R shiny how to make the column names vertical?

Question

I have below code to use excelR to output a table of mtcars. I want to have the column names in vertical position instead of horizontally, how can I do that? It needs to be in excelR package as the user will need to update some of the information. Thanks!

library(shiny)
library(excelR)

ui <- fluidPage(
  excelOutput("v1")
)

server <- function(input, output, session) {
  df <- reactive({mtcars})

  output$v1 = renderExcel({
    excelTable(df())
  })
}

shinyApp(ui, server)

Edit:

The below answer from gdevaux is greatly appreciated and he has shown me it works on his pc. But somehow we couldn't figure out what went wrong that it didn't work on my Mac or Windows, tried both safari and chrome, R version are updated and tried opening from external browser.

Can someone else run the code below to see if works and if anyone knows what might be the reasons that it didn't work on mine?

Answer 1

You can do it with CSS. Check out CSS documentation on text-orientation property to see the various possibilities of orientation.

library(shiny)
library(excelR)

ui <- fluidPage(
  
  # add CSS
  tags$head(
    tags$style(HTML("
    #your_table .resizable {
      writing-mode: vertical-rl;
      -webkit-text-orientation: sideways;
      text-orientation: sideways;
      }
    "))
  ),
  
  div(
    id = "your_table",
    excelOutput("v1")
  )
  
)

server <- function(input, output, session) {
  df <- reactive({mtcars})
  
  output$v1 = renderExcel({
    excelTable(df())
  })
}

shinyApp(ui, server)

EDIT : not working in RStudio viewer pane or window, you must use "run external"