Data and streaming

Typed-array ingress

Ten minutes of readings a second apart, drawn twice. The only difference is the array the timestamps went up in: seconds since 1970 need thirty-one bits and a `Float32Array` keeps twenty-four, so that copy has rounded every reading into a two-minute step.

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The call

plot.uploadBuffer(values: Float32Array | Float64Array): BufferHandle

Upload a block of scalars and return a handle naming it.

A buffer keeps the precision it arrived in. Use Float64Array for time and for anything where f32's twenty-four bits of mantissa would lose something real: a millisecond timestamp narrowed to f32 rounds every sample into a five-minute bucket, and it does that silently.

calls/typed-array-ingress

const seconds = Float64Array.from({ length: 600 }, (_, i) => 1_760_000_000 + i);
const value = plot.uploadBuffer(Float32Array.from(seconds, (_, i) => signal(i)));
// A buffer keeps the precision it arrived in. Nothing widens the second
// one and nothing narrows the first.
const exact = plot.uploadBuffer(seconds);
const rounded = plot.uploadBuffer(Float32Array.from(seconds));
plot.setCharts({
  charts: [
    {
      series: [
        { x: exact, y: value, label: "time as Float64Array" },
        { x: rounded, y: value, label: "time as Float32Array" },
      ],
      x: { format: "dateTime" },
    },
  ],
});

Also called

1 in the code above, in the order it makes them

plot.setCharts(document: ChartDocument): readonly ChartHandle[]

Draw a document of charts, and get a handle for each one.

The handles come back in document order and are what names a chart afterwards: chartView, setChartView, chartPicked, and the chart on a hover, a hit or any other event. A page linking two charts holds two handles rather than allocating ids.

Replaces the charts and the series each one reads.

Throws rather than drawing a partial document, and a throw leaves the previous document in place. What it refuses: a misspelled key, a handle that names something other than a buffer, a range whose ends are the wrong way round, and a column on a chart kind that cannot read it. All four would otherwise be a chart that draws something subtly wrong, or nothing, with nothing said.

Setting a document again is the way to change one: there is no per-chart edit, and the compile is cheap because the data does not move. The buffers are named by handle, so a live chart writes to them with writeBuffer and never sets a document at all.