breqn

\dmath*
\enddmath*
460 \begingroup
461 \eq@setup@a
462 \eq@startup
463 }
Before it finishes off the box holding the equation body, \enddmath needs to look
ahead for punctuation (and \qed?).
464 \def\enddmath#1{\check@punct@or@qed}
465 \def\end@dmath{%
466 \gdef\EQ@setwdL{}% Occasionally undefined ???
467 \eq@capture
468 \endgroup
469 \EQ@setwdL
Measure (a copy of) the equation body to find the minimum width required to get
acceptable line breaks, how many lines will be required at that width, and whether
the equation number needs to be shifted to avoid overlapping. This information
will then be used by \eq@finish to do the typesetting of the real equation body.
470 \eq@measure
Piece together the equation from its constituents, recognizing current constraints.
If we are in an equation group, this might just save the material on a stack for
later processing.
471 \if\eq@group \grp@push \else \eq@finish\fi
472 }
Ah yes, now the lovely dmath* environment.
473 \newenvironment{dmath*}{%
474 \let\eq@hasNumber\@False \@optarg\@dmath{}%
475 }{}
476 \@namedef{end@dmath*}{\end@dmath}
477 \@namedef{enddmath*}#1{\check@punct@or@qed}
\eq@prelim If \everypar has a non-null value, it’s probably some code from \@afterheading
that sets \clubpenalty and/or removes the parindent box. Both of those actions
are irrelevant and interfering for our purposes and need to be deflected for the
time being. If an equation appears at the very beginning of a list item (possibly
from a trivlist such as proof), we need to trigger the item label.
478 \def\eq@prelim{%
479 \if@inlabel \indent \par \fi
480 \if@nobreak \global\@nobreakfalse \predisplaypenalty\@M \fi
481 \everypar\@emptytoks
If for some reason dmath is called between paragraphs, \noindent is better than
\leavevmode, which would produce an indent box and an empty line to hold it. If
we are in a list environment, \par is defined as {\@@par} to preserve \parshape.
482 \noindent
483 \eq@nulldisplay
484 \par %% \eq@saveparinfo %% needs work
485 \let\intertext\breqn@intertext
486 }
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