R Leaflet Offline Tiles within Shiny

Question

Is it possible to load offline/local leaflet map tiles within a Shiny app? I am able to load the tiles in an interactive R session as shown here, but I now want to try and load them for use in a Shiny app. Here's an example of what I have so far. I'm thinking it has something to do with Shiny running through an IP and port and needing to load the tiles through an IP and port as well. I've tried a few things to change IPs and ports (making them the same) as explained here but haven't figured out anything that works. I can also get it to work using online tiles, but I need it to work with local map tiles.

library(shiny)
library(leaflet)
library(RColorBrewer)
library(RgoogleMaps)

options(shiny.port = 8000)

  (bwi <- getGeoCode("BWI;MD"))

df <- as.data.frame(rbind(bwi))
df$col <- c("orange")
df$name <- c("BWI")

icons <- awesomeIcons(
  icon = 'ios-close',
  iconColor = 'black',
  library = 'ion',
  markerColor = df$col
)
#################################################################################

ui <- bootstrapPage(
  tags$style(type = "text/css", "html, body {width:100%;height:100%}"),
  leafletOutput("map", width = "100%", height = "100%"),
  absolutePanel(top = 10, right = 10,
                style = "padding: 8px; background: #FFFFEE; opacity:.9",
    checkboxInput("markers", "Show Markers?", TRUE)
  )
)    
#################################################################################

server <- function(input, output, session) {

  output$map <- renderLeaflet({
    leaflet() %>% 
      addTiles(urlTemplate = "http:/localhost:8000/C:/Users/OTAD USER/Documents/mapTiles/ESRIWorldTopoMap/{z}_{x}_{y}.png") %>%
      setView(lat = bwi[1], lng = bwi[2], zoom = 8)
  })

  observe({
    proxy <- leafletProxy("map", data = df)

    # Remove/show any markers
    proxy %>% clearMarkers()
    if (input$markers) {
      proxy %>% addAwesomeMarkers(lat = df$lat, lng = df$lon,
                                  icon = icons, label = df$name)
    }
  })
}

#Put the ui and server together and run
runApp(shinyApp(ui = ui, 
         server = server), launch.browser=TRUE
)

Answer 1

1- You have to authorize shiny to serve tiles in that folder by providing an "alias" on the ressource with addResourcePath

2- then use that alias as the base URL in addTiles

server <- function(input, output, session) {
    addResourcePath("mytiles", "C:/Users/OTAD USER/Documents/mapTiles/ESRIWorldTopoMap")
    output$map <- renderLeaflet({
      leaflet() %>% 
        addTiles(urlTemplate = "/mytiles/{z}_{x}_{y}.png") %>%
        setView(lat = bwi[1], lng = bwi[2], zoom = 8)
    })
...