preserve_board: Serialization plugin module

Description

Board state can be preserved by serializing all contained objects and restored via de-serialization. This mechanism can be used to power features such as save/restore (via download, as implemented in the default preserve_board plugin), but more refined user experience is conceivable in terms of undo/redo functionality and (automatic) saving of board state. Such enhancements can be implemented in a third-party preserve_board module.

Usage

preserve_board(server = preserve_board_server, ui = preserve_board_ui)
preserve_board_server(id, board, ...)
restore_board(x, new, result, ..., session = get_session())
preserve_board_ui(id, board)
serialize_board(x, blocks, id = NULL, ..., session = get_session())

Value

A plugin container inheriting from preserve_board is returned by preserve_board(), while the UI component (e.g. preserve_board_ui()) is expected to return shiny UI (i.e. shiny::tagList()) and the server component a shiny::reactiveVal() evaluating to NULL or the board to restore.

Arguments

server, ui: Server/UI for the plugin module
id: Namespace ID
board: The initial board object
...: Extra arguments passed from parent scope
x: The current board object
new: Serialized (list-based) representation of the new board
result: A shiny::reactiveVal() to hold the new board object
session: Shiny session
blocks: Block state reactive values

Details

The session$reload() that a restore triggers is handled by the app's board_loader() (passed to serve()), not by the plugin -- the plugin server simply returns the board to restore and never reloads.