r - Shiny saving URL state subpages and tabs

Question

I would like to have a shiny website that keeps the dynamic choices in the URL as output, so you can copy and share the URL. I took this code as an example: https://gist.github.com/amackey/6841cf03e54d021175f0

And modified it to my case, which is a webpage with a navbarPage and multiple tabs per element in the bar.

What I would like is the URL to direct the user to the right element in the first level tabPanel, and the right tab in the second level tabPanel.

This is, if the user has navigated to "Delta Foxtrot" and then to "Hotel", then changed the parameters to #beverage=Tea;milk=TRUE;sugarLumps=3;customer=mycustomer, I would like the URL to send the user to "Delta Foxtrot" -> "Hotel", instead of starting at the first tab of the first panel element.

Ideally I would like a working example, since everything I tried so far hasn't worked.

Any ideas?

# ui.R
library(shiny)

hashProxy <- function(inputoutputID) {
  div(id=inputoutputID,class=inputoutputID,tag("div",""));
}

# Define UI for shiny d3 chatter application
shinyUI(navbarPage('URLtests', id="page", collapsable=TRUE, inverse=FALSE,
 tabPanel("Alfa Bravo",
   tabsetPanel(
    tabPanel("Charlie",
    tags$p("Nothing to see here. Everything is in the 'Delta Foxtrot' 'Hotel' tab")
             )
       )
    )
 ,tabPanel("Delta Foxtrot",
    tabsetPanel(
    tabPanel("Golf",
    tags$p("Nothing to see here. Everything is in the 'Delta Foxtrot' 'Hotel' tab")
             )
    ,tabPanel("Hotel",

    tags$p("This widget is a demonstration of how to preserve input state across sessions, using the URL hash."),
    selectInput("beverage", "Choose a beverage:",
                choices = c("Tea", "Coffee", "Cocoa")),
    checkboxInput("milk", "Milk"),
    sliderInput("sugarLumps", "Sugar Lumps:",
                min=0, max=10, value=3),
    textInput("customer", "Your Name:"),
    includeHTML("URL.js"),
    h3(textOutput("order")),
    hashProxy("hash")
       )
     )
   )
))


# server.R
library(shiny)
url_fields_to_sync <- c("beverage","milk","sugarLumps","customer");

# Define server logic required to respond to d3 requests
shinyServer(function(input, output, clientData) {

  # Generate a plot of the requested variable against mpg and only
  # include outliers if requested
  output$order <- reactiveText(function() {
    paste(input$beverage,
          if(input$milk) "with milk" else ", black",
          "and",
          if (input$sugarLumps == 0) "no" else input$sugarLumps,
          "sugar lumps",
          "for",
          if (input$customer == "") "next customer" else input$customer)
  })

  firstTime <- TRUE

  output$hash <- reactiveText(function() {

    newHash = paste(collapse=";",
                    Map(function(field) {
                          paste(sep="=",
                                field,
                                input[[field]])
                        },
                        url_fields_to_sync))

    # the VERY FIRST time we pass the input hash up.
    return(
      if (!firstTime) {
        newHash
      } else {
        if (is.null(input$hash)) {
          NULL
        } else {
          firstTime<<-F;
          isolate(input$hash)
        }
      }
    )
  })
})


# URL.js
<script type="text/javascript">
(function(){

  this.countValue=0;

  var changeInputsFromHash = function(newHash) {
    // get hash OUTPUT
    var hashVal = $(newHash).data().shinyInputBinding.getValue($(newHash))
    if (hashVal == "") return
    // get values encoded in hash
    var keyVals = hashVal.substring(1).split(";").map(function(x){return x.split("=")})
    // find input bindings corresponding to them
    keyVals.map(function(x) {
      var el=$("#"+x[0])

      if (el.length > 0 && el.val() != x[1]) {

        console.log("Attempting to update input " + x[0] + " with value " + x[1]);
        if (el.attr("type") == "checkbox") {
            el.prop('checked',x[1]=="TRUE")
            el.change()
        } else if(el.attr("type") == "radio") {
          console.log("I don't know how to update radios")
        } else if(el.attr("type") == "slider") {
          // This case should be setValue but it's not implemented in shiny
          el.slider("value",x[1])
          //el.change()
        } else { 
            el.data().shinyInputBinding.setValue(el[0],x[1])
            el.change()
        }
      }
    })
  }

  var HashOutputBinding = new Shiny.OutputBinding();
  $.extend(HashOutputBinding, {
    find: function(scope) {
      return $(scope).find(".hash");
    },
    renderError: function(el,error) {
      console.log("Shiny app failed to calculate new hash");
    },
    renderValue: function(el,data) {
      console.log("Updated hash");
      document.location.hash=data;
      changeInputsFromHash(el);
    }
  });
  Shiny.outputBindings.register(HashOutputBinding);

  var HashInputBinding = new Shiny.InputBinding();
  $.extend(HashInputBinding, {
    find: function(scope) {
      return $(scope).find(".hash");
    },
    getValue: function(el) {
      return document.location.hash;
    },
    subscribe: function(el, callback) {
      window.addEventListener("hashchange",
        function(e) {
          changeInputsFromHash(el);
          callback();
        }
        , false);
    }
  });
  Shiny.inputBindings.register(HashInputBinding);


})()
</script>

EDITED: I ran the example code in the answer, but couldn't get it to work. See screenshot.

Answer 1

UPDATE

Shiny .14 now available on CRAN supports saving app state in a URL. See this article

---

This answer is a more in-depth answer than my first that uses the entire sample code provided by OP. I've decided to add it as a new answer in light of the bounty. My original answer used a simplified version of this so that someone else coming to the answer wouldn't have to read through any extraneous code to find what they're looking for. Hopefully, this extended version will clear up any difficulties you're having. Parts I've added to your R code are surrounded with ### ... ###.

server.r

# server.R
library(shiny)
url_fields_to_sync <- c("beverage","milk","sugarLumps","customer");

# Define server logic required to respond to d3 requests
shinyServer(function(input, output, session) { # session is the common name for this variable, not clientData

  # Generate a plot of the requested variable against mpg and only
  # include outliers if requested
  output$order <- reactiveText(function() {
    paste(input$beverage,
          if(input$milk) "with milk" else ", black",
          "and",
          if (input$sugarLumps == 0) "no" else input$sugarLumps,
          "sugar lumps",
          "for",
          if (input$customer == "") "next customer" else input$customer)
  })

  firstTime <- TRUE

  output$hash <- reactiveText(function() {

    newHash = paste(collapse=";",
                    Map(function(field) {
                          paste(sep="=",
                                field,
                                input[[field]])
                        },
                        url_fields_to_sync))

    # the VERY FIRST time we pass the input hash up.
    return(
      if (!firstTime) {
        newHash
      } else {
        if (is.null(input$hash)) {
          NULL
        } else {
          firstTime<<-F;
          isolate(input$hash)
        }
      }
    )
  })

  ###

  # whenever your input values change, including the navbar and tabpanels, send
  # a message to the client to update the URL with the input variables.
  # setURL is defined in url_handler.js
  observe({
      reactlist <- reactiveValuesToList(input)
      reactvals <- grep("^ss-|^shiny-", names(reactlist), value=TRUE, invert=TRUE) # strip shiny related URL parameters
      reactstr <- lapply(reactlist[reactvals], as.character) # handle conversion of special data types
      session$sendCustomMessage(type='setURL', reactstr)
  })

  observe({ # this observer executes once, when the page loads

      # data is a list when an entry for each variable specified 
      # in the URL. We'll assume the possibility of the following 
      # variables, which may or may not be present:
      #   nav= The navbar tab desired (either Alfa Bravo or Delta Foxtrot)
      #   tab= The desired tab within the specified nav bar tab, e.g., Golf or Hotel
      #   beverage= The desired beverage selection
      #   sugar= The desired number of sugar lumps
      # 
      # If any of these variables aren't specified, they won't be used, and 
      # the tabs and inputs will remain at their default value.
      data <- parseQueryString(session$clientData$url_search)
      # the navbar tab and tabpanel variables are two variables 
      # we have to pass to the client for the update to take place
      # if nav is defined, send a message to the client to set the nav tab
      if (! is.null(data$page)) {
          session$sendCustomMessage(type='setNavbar', data)
      }

      # if the tab variable is defined, send a message to client to update the tab
      if (any(sapply(data[c('alfa_bravo_tabs', 'delta_foxtrot_tabs')], Negate(is.null)))) {
          session$sendCustomMessage(type='setTab', data)
      }

      # the rest of the variables can be set with shiny's update* methods
      if (! is.null(data$beverage)) { # if a variable isn't specified, it will be NULL
          updateSelectInput(session, 'beverage', selected=data$beverage)
      }

      if (! is.null(data$sugarLumps)) {
          sugar <- as.numeric(data$sugarLumps) # variables come in as character, update to numeric
          updateNumericInput(session, 'sugarLumps', value=sugar)
      }
  })

  ###
})

ui.r

library(shiny)

hashProxy <- function(inputoutputID) {
  div(id=inputoutputID,class=inputoutputID,tag("div",""));
}

# Define UI for shiny d3 chatter application
shinyUI(navbarPage('URLtests', id="page", collapsable=TRUE, inverse=FALSE,
 tabPanel("Alfa Bravo",
   tabsetPanel(
    ###
    id='alfa_bravo_tabs', # you need to set an ID for your tabpanels
    ###
    tabPanel("Charlie",
    tags$p("Nothing to see here. Everything is in the 'Delta Foxtrot' 'Hotel' tab")
             )
       )
    )
 ,tabPanel("Delta Foxtrot",
    tabsetPanel(
    ###
    id='delta_foxtrot_tabs', # you need to set an ID for your tabpanels
    ###
    tabPanel("Golf",
    tags$p("Nothing to see here. Everything is in the 'Delta Foxtrot' 'Hotel' tab")
             )
    ,tabPanel("Hotel", id='hotel',

    tags$p("This widget is a demonstration of how to preserve input state across sessions, using the URL hash."),
    selectInput("beverage", "Choose a beverage:",
                choices = c("Tea", "Coffee", "Cocoa")),
    checkboxInput("milk", "Milk"),
    sliderInput("sugarLumps", "Sugar Lumps:",
                min=0, max=10, value=3),
    textInput("customer", "Your Name:"),
    #includeHTML("URL.js"),
    ###
    includeHTML('url_handler.js'), # include the new script
    ###
    h3(textOutput("order")),
    hashProxy("hash")
       )
     )
   )
))

url_handler.js

<script>
Shiny.addCustomMessageHandler('setNavbar',
    function(data) {
        // create a reference to the desired navbar tab. page is the 
        // id of the navbarPage. a:contains says look for 
        // the subelement that contains the contents of data.nav
        var nav_ref = '#page a:contains("' + data.page + '")';
        $(nav_ref).tab('show');
    }
)

Shiny.addCustomMessageHandler('setTab',
    function(data) {
       // pick the right tabpanel ID based on the value of data.nav
       if (data.page == 'Alfa Bravo') {
            var tabpanel_id = 'alfa_bravo_tabs';
       } else {
            var tabpanel_id = 'delta_foxtrot_tabs';
       }
       // combine this with a reference to the desired tab itself.
       var tab_ref = '#' + tabpanel_id + ' a:contains("' + data[tabpanel_id] + '")';
       $(tab_ref).tab('show');
    }
)

Shiny.addCustomMessageHandler('setURL',
    function(data) {
        // make each key and value URL safe (replacing spaces, etc.), then join
        // them and put them in the URL
        var search_terms = [];
        for (var key in data) {
            search_terms.push(encodeURIComponent(key) + '=' + encodeURIComponent(data[key]));
        }
        window.history.pushState('object or string', 'Title', '/?' + search_terms.join('&'));
    }
);

</script>

To test this, call runApp(port=5678) in the directory with your source files. By default, no parameters are specified in the URL, so this will default to the first navbar item and the first tab within that item. To test it with URL parameters, point your browser to: http://127.0.0.1:5678/?nav=Delta%20Foxtrot&tab=Hotel&beverage=Coffee. This should point you to the second navbar tab and the second tab in that navbar item with coffee as the selected beverage.