Filter a leaflet map by another leaflet maps click event R

I am currently trying to set something up in my Shiny application where I can click using the input$map_shape_click event on a smaller leaflet map to filter another leaflet map. However, I have hit a bit of a brick wall and the solution I thought might work is resulting in no change to the map. The full replicable application can be found here:

The full code is here:

library(tidyverse)

library(vroom)

library(sf)

library(tigris)

library(leaflet)

library(htmlwidgets)

library(shiny)

library(googleway)

library(leaflet.extras)

library(leaflet.extras2)

library(mapboxapi)

library(fontawesome)

library(mapview)

library(shinyjs)

library(prettymapr)

#Set the working directory
SNALayer <- readRDS("data/SNALayer.RDS")

ULEZLayer <- readRDS("data/ULEZ.RDS")

BoroughLayer <- readRDS("data/borough.RDS")

vars1 <- c(
  "Disable layer..." = "None",
  "Average NO2" = "NO2 Mean",
  "Average NOx" = "NOx Mean"
)

vars2 <- c(
  "Mapbox Standard" = "standard",
  "Mapbox Light" = "light",
  "Mapbox Streets" = "streets",
  "Mapbox Dark" = "dark",
  "Mapbox Satellite" = "satellite"
  
)


# Define UI for application that draws a histogram
ui <- fluidPage(
  useShinyjs(),
  title = "TfL SNA Tool",
  titlePanel(h5("TfL SNA Tool",align = "center",style="background-color:#10006A;color:#FFFFFF;font-size:5em;font-weight:bold;")),
  sidebarPanel(id="sidebar",h5("Pollution Map",style="color:#FFFFFF;font-size:30px;font-weight:bold;"),
               width = 3,
               h5("The pollution map includes a number of air and noise pollution datasets that are aggregated to the SNA cells as average values.
                  The headline data is LAEI data produced to show key air quality metrics such as NO2, NOx and PM2.5/10. More information about the LAEI data
                  can be found in the latest Travel in London report:",
                  style="color:#FFFFFF;font-size:16px;"),
               tags$a(href="https://tfl.gov.uk/corporate/publications-and-reports/travel-in-london-reports", h5("Travel in London Report",style="color:#68e2ed;font-size:16px;"),target="blank"),
               h5("Toggle Map Options:",style="color:#FFFFFF;font-size:20px;font-weight:bold;"),
               checkboxInput(label = h5("On map legend*",style="color:#FFFFFF;font-size:16px;position:relative;top:-7px;"),
                                       inputId = "maplegend",
                                       value=FALSE),
               checkboxInput(label = h5("Scalebar*",style="color:#FFFFFF;font-size:16px;position:relative;top:-7px;"),
                             inputId = "mapscale",
                             value=FALSE),
               checkboxInput(label = h5("Auto-generated title*",style="color:#FFFFFF;font-size:16px;position:relative;top:-7px;"),
                             inputId = "title",
                             value=FALSE),
               h5("* These items will render when the map is downloaded. It is recomended that these items be switched on before the Download Map option is used.",
                  style="color:#FFFFFF;font-size:16px;"),
               h5("Toggle App Options:",style="color:#FFFFFF;font-size:20px;font-weight:bold;"),
               checkboxInput(label = h5("Map Controls**",style="color:#FFFFFF;font-size:16px;position:relative;top:-7px;"),
                             inputId = "mapcontrol",
                             value=TRUE),
               checkboxInput(label = h5("SNA Layer Controls**",style="color:#FFFFFF;font-size:16px;position:relative;top:-7px;"),
                             inputId = "snalayercontrol",
                             value=TRUE),
               h5("** These items will not render when the map is downloaded.",
                  style="color:#FFFFFF;font-size:16px;"),
               tags$div(actionButton(inputId = "exp",label = "Set Default Export Options",icon = shiny::icon("fa-solid fa-map-location-dot",verify_fa = FALSE)),align="center",style="padding:5px;"),
               tags$div(actionButton(inputId = "exp_can",label = "Clear Default Export Options",icon = shiny::icon("fa-solid fa-map",verify_fa = FALSE)),align="center",style="padding:5px;"),
               tags$div(actionButton(inputId = "dl",label = "Download Map",icon = shiny::icon("fa-solid fa-download",verify_fa = FALSE)),align="center",style="padding:5px;")),
  tags$head(tags$style(HTML("#sidebar{background-color:#10006A;"))),
  mainPanel(
    leafletOutput("SNA",width = "auto",height = "auto"),tags$style(type = "text/css", "#SNA {height: calc(97vh - 80px) !important;}"),width = 9),
  absolutePanel(id = "controls",class ="panel panel-default",fixed = TRUE,
                draggable = TRUE,top = 110,left = "auto",right = 35, bottom = "auto",width = 250,height = "auto",
                tags$div("SNA Layer Control",align = "center",style="background-color:#10006A;color:#FFFFFF;font-size:2em;font-weight:bold;padding:10px;"),
                selectInput("baselayer",h5("Base Map",style="color:#FFFFFF;font-weight:bold;"),vars2),
                selectInput("snalayer",h5("SNA Selection",style="color:#FFFFFF;font-weight:bold;"),vars1,selected = "NO2 Mean")),
  absolutePanel(id = "mapcontrols",class ="panel panel-default",fixed = TRUE,
                draggable = TRUE,top = 110,left = "auto",right = "70.0%", bottom = "auto",width = 100,height = "auto",
                tags$div("Map",tags$br(),"Controls",align = "center",style="background-color:#10006A;color:#FFFFFF;font-size:1em;font-weight:bold;padding:10px;"),
                tags$div(actionButton(inputId = "map_zoom_in",shiny::icon("fa-solid fa-plus",verify_fa = FALSE),title ="Zoom In"),actionButton(inputId = "map_zoom_out",shiny::icon("fa-solid fa-minus",verify_fa = FALSE),title ="Zoom Out"),align="center"),
                tags$div(actionButton(inputId = "reset",shiny::icon("fa-solid fa-arrows-to-circle",verify_fa = FALSE)),align="center", style = "padding:10px",title ="Reset Default Extent")),
  absolutePanel(id = "boroughselect",class ="panel panel-default",fixed = TRUE,
               draggable = TRUE,top = 975,left = "auto",right = "60.0%", bottom = "auto",width = 350,height = "auto",
               tags$div("Borough Select",align = "center",style="background-color:#10006A;color:#FFFFFF;font-size:2em;font-weight:bold;padding:10px;"),
               tags$div(leafletOutput("Borough1",width = 300,height = 250),align="center")),
  tags$head(tags$style(HTML("#controls {opacity:0.6;background-color:#10006A;padding:0 20px 20px 20px;transition:opacity 1000ms;transition-delay:500ms;z-index:9998 !important;}#controls:hover{opacity:1;transition:opacity 1000ms;}"))),
  tags$head(tags$style(HTML("#mapcontrols {opacity:0.6;background-color:#10006A;padding:0 10px 10px 10px;transition:opacity 1000ms;transition-delay:500ms;z-index:9999 !important;}#mapcontrols:hover{opacity:1;transition:opacity 1000ms;}"))),
  tags$head(tags$style(HTML("#boroughselect {opacity:0.6;background-color:#10006A;padding:0 10px 10px 10px;transition:opacity 1000ms;transition-delay:500ms;z-index:9999 !important;}#boroughselect:hover{opacity:1;transition:opacity 1000ms;}"))),
  tags$head(tags$style(HTML("#Borough1 {background:#10006A;}")))
)

# Define server logic required to draw a histogram
server <- function(input, output) {

  
  
  
    output$SNA <- renderLeaflet({
      leaflet(options = leafletOptions(minZoom = 11,zoomControl=FALSE)) %>%
        addMapPane("base",zIndex = 410) %>%
        addMapPane("pollution",zIndex = 420) %>%
        addMapPane("overlay",zIndex = 430) %>%
        setView(lng = -0.10932017,
                lat = 51.500493,
                zoom = 11) %>%
        setMaxBounds(lng1 = -0.64469747,
                     lat1 = 51.832822,
                     lng2 = 0.46418831,
                     lat2 = 51.244695) %>%
        addEasyprint(options = easyprintOptions(hidden = TRUE,exportOnly = TRUE,sizeModes = "CurrentSize",hideControlContainer = FALSE))
})  
    output$Borough1 <- renderLeaflet({
      labels4 <- sprintf("<strong>Borough Name:</strong> %s",
                        BoroughLayer$BOROUGH) %>%
        lapply(htmltools::HTML)
      leaflet(options = leafletOptions(minZoom = 8.75,maxZoom = 8.75, zoomControl=FALSE,dragging=FALSE,keyboard=FALSE,tap=FALSE,touchzoom=FALSE,doubleClickZoom=FALSE)) %>%
        setView(lng = -0.10932017,
                lat = 51.500493,
                zoom = 8.75) %>%
        setMaxBounds(lng1 = -0.64469747,
                     lat1 = 51.832822,
                     lng2 = 0.46418831,
                     lat2 = 51.244695) %>%
        addPolygons(data = BoroughLayer,
                    stroke=TRUE,
                    color="white",
                    weight=1,
                    label = labels4,
                    layerId = BoroughLayer$BOROUGH,
                    highlightOptions = highlightOptions(weight = 2,
                                                        color="yellow",
                                                        bringToFront = TRUE,
                                                        fillColor = "#001630"
                    ))
    })
    
    sna_click <- reactiveVal()
    
    observeEvent(input$Borough1_shape_click,{
      if(!is.null(sna_click()) && sna_click() == input$Borough1_shape_click$id) {
        sna_click(NULL)
        }
      else {
        sna_click(input$Borough1_shape_click$id)
        }
    })
    
    filtered_sna <- reactive({
      if (is.null(sna_click())) {
        SNALayer
      }
      else if (!is.null(sna_click())){
        SNALayer %>% dplyr::filter(SNALayer$SNAMaster_Borough %in% sna_click())
      }
        })
    
    
    

    observeEvent(input$exp,{
      updateCheckboxInput(getDefaultReactiveDomain(),"mapscale",value = TRUE)
    })
    
    observeEvent(input$exp,{
      updateCheckboxInput(getDefaultReactiveDomain(),"maplegend",value = TRUE)
    })
    
    observeEvent(input$exp,{
      updateCheckboxInput(getDefaultReactiveDomain(),"title",value = TRUE)
    })
    
    observeEvent(input$exp_can,{
      updateCheckboxInput(getDefaultReactiveDomain(),"mapscale",value = FALSE)
    })
    
    observeEvent(input$exp_can,{
      updateCheckboxInput(getDefaultReactiveDomain(),"maplegend",value = FALSE)
    })
    
    observeEvent(input$exp_can,{
      updateCheckboxInput(getDefaultReactiveDomain(),"title",value = FALSE)
    })
    
    observeEvent(input$mapcontrol,{
      if (input$mapcontrol == TRUE){
        show("mapcontrols",anim = TRUE,animType = "slide")
      }
      else {
        hide("mapcontrols",anim = TRUE,animType = "slide")
      }
    })
    
    observeEvent(input$snalayercontrol,{
      if (input$snalayercontrol == TRUE){
        show("controls",anim = TRUE,animType = "slide")
      }
      else {
        hide("controls",anim = TRUE,animType = "slide")
      }
    })
    
    TitleName <- reactive({
    if (input$snalayer == "None"){
      TitleName <- sprintf("No SNA Layer Selected...")
    }
    else if (input$snalayer == "NO2 Mean"){
      TitleName <- sprintf("Annual Mean NO<sub style='font-size:20px;'>2</sub> (<span>&#xB5;</span>g/m<sup style='font-size:20px;'>3</sup>) LAEI 2019")
    }
    else if (input$snalayer == "NOx Mean"){
      TitleName <- sprintf("Annual Mean NO<sub style='font-size:20px;'>X</sub> (<span>&#xB5;</span>g/m<sup style='font-size:20px;'>3</sup>) LAEI 2019")
    }
  })
    
    observeEvent(input$reset,{
      leafletProxy("SNA") %>%
        setView(lng = -0.10932017,
                lat = 51.500493,
                zoom = 11)
    })
    
    observeEvent(input$map_zoom_in,{
      leafletProxy("SNA") %>%
        setView(lat  = (input$SNA_bounds$north + input$SNA_bounds$south) / 2,
                lng  = (input$SNA_bounds$east + input$SNA_bounds$wes) / 2,
                zoom = input$SNA_zoom + 1)
    })
    
    observeEvent(input$map_zoom_out,{
      leafletProxy("SNA") %>%
        setView(lat  = (input$SNA_bounds$north + input$SNA_bounds$south) / 2,
                lng  = (input$SNA_bounds$east + input$SNA_bounds$wes) / 2,
                zoom = input$SNA_zoom - 1)
    })
 
    observe({
      proxy4 <- leafletProxy("SNA")
      if (input$mapscale == TRUE){
        proxy4 %>%
        addScaleBar(position = "bottomleft",options = scaleBarOptions(maxWidth = 250, metric = TRUE, imperial = TRUE,updateWhenIdle = FALSE))
      }
      else {
        proxy4 %>%
        removeScaleBar()
      }
    })
    
    observe({
      proxy6 <- leafletProxy("SNA")
      if (input$title == TRUE){
        proxy6 %>%
        removeControl("title1") %>%
        addControl(sprintf("<strong style='font-size:40px;color:white;text-shadow:-1px 0 black, 0 1px black, 1px 0 black, 0 -1px black;font-family:arial;'>SNA Pollution Map: %s</strong>",TitleName()),position = "topleft",layerId = "title1",className = "fieldset{border:0}")
      }
      else {
        proxy6 %>%
          removeControl("title1")
      }
    })

    observeEvent(input$baselayer,{
      proxy2 <- leafletProxy("SNA")
      if (input$baselayer == "standard"){
        proxy2 %>%
          clearTiles() %>%
          addMapboxTiles(style_url = "mapbox://styles/joemarangos/cl2g1ochw001s14muumlqzopk", access_token = "hidden",group = "standard",options = pathOptions(pane = "base"))
      }
      else if (input$baselayer == "light"){
        proxy2 %>%
          clearTiles() %>%
          addMapboxTiles(style_url = "mapbox://styles/joemarangos/cl2g1wt17002m14piyxlvvdat", access_token = "hidden",group = "light",options = pathOptions(pane = "base"))
      }
      else if (input$baselayer == "streets"){
        proxy2 %>%
          clearTiles() %>%
          addMapboxTiles(style_url = "mapbox://styles/joemarangos/cl2g1z2ai002b14ksruxzlpe9", access_token = "hidden",group = "streets",options = pathOptions(pane = "base"))
      }
      else if (input$baselayer == "dark"){
        proxy2 %>%
          clearTiles() %>%
          addMapboxTiles(style_url = "mapbox://styles/joemarangos/cl2ex322t001814piusq8f1p0", access_token = "hidden",group = "dark",options = pathOptions(pane = "base"))
      }
      else if (input$baselayer == "satellite"){
        proxy2 %>%
          clearTiles() %>%
          addMapboxTiles(style_url = "mapbox://styles/joemarangos/cl2g1ucmp00d817prb81qbg43", access_token = "hidden",group = "satellite",options = pathOptions(pane = "base"))
      }
    })
    
    observeEvent(input$snalayer, {
        proxy1 <- leafletProxy("SNA")
        labels <- sprintf("<strong>SNA ID:</strong> %s <br/> <strong>Average Polution Value:</strong> %s",
                          SNALayer$SNA_ID,SNALayer$SNAMaster_NO2_mean) %>%
          lapply(htmltools::HTML)
        
        labels2 <- sprintf("<strong>ULEZ</strong>") %>%
          lapply(htmltools::HTML)
        
        labels3 <- sprintf("<strong>SNA ID:</strong> %s <br/> <strong>Average Polution Value:</strong> %s",
                           SNALayer$SNA_ID,SNALayer$SNAMaster_NOX_mean) %>%
          lapply(htmltools::HTML)
        if (input$snalayer == "NO2 Mean"){
          proxy1 %>%
            clearShapes() %>%
            addPolygons(data = filtered_sna(), label = labels,
                        stroke=TRUE,
                        color = "white",
                        weight = .5,
                        smoothFactor = .5,
                        opacity = 1,
                        fillOpacity = 0.6,
                        fillColor = SNALayer$LegendColNO2,
                        group = "NO2 Mean",
                        popup = labels,
                        options = pathOptions(pane = "pollution"),
                        highlightOptions = highlightOptions(weight = 2,
                                                            fillOpacity = 0.8,
                                                            color = "yellow",
                                                            opacity = 1,
                                                            bringToFront = TRUE))}
        else if (input$snalayer == "NOx Mean"){
          proxy1 %>%
            clearShapes() %>%
            addPolygons(data = filtered_sna(), label = labels3,
                        stroke = TRUE,
                        color = "white",
                        weight = .5,
                        smoothFactor = .5,
                        opacity = 1,
                        fillOpacity = 0.6,
                        fillColor = SNALayer$LegendColNOX,
                        group = "NOx Mean",
                        popup = labels3,
                        options = pathOptions(pane = "pollution"),
                        highlightOptions = highlightOptions(weight = 2,
                                                            fillOpacity = 0.8,
                                                            color = "yellow",
                                                            opacity = 1,
                                                            bringToFront = TRUE))
          }
        else if (input$snalayer == "None"){
          proxy1 %>%
            clearShapes()
        }
        })
    
    observeEvent(input$dl,{
      leafletProxy("SNA") %>%
        easyprintMap(sizeModes = "CurrentSize",filename = paste0(Sys.Date(),"_SNA_Custom"))
    })

}


# Run the application 
shinyApp(ui = ui, server = server)

The code in question specifically related to the map interaction is here:

    sna_click <- reactiveVal()
    
    observeEvent(input$Borough1_shape_click,{
      if(!is.null(sna_click()) && sna_click() == input$Borough1_shape_click$id) {
        sna_click(NULL)
        }
      else {
        sna_click(input$Borough1_shape_click$id)
        }
    })
    
    filtered_sna <- reactive({
      if (is.null(sna_click())) {
        SNALayer
      }
      else if (!is.null(sna_click())){
        SNALayer %>% dplyr::filter(SNALayer$SNAMaster_Borough %in% sna_click())
      }
        })
observeEvent(input$snalayer, {
        proxy1 <- leafletProxy("SNA")
        labels <- sprintf("<strong>SNA ID:</strong> %s <br/> <strong>Average Polution Value:</strong> %s",
                          SNALayer$SNA_ID,SNALayer$SNAMaster_NO2_mean) %>%
          lapply(htmltools::HTML)
        
        labels2 <- sprintf("<strong>ULEZ</strong>") %>%
          lapply(htmltools::HTML)
        
        labels3 <- sprintf("<strong>SNA ID:</strong> %s <br/> <strong>Average Polution Value:</strong> %s",
                           SNALayer$SNA_ID,SNALayer$SNAMaster_NOX_mean) %>%
          lapply(htmltools::HTML)
        if (input$snalayer == "NO2 Mean"){
          proxy1 %>%
            clearShapes() %>%
            addPolygons(data = filtered_sna(), label = labels,
                        stroke=TRUE,
                        color = "white",
                        weight = .5,
                        smoothFactor = .5,
                        opacity = 1,
                        fillOpacity = 0.6,
                        fillColor = SNALayer$LegendColNO2,
                        group = "NO2 Mean",
                        popup = labels,
                        options = pathOptions(pane = "pollution"),
                        highlightOptions = highlightOptions(weight = 2,
                                                            fillOpacity = 0.8,
                                                            color = "yellow",
                                                            opacity = 1,
                                                            bringToFront = TRUE))}
        else if (input$snalayer == "NOx Mean"){
          proxy1 %>%
            clearShapes() %>%
            addPolygons(data = filtered_sna(), label = labels3,
                        stroke = TRUE,
                        color = "white",
                        weight = .5,
                        smoothFactor = .5,
                        opacity = 1,
                        fillOpacity = 0.6,
                        fillColor = SNALayer$LegendColNOX,
                        group = "NOx Mean",
                        popup = labels3,
                        options = pathOptions(pane = "pollution"),
                        highlightOptions = highlightOptions(weight = 2,
                                                            fillOpacity = 0.8,
                                                            color = "yellow",
                                                            opacity = 1,
                                                            bringToFront = TRUE))
          }
        else if (input$snalayer == "None"){
          proxy1 %>%
            clearShapes()
        }
        })

The idea is that clicking on the borough map will result in the borough ID being stored as a reactive value and then this value filters the dataset used in the Leaflet Proxy. When I click a map shape on the borough map, it should filter the SNA map to the correct data but instead a click results in nothing changing. Please refer to my github link to get a full oversight of the code and data. I feel like I'm missing something painfully obvious here, what is it?

Thanks,
Joe

I've resolved my own issue. For those trying to replicate, or curious how I resolved this, I added a second observeEvent function for the map_shape_click that also adds polygon proxy to the map.

observeEvent(input$Borough1_shape_click, {
      proxy1 <- leafletProxy("SNA")
      labels <- sprintf("<strong>SNA ID:</strong> %s <br/> <strong>Average Polution Value:</strong> %s",
                        SNALayer$SNA_ID,SNALayer$SNAMaster_NO2_mean) %>%
        lapply(htmltools::HTML)
      
      labels2 <- sprintf("<strong>ULEZ</strong>") %>%
        lapply(htmltools::HTML)
      
      labels3 <- sprintf("<strong>SNA ID:</strong> %s <br/> <strong>Average Polution Value:</strong> %s",
                         SNALayer$SNA_ID,SNALayer$SNAMaster_NOX_mean) %>%
        lapply(htmltools::HTML)
      if (input$snalayer == "NO2 Mean"){
        proxy1 %>%
          clearShapes() %>%
          addPolygons(data = filtered_sna(), label = labels,
                      stroke=TRUE,
                      color = "white",
                      weight = .5,
                      smoothFactor = .5,
                      opacity = 1,
                      fillOpacity = 0.6,
                      fillColor = SNALayer$LegendColNO2,
                      group = "NO2 Mean",
                      popup = labels,
                      options = pathOptions(pane = "pollution"),
                      highlightOptions = highlightOptions(weight = 2,
                                                          fillOpacity = 0.8,
                                                          color = "yellow",
                                                          opacity = 1,
                                                          bringToFront = TRUE))}
      else if (input$snalayer == "NOx Mean"){
        proxy1 %>%
          clearShapes() %>%
          addPolygons(data = filtered_sna(), label = labels3,
                      stroke = TRUE,
                      color = "white",
                      weight = .5,
                      smoothFactor = .5,
                      opacity = 1,
                      fillOpacity = 0.6,
                      fillColor = SNALayer$LegendColNOX,
                      group = "NOx Mean",
                      popup = labels3,
                      options = pathOptions(pane = "pollution"),
                      highlightOptions = highlightOptions(weight = 2,
                                                          fillOpacity = 0.8,
                                                          color = "yellow",
                                                          opacity = 1,
                                                          bringToFront = TRUE))
      }
      else if (input$snalayer == "None"){
        proxy1 %>%
          clearShapes()
      }
    })
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