input_task_button: Button for launching longer-running operations

Description

input_task_button is a button that can be used in conjuction with shiny::bindEvent() (or the older shiny::eventReactive() and shiny::observeEvent() functions) to trigger actions or recomputation.

It is similar to shiny::actionButton(), except it prevents the user from clicking when its operation is already in progress.

Upon click, it automatically displays a customizable progress message and disables itself; and after the server has dealt with whatever reactivity is triggered from the click, the button automatically reverts to its original appearance and re-enables itself.

Usage

input_task_button(
  id,
  label,
  ...,
  icon = NULL,
  label_busy = "Processing...",
  icon_busy = rlang::missing_arg(),
  type = "primary",
  auto_reset = TRUE
)
update_task_button(id, ..., state = NULL, session = get_current_session())

Arguments

id: The input slot that will be used to access the value.
label: The label of the button while it is in ready (clickable) state; usually a string.
...: Named arguments become attributes to include on the <button> element.
icon: An optional icon to display next to the label while the button is in ready state. See fontawesome::fa_i().
label_busy: The label of the button while it is busy.
icon_busy: The icon to display while the button is busy. By default, fontawesome::fa_i("refresh", class = "fa-spin", "aria-hidden" = "true") is used, which displays a spinning "chasing arrows" icon. You can create spinning icons out of other Font Awesome icons by using the same expression, but replacing "refresh" with a different icon name. See fontawesome::fa_i().
type: One of the Bootstrap theme colors ("primary", "default", "secondary", "success", "danger", "warning", "info", "light", "dark"), or NULL to leave off the Bootstrap-specific button CSS classes altogether.
auto_reset: If TRUE (the default), automatically put the button back in "ready" state after its click is handled by the server.
state: If "busy", put the button into busy/disabled state. If "ready", put the button into ready/enabled state.
session: The session object; using the default is recommended.

Manual button reset

In some advanced use cases, it may be necessary to keep a task button in its busy state even after the normal reactive processing has completed. Calling update_task_button(id, state = "busy") from the server will opt out of any currently pending reset for a specific task button. After doing so, the button can be re-enabled by calling update_task_button(id, state = "ready") after each click's work is complete.

You can also pass an explicit auto_reset = FALSE to input_task_button(), which means that button will never be automatically re-enabled and will require update_task_button(id, state = "ready") to be called each time.

Note that, as a general rule, Shiny's update family of functions do not take effect at the instant that they are called, but are held until the end of the current reactive cycle. So if you have many different reactive calculations and outputs, you don't have to be too careful about when you call update_task_button(id, state = "ready"), as the button on the client will not actually re-enable until the same moment that all of the updated outputs simultaneously sent to the client.

Server value

An integer of class "shinyActionButtonValue". This class differs from ordinary integers in that a value of 0 is considered "falsy". This implies two things:

Event handlers (e.g., shiny::observeEvent(), shiny::eventReactive()) won't execute on initial load.
Input validation (e.g., shiny::req(), shiny::need()) will fail on initial load.

Examples

Run this code

if (FALSE) { # interactive()
library(shiny)
library(bslib)

ui <- page_sidebar(
  sidebar = sidebar(
    open = "always",
    input_task_button("resample", "Resample"),
  ),
  verbatimTextOutput("summary")
)

server <- function(input, output, session) {
  sample <- eventReactive(input$resample, ignoreNULL=FALSE, {
    Sys.sleep(2)  # Make this artificially slow
    rnorm(100)
  })

  output$summary <- renderPrint({
    summary(sample())
  })
}

shinyApp(ui, server)
}