Gauge chart

A semicircular gauge — value vs target with colour-coded threshold zones and a needle indicator. The default ops/SLA dashboard chart.

The demo reports Apollo 11's Command Module cabin pressure during the trans-lunar coast — ≈ 5.0 psi of pure O₂. NASA adopted the 5-psi standard after the Apollo 1 fire (Jan 1967) ruled out the original 14.7-psi atmosphere; everything above this nominal sits in the orange "caution" band, with the red fault zone at 8 psi.

Source: Apollo 1 — Wikipedia

Public surface

use wisp_chart::indicator::{Gauge, Zone};
use wisp_chart::color::Color;

let gauge = Gauge {
    value: 73.0,
    domain: (0.0, 100.0),
    zones: vec![
        Zone::new((0.0, 60.0),   Color::from_hex("#27ae60").unwrap()),
        Zone::new((60.0, 85.0),  Color::from_hex("#f5a623").unwrap()),
        Zone::new((85.0, 100.0), Color::from_hex("#e74c3c").unwrap()),
    ],
};

let g = gauge.emit_graphics(&theme, Vec2::new(240.0, 160.0));
let _ = stage.add_child(root, g);

let labels = gauge.emit_text_labels(&theme, Vec2::new(240.0, 160.0), &font);
for t in labels { let _ = stage.add_child(root, t); }

Angle convention

Layout primitives

The renderer composes:

1. Track — a neutral-grey full semicircle annular sector.
2. Zones — one annular sector per zone, painted in order (later zones overlap earlier ones).
3. Needle — a thin radial line from the gauge centre to the value's angle on the outer radius.
4. Hub — a small filled circle at the pivot for visual completion.

All four use primitives that landed in AUT-224's arc support — no new geometry needed in wisp.

Theme integration