Delta

<talos-delta> reports the change in a value, not the level: the sign of value − previous picks the arrow (▲ up / ▼ down / ▬ flat), |Δ| is the figure, and colour is the verdict — up is good, down is bad by default, and good="down" flips that for metrics where falling is healthy. The verdict rides the glyph itself, so a glance reads “which way, and is that good” before you read the number. Δ is computed against the last reading, so a fresh element with one value has no prior and shows flat ▬ 0 until value changes again.

Default — first reading

<talos-delta value="42"></talos-delta>

With no prior reading there is no change to report, so the element rests at ▬ 0 in the tertiary (flat) colour. Set value again — via the attribute or el.update(n) — and the next render shows the signed Δ vs this reading.

Direction — up, down, flat

The arrow and colour come from the sign of value − previous. Up reads --talos-success, down reads --talos-danger (with the default good="up"); a step within eps reads flat in the tertiary colour.

<talos-delta value="42"></talos-delta>
<!-- later, against a prior of 40 → ▲ in success -->
el.update(45);
<!-- against a prior of 45 → ▼ in danger -->
el.update(41);

Direction needs a prior, so it only appears once value changes against an earlier reading — feed it each tick to turn a static number into a monitorable one. Pair it beside a level readout: the number is where, the delta is which way and how much.

good=“down” — falling is healthy

<talos-delta value="120" good="down"></talos-delta>

Flips the colour mapping: a downward step reads --talos-success and an upward step reads --talos-danger. For latency, error rate, cost, queue depth — any metric where down is the win — a falling Δ reads green without inverting the data.

precision — decimal places

<talos-delta value="3.14159" precision="2"></talos-delta>

precision sets the decimal places on the magnitude figure (default 0, floored at 0). The arrow and colour are unaffected — only the rendered |Δ| is formatted.

eps — dead-zone

<talos-delta value="50" eps="0.5"></talos-delta>

eps is a dead-zone: any change with |Δ| ≤ eps reads flat (▬, tertiary colour) instead of tripping an arrow. Use it to keep jittery signals from flickering direction on noise (default 0 — every non-zero step shows).

Attributes

value is reactive — re-set it (or call el.update(value)) and the delta recomputes against the prior reading. Exposes ::part(arrow) and ::part(mag) for styling the glyph and figure; --talos-delta-size sets the font size.