Re: Bold figure caption prefix in docx output with filter

[Stephan Boltzmann <stephan2boltzmann-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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Thanks a lot for not only suggesting an answer, but also explaining how to 
debug Lua filters as well as providing the logging script, which helped me 
a lot.

My final solution looks like this and I hope it is of help to anyone arrive 
at this question via internet search:

function Figure (fig)  -- works on Windows
  if FORMAT:match 'docx' then
    caption = pandoc.utils.stringify(fig.caption.long)
    if (string.find(caption, 'Fig') ~= nil) then
      cap = fig.caption.long[1].content
      fig.caption.long[1].content[1] = pandoc.Strong(cap[1])
      num_suffix = string.gsub(cap[3].text,':','.')
      fig.caption.long[1].content[3] = pandoc.Strong(num_suffix)
      fig_num_string = string.sub(pandoc.utils.stringify(cap[3]), 1, 1)
      fig_num = math.floor(tonumber(fig_num_string))
      if (fig_num > 6) then
        num_str = "S" .. tostring(8-fig_num) .. '.'
        fig.caption.long[1].content[3] = pandoc.Strong(num_str)
      end
    end
  end
  return fig
end

 I'm happy to add when to use short captions:
In case one generates a list of figures in analogy to a table of contents, 
it can be very helpful to have short captions whereas longer captions might 
be required to explain in more detail what is shown in a figure.

William Lupton schrieb am Dienstag, 13. Juni 2023 um 15:57:05 UTC+2:

> I think that the main thing here is that you need to operate on the Figure 
> rather than the Image. Also note that image and figure captions are 
> different: 
>
>    - An image caption is an Inlines list; 
>    https://pandoc.org/lua-filters.html#type-image
>    - A figure caption is a Caption object, which has a long (Blocks list) 
>    caption with option short (Inlines list) caption; 
>    https://pandoc.org/lua-filters.html#type-figure
>
> I'm not quite sure when or if you should use the short figure caption, but 
> am pretty sure that you do need to set the long figure caption.
>
> Finally, a plug for the https://github.com/pandoc-ext/logging module, 
> which can help to shed light on the AST structure. With this document (I 
> guessed your input format):
>
> ![Figure 1: Cat](Cat.png)
>
> ...and with this lua filter (derived from yours):
>
> local logging = require 'logging'
>
> function Figure(fig)
>     logging.temp('figure', fig)
> end
>
> function Image(img)
>     logging.temp('image', img)
>     local caption = pandoc.utils.stringify(img.caption)
>
>     if (string.find(caption, 'Fig') ~= nil) then
>         img.caption[1] = pandoc.Strong(img.caption[1])
>         img.caption[3] = pandoc.Str(string.gsub(img.caption[3].text, ":", 
> "."))
>         img.caption[3] = pandoc.Strong(img.caption[3])
>         local fig_num_string = string.sub(
>             pandoc.utils.stringify(img.caption[3]),1,2)
>         local fig_num = math.floor(tonumber(fig_num_string))
>
>         if (fig_num > 6) then
>             img.caption[3] = pandoc.Strong("S" .. tostring(8-fig_num) .. 
> '.')
>         end
>         img.caption.long = pandoc.Strong('A')
>         img.caption = pandoc.Strong('A')
>     end
>     logging.temp('->', img)
>     return img
> end
>
> ...you get this output:
>
> % pandoc figure.md -L figure.lua
> (#) image Image {
>   attr: Attr {
>     attributes: AttributeList {}
>     classes: List {}
>     identifier: ""
>   }
>   caption: Inlines[5] {
>     [1] Str "Figure"
>     [2] Space
>     [3] Str "1:"
>     [4] Space
>     [5] Str "Cat"
>   }
>   src: "Cat.png"
>   title: ""
> }
> (#) -> Image {
>   attr: Attr {
>     attributes: AttributeList {}
>     classes: List {}
>     identifier: ""
>   }
>   caption: Inlines[1] {
>     [1] Strong {
>       content: Inlines[1] {
>         [1] Str "A"
>       }
>     }
>   }
>   src: "Cat.png"
>   title: ""
> }
> (#) figure Figure {
>   attr: Attr {
>     attributes: AttributeList {}
>     classes: List {}
>     identifier: ""
>   }
>   caption: {
>     long: Blocks[1] {
>       [1] Plain {
>         content: Inlines[5] {
>           [1] Str "Figure"
>           [2] Space
>           [3] Str "1:"
>           [4] Space
>           [5] Str "Cat"
>         }
>       }
>     }
>   }
>   content: Blocks[1] {
>     [1] Plain {
>       content: Inlines[1] {
>         [1] Image {
>           attr: Attr {
>             attributes: AttributeList {}
>             classes: List {}
>             identifier: ""
>           }
>           caption: Inlines[1] {
>             [1] Strong {
>               content: Inlines[1] {
>                 [1] Str "A"
>               }
>             }
>           }
>           src: "Cat.png"
>           title: ""
>         }
>       }
>     }
>   }
> }
> <figure>
> <img src="Cat.png" alt="A" />
> <figcaption>Figure 1: Cat</figcaption>
> </figure>
>
> On Tue, 13 Jun 2023 at 14:16, Stephan Boltzmann <stephan2...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 
> wrote:
>
>> Hello everybody out there using Pandoc,
>>
>> The following Lua (used with RMarkdown in RStudio) filter should put "*Figure 
>> n.*" in bold at the beginning of every figure caption, but it doesn't 
>> change my output:
>>
>> function Image (img)
>>   if FORMAT:match 'docx' then
>>     caption = pandoc.utils.stringify(img.caption)
>>     if (string.find(caption, 'Fig') ~= nil) then
>>       img.caption[1] = pandoc.Strong(img.caption[1])
>>       img.caption[3] = pandoc.Str(string.gsub(img.caption[3].text, ":", 
>> "."))
>>       img.caption[3] = pandoc.Strong(img.caption[3])
>>       fig_num_string = 
>> string.sub(pandoc.utils.stringify(img.caption[3]),1,2)
>>       fig_num = math.floor(tonumber(fig_num_string))
>>       if (fig_num > 6) then
>>         img.caption[3] = pandoc.Strong("S" .. tostring(8-fig_num) .. '.')
>>       end
>>       img.caption.long = pandoc.Strong('A')
>>       img.caption = pandoc.Strong('A')
>>     end
>>   end
>>   print(pandoc.utils.stringify(img.caption.long))
>>   return img
>> end
>>
>> By putting print statements, I can partially verify that the filter 
>> operates on the correct elements, but it doesn't change the output.
>>
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>> .
>>
>

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