Is possible to restore the extra space at beginning and end of the table?

[cebarobot]

Hi, everyone, I'm working on an Chinese document using pandoc. I find that the left and right margin of table is weird, like this:

Actually, I prefer something like this:

I find that pandoc add @{} to the begin and end column declaration, like \begin{longtable}[]{@{}ccccc@{}}, which is done here:

pandoc/src/Text/Pandoc/Writers/LaTeX/Table.hs

Lines 102 to 104 in a2dfda0

	$ "\\begin{longtable}[]" <>
	braces ("@{}" <> colDescriptors isSimpleTable tbl <> "@{}")
	-- the @{} removes extra space at beginning and end

Digging more, I find that this feature was imported in the commit 229c225, from 2013.

Why does pandoc remove "extra space at beginning and end"? Also, Is it possible to add a switch to control this feature?

Thanks a lot.

[jgm]

Perhaps @njbart could comment as he suggested this originally (according to the commit).

[jgm]

For what it's worth, I looked in the Chicago Manual of Style (14th edition) and its sample tables don't have that extra space.

[cebarobot]

Get it. I also find that the documentation of booktabs package also remove the extra space by @{}...

However, I still want to add an option to control this, because no extra space is weird in Chinese files. I'd like to contribute some codes to implement this, but I'm still not familar with pandoc.

[cebarobot]

If I want to add such an option, should I add a command option or a varible?

[jgm]

I'm not sure, I'd have to think about this -- and even about whether to have such an option. Any additional switch adds complexity, which is bad.

You could always postprocess the output and remove the @{}. Could even do this in a custom writer.

[cebarobot]

I agree. Currently, I just use sed to remove all @{} as a workaround.

Thanks a lot for your help~

[jgm]

See #3929 -- this is actually a longstanding issue that at least ten people have commented about. I'm actually tempted to simply remove the @{}s, on the grounds that it's better to emit "vanilla", default LaTeX. But I'd like to understand better the reasons for including them, and it would be good to get feedback from lots of people on this.
@tarleb

[tarleb]

I'm all for it and can't think of any real downsides.

[jgm]

Looks like tabularray would allow us to customize this in the preamble:
#7475 (comment)

[jdelker]

Hi @jgm, have you received any objections regarding this issue?
Do you see a chance, that the @{} will be removed soon?

[njbart]

For my part, I am still firmly against any wholesale removal of the @{}. A switch would be ok, though, preferably with a default of “no space“.

My reasons have not changed: Apart from the fact that I personally find tables without spaces much more appealing typographically, the vast majority of reputable style manuals also recommend designing tables without any extra horizontal space at the beginning or the end of a line.

• The Oxford Style Manual (2003) explicity states: “When tables are open at the sides, the horizontal rules should not
  extend beyond the width of the first and last columns.“ – Example:

  

• Tschichold, one of the greatest typographers, provides examples like the following (Asymmetric Typography, 1967):

  

• @jgm noted that the sample tables in CMoS, 14e do not have the extra space; in the 17e, this has not changed. The same goes for the sample tables in Turabian, 9e.

• The AMA Manual of Style, 11e, contains 12 examples of tables without spaces (one example below). The two exceptions are a table with shading, and one containing vertical lines (the latter, according to the Manual, might as well be considered to be a figure).

  

• Burke D. Best practices in table design. Sci Ed. 2021;44:122-125. contains 14 example tables, most of which do not contain spaces. Exceptions involve shading and/or centering of the rightmost colums, but in any case none of the left-justified leftmost columns ever show a space. – Example:

  

• The LaTeX booktabs package, designed to “to enhance the quality of tables”, recommends using @{}, the manual’s examples, accordingly, contain no spaces either.

• The APA manual, 7e, admittedly represents an exception.

[Wandmalfarbe]

Just another perspective on this topic: The Bootstrap tables have had spacing on the sides for years (and use open tables on the sides). Here's the Bootstrap 5 documentation, the Bootstrap 4 documentation and the Bootstrap 1 documentation from 2011.

It seems that tables with the spacing on the sides are totally normal on the web. They are used in the major UI component frameworks:

• Vuetify (https://vuetifyjs.com/en/components/tables/)
• PrimeNG (https://primeng.org/table)
• PrimeFaces (https://www.primefaces.org/showcase/ui/data/datatable/basic.xhtml)
• Angular Material (https://material.angular.io/components/table/overview)
• Chakra UI (https://chakra-ui.com/docs/components/table)
• Ant Design (https://ant.design/components/table)

There are a few frameworks that use bordered tables:

• Foundation (https://get.foundation/sites/docs/table.html)
• Material UI (https://mui.com/material-ui/react-table/)
• Quasar: https://quasar.dev/vue-components/table
• Shadcdn UI (https://ui.shadcn.com/docs/components/data-table)
• Material 3 (https://m2.material.io/components/data-tables)

I also found one Framework that uses unbordered tables without spacing:

• Tailwinds UI (https://tailwindcss.com/plus/ui-blocks/application-ui/lists/tables)

[njbart]

Thanks for the additional data points. However, that might be true for web design, but this discussion is about LaTeX tables. Here, the standards of traditional typography and the advice from authoritative style guides seem more relevant.

And, for what it's worth, there are also reputable web typography manuals that exclusively recommend tables that are open on the sides and where the horizontal rules do not extend beyond the width of the first and last columns.

From Richard Rutter, Web Typography: A Handbook for Designing Beautiful and Effective Responsive Typography (Brighton: Ampersand Type, 2017), p. 139:

Ultimately, my main concern is for Pandoc to keep the no-space option available for LaTeX tables. If there's no switch, just leave things as they are. And if a switch is deemed necessary, keep no-space as the default.

[priiduonu]

Instead of removing @{}, you could insert \setlength{\tabcolsep{0pt}} before the beginning of the table and switch back to default value by inserting \setlength{\tabcolsep{6pt}} at the end.

[jgm]

Interesting suggestion. But wouldn't this also have the effect of removing space between columns? We don't want that.

[priiduonu]

@jgm - you are right, it will remove space between columns as well (as seen in tbl.3 below).

This would affect (mostly, I think) narrow tables. But this could be solved with calculating the fixed column widths for narrow tables, like it is done for page-wide tables. Only instead of normalizing the number of dashes in header separator to 100%, the column widths could be calculated as "number of dashes for current column" divided by the --columns parameter.

As a result, we can:

• leave @{} as it is (and as it should be according my understanding, see tbl.5 below for explanation)
• give the user full control over narrow table's absolute column widths in markdown source (by using the corresponding number of dashes)
• users who produce "striped" tables, can get typographically better result (the colored area does not protrude from table sides)
  (see discussion in issue Disable the generation of smaller tables when using LaTeX/PDF? #3929)

con:

• LaTeX will probably do better job in calculating column widths for narrow tables
• setting tabcolsep=0 will probably affect many existing tables

I'm adding some illustrative material here (I used the showframe package to display the text area).

a) for "narrow" tables:

b) for "wide" tables:

c) and finally, for "narrow" table with calculated fixed widths (see tbl.7):

[jgm]

Thanks for that detailed analysis. Unfortunately we do not always have column widths; many tables in various formats get converted with ColWidthDefault. Since that is a very common case, we need it to work well. Guessing at widths is likely to produce vastly worse output that just letting LaTeX do its thing. Note also that the LaTeX writer doesn't have access to the original (e.g. Markdown) source and couldn't use it to calculate widths.

[jgm]

btw, how do you get the alternating grey bands in the tables?