r-ywidget

Reactive widget models whose state is synchronised through Conflict-free Replicated Data Type (CRDT) via the yrs package.

Requirements

• R >= 4.1
• yr, R6
• An xeus-r Jupyter kernel (provides hera) and a frontend that speaks the ywidget comm protocol, e.g. JupyterLab with yjs-widgets.

Usage

make_comm_widget() defines an R6 class whose named attributes are backed by a shared ydoc. Constructing an instance opens a Jupyter comm and keeps the attributes in sync with the connected frontend.

library(ywidget)

# Define a widget class with two synced attributes.
Counter <- make_comm_widget("Counter", label = "", count = 0L)

# Constructing opens the comm and starts syncing. Run this in an xeus-r kernel.
w <- Counter$new(label = "clicks")

# Attributes are active bindings: read and write them directly.
w$count
w$count <- w$count + 1L

# React to changes coming from the frontend.
w$connect(count = function(value) {
  message("count is now ", value)
})

Writes to an attribute update the ydoc and propagate to the frontend; remote changes update the attribute and fire the callbacks registered with $connect().

See also

• yr: the R bindings to the Rust yrs CRDT library.
• yjs-widgets A core CRDT library to build widget frontends.
• ypywidgets A similar Python core widget library from which this project is inspired.