fix(hud): carry rounded DMS seconds into the minutes (#1339)

Carry rounded HUD coordinate seconds into minutes and degrees.

Contribution by @rudycelekli.

changelog.d/1339-hud-dms-carry.md

@@ -0,0 +1,3 @@
+- Carry HUD LAT/LON seconds that round up to 60.00" into the minutes and
+  degrees, so longitude -122.35 reads `122°21'00.00"W` instead of
+  `122°20'60.00"W` (rudycelekli, #1339).

docs/CURRENT-STATE.md

@@ -4,6 +4,12 @@ Docker Compose mounts the checkout with the shared SELinux `:z` label so
 containers can read it on enforcing SELinux hosts. The separate image-owned
 `node_modules` volume and loopback-only port publishing remain unchanged.
 
+The HUD's LAT/LON degrees-minutes-seconds readout rounds the coordinate once, to
+hundredths of a second, and then splits it. A value within 0.005" of the next
+whole minute carries into the minutes and degrees, so `-122.35` reads
+`122°21'00.00"W` rather than `122°20'60.00"W`. The field widths and hemisphere
+letters are unchanged.
+
 Aircraft detection candidates reuse normalized display text until callsign or
 registration changes, including in-place enrichment. Each candidate resolves its
 fleet model once per collection. Positions, model ownership and tracked-aircraft

scripts/format-scope.json

@@ -1087,5 +1087,6 @@
   "scripts/qa-status-badges.mjs",
   "src/dockerTrustedPeers.test.mjs",
   "src/cameraGlobeRotation.test.mjs",
-  "src/voice/globeResetConfirmation.test.mjs"
+  "src/voice/globeResetConfirmation.test.mjs",
+  "src/hudDms.test.mjs"
 ]

src/hud.js

@@ -574,11 +574,12 @@ export class IntelHUD {
    * @returns {string} Formatted DMS string, e.g. `"38°53'23.10"N"`.
    */
   _toDMS(decimal, type) {
-    const abs = Math.abs(decimal);
-    const deg = Math.floor(abs);
-    const minFloat = (abs - deg) * 60;
-    const min = Math.floor(minFloat);
-    const sec = ((minFloat - min) * 60).toFixed(2);
+    // Round once, in hundredths of a second, so a value that rounds up to
+    // 60.00" carries into the minutes and degrees instead of printing 60.
+    const hundredths = Math.round(Math.abs(decimal) * 360000);
+    const deg = Math.floor(hundredths / 360000);
+    const min = Math.floor(hundredths / 6000) % 60;
+    const sec = ((hundredths % 6000) / 100).toFixed(2);
 
     let dir;
     if (type === 'lat') dir = decimal >= 0 ? 'N' : 'S';

src/hudDms.test.mjs

@@ -0,0 +1,106 @@
+// The HUD's LAT/LON readout in degrees-minutes-seconds. Seconds are printed to
+// two decimals, so a value within 0.005" of the next whole minute rounds up.
+// That carry must reach the minutes (and degrees): `122°20'60.00"W` is not a
+// coordinate. Ordinary decimal inputs land there through binary floating
+// point: 122.35 - 122 is 0.34999999999999432, so -122.35 read 20'60.00".
+//
+// hud.js imports `mgrs`, a CommonJS package whose named exports Node's ESM
+// loader cannot see, so this installs the same one-specifier stub as
+// hudAltitudeDatum.test.mjs before importing it.
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { registerHooks } from 'node:module';
+
+const MGRS_STUB_URL = 'gev-test-stub:mgrs';
+registerHooks({
+  resolve(specifier, context, next) {
+    if (specifier === 'mgrs') return { url: MGRS_STUB_URL, shortCircuit: true };
+    return next(specifier, context);
+  },
+  load(url, context, next) {
+    if (url === MGRS_STUB_URL) {
+      return {
+        format: 'module',
+        shortCircuit: true,
+        source:
+          'export function forward() { return "10SEG55776339"; }\nexport default { forward };\n',
+      };
+    }
+    return next(url, context);
+  },
+});
+
+const { IntelHUD } = await import('./hud.js');
+
+const toDMS = (decimal, type) => IntelHUD.prototype._toDMS(decimal, type);
+
+test('a rounded-up second carries into the minutes', () => {
+  assert.equal(toDMS(-122.35, 'lon'), `122°21'00.00"W`);
+  assert.equal(toDMS(139.7, 'lon'), `139°42'00.00"E`);
+  assert.equal(toDMS(37.0166666, 'lat'), `37°01'00.00"N`);
+});
+
+test('a carry through 59 minutes reaches the degrees', () => {
+  assert.equal(toDMS(38.999999, 'lat'), `39°00'00.00"N`);
+  assert.equal(toDMS(-0.999999, 'lat'), `01°00'00.00"S`);
+  assert.equal(toDMS(179.999999, 'lon'), `180°00'00.00"E`);
+});
+
+test('ordinary values keep their existing format', () => {
+  assert.equal(toDMS(38.889722, 'lat'), `38°53'23.00"N`);
+  assert.equal(toDMS(-77.035278, 'lon'), `077°02'07.00"W`);
+  assert.equal(toDMS(51.5, 'lat'), `51°30'00.00"N`);
+  assert.equal(toDMS(-33.8568, 'lat'), `33°51'24.48"S`);
+  assert.equal(toDMS(0, 'lon'), `000°00'00.00"E`);
+  assert.equal(toDMS(90, 'lat'), `90°00'00.00"N`);
+});
+
+test('the telemetry tick paints the carried value into both readouts', () => {
+  const elements = new Map(
+    [
+      'hud-alt',
+      'hud-summary',
+      'hud-mgrs',
+      'hud-latlon',
+      'hud-bottom-line',
+      'hud-gsd',
+      'hud-coll',
+      'hud-ona',
+      'hud-mode',
+    ].map((id) => [id, { textContent: '' }]),
+  );
+  const previousDocument = globalThis.document;
+  globalThis.document = {
+    getElementById: (id) => elements.get(id) ?? null,
+    querySelectorAll: () => [],
+    addEventListener() {},
+    removeEventListener() {},
+  };
+  const viewer = {
+    camera: {
+      pitch: -Math.PI / 2,
+      positionCartographic: {
+        latitude: (37.75 * Math.PI) / 180,
+        longitude: (-122.35 * Math.PI) / 180,
+        height: 1500,
+      },
+      computeViewRectangle: () => undefined,
+      moveStart: { addEventListener() {}, removeEventListener() {} },
+      moveEnd: { addEventListener() {}, removeEventListener() {} },
+    },
+  };
+  let hud;
+  try {
+    hud = new IntelHUD(viewer);
+    hud._updateCameraData();
+    const latlon = elements.get('hud-latlon').textContent;
+    const bottom = elements.get('hud-bottom-line').textContent;
+    assert.equal(latlon, `37°45'00.00"N 122°21'00.00"W`);
+    assert.match(bottom, /LON: 122°21'00\.00"W/);
+    assert.doesNotMatch(`${latlon} ${bottom}`, /60\.00"/);
+  } finally {
+    hud?.destroy();
+    if (previousDocument === undefined) delete globalThis.document;
+    else globalThis.document = previousDocument;
+  }
+});