Download DT::datatable as pdf in shiny app

Question

Is it possible to download a DT::datatable as pdf through a shiny app ?

#app.r
library(shiny)
library(ggplot2)
library(magrittr)
library(DT)
ui <- shinyUI(
  fluidPage(
    column(3,
      
      downloadButton(
        outputId = "downloader",
        label = "Download PDF"
      )
    ),
    column(
      width = 3,
      dataTableOutput("table")
    )
    
  )
)

server <- shinyServer(function(input, output, session){
  
  #****************************************
  #* Reactive Values
  
  table <- reactive({
    mtcars
  })
  

  
  #****************************************
  #* Output Components
  
  output$table <- 
    renderDataTable({
      table()
    })
  
  
  
  #****************************************
  #* Download Handlers
  
  output$downloader <- 
    downloadHandler(
      "results_from_shiny.pdf",
      content = 
        function(file)
        {
          rmarkdown::render(
            input = "report_file.Rmd",
            output_file = "built_report.pdf",
            params = list(table = table()
                          )
          ) 
          readBin(con = "built_report.pdf", 
                  what = "raw",
                  n = file.info("built_report.pdf")[, "size"]) %>%
            writeBin(con = file)
        }
    )
})

shinyApp(ui, server)

and

#report_file.rmd
---
title: "Parameterized Report for Shiny"
output: pdf_document
params:
  table: 'NULL'
---


```{r}
params[["table"]]
```

Answer 1

You can try the pdf button of the Buttons datatables extension. In this way you don't need a downloadHandler. Otherwise, below is a solution using the good old xtable package. For more sophisticated tables, use kableExtra.

library(shiny)
library(DT)
library(xtable)
library(withr)
library(shinybusy)

ui <- fluidPage(
  add_busy_spinner(spin = "cube-grid", onstart = FALSE),
  column(
    width = 3,
    downloadButton(
      outputId = "downloader",
      label = "Download PDF"
    )
  ),
  column(
    width = 3,
    DTOutput("table")
  )
  
)


server <- function(input, output, session){
  
  table <- reactive({
    mtcars
  })
  
  #****************************************
  #* Output Components
  
  output[["table"]] <- renderDT({
    datatable(table())
  })
  
  #****************************************
  #* Download Handlers
  
  output[["downloader"]] <- downloadHandler(
    filename = "results_from_shiny.pdf",
    content = function(file){
      texfile <- paste0(tools::file_path_sans_ext(file), ".tex")
      latex <- print.xtable(
        xtable(table()), print.results = FALSE, 
        floating = FALSE, scalebox = "0.7"
      )
      writeLines(
        c(
          "\\documentclass[12pt]{standalone}",
          "\\usepackage{graphics}",
          "\\usepackage{caption}",
          "\\begin{document}",
          "\\minipage{\\textwidth}",
          latex,
          "\\captionof{table}{My caption}",
          "\\endminipage",
          "\\end{document}"
        ),
        texfile
      )
      with_dir(
        dirname(texfile), 
        tools::texi2pdf(texfile, clean = TRUE)
      )
    }
  )
}

shinyApp(ui, server)