ADR-0104 A trend is a meter over time

Amends: ADR-0021

#Context

The roster closed at 36 with no way to draw a reading's history. A supervision screen needs one: a pressure that has just crossed its limit and a pressure that has climbed toward it for twenty minutes are different situations, and a meter shows the same bar for both. Carbon keeps charts in a separate library and publishes no sparkline among its components, so ADR-0021's audit of Carbon's roster never met the question.

ADR-0050's test asks what a candidate differs on once its rules are extracted: layer, legal levels, interactivity, governed copy, and the axes added since (vouching, persistence, acknowledgement). Against meter, a sparkline is identical on all of them. What it adds is not a rule but data: a series, and the direction the series took.

#Decision

trend joins the roster in section F, as the meter over time. It is the fifth r136-native component and the thirty-seventh on the roster.

• Layer, levels, variants, marks: the meter's. An Emitter at levels 1 to

3, the three threshold states, attention and critical refused at Ambient (ADR-0044), the shared triangle and octagon beside the reading (ADR-0093), and vouched required (ADR-0048).

• Governed copy: one part, the label, as for the meter. The reading and

the window (span) are the product's words.

• Drawing: a plot on surface-inset, a line through the readings at the

level's weight in the level's mark, the limit across the plot in border-strong, and the newest reading marked at the line's end at the level's size. The plot is target-min tall.

• Words for the line. The component states which way the series went,

rising, falling or steady, in its accessible name, with the reading and the window, so a reader who cannot see the line is told what it did. A change of less than a hundredth of the range reads as steady.

• Motion: a new reading replaces the line. Nothing slides.

Scene 76 measures a panel of six trends on the instrumentation layout, with three themed siblings. All four pass.

#Consequences

• The roster is 37: 25 from Carbon, 4 this system's own, 5 r136-native, 3

from Lightning. roster:check derives every figure.

• linux-x64 has no record for scene 76 until one CI run records it

(standing item 12, reopened).

• The proof product can now show the history behind its readings.

#Rejected

• A chart library. An axis, a legend and a tooltip are a product's

analysis tool, not a supervision signal, and none of them answers a question the ladder asks.

• A trend prop on meter. A bar and a line are different drawings with

different parts; one component carrying both would carry two stylesheets' worth of conditions.