# Extensions Guide

#### DT2 Team

#### 2026-04-29

## How Extensions Work

DT2 loads extensions on demand. Instead of shipping all 15+ extensions to every page, only the CSS/JS for extensions you actually use are included.

There are two ways to specify extensions:

1. Explicit — pass `extensions = c("Buttons", "Select")` to `dt2()`
2. Auto-detection — DT2 scans your `options` list and infers which extensions are needed (this is the default when `extensions = NULL`)

### Listing Available Extensions

    dt2_extensions()
    #>                        name version           dir
    #> Buttons             Buttons   3.2.5       buttons
    #> ColReorder       ColReorder   2.1.1    colreorder
    #> ColumnControl ColumnControl   1.1.0 columncontrol
    #> DateTime           DateTime   1.6.0      datetime
    #> FixedColumns   FixedColumns   5.0.5  fixedcolumns
    #> FixedHeader     FixedHeader   4.0.3   fixedheader
    #> KeyTable           KeyTable  2.12.1      keytable
    #> Responsive       Responsive   3.0.6    responsive
    #> RowGroup           RowGroup   1.6.0      rowgroup
    #> RowReorder       RowReorder   1.5.0    rowreorder
    #> Scroller           Scroller   2.4.3      scroller
    #> SearchBuilder SearchBuilder   1.8.4 searchbuilder
    #> SearchPanes     SearchPanes   2.3.5   searchpanes
    #> Select               Select   3.1.0        select
    #> StateRestore   StateRestore   1.4.2  staterestore

## Buttons (Export / Copy / Print)

The Buttons extension adds export and utility buttons.

    dt2(mtcars[1:15, ], extensions = "Buttons", options = list(
      pageLength = 8,
      layout = list(
        topEnd = list(
          buttons = list("copy", "csv", "excel", "pdf", "print")
        )
      )
    ))

### Grouped Buttons with Labels

    dt2(iris[1:20, ], options = list(
      pageLength = 10,
      layout = list(
        topStart = "pageLength",
        topEnd = list(
          buttons = list(
            list(extend = "collection", text = "Export",
                 buttons = list(
                   list(extend = "copyHtml5", text = "Copy"),
                   list(extend = "csvHtml5"),
                   list(extend = "excelHtml5", title = "My Data"),
                   list(extend = "pdfHtml5",   title = "My Data")
                 )),
            list(extend = "colvis", text = "Columns")
          ),
          search = list(placeholder = "Filter...")
        ),
        bottomEnd = "paging"
      )
    ))

Note: DT2 auto-detected that `layout` contains `buttons`, so it loaded the Buttons extension automatically (no need to set `extensions` explicitly).

## Select (Row Selection)

Enable row selection with the Select extension:

    dt2(iris[1:20, ], options = list(
      select = list(style = "os", items = "row"),
      pageLength = 10
    ))

In Shiny, selected rows are available via `input$<id>_state$selected`.

## Responsive

DT2 enables the Responsive extension by default. Tables fill 100% width and columns that don’t fit are collapsed into expandable child rows.

To disable for a specific table:

    dt2(iris, responsive = FALSE, options = list(pageLength = 5))

To customise Responsive behaviour (e.g., disable child rows):

    dt2(iris, options = list(
      responsive = list(details = FALSE)  # hide overflow silently
    ))

## ColumnControl

ColumnControl adds per-column controls (order indicators, search dropdowns, column visibility) directly in the table header:

    dt2(iris, options = list(
      pageLength = 8,
      columnControl = list("order", "searchDropdown",
        list(
          list(extend = "orderAsc",  text = "Sort Ascending"),
          list(extend = "orderDesc", text = "Sort Descending"),
          "spacer",
          list(extend = "colVisDropdown", text = "Toggle Columns")
        )
      ),
      ordering = list(indicators = FALSE, handler = FALSE)
    ))

## FixedHeader

Keep the header visible while scrolling:

    dt2(iris, options = list(fixedHeader = TRUE, pageLength = 50))

## Combining Extensions

Extensions compose naturally. Here’s Buttons + Select + ColumnControl:

    dt2(iris, options = list(
      pageLength = 8,
      select = list(style = "multi", items = "row"),
      layout = list(
        topEnd = list(
          buttons = list(
            list(extend = "selected",  text = "Selected Only"),
            list(extend = "selectAll", text = "Select All"),
            list(extend = "selectNone", text = "Deselect"),
            "spacer",
            list(extend = "csvHtml5", exportOptions = list(modifier = list(selected = TRUE)))
          )
        )
      ),
      columnControl = list("order", "searchDropdown"),
      ordering = list(indicators = FALSE, handler = FALSE)
    ))

## Adding New Plugins

To add a DataTables plugin not yet in the registry:

1. Add version variable and download commands in `tools/get-dt2-libs.sh`
2. Register it in `R/dt2_extensions.R` (`.dt2_extension_registry()`)
3. Add auto-detection rules in `.dt2_detect_extensions()`
4. Add npm mapping in `R/dt2_check_updates.R` (`.dt2_npm_map()`)
5. Run `bash tools/get-dt2-libs.sh` to download the files
6. Test with `dt2(data, extensions = "YourPlugin")`

The declarative registry in `dt2_extensions.R` is the single source of truth for extension metadata (version, JS files, CSS files, dependencies).

## Updating Library Versions

Check for newer versions of all bundled JS/CSS libraries:

    dt2_check_updates()

    Library            Installed   Latest      Compat.     Status
    -----------------------------------------------------------------
    DataTables         2.3.4       2.3.7       2.3.7       ⚠️  UPDATE
    jQuery             3.7.0       4.0.0       3.7.1       🔒 PINNED [pin: 3.x]
    Buttons            3.2.5       3.2.6       3.2.6       ⚠️  UPDATE
    ...

If you are developing DT2 (working from the source tree), apply compatible updates automatically:

    dt2_update_libs()                    # patch files + download new JS/CSS
    dt2_update_libs(dry_run = TRUE)      # preview without changing anything
    dt2_update_libs(download = FALSE)    # patch R files only (manual download)

Version constraints prevent incompatible upgrades:

- jQuery pinned to 3.x (DataTables 2 requires jQuery 3)
- pdfmake pinned to 0.2.x (0.3.x has breaking changes)
- Bootstrap pinned to 5.x

Libraries marked as `PINNED` are up to date within their allowed range. Edit `.dt2_version_constraints()` to change the allowed ranges.