Driving the sidebar primitive

Minimal example

library(shiny)
library(blockr.ui)

ui <- fluidPage(
  actionButton("open", "Open sidebar"),
  sidebar_ui("main_sidebar")
)

server <- function(input, output, session) {
  observeEvent(input$open, {
    show_sidebar(
      "main_sidebar",
      title = "Add a new block",
      ui = tagList(
        textInput("block_name", "Name"),
        selectInput("block_kind", "Type", c("data", "transform", "plot")),
        actionButton("confirm", "Add", class = "btn-primary")
      )
    )
  })

  observeEvent(input$confirm, {
    # validate, mutate state, ...
    hide_sidebar("main_sidebar")
  })
}

shinyApp(ui, server)

The inputs inside the body (input$block_name, input$block_kind, input$confirm) live in the calling session - exactly as they would inside a modalDialog(). No nested moduleServer() is required.

Observing user-driven dismissals

Each sidebar_ui() call also registers a Shiny input under the same id, exposing two logical fields:

• input[[id]]$open - TRUE while the panel is open, FALSE once the user closes it (Esc, X button) or the server calls hide_sidebar().
• input[[id]]$pinned - TRUE while the user has the panel pinned.

observe({
  state <- input$main_sidebar
  req(state)
  cat("open:", state$open, " pinned:", state$pinned, "\n")
})

Static body + client-side trigger

For a panel whose body is known at UI-build time (a settings form, a help panel, an “About” sheet), you don’t need a server round-trip to open it. Pre-render the body at sidebar_ui() time and put data-blockr-sidebar-target = "<id>" on any element that should toggle it.

ui <- fluidPage(
  actionButton(
    "settings_btn", icon("gear"),
    `data-blockr-sidebar-target` = "settings_sidebar"
  ),
  sidebar_ui(
    "settings_sidebar",
    side = "left",
    title = "Board options",
    ui = tagList(
      checkboxInput("opt_a", "Option A", value = TRUE),
      sliderInput("opt_b", "Option B", min = 0, max = 100, value = 50)
    )
  )
)

Clicking the gear toggles the panel open / closed entirely on the client. The inputs inside (input$opt_a, input$opt_b) are observable from the server exactly as if they sat in the page directly. A later show_sidebar("settings_sidebar") (no ui) still opens the panel from the server when needed; show_sidebar("settings_sidebar", ui = <tags>) replaces the pre-rendered body if you want to swap it dynamically.

One id per concern

show_sidebar() replaces the panel’s body and title in place, and pin state is bound to the panel element. Re-showing the same panel with fresh content from the same caller (the “chain after confirm” flow, which keep_or_hide_sidebar() builds on) is the supported pattern.

Two unrelated concerns - say a “Settings” panel and an “Add block” form - should mount two sidebar_ui() panels with distinct ids. Sharing one id between unrelated callers means the second show_sidebar() will silently overwrite the first, including any pinned content the user expected to stay put.

Auto-open on an empty board

A common renderer pattern is to open the sidebar with a “first block” hint when the session starts on an empty board, while still respecting a later user dismissal. The recipe is built on top of show_sidebar() and input[[id]]$open - no special opt-in is needed on sidebar_ui().

empty_board_renderer <- function(id, board) {
  moduleServer(id, function(input, output, session) {
    auto_opened <- reactiveVal(FALSE)

    observe({
      if (auto_opened()) return()
      if (length(blockr.core::board_blocks(board)) > 0L) return()

      show_sidebar(
        session$ns("main_sidebar"),
        title = "Add your first block",
        ui = tagList(
          p("Pick a block to get started."),
          actionButton(session$ns("add_dataset"), "Dataset block"),
          actionButton(session$ns("add_import"), "Import data")
        )
      )
      auto_opened(TRUE)
    })

    # Once the user dismisses the hint, input[[id]]$open flips to FALSE
    # and the auto_opened flag prevents this observer from re-opening.
  })
}

Push-mode panels reflow the page content via padding on <html>, driven by --blockr-sidebar-width-left and --blockr-sidebar-width-right custom properties (both nonzero when both sides are open). The legacy --blockr-sidebar-width is also set to the open side’s width when a single panel is open, so existing consumers of the form margin-right: var(--blockr-sidebar-width, 0px) keep working.