dynamically change favicon in browser with shiny and R.devices

Readme.md

Favicon from Plot in R Shiny

Once I saw R.devices function toFavicon I just had to figure out how to use it to dynamically change the favicon with a plot from R. Here is one way to accomplish it, but note the dangerous eval(parse(...)) in line 14, so be careful if you are using for nonpersonal use.

Non-Shiny Use

For non-shiny use, we can see it work with htmltools.

library(htmltools)
library(R.devices)

html_print(
  HTML(
    toFavicon( plot(1:10) )
  )
  ,viewer = browseURL #  since RStudio Viewer doesn't show favicon open in browser
)

code.R

library(shiny)
library(htmltools)
library(R.devices)

ui = shinyUI(fluidPage(
  textInput("plotExpr","plot:","plot(1:10)")
  ,uiOutput("fav")
))

server =  function(input, output){
  output$fav= renderUI( {
    return(
      HTML(
        gsub(
          x =  toFavicon( eval(parse(text=input$plotExpr)) )
          ,pattern = '<script>'
          ,replacement='
            <script>
                var l = document.getElementsByTagName("link")
                for( i = 0; i< l.length; i++){
                  if(l[i].rel  && l[i].rel==="icon"){
                    l[i].remove();
                  }
                }
            '
        )
      )
    )
  })
}
  
runApp( list( ui=ui, server=server ) )