[R-sig-Geo] "Preselecting" shapes on leaflet map shiny using mapedit::selectmod

[nevil amos]

Hi I  am  putting together a shiny map app in which I want to allow for
selection or deselection of polygons from  a map layer.
Importantly At the beginning of the process I would like a subset of the
polygons to be already selected ( and they can then be deselected using a
click if required).
The final set of selected polygons is then saved to disk.

Ideally I would like to be able ( eg using a shiny action button) to reset
the selection to the pre-selected polygons.

I have the basic click select working fine, but cannot work out how to
pre-select some polygons so that they are dis as selected ( and can be
deselected with a click) at the start of the process.
Secondly is there a way to reset the selection to the pre-selected set.

The pre-selected polygon ids will change  depending on another interactive.

toy example of code is below  with comments about the two issues that I
cannot figure out:

library(shiny)
library(mapedit)
library(leaflet)
outputDir<-getwd()
saveData <- function(data,fileName) {
  # Write the file to the local system
  write.csv(
    x = data,
    file = file.path(outputDir, fileName),
    row.names = FALSE, quote = TRUE
  )
}


# An example se of preslected values for the polygon layer
# in the real app this will change based on other selections in the UI
preselected1<-gadmCHE$NAME_1[1:3]
preselected2<-gadmCHE$NAME_1[5:8]


ui <- fluidPage(
  radioButtons(inputId = "presel",label = "Preselection",choiceNames =
c("preselected1","preselected2"),choices =
c("preselected1","preselected2")),
  actionButton("startSel", "Show Polygons"),
  actionButton("endSel", "Do not Save"),
  actionButton("saveSel","Save Revised Selection"),
  actionButton("resetSel","Reset Selection\n does not work at the moment"),
  selectModUI("selector")

)

server <- function(input, output) {

  ns <<- NS("selector")

  base_map <- leaflet() %>%
  addTiles()%>%
  addPolygons(data =gadmCHE,
              label = ~NAME_1,
              layerId = ~NAME_1,
              group="Polygons")
  #####
  #####
  ####HOW can I feed in the preslected ids to the process so they
  ####are displayed when the polygons group is shown ?
  Selects<<-callModule(selectMod,
                    "selector",
                    base_map,
                    styleFalse = list(fillOpacity =0,
                                      weight = 1,
                                      opacity = 1),
                    styleTrue = list(fillOpacity = 1,
                                     weight= 1,
                                     opacity = 0))
  leafletProxy(ns("map"))%>%
    hideGroup("Polygons")

  observe({selOuts<-Selects()
  selOuts<<-selOuts
  selOut<<-t(selOuts[selOuts$selected==TRUE,"id"])})


  observeEvent(input$startSel,{
*    #####*
*    ####HOW can I feed in the preslected ids to the process so they*
*    ####are displayed when the polygons group is shown ?*
    leafletProxy(ns("map"))%>%
      showGroup("Polygons")})

   observeEvent(input$resetSel,{
    * ####*
*     ####*
*     ####How can I reset the polygons to the preselected set?*
    leafletProxy(ns("map"))%>%
      showGroup("Polygons")})

  observeEvent(input$endSel,{
    leafletProxy(ns("map"))%>%
      hideGroup("Polygons")})

  observeEvent(input$saveSel,{
    outname<-"Revision.csv"
    saveData(selOut,outname)
    rm(outname)
  })

}


shinyApp(ui = ui, server = server)

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