         return [hlist]
 
-    def overset(self, s, loc, toks):
-        assert len(toks) == 1
-        assert len(toks[0]) == 2
-
-        state = self.get_state()
-        annotation, body = toks[0]
-
-        return self._genset(state, annotation, body, overunder="over")
-
-    def underset(self, s, loc, toks):
-        assert len(toks) == 1
-        assert len(toks[0]) == 2
-
-        state = self.get_state()
-        annotation, body = toks[0]
-
-        return self._genset(state, annotation, body, overunder="under")
-
     def _auto_sized_delimiter(self, front, middle, back):
         state = self.get_state()
         if len(middle):