ORS directions demo Shiny app https://aoles.shinyapps.io/directions

app.R

library(shiny)
library(leaflet)
library(openrouteservice)

## User interface definition
ui <- bootstrapPage(
  includeScript("busy_indicator.js"),
  includeCSS("style.css"),
  leafletOutput("map", width = "100%", height = "100%"),
  absolutePanel(top = 10, right = 10, id="controls",
                selectInput("profile", "Profile", c(driving = "driving-car",
                                                    cycling = "cycling-regular",
                                                    walking = "foot-walking")),
                conditionalPanel(
                  condition = "input.profile == 'driving-car'",
                  checkboxInput("highways", "Avoid highways", value = FALSE)
                ),
                conditionalPanel(
                  condition = "input.profile != 'driving-car'",
                  checkboxInput("steps", "Avoid steps", value = FALSE)
                )
  ),
  div(id = 'loader')
)

## Application logic
server <- function(input, output) {

  ## Draw map
  output$map <- renderLeaflet({
    leaflet() %>%
      addTiles() %>%
      setView(8.675581, 49.418579, zoom = 9)
  })

  ## Capture clicks and save their coordinates
  points <- reactiveVal(NULL)
  observeEvent(input$map_click, {
    if (nrow(points())>=2 || is.null(points())) {
      points(data.frame(lng = input$map_click$lng, lat = input$map_click$lat))
      leafletProxy("map") %>% clearGeoJSON()
    }
    else {
      points(rbind(points(), c(input$map_click$lng, input$map_click$lat)))
    }
    leafletProxy("map") %>% clearMarkers() %>% addMarkers(points()$lng, points()$lat)
  }, ignoreNULL = TRUE)

  ## Get routing options
  avoid <- reactive({
    if (input$profile == 'driving-car') {
      if (isTRUE(input$highways))
        "highways"
    }
    else if (isTRUE(input$steps))
      "steps"
  })

  ## Compute route
  route <- reactive({
    req(points())
    if (nrow(points()) %% 2 == 0)
      ors_directions(coordinates = points(),
                     profile = input$profile,
                     options = list(avoid_features = avoid()),
                     format = "geojson")
  })

  ## Draw route on map
  observeEvent(route(), {
    leafletProxy("map") %>%
      clearGeoJSON() %>%
      addGeoJSON(route(), fill=FALSE)
  })

}


shinyApp(ui, server)

busy_indicator.js

$(function() {
  $(document).on({

    'shiny:busy': function(event) {
      $('#loader').show();
    },

    'shiny:idle': function(event) {
      $('#loader').hide();
    }

  });
});

style.css

html, body {
  width: 100%;
  height: 100%;
}

#controls {
  background: rgba(255, 255, 255, 0.8);
  padding: 10px;
  border-radius: 5px;
}

/* Center the loader */
#loader {
  position: absolute;
  left: 50%;
  top: 50%;
  z-index: 1;
  width: 150px;
  height: 150px;
  margin: -75px 0 0 -75px;
  border: 16px solid #f3f3f3;
  border-radius: 50%;
  border-top: 16px solid #3498db;
  -webkit-animation: spin 2s linear infinite;
  animation: spin 2s linear infinite;
}

@-webkit-keyframes spin {
  0% { -webkit-transform: rotate(0deg); }
  100% { -webkit-transform: rotate(360deg); }
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}