[tex4ht] At tweak for align and alignat.

Beuthe, Thomas beuthet at aecl.ca
Tue Sep 7 17:05:17 CEST 2010

UNRESTRICTED | ILLIMITÉ

As mentioned earlier, when using htlatex with the
align and alignat environment, by default TeX4ht will
mix html and picmath in this environment.

Putting the whole thing into picmath ends up including the equation
number in to the picture, which is not desirable.
Using the \left. \right. method mentioned in an earlier email
will work to put the individual aligned sections into picmath,
but the vertical alignment between columns may still be wrong,
as illustrated by the following example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
Under certain circumstances, the default behaviour of TeX4ht
can produce somewhat less than desirable results. In the
following mixed mode'' (pic + html) math, note the improper
placement of = and the 1/4 superscript. Note also the improper
placement of the equation numbers (too far to the right.
\begin{align}
A & = B + \left( 1 - C \right) \left( \frac{D}{E}
\right)^{\frac{1}{4}} \\ F & = \frac{1 + 2 \left(
\dfrac{G_g}{H_h} \right) }{1 - I}
\end{align}
Adding a do nothing'' left. and right. pair as well as a
blank notag line helps position of equation number and vertical
placement of equations. It's better than before, but still not
perfect.
\begin{align}
\left. A \right. & \left. = B + \left( 1 - C \right) \left(
\frac{D}{E} \right)^{\frac{1}{4}} \right. \\
& \notag \\[-\baselineskip]
\left. F \right. & \left. = \frac{1 + 2 \left( \dfrac{G_g}{H_h}
\right) }{1 - I} \right.
\end{align}
\end{document}

At least this method gives a little better control without introducing
and special coding that will affect the result if the document is rendered
in LaTeX.

Thomas

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