New points for a chart on the page, without sending its data again.

A chart follows its assigns: when the data of <.chart> changes, the chart draws again in place, its marks moving to their new places. For a chart that grows a point at a time (a reading every second, the orders of the day), append/5 sends only the new rows: the chart takes them in, keeps the last max of them, and moves.

def mount(_params, _session, socket) do
  if connected?(socket), do: Phoenix.PubSub.subscribe(MyApp.PubSub, "readings")
  {:ok, assign(socket, chart: Fude.line(x: :at, y: :load), readings: Readings.last(60))}
end

def handle_info({:reading, reading}, socket) do
  {:noreply, Fude.Live.append(socket, "load", socket.assigns.chart, [reading], max: 60)}
end

<.chart id="load" chart={@chart} data={@readings} />

The new rows go through the chart's rules as its data does (types, units of time, formats), and are added to its marks: a chart whose marks are its rows (lines, areas and points with no aggregate). A chart that sums or counts its rows draws again from its assigns instead.

The page's table of the data is the one of the last render.