Re: Lua filter to modify captions in tables

[Albert Krewinkel <albert+pandoc-9EawChwDxG8hFhg+JK9F0w@public.gmane.org>]

Abhishek Ulayil <abhiman2000-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:

> I was working on a lua filter to change the Table caption to add
> numbering
>
> ```
> tables = 0
> function Table(el)
>     tables = tables + 1
>     local caption = "Table " .. tostring(tables) .. ": " ..
>       pandoc.utils.stringify(el.caption)
>     print(caption)
>
>     el.caption = caption --facing problem here
>     return el
> end
> ```
>
> I am facing a problem to set the caption back to the element,
>
> what will be the correct way to set the caption.

Captions consist of two parts, the normal (long) caption and a shorter
(short) description that can be used in a list of tables, for example.
The problematic line should be changed to

    el.caption.long = caption

As you noticed, it's not very user-friendly though, and we should
definitely improve that.

You'll probably want to keep the markup in the caption. I'm attaching a
version that's a bit longer, but will preserve the caption's markup.

HTH!


```
tables = 0
function Table(el)
  tables = tables + 1
  local label = pandoc.Inlines("Table " .. tostring(tables))
  local caption = el.caption.long
  if not caption[1] then
    -- Table has no caption, just add the label
    caption = pandoc.Blocks{label}
  elseif caption[1].tag == 'Plain' or caption[1].tag == 'Para' then
    -- Prepend label to paragraph
    label:extend{pandoc.Str ':', pandoc.Space()}
    caption[1].content = label .. caption[1].content
  else
    -- Add label as plain block element
    label:extend{pandoc.Str ':', pandoc.Space()}
    caption:insert(1, pandoc.Plain(label))
  end

  el.caption.long = caption
  return el
end
```