rmarkdown 内置的 Pandoc Filter 脚本不支持 beamer 幻灯片输出

[XiangyunHuang]

问题

rmarkdown 自带的两个 lua 脚本 rmarkdown:::pandoc_lua_filters() 对 html 和 pdf 输出自动加持了，但是对 beamer 幻灯片没有启用，感觉有点奇怪（beamer 的输出也是 pdf 呀），一个暗黑的做法是在输出格式的地方如下传递 Pandoc 的参数

pandoc_args: !expr c("--lua-filter", list.files(rmarkdown:::pandoc_lua_filters(), full.names = T)[1])

但是，是不是可以也自动支持一下？

动机

beamer 主题通常自定了很多 block，有了 Pandoc 的 lua 脚本外挂，不需要额外增加上面那个魔法

可重复的例子

---
title: "R Markdown 制作 beamer 幻灯片"
author: "xx"
date: "`r Sys.Date()`"
documentclass: ctexbeamer
output: 
  bookdown::pdf_book: 
    number_sections: yes
    toc: no
    base_format: rmarkdown::beamer_presentation
    latex_engine: xelatex
    citation_package: natbib
    keep_tex: no # yes for debug
    template: null
    theme: Verona 
    pandoc_args: !expr c("--lua-filter", list.files(rmarkdown:::pandoc_lua_filters(), full.names = T)[1])
themeoptions: 
  - colorblocks
biblio-style: plainnat
link-citations: yes
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
```

## 设置主题 {#sec:setup-verona}
 
Ivan Valbusa 开发了 [Verona 主题的 Beamer 模版](https://bitbucket.org/rivanvx/beamer)，
目前 CTAN 上的版本是 0.2，文档说明见 <https://www.ctan.org/pkg/beamer-verona>
这个主题的宏包依赖很少！我很喜欢！

```r
tinytex::tlmgr_install('beamer-verona')
```


## 自定义的块 {#sec:custom-blocks}

::: {.exampleblock data-latex="{提示}"}
提示
:::

::: {.alertblock data-latex="{警告}"}
警告
:::

::: {.block data-latex="{注意}"}
请读者注意
:::

运行环境

xfun::session_info(c('rmarkdown','tinytex','knitr'))
R version 3.6.3 (2020-02-29)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: CentOS Linux 8 (Core), RStudio 1.2.5033

Locale:
  LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8     LC_MONETARY=en_US.UTF-8   
  LC_MESSAGES=en_US.UTF-8    LC_PAPER=en_US.UTF-8       LC_NAME=C                  LC_ADDRESS=C               LC_TELEPHONE=C            
  LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

Package version:
  base64enc_0.1.3  digest_0.6.25    evaluate_0.14    glue_1.4.0       graphics_3.6.3   grDevices_3.6.3  highr_0.8        htmltools_0.4.0  jsonlite_1.6.1  
  knitr_1.28.5     magrittr_1.5     markdown_1.1     methods_3.6.3    mime_0.9         Rcpp_1.0.4.10    rlang_0.4.5.9000 rmarkdown_2.1.3  stats_3.6.3     
  stringi_1.4.6    stringr_1.4.0    tinytex_0.22.2   tools_3.6.3      utils_3.6.3      xfun_0.13        yaml_2.2.1      

Pandoc version: 2.9.2

我想对运行环境应该没什么特殊要求，不一定要上面的开发版

运行输出

输出是一个 PDF 文件，见

beamer-verona.pdf

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[yihui]

之前忘记加了。现在已经加上。谢谢！

[yihui]

我撤销了这个，因为我发现 Pandoc 自己有一些特殊环境，如 https://pandoc.org/MANUAL.html#incremental-lists 这些不能翻译为 LaTeX 环境（::: incremental 不能翻译为 \begin{incremental}）。

如果你的幻灯片中不存在 Pandoc 默认支持的那些幻灯片环境（如 incremental/notes 等），那你可以自己启用我们的支持，不过你的语法不太对：

    pandoc_args: !expr c("--lua-filter", list.files(rmarkdown:::pandoc_lua_filters(), full.names = T)[1])

应该是：

    pandoc_args: !expr rmarkdown:::pandoc_lua_filters("latex-div.lua")

[XiangyunHuang]

@yihui 确实，你的解决方案更好

[yihui]

我又重新加上了，但要注意 ::: {} 里面 data-latex 属性是必需的（你的例子里都有了），这样 rmarkdown 的 Lua 过滤器才不会干涉 Pandoc 的内置环境。

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