Toggle Downloading Button in Shiny - r

Question

I have an app which generates a csv file to download. The process takes some time, and I'm trying to display a downloading..... message in the meanwhile. Based on some other answers on SO, I have figured out how to display that message when I'm trying to render a plot/table, but in this case I'm just trying to download a file. Currently, this is what I have-
library(shiny)
library(dplyr)
library(shinyjs)
jsResetCode <- "shinyjs.reset = function() {history.go(0)}" # Define the js method that resets the page
shinyApp(
ui = fluidPage(
useShinyjs(),
extendShinyjs(text = jsResetCode),
tags$head(tags$style(type="text/css", "
#loadmessage {
position: fixed;
bottom: 0px;
right: 0px;
width: 20%;
padding: 10px 0px 10px 0px;
text-align: center;
font-weight: bold;
font-size: 150%;
color: white;
background-color: #034f84;
z-index: 10;}")),
conditionalPanel(condition="$('html').hasClass('shiny-busy')",
tags$div("Loading...",id="loadmessage")),
downloadButton('dwd', "Download!"),
textOutput("text"),
actionButton("calc", 'Calculate'),
actionButton("reset", "Reset"),
dataTableOutput("tbl")
),
server = function(input, output) {
observeEvent(input$reset, {js$reset()}) # Reset the app
output$text <- renderText({
if(input$rnd > 0)
paste("loading....")
})
output$dwd <- downloadHandler(
filename = function(){
paste0("Iris.csv")
},
content = function(file){
Sys.sleep(3)
write.csv(iris, file)
}
)
observeEvent(input$calc, {
Sys.sleep(3)
output$tbl <- DT::renderDataTable(
DT::datatable(iris)
)
})
observe({
if(is.null(input$rnd)){
runjs("
var click = 0;
Shiny.onInputChange('rnd', click)
var dwnldBtn = document.getElementById('dwd')
dwnldBtn.onclick = function() {click += 1; Shiny.onInputChange('rnd', click)}
click = 0;
")
}
})
}
)
This displays the loading... message when I first download the file, but then the message persists. Is there any way that the Loading... message which is displayed during rendering the table can be displayed when trying to download the file too?
Thanks!