Conditional vertical scrolling in datatables embedded in a shiny app

问题

Actual questions

I have a DataTable interfaced/created via DT::datatable and rendered via DT::renderDataTable.

How do I conditionally enable vertical scrolling by basing the decision on the value of shiny::checkboxInput?
How do I control the height of my datatable when vertical scrolling is enabled?

I'm a bit at loss with exactly understanding the implications of options scrollY and scrollCollapse and their interaction with other options of DT::renderDataTable or the app itself (e.g. vertical scrolling of the "app windows" itself).

Example

In the following example, I tried to make the value of option scrollY of DT::renderDataTable dependent on a checkbox input (input$action_enable_scrolling) as well as an input that defines the height in pixels (input$scrolling_y_limit).

Problem:

The resulting rendered table does not reactively reflect the choice being made. It seems like once the initial value of input$action_enable_scrolling and input$scrolling_y_limit are considered, they cannot be reactively changed anymore

You'll see that by changing the default values the datatable part behaves differently:

DFLT_action_enable_scrolling <- TRUE
DFLT_scrolling_y_limit <- 400

Globals

# Packages ----------------------------------------------------------------

library(shiny)

# Variables ----------------------------------------------------------------

DFLT_action_enable_scrolling <- FALSE
DFLT_scrolling_y_limit <- 800

# Functions ---------------------------------------------------------------

createRecord <- function(input, db) {
  db$data <- rbind(
    db$data,
    data.frame(
      task = input$task,
      time = input$time,
      time_unit = "hour",
      stringsAsFactors = FALSE
    )
  )
}
updateRecord <- function(input, db, selection) {
  db$data[selection,] <- data.frame(
    task = input$task,
    time = input$time,
    time_unit = "hour",
    stringsAsFactors = FALSE
  )
}
deleteRecord <- function(db, selection) {
  db$data <- db$data[-selection,]
}
niceNames <- function(x) {
  s <- strsplit(x, " |_|\\.", perl = TRUE)[[1]]
  paste(toupper(substring(s, 1,1)), substring(s, 2),
    sep = "", collapse = " ")
}

ui <- fluidPage(
  div(
    style = "display:inline-block",
    p(),
    actionButton("action_trigger", "Create")
  ),
  tabsetPanel(
    tabPanel(
      title = "Scrolling options",
        checkboxInput("action_enable_scrolling", "Enable Y-scrolling",
          value = DFLT_action_enable_scrolling),
        numericInput("scrolling_y_limit", "Height limit for Y-scrolling (in px)",
          value = DFLT_scrolling_y_limit)
    )
  ),
  hr(),
  uiOutput("ui_input"),
  hr(),
  h3("Database"),
  DT::dataTableOutput("dt")
)

Server

server <- function(input, output, session) {
  ## Initialize DB //
  db <- reactiveValues(data = data.frame(
    task = character(),
    time = numeric(),
    time_unit = character()
  )[-1,])

  ## UI control //
  ui_control <- reactiveValues(
    case = c("hide", "create", "update")[1],
    selection = NULL,
    refresh = TRUE
  )
  observeEvent(input$action_trigger, {
    ui_control$case <- "create"
  })

  ## Render UI //
  output$ui_input <- renderUI({
    case <- ui_control$case
    if (case == "hide")
      return()

    ## Case dependent input //
    if (case == "create") {
      task <- ifelse(is.null(tmp <- isolate(input$task)), "", tmp)
      time <- ifelse(is.null(tmp <- isolate(input$time)), "", tmp)

      buttons <- div(
        style = "display:inline-block",
        actionButton("action_create", "Create"),
        actionButton("action_cancel", "Cancel")
      )
      updateTextInput(session, "first")
    } else if (case == "update") {
      task <- db$data[ui_control$selection, "task"]
      time <- db$data[ui_control$selection, "time"]
      buttons <- div(
        style = "display:inline-block",
        actionButton("action_update", "Update"),
        actionButton("action_cancel", "Cancel"),
        p(),
        actionButton(
          "action_delete",
          "Delete",
          icon = icon("exclamation-triangle")
        )
      )
    } else {
      stop(sprintf("Invalid case: %s", case))
    }

    tagList(
      textInput("task", "Task", task),
      numericInput("time", "Time", time),
      buttons
    )
  })

  ## CRUD operations //
  observeEvent(input$action_create, {
    createRecord(input, db = db)
    ui_control$case <- "hide"
  })
  observeEvent(input$action_update, {
    updateRecord(input, db = db, selection = ui_control$selection)
    ui_control$refresh <- NULL
    ui_control$refresh <- TRUE
    # ui_control$case <- "hide"
  })
  observeEvent(input$action_delete, {
    deleteRecord(db = db, selection = ui_control$selection)
    tmp <- ui_control$selection[1] - 1
    if (tmp == 0) tmp <- NULL
    ui_control$selection <- tmp
    ui_control$refresh <- NULL
    ui_control$refresh <- TRUE
    # ui_control$case <- "hide"
  })
  observeEvent(input$action_cancel, {
    ui_control$case <- "hide"
  })

  ## Selection //
  observe({
    idx <- input$dt_rows_selected
    ui_control$selection <- idx
  })
  observe({
    idx <- ui_control$selection
    if (!is.null(idx)) {
      ui_control$case <- "update"
    } else {
      ui_control$case <- "hide"
    }
  })

  ## Render table: preparations //
  observeEvent(input$action_enable_scrolling, {
    ui_control$refresh <- NULL
    ui_control$refresh <- TRUE
  })
  observeEvent(input$scrolling_y_limit, {
    ui_control$refresh <- NULL
    ui_control$refresh <- TRUE
  })
  dt_options = reactive({
    scroll <- input$action_enable_scrolling
    list(
      dom = "ltipr",
      autoWidth = TRUE,
      scrollX = TRUE,
      scrollY = if (scroll) {
        sprintf("%spx", input$scrolling_y_limit * 1)
      },
      scrollCollapse = if (scroll) {
        TRUE
      },
      lengthMenu = list(
        c(3, 5, -1),
        c(3, 5, "All")
      ),
      iDisplayLength = 3
    )
  })

  # Render table: DT //
  output$dt <- DT::renderDataTable({
    if (!ui_control$refresh) {
      return()
    }
    ## Note:
    ## Not really necessary for this example use case as `db$data` already
    ## introduces a reactive dependency.
    ## However, that might not always be the case for data I/O when an
    ## actual database is involved. In this case, this part will most likely
    ## have to be informed about required re-rendering by an explicit reactive
    ## value that other parts update upon I/O operations

    tmp <- db$data
    names(tmp) <- sapply(names(tmp), niceNames)
    tmp
  }, selection = "single", options = dt_options())

  # DT proxy //
  proxy <- DT::dataTableProxy("dt")

  ## Keep/restory previous selection //
  observe({
    ui_control$refresh
    DT::selectRows(proxy, as.numeric(ui_control$selection))
  })

  ## Resets //
  observe({
    if (ui_control$case == "create") {
      updateTextInput(session, "task", value = sprintf("Test %s", Sys.time()))
      updateTextInput(session, "time", value = 1)
    }
  })
}

Run

shinyApp(ui, server)

Reference app on Gist

The sections used above are also contained in my reference app which bundles some stuff/learnings that's related to datable functionality in case you're interested:

shiny::runGist("https://gist.github.com/rappster/d48916fbf8e8d0456ae2")

来源：https://stackoverflow.com/questions/34548209/conditional-vertical-scrolling-in-datatables-embedded-in-a-shiny-app

标签

javascript

datatables

Shiny