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ResizeGroup is a React component that can be used to help fit the right amount of content within a container. The consumer of the ResizeGroup provides some initial data, a reduce function, and a render function. The render function is responsible for populating the contents of a the container when given some data. The initial data should represent the data that should be rendered when the ResizeGroup has infinite width. If the contents returned by the render function do not fit within the ResizeGroup, the reduce function is called to get a version of the data whose rendered width should be smaller than the data that was just rendered.

An example scenario is shown below, where controls that do not fit on screen are rendered in an overflow menu. The data in this situation is a list of 'primary' controls that are rendered on the top level and a set of overflow controls rendered in the overflow menu. The initial data in this case has all the controls in the primary set. The implementation of onReduceData moves a control from the overflow well into the primary control set.

This component queries the DOM for the dimensions of elements. Too many of these dimension queries will negatively affect the performance of the component and could cause poor interactive performance on websites. One way to reduce the number of measurements performed by the component is to provide a cacheKey in the initial data and in the return value of onReduceData. Two data objects with the same cacheKey are assumed to have the same width, resulting in measurements being skipped for that data object. In the controls with an overflow example, the cacheKey is simply the concatenation of the keys of the controls that appear in the top level.

There is a boolean context property (isMeasured) added to let child components know if they are only being used for measurement purposes. When isMeasured is true, it will signify that the component is not the instance visible to the user. This will not be needed for most scenarios. It is intended to be used to to skip unwanted side effects of mounting a child component more than once. This includes cases where the component makes API requests, requests focus to one of its elements, expensive computations, and/or renders markup unrelated to its size. Be careful not to use this property to change the components rendered output in a way that effects it size in any way.

For more details and examples visit the official docs. The R package cannot handle each and every case, so for advanced use cases you need to work using the original docs to achieve the desired result.





Props to pass to the component. The allowed props are listed below in the Details section.


Object with shiny.tag class suitable for use in the UI of a Shiny app.


  • className string
    Additional css class to apply to the Component

  • componentRef IRefObject<IResizeGroup>
    Optional callback to access the IResizeGroup interface. Use this instead of ref for accessing the public methods and properties of the component.

  • data any
    Initial data to be passed to the onRenderData function. When there is no onGrowData provided, this data should represent what should be passed to the render function when the parent container of the ResizeGroup is at its maximum supported width. A cacheKey property may optionally be included as part of the data. Two data objects with the same cacheKey will be assumed to take up the same width and will prevent measurements. The type of cacheKey is a string.

  • dataDidRender (renderedData: any) => void
    Function to be called every time data is rendered. It provides the data that was actually rendered. A use case would be adding telemetry when a particular control is shown in an overflow well or dropped as a result of onReduceData or to count the number of renders that an implementation of onReduceData triggers.

  • direction ResizeGroupDirection
    Direction of this resize group, vertical or horizontal

  • onGrowData (prevData: any) => any
    Function to be performed on the data in order to increase its width. It is called in scenarios where the container has more room than the previous render and we may be able to fit more content. If there are no more scaling operations to perform on teh data, it should return undefined to prevent an infinite render loop.

  • onReduceData (prevData: any) => any
    Function to be performed on the data in order to reduce its width and make it fit into the given space. If there are no more scaling steps to apply, it should return undefined to prevent an infinite render loop.

  • onRenderData (data: any) => JSX.Element
    Function to render the data. Called when rendering the contents to the screen and when rendering in a hidden div to measure the size of the contents.

  • styles IStyleFunctionOrObject<IResizeGroupStyleProps, IResizeGroupStyles>
    Call to provide customized styling that will layer on top of the variant rules

  • theme ITheme
    Theme provided by HOC.



data <- list(
  items = list(
    "many", "strings", "with", "varying", "length", "sometimes", "very", "short",
    "other", "times", "extraordinarily", "long"
onRenderData <- JS("data => =>
        style: {
          display: 'inline-block',
          backgroundColor: 'orange',
          padding: '10px',
          margin: '10px',
          fontSize: '20px',
onReduceData <- JS("data => ({ items: data.items.slice(0, -1) })")

ui <- function(id) {
  ns <- NS(id)
    p("Resize the browser to see how the elements are hidden when they do not fit:"),
      data = data,
      onRenderData = onRenderData,
      onReduceData = onReduceData

server <- function(id) {
  moduleServer(id, function(input, output, session) {})

if (interactive()) {
  shinyApp(ui("app"), function(input, output) server("app"))