Revert "Switch TeX baseline detection to use a dvi special."

This reverts commit c973552.

Author: QuLogic

lib/matplotlib/dviread.py

@@ -352,10 +352,40 @@ def _read(self):
         Read one page from the file. Return True if successful,
         False if there were no more pages.
         """
+        # Pages appear to start with the sequence
+        #   bop (begin of page)
+        #   xxx comment
+        #   <push, ..., pop>  # if using chemformula
+        #   down
+        #   push
+        #     down
+        #     <push, push, xxx, right, xxx, pop, pop>  # if using xcolor
+        #     down
+        #     push
+        #       down (possibly multiple)
+        #       push  <=  here, v is the baseline position.
+        #         etc.
+        # (dviasm is useful to explore this structure.)
+        # Thus, we use the vertical position at the first time the stack depth
+        # reaches 3, while at least three "downs" have been executed (excluding
+        # those popped out (corresponding to the chemformula preamble)), as the
+        # baseline (the "down" count is necessary to handle xcolor).
+        down_stack = [0]
         self._baseline_v = None
         while True:
             byte = self.file.read(1)[0]
             self._dtable[byte](self, byte)
+            name = self._dtable[byte].__name__
+            if name == "_push":
+                down_stack.append(down_stack[-1])
+            elif name == "_pop":
+                down_stack.pop()
+            elif name == "_down":
+                down_stack[-1] += 1
+            if (self._baseline_v is None
+                    and len(getattr(self, "stack", [])) == 3
+                    and down_stack[-1] >= 4):
+                self._baseline_v = self.v
             if byte == 140:                         # end of page
                 return True
             if self.state is _dvistate.post_post:   # end of file
@@ -488,8 +518,6 @@ def _fnt_num(self, new_f):
     @_dispatch(min=239, max=242, args=('ulen1',))
     def _xxx(self, datalen):
         special = self.file.read(datalen)
-        if special == b'matplotlibbaselinemarker':
-            self._baseline_v = self.v
         _log.debug(
             'Dvi._xxx: encountered special: %s',
             ''.join([chr(ch) if 32 <= ch < 127 else '<%02x>' % ch

lib/matplotlib/texmanager.py

@@ -231,7 +231,6 @@ def _get_tex_source(cls, tex, fontsize):
             rf"\fontsize{{{fontsize}}}{{{baselineskip}}}%",
             r"\ifdefined\psfrag\else\hbox{}\fi%",
             rf"{{{fontcmd} {tex}}}%",
-            r"\special{matplotlibbaselinemarker}%",
             r"\end{document}",
         ])