how do i know which tab is exposed in an observeEvent()?

I need to know, within observeEvent( ... ) whether a particular tab is exposed in the interface. How do I do this? This is similar to the workaround suggested in https://github.com/rstudio/leaflet/issues/590 but with shiny, namely, by adding an "id" to the tabSetPanel(). Can I do this with flexdashboard so I can reference its state within observeEvent()???

ui <- fluidPage(
  tabsetPanel(
    id = "tab_being_displayed", # will set input$tab_being_displayed
    tabPanel("Tab 1"),
    tabPanel("Map Tab",
             leafletOutput("map"),
             selectInput("colors", "Color Scheme",
                         rownames(subset(brewer.pal.info, category %in% c("seq", "div")))
             )
    ),
    selected = "Tab 1"
  )
)

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

  # Leaflet Output
  output$map <- renderLeaflet({
    leaflet(quakes) %>% addTiles() %>%
      fitBounds(~min(long), ~min(lat), ~max(long), ~max(lat))
  })
  
 
  # leaflet Proxy
  observe({
    req(input$tab_being_displayed == "Map Tab") # Only display if tab is 'Map Tab'
    # code here.
  })
}

Start with the supplied R tabsetPanel and observeEvent example, then review the linked Leaflet issue for the proposed tab-state workaround. Reproduce the flexdashboard case and determine whether the active tab is exposed to observeEvent; done means documenting the supported approach or confirming the limitation.