Re: underbraces get progressively more misaligned (w/ minimal example)

From: Wolfgang Schuster <schuster.wolfgang@gmail.com>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>
Cc: Hans Hagen <pragma@wxs.nl>, sanjoy@MIT.EDU
Subject: Re: underbraces get progressively more misaligned	(w/ minimal example)
Date: Thu, 3 Jul 2014 21:21:55 +0200	[thread overview]
Message-ID: <66D45391-7643-4952-BF98-7439FCEC856B@gmail.com> (raw)
In-Reply-To: <87k37u7m4e.fsf@approx.mit.edu>

Am 03.07.2014 um 12:49 schrieb Sanjoy Mahajan <sanjoy@MIT.EDU>:

> I thought the problem might lie with the general
> \definemathunderextensible (math-stc.mkvi), because underbrace is
> defined as
> 
> \definemathunderextensible  [vfenced] [underbrace]    ["FE3DF]          % ["023DF]
> 
> Other underextensibles include \underbar:
> 
> \definemathunderextensible  [vfenced] [underbar]      ["FE33F]
> % ["203E]
> 
> So I tried my example replacing \underbrace with \underbar but the
> alignment comes out fine (and \overbrace works fine too).  So that
> debugging idea didn't work, except to indicate that something special
> about underbrace isn't working right.
> 
> Does anyone have suggestions for further debugging ideas?

math-stc.mkvi:

\unexpanded\def\math_stackers_make_double#top#bottom#category#codepoint#codeextra#text%
  {\begingroup
   \edef\currentmathstackers{#category}%
   \mathstackersparameter\c!left\relax
   \ifmmode\math_class_by_parameter\mathstackersparameter\else\dontleavehmode\fi
     {\edef\currentmathstackers{#category}%
      \edef\m_math_stackers_text_middle {#text}%
      %
      ...
      %
-     \ifx\currentmathtext\empty
+     \ifx\m_math_stackers_text_middle\empty
        \setbox\scratchboxthree\emptyhbox
      \else
        \setmathtextbox\scratchboxthree\hbox{\math_stackers_middletext}%
      \fi
      ...
      \fi}%
  \mathstackersparameter\c!right\relax
  \edef\p_limits{\mathstackersparameter\c!mathlimits}%
  \ifx\p_limits\v!yes
    \expandafter\endgroup\expandafter\limits
  \else
    \expandafter\endgroup
  \fi}

Wolfgang
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________