ADR-0139 An instrument states its datum, and its scale states its bounds

Amends: ADR-0135

#Context

ADR-0135 gave the meter's figure, tape and arc drawings a required range, a line of the product's words under the reading, for ADR-0089's reason: a number with no unit and no bounds is not a reading. Set in a housing and read at arm's length, the line was the longest thing on the screen. "below keel, 0 to 200 m" under an 18.2 took more room than the reading, and on the engine page every tape carried one.

Marine instruments state the same facts in less. A digital readout carries a large number, a small unit, and the datum it is measured from set small beside it: "295° Mag", "186° T", "120 ft" under a corner label of "Depth". Nothing states a range, because a depth sounder's range is the instrument's capability, not a fact about the water. A gauge prints its first and last numbers on its own scale, where the bounds can be read against the reading rather than beside it.

Building the helm display as a running card also found that a selected Button drew in --wr-selected, a blue the four-theme tier does not emit. In field-night the selected soft key was the one thing on the screen outside the theme's hue, against ADR-0006.

#Decision

range is removed from the instrument drawings. Each still owes its unit.

• A figure may state its reference, the short datum it is measured from ("keel", "mag", "true", "house"), set small under the unit.
• A tape or an arc prints its two ends on its scale. The tape's ends stand to the right of its track and its reading sits under it, so tapes set side by side keep their bars at one length; the arc's ends sit inside its two ends.
• limit is the one threshold a reader has to know, optional, in the product's words, and short ("low 25", "limit 95").

The tokens that carried the range line are note-color and note-size, and carry all three kinds of small print.

A selected Button reads its tier. selected-color resolves to accent-subtle and on-selected-color to text-accent, the same pair the flat blue was, resolved per theme.

The helm display runs as a card, /card/helm on the docs site, under the contract every live tile on davidpaterni.com is mounted with: four pages behind glass in a housing set into a dash, six physical keys under six soft key labels, and a brightness key between the two field themes. ?view=states lays out every page and every key and alarm state.

#Rejected options

Keep range and shorten the words. It keeps ADR-0135's contract. It lost because the words were not the problem: the bounds were stated in the wrong place, as a sentence beside a reading instead of as marks on a scale, and a figure's bounds were not a fact the reader needed.

Drop the bounds entirely. The shortest screen. It lost because a tape with no ends is a bar with no scale; its fill says "some" and not "how much of what".

Style the selected key in the card's own stylesheet. One rule and no token change. It lost because every selected button in field-night has the same fault, not the helm's.

#Consequences

Scene 77 and its three siblings moved on darwin-arm64, and no verdict changed. No other scene renders an instrument drawing or a selected button.

ADR-0089 is unchanged. number-input still owes its range: a field states what it will accept before the reader types, which a scale cannot do for it.