pasture15_reprex.rmd

---
title: "Leaflet Reprex"
runtime: shiny
output: html_document
---

```{r echo=FALSE, eval=TRUE}
library(leaflet) 

my <- reactiveValues(long=175.619105, lat=-40.386396)
v <- reactiveValues(zoom=5, minzoom=5, maxzoom=15, long=NA, lat=NA) 

isolate({
  cat(file=stderr(), paste("initialise location"), "\n")
  v$long <- my$long
  v$lat <- my$lat
})

#### make initial map ####
output$map <- renderLeaflet({
  cat(file=stderr(), paste("render leaflet"), "\n")
  
    isolate({ # prevent redraw if arguments change

      leaflet(options=leafletOptions(minZoom=v$minzoom, maxZoom=v$maxzoom)) %>%
        setView(v$long, v$lat, zoom=v$zoom)  %>%
        addTiles() %>% # default map
        addMarkers(my$long, my$lat, "layer1", options=pathOptions(clickable=FALSE)) 
      
    })

  }) # end renderLeaflet

#### ui ####
shinyUI(fluidPage(
      leafletOutput("map", width="100%", height=480) # can manipulate size here
)) # end fluidPage

#### react to mouse clicks ####
observeEvent(input$map_click, {
  
  cat(file=stderr(), "\n")
  cat(file=stderr(), paste("observed map_click"), "\n")    

  click <- input$map_click
  my$long <- click$lng
  my$lat <- click$lat

  # mark map
  leafletProxy("map", deferUntilFlush=FALSE) %>%
    addMarkers(my$long, my$lat, "layer1", options=pathOptions(clickable=FALSE)) 
  
}) # end observe mouse click

```