---
title: "Introduction"
author: ""
date: '`r Sys.Date()`'
output:
  beamer_presentation:
    keep_tex: yes
    theme: metropolis
    latex_engine: xelatex
    slide_level: 2
    incremental: no
fontsize: 12pt
classoption: compress
header-includes:
  \setbeamercolor{frametitle}{bg=darkgray}
    \hypersetup{colorlinks,citecolor=orange,filecolor=red,linkcolor=brown,urlcolor=blue}
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)

.normal-code {
  background-color: darkgray;
  border: 3px solid red;
  font-weight: bold;
}

# Load R package
library(tidyverse)

目前，代码周围既没有背景颜色的更改，也没有边框。
<details>
<summary>英文:</summary>
I am trying to highlight (background colors and border) a code block in R Markdown with the output format being beamer presentation. I use the metropolis theme. The sample code is as follows
    ---
    title: &quot;Introduction&quot;
    author: &quot;&quot;
    date: &#39;`r Sys.Date()`&#39;
    output:
      beamer_presentation:
        keep_tex: yes
        theme: metropolis
        latex_engine: xelatex
        slide_level: 2
        incremental: no
    fontsize: 12pt
    classoption: compress
    header-includes:
      \setbeamercolor{frametitle}{bg=darkgray}
        \hypersetup{colorlinks,citecolor=orange,filecolor=red,linkcolor=brown,urlcolor=blue}
    ---
    
    
    ```{r setup, include=FALSE}
    knitr::opts_chunk$set(echo = TRUE)
    ```
    
    ```{css, echo=FALSE}
    .normal-code {
      background-color: darkgray;
      border: 3px solid red;
      font-weight: bold;
    }
    ```
    ## First Slide
    
    ```{r class.source=&quot;normal-code&quot;,warning=FALSE,message=FALSE,eval=TRUE,echo=TRUE}
    # Load R package
    library(tidyverse)
    ```
Currently, there is neither a change of background color nor a border around the code.
</details>
# 答案1
**得分**: 3
CSS在beamer输出上不会产生任何效果。您需要使用与LaTeX相关的解决方案。
我提出了两种解决方案；第一种更简单，而第二种则更复杂（但看起来更好且可自定义）。
## 第一种方法
第一种方法非常简单。只需使用`\definecolor{shadecolor}{RGB}{225, 225, 225}`重新定义`shadecolor`，将其更改为您喜欢的任何颜色，这将更改`Shaded`环境的背景颜色，并使用块选项`class.output="shaded"`。
*注意：`Shaded`被rmarkdown用于代码块，如果您使用`class.output`块选项，`Shaded`也用于代码输出。*
<details>
<summary>英文:</summary>
CSS won&#39;t have any effect on beamer output. You need latex-oriented solutions.
I have proposed two solutions; the first one is simpler whereas the second one gets a bit complicated (but looks better and customizable).
## Approach One
First one is really simple. Just redefine the `shadecolor` with whatever color you like using, `\definecolor{shadecolor}{RGB}{225, 225, 225}` which changes the bg color of `Shaded` environemnt and use chunk opiton `class.output=&quot;shaded&quot;`
*Note: `Shaded` is used by rmarkdown for code blocks and if you use `class.output` chunk option, `Shaded` used for code output too.*
~~~
---
title: &quot;Introduction&quot;
author: &quot;&quot;
date: &#39;`r Sys.Date()`&#39;
output:
  beamer_presentation:
    keep_tex: yes
    theme: metropolis
    latex_engine: xelatex
    slide_level: 2
    incremental: no
fontsize: 12pt
classoption: compress
header-includes:
  - \setbeamercolor{frametitle}{bg=darkgray}
  - \hypersetup{colorlinks,citecolor=orange,filecolor=red,linkcolor=brown,urlcolor=blue}
---
## First Slide
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)

a <- c(1,2,3,4,5)
b <- c(1,2,3,4,5)
df <- data.frame(a, b)
# take a look at our data frame
df

<hr>
[![bg color for code blocks and output][1]][1]
<hr>
## Approach Two
Now for more customization, we may try with [`tcolorbox`](https://www.ctan.org/pkg/tcolorbox) latex package. So in this second approach, I have done the followings,
- Firstly, defined a colored box using `\newtcolorbox` along with options for bg color and border color (Refer to package docs for the details)
- And then secondly, modified the [source and output knitr hooks](https://yihui.org/knitr/hooks/#output-hooks), so that source code and output is wrapped within the previously defined color box. 

\definecolor{shadecolor}{RGB}{249, 247, 223}
\newtcolorbox{codebox}{
    colback=shadecolor,
    colframe=orange,
    boxsep=2pt,
    arc=2pt}

library(knitr)
default_source_hook <- knit_hooks$get('source')
default_output_hook <- knit_hooks$get('output')
knit_hooks$set(
  source = function(x, options) {
    paste0(
      "\n::: {.codebox data-latex=\"\"}\n\n",
      default_source_hook(x, options),
      "\n\n:::\n\n")
  }
)
knit_hooks$set(
  output = function(x, options) {
    paste0(
      "\n::: {.codebox data-latex=\"\"}\n\n",
      default_output_hook(x, options),
      "\n\n:::\n\n")
  }
)
knitr::opts_chunk$set(echo = TRUE)

a <- c(1,2,3,4,5)
b <- c(1,2,3,4,5)
df <- data.frame(a, b)
# take a look at our data frame
df

<hr>
[![customized code block and output block in beamer][2]][2]
  [1]: https://i.stack.imgur.com/6yGTr.png
  [2]: https://i.stack.imgur.com/G0sVn.png
</details>