Add a popover to a UI element

Display additional information when clicking on a UI element (typically a button).

Usage

popover(
  trigger,
  ...,
  title = NULL,
  id = NULL,
  placement = c("auto", "top", "right", "bottom", "left"),
  options = list()
)

toggle_popover(id, show = NULL, session = get_current_session())

update_popover(id, ..., title = NULL, session = get_current_session())

Arguments

trigger: The UI element to serve as the popover trigger (typically a shiny::actionButton() or similar). If trigger renders as multiple HTML elements (e.g., it's a tagList()), the last HTML element is used for the trigger. If the trigger should contain all of those elements, wrap the object in a div() or span().
...: UI elements for the popover's body. Character strings are automatically escaped unless marked as HTML().
title: A title (header) for the popover. To remove a header with update_popover(), provide a either an empty string or character(0).
id: A character string. Required to re-actively respond to the visibility of the popover (via the input[[id]] value) and/or update the visibility/contents of the popover.
placement: The placement of the popover relative to its trigger.
options: A list of additional options.
show: Whether to show (TRUE) or hide (FALSE) the popover. The default (NULL) will show if currently hidden and hide if currently shown. Note that a popover will not be shown if the trigger is not visible (e.g., it's hidden behind a tab).
session: A Shiny session object (the default should almost always be used).

Functions

popover(): Add a popover to a UI element
toggle_popover(): Programmatically show/hide a popover.
update_popover(): Update the contents of a popover.

Closing popovers

In addition to clicking the close_button, popovers can be closed by pressing the Esc/Space key when the popover (and/or its trigger) is focused.

Theming/Styling

Like other bslib components, popovers can be themed by supplying relevant theming variables to bs_theme(), which effects styling of every popover on the page. To style a specific popover differently from other popover, utilize the customClass option:

popover(
  "Trigger", "Popover message",
  options = list(customClass = "my-pop")
)

And then add relevant rules to bs_theme() via bs_add_rules():

bs_theme() |> bs_add_rules(".my-pop { max-width: none; }")

Accessibility of Popover Triggers

Because the user needs to interact with the trigger element to see the popover, it's best practice to use an element that is typically accessible via keyboard interactions, like a button or a link. If you use a non-interactive element, like a <span> or text, bslib will automatically add the tabindex="0" attribute to the trigger element to make sure that users can reach the element with the keyboard. This means that in most cases you can use any element you want as the trigger.

One place where it's important to consider the accessibility of the trigger is when using an icon without any accompanying text. In these cases, many R packages that provide icons will create an icon element with the assumption that the icon is decorative, which will make it inaccessible to users of assistive technologies.

When using an icon as the primary trigger, ensure that the icon does not have aria-hidden="true" or role="presentation" attributes. Icon packages typically provide a way to specify a title for the icon, as well as a way to specify that the icon is not decorative. The title should be a short description of the purpose of the trigger, rather than a description of the icon itself.

If you're using bsicons::bs_icon(), provide a title.
If you're using fontawesome::fa(), set a11y = "sem" and provide a title.

For example:

popover(
  bsicons::bs_icon("gear", title = "Settings"),
  title = "Settings",
  sliderInput("n", "Number of points", 1, 100, 50)
)

popover(
  fontawesome::fa("gear", a11y = "sem", title = "Settings"),
  title = "Settings",
  sliderInput("n", "Number of points", 1, 100, 50)
)

References

Popovers are based on Bootstrap's Popover component. See the bslib website for an interactive introduction to tooltips and popovers.

Examples

if (FALSE) { # rlang::is_interactive()

popover(
  shiny::actionButton("btn", "A button"),
  "Popover body content...",
  title = "Popover title"
)

library(shiny)

ui <- page_fixed(
  card(class = "mt-5",
    card_header(
      popover(
        uiOutput("card_title", inline = TRUE),
        title = "Provide a new title",
        textInput("card_title", NULL, "An editable title")
      )
    ),
    "The card body..."
  )
)

server <- function(input, output) {
  output$card_title <- renderUI({
    list(input$card_title, bsicons::bs_icon("pencil-square"))
  })
}

shinyApp(ui, server)
}