Bull bar

Marks every bar that closes above its open. The payload carries the bar's range so a study can filter on it later.

What it defines

An event bull_bar on every bar where close > open.

Key decisions

Piece	Why it matters
`kind: "flow"`	Enables `events.declare` and `ctx.emit`.
`events.declare` with a payload schema	The contract studies read. Every field has a `description`.
`label` on `ctx.emit`	An emit without a label is dropped.
Early `return` on other bars	Keeps `onBar` cheap when the setup is false.
No `ctx.accum`	The script keeps no state, so it declares no `warmup`.

Full script

meta({
  name: "Bull bar",
  kind: "flow",
  slug: "bull-bar",
  shortName: "BullBar",
});

events.declare({
  id: "bull_bar",
  intent: "signal",
  payload: {
    range: { type: "number", description: "High minus low of the bar" },
    close: { type: "number", description: "Close of the bar" },
  },
  paint: "pin",
});

outputs.declare({
  id: "close_line",
  kind: "line",
  name: "Close",
  color: "#64b5f6",
});

export function onBar(ctx) {
  ctx.plot("close_line", ctx.close);

  if (ctx.close <= ctx.open) return;

  const range = ctx.high - ctx.low;
  ctx.emit(
    "bull_bar",
    { range, close: ctx.close },
    {
      label: `Bull · R=${range.toFixed(2)}`,
      subtitle: `close ${ctx.close.toFixed(2)}`,
      price: ctx.close,
    }
  );
}

timeStart and timeEnd default to the bar's time, so a one-bar event needs neither. Next, EMA cross reads another indicator.

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