Settle pending Traffic height work when the population empties

A closure that removes the last animated points mid height correction
released the render hold, and animate() then returned before easeHeights()
could run, leaving _heightPending (and getStats().loading) true. Settle
every retained road on its corrected heights before the hold is released.

Adds a regression combining height correction, a late closure and an
empty population.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/layers/traffic/animation.js

@@ -25,6 +25,9 @@ export function createAnimation({
       layerState._enabled &&
       (layerState._dots.length || layerState._heatJamPrim),
     );
+    // Height easing only runs in a held frame. Settle it before releasing, so
+    // a population emptied mid-correction cannot report loading forever.
+    if (!needed && layerState._heightPending) parts.retention.finishHeights();
     if (needed === Boolean(layerState._renderHeld)) return;
     layerState._renderHeld = needed;
     if (needed) {

src/layers/traffic/motion.test.mjs

@@ -565,6 +565,37 @@ test('provisional opposite-direction heights cannot overwrite a measured sibling
   assert.notEqual(forward.waypoints, reverse.waypoints);
 });
 
+test('a closure that empties the population mid-correction settles heights and clears loading before release', (t) => {
+  const h = setup(t);
+  h.parts.retention.reconcile(h.roads(), 450, true);
+  h.settle();
+  assert.equal(h.state._renderHeld, true);
+  const road = h.state._roads[0];
+  // Republishing the sole road starts a height correction.
+  const corrected = h.roads(0, 120);
+  h.parts.retention.reconcile(corrected, 450, true);
+  assert.equal(h.state._heightPending, true);
+  assert.equal(road.heightMoving, true);
+  // The closure arrives before the next population pass, which then removes
+  // the final points after their fade, long before the correction finishes.
+  corrected[0].flow = { level: 0, closure: true };
+  for (let i = 0; i < 20 && h.state._dots.length; i++) h.frame();
+  assert.equal(h.state._dots.length, 0);
+  assert.equal(h.state._heatJamPrim, null);
+  assert.equal(h.state._renderHeld, false);
+  assert.equal(h.state._heightPending, false);
+  assert.equal(h.state._populationPending, false);
+  assert.equal(road.heightMoving, false);
+  assert.ok(
+    Math.abs(C.Cartographic.fromCartesian(road.waypoints[0]).height - 120) <
+      0.01,
+  );
+  // Frames driven by other layers stay idle and cannot revive the work.
+  h.frame();
+  assert.equal(h.state._heightPending, false);
+  assert.equal(h.state._renderHeld, false);
+});
+
 test('large height corrections obey a screen-pixel bound and reuse projection scratch objects', (t) => {
   const h = setup(t);
   h.state._viewer.scene = {

src/layers/traffic/retention.js

@@ -242,6 +242,29 @@ export function createRetention({ state, parts }) {
       road.heightMoving = moving;
     }
   }
+  /**
+   * Settle every retained road on its corrected heights at once. Easing only
+   * runs inside the held animation frame, so once nothing is left to animate
+   * the remaining correction would otherwise stay pending indefinitely.
+   * Published roads whose record was just dropped are settled too, so a later
+   * held frame cannot revive their correction.
+   */
+  function finishHeights() {
+    const roads = new Set(state._roads);
+    for (const record of records.values()) roads.add(record.road);
+    for (const road of roads) {
+      if (!road.heightMoving) continue;
+      for (let i = 0; i < road.waypoints.length; i++)
+        Cesium.Cartesian3.clone(road.targetWaypoints[i], road.waypoints[i]);
+      for (let i = 0; i < road.segmentDist.length; i++)
+        road.segmentDist[i] = Cesium.Cartesian3.distance(
+          road.waypoints[i],
+          road.waypoints[i + 1],
+        );
+      road.heightMoving = false;
+    }
+    state._heightPending = false;
+  }
   function clear() {
     if (timer !== null) {
       if (typeof cancelAnimationFrame === 'function')
@@ -253,5 +276,5 @@ export function createRetention({ state, parts }) {
     state._populationPending = false;
     state._heightPending = false;
   }
-  return { reconcile, easeHeights, clear, refreshCounts };
+  return { reconcile, easeHeights, finishHeights, clear, refreshCounts };
 }