Simplify LaTeX mark-up for table column widths (ref #3379)

[jfbu]

The \X token is used as column-specifier: this does not define or redefine \X as a LaTeX macro. Using a letter could have led to conflict with user custom column types or table packages. This column specifier takes two arguments which must be positive integers, as produced by LaTeX writer for :widths: option or for equal widths columns. As it always uses \linewidth the latter was not abstracted into a third argument.

There is no new functionality, but it shortens the produced .tex files.

[tk0miya]

LGTM!

[jfbu]

@tk0miya thanks! may I ask you to check again : I have added commit with uses tabular, not tabulary in this case of use of :widths:. Indeed in this case the column widths are all know as a fraction of \linewidth hence use of tabulary is not needed.

Also, in passing I have a bit streamlined else and elif conditionals to make code simpler to read and I have removed a code comment which appears now un-necessary.

Memo: if there was a way for user to specify a target :width: additionally to :widths: this could now be handled easily, with a third argument to the \X columns type which will come in front of \linewidth. This mark-up:

.. table:: My Table
   :width: 80%
   :widths: 20,40,30

would mean that the table occupies 80% of available line width, in the 20:40:30 proportion. But as far as I know currently there is no such option in docutils. Sphinx could add a directive like tabularcolumns but I think it is not too good to add too much target specific directives. But there could be in the same spirit a tablewidth directive. Best would be if docutils allowed syntax like the above. (Together with the :align:, then we could try text flowing around tables like for figures; not easy in LaTeX but partially obtained with wrapfig).

memo2: I tested that our \X column specifier for tabular, tabulary, longtable does also work with tabu package. But tabu is not compatible with threeparttable.

[tk0miya]

LGTM again!

Your idea, the :width: option sounds good. How about propose it to docutils project? I will make patch.

[jfbu]

thanks @tk0miya for re-iterated review and +1 for proposing :width: to docutils. Now merged and CHANGES updated (a542ca2). I fixed an unrelated typo in CHANGES at 87ab6b0.

[jfbu]

about :width: option there is already a proposed patch at the doctutils issue tracker