refactor(street-level): draw the selected sequence as its own line; drop old-zoom tiles at once

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

src/layers/streetLevel/providers/mapillary/coverage.js

@@ -17,8 +17,6 @@ import {
   SEQUENCE_VIEW_RANGE_PER_HEIGHT,
 } from './policy.js';
 
-/** Old-zoom tiles are kept at most this long after a zoom change. */
-const STALE_TILE_MAX_MS = 6000;
 /** Sequences per primitive: smaller batches build, and show, sooner. */
 const SEQUENCE_PRIMITIVE_BATCH = 120;
 
@@ -26,32 +24,48 @@ const PER_TILE_SEQUENCE_CAP = Math.floor(
   COVERAGE_MAX_SEQUENCES / COVERAGE_MAX_TILES,
 );
 
-/** Colour for a sequence: Mapillary green, GEV cyan while selected. */
-function sequenceColor({ selected = false } = {}) {
-  return selected
-    ? Cesium.Color.fromCssColorString(COLORS.selected)
-    : Cesium.Color.fromCssColorString(COLORS.coverage).withAlpha(0.92);
-}
-
-/** Separates a multi-part sequence's part index from its id in pick ids. */
-const PART_SEPARATOR = '~';
-
-/** Pick ids for every part of a sequence; the first part is unsuffixed. */
-function partIds(sequence) {
-  return sequence.parts.map((_, index) =>
-    index
-      ? `${PICK_PREFIX.sequence}${sequence.id}${PART_SEPARATOR}${index}`
-      : `${PICK_PREFIX.sequence}${sequence.id}`,
-  );
-}
-
-/** Sequence id for any part's pick id (`mly:seq:<id>[~<part>]`), else null. */
+/** Sequence id for a line's pick id (`mly:seq:<id>`), else null. */
 export function sequenceIdFromPick(pickId) {
   if (typeof pickId !== 'string' || !pickId.startsWith(PICK_PREFIX.sequence))
     return null;
-  const rest = pickId.slice(PICK_PREFIX.sequence.length);
-  const cut = rest.indexOf(PART_SEPARATOR);
-  return cut === -1 ? rest : rest.slice(0, cut);
+  return pickId.slice(PICK_PREFIX.sequence.length);
+}
+
+/** Line instances for sequences' parts, every part picking its sequence. */
+function lineInstances(sequences, color, width) {
+  const attributes = {
+    color: Cesium.ColorGeometryInstanceAttribute.fromColor(color),
+  };
+  const instances = [];
+  for (const sequence of sequences)
+    for (const coordinates of sequence.parts) {
+      let positions;
+      try {
+        positions = Cesium.Cartesian3.fromDegreesArray(coordinates.flat());
+      } catch {
+        continue;
+      }
+      if (positions.length < 2) continue;
+      instances.push(
+        new Cesium.GeometryInstance({
+          geometry: new Cesium.GroundPolylineGeometry({ positions, width }),
+          id: `${PICK_PREFIX.sequence}${sequence.id}`,
+          attributes,
+        }),
+      );
+    }
+  return instances;
+}
+
+/** Draped lines that follow terrain and 3D tiles (Google 3D) alike. */
+function linePrimitive(geometryInstances, asynchronous) {
+  return new Cesium.GroundPolylinePrimitive({
+    geometryInstances,
+    appearance: new Cesium.PolylineColorAppearance(),
+    classificationType: Cesium.ClassificationType.BOTH,
+    asynchronous,
+    allowPicking: true,
+  });
 }
 
 /** Hint above the street-zoom ceiling, where no coverage is drawn. */
@@ -99,54 +113,48 @@ export function createCoverage({ state, source }) {
     return drawn;
   }
 
-  /**
-   * Batched draped primitives for a tile's sequence parts. Each batch records
-   * the selection its colours were built with.
-   */
+  /** Batched draped primitives for a tile's sequences. */
   function buildSequencePrimitives(sequences) {
-    const selectedId = state.sequence.selectedId ?? null;
-    const instances = [];
-    for (const sequence of sequences) {
-      const color = Cesium.ColorGeometryInstanceAttribute.fromColor(
-        sequenceColor({ selected: sequence.id === selectedId }),
-      );
-      const ids = partIds(sequence);
-      sequence.parts.forEach((coordinates, index) => {
-        let positions;
-        try {
-          positions = Cesium.Cartesian3.fromDegreesArray(coordinates.flat());
-        } catch {
-          return;
-        }
-        if (positions.length < 2) return;
-        instances.push(
-          new Cesium.GeometryInstance({
-            geometry: new Cesium.GroundPolylineGeometry({
-              positions,
-              width: COVERAGE_LINE_WIDTH_PX,
-            }),
-            id: ids[index],
-            attributes: { color },
-          }),
-        );
-      });
-    }
+    const instances = lineInstances(
+      sequences,
+      Cesium.Color.fromCssColorString(COLORS.coverage).withAlpha(0.92),
+      COVERAGE_LINE_WIDTH_PX,
+    );
     const primitives = [];
     for (let i = 0; i < instances.length; i += SEQUENCE_PRIMITIVE_BATCH)
-      primitives.push({
-        selectedId,
-        primitive: new Cesium.GroundPolylinePrimitive({
-          geometryInstances: instances.slice(i, i + SEQUENCE_PRIMITIVE_BATCH),
-          appearance: new Cesium.PolylineColorAppearance(),
-          // Drapes on the globe and on 3D tiles (Google 3D) alike.
-          classificationType: Cesium.ClassificationType.BOTH,
-          asynchronous: true,
-          allowPicking: true,
-        }),
-      });
+      primitives.push(
+        linePrimitive(instances.slice(i, i + SEQUENCE_PRIMITIVE_BATCH), true),
+      );
     return primitives;
   }
 
+  /**
+   * Draw the selected sequence again over the coverage, in the selection
+   * colour, from every loaded tile it crosses; none when nothing is selected.
+   * Built at once: its tiles loaded, so the terrain table has too.
+   */
+  function highlight(sequenceId = state.sequence.selectedId) {
+    const scene = state.viewer?.scene;
+    if (state.coverage.highlight) {
+      scene?.groundPrimitives?.remove(state.coverage.highlight);
+      state.coverage.highlight = null;
+    }
+    if (!sequenceId || !scene) return;
+    const parts = [];
+    for (const entry of state.coverage.tiles.values())
+      parts.push(...(entry.sequences.get(sequenceId)?.parts || []));
+    const instances = lineInstances(
+      [{ id: sequenceId, parts }],
+      Cesium.Color.fromCssColorString(COLORS.selected),
+      COVERAGE_LINE_WIDTH_PX + 1,
+    );
+    if (!instances.length) return;
+    state.coverage.highlight = scene.groundPrimitives.add(
+      linePrimitive(instances, false),
+    );
+    requestRender();
+  }
+
   function attachPrimitive(entry) {
     const scene = state.viewer?.scene;
     if (!scene) return;
@@ -155,14 +163,13 @@ export function createCoverage({ state, source }) {
     entry.sequences = new Map(sequences.map((s) => [s.id, s]));
     entry.primitives = buildSequencePrimitives(sequences);
     entry.count = sequences.length;
-    for (const { primitive } of entry.primitives)
+    for (const primitive of entry.primitives)
       scene.groundPrimitives.add(primitive);
-    watchSelection();
   }
 
   function detachPrimitive(entry) {
     const scene = state.viewer?.scene;
-    for (const { primitive } of entry.primitives || []) {
+    for (const primitive of entry.primitives || []) {
       try {
         scene?.groundPrimitives?.remove(primitive);
       } catch {
@@ -195,7 +202,7 @@ export function createCoverage({ state, source }) {
         }),
         ensureTerrainReady(),
       ]);
-      // Only an abort, a retire, a clear or a newer request for this tile
+      // Only an abort, a zoom change, a clear or a newer request for this tile
       // discards the bytes; a refresh that still wants the tile keeps them.
       if (
         controller.signal.aborted ||
@@ -213,6 +220,8 @@ export function createCoverage({ state, source }) {
       attachPrimitive(entry);
       state.coverage.tiles.set(key, entry);
       state.coverage.lastError = null;
+      // Over the new lines, and along any of the selection's parts they add.
+      if (entry.sequences.has(state.sequence.selectedId)) highlight();
       requestRender();
     } catch (error) {
       if (
@@ -228,10 +237,8 @@ export function createCoverage({ state, source }) {
     } finally {
       // Only the request that still owns the key settles it: a superseded one
       // must not drop a newer request's entry (which is what counts as loading).
-      if (state.coverage.pending.get(key) === controller) {
+      if (state.coverage.pending.get(key) === controller)
         state.coverage.pending.delete(key);
-        if (!state.coverage.pending.size) purgeStale();
-      }
       notify();
     }
   }
@@ -275,31 +282,6 @@ export function createCoverage({ state, source }) {
     notify();
   }
 
-  /** Drop the previous zoom's tiles once the new ones are on screen. */
-  function purgeStale() {
-    clearTimeout(state.coverage.staleTimer);
-    state.coverage.staleTimer = null;
-    if (!state.coverage.stale.size) return;
-    for (const entry of state.coverage.stale.values()) detachPrimitive(entry);
-    state.coverage.stale.clear();
-    requestRender();
-  }
-
-  /** Move tiles to the stale set: the old zoom shows until the new one loads. */
-  function retire() {
-    for (const controller of state.coverage.pending.values())
-      controller.abort();
-    state.coverage.pending.clear();
-    for (const [key, entry] of state.coverage.tiles) {
-      const previous = state.coverage.stale.get(key);
-      if (previous) detachPrimitive(previous);
-      state.coverage.stale.set(key, entry);
-    }
-    state.coverage.tiles.clear();
-    clearTimeout(state.coverage.staleTimer);
-    state.coverage.staleTimer = setTimeout(purgeStale, STALE_TILE_MAX_MS);
-  }
-
   function notify() {
     state.notify?.();
   }
@@ -348,10 +330,7 @@ export function createCoverage({ state, source }) {
       return;
     }
     state.coverage.hint = '';
-    if (zoom !== state.coverage.zoom) {
-      retire();
-      state.coverage.zoom = zoom;
-    }
+    state.coverage.zoom = zoom;
     const wanted = new Set(tiles.map(tileKey));
     for (const key of [...state.coverage.tiles.keys()])
       if (!wanted.has(key)) removeTile(key);
@@ -363,7 +342,6 @@ export function createCoverage({ state, source }) {
         state.coverage.pending.delete(key);
       }
     for (const tile of tiles) loadTile(tile);
-    if (!state.coverage.pending.size) purgeStale();
     notify();
   }
 
@@ -398,104 +376,22 @@ export function createCoverage({ state, source }) {
       controller.abort();
     state.coverage.pending.clear();
     for (const key of [...state.coverage.tiles.keys()]) removeTile(key);
-    purgeStale();
+    highlight(null);
     state.coverage.zoom = null;
-    stopSelectionWatch();
     requestRender();
   }
 
   /** Rebuild every loaded tile from its decoded cache (after a filter change). */
   function rebuild() {
-    purgeStale();
     for (const entry of state.coverage.tiles.values()) {
       detachPrimitive(entry);
       attachPrimitive(entry);
     }
+    highlight();
     requestRender();
     notify();
   }
 
-  /** Recolour every part of a sequence in one ready primitive. */
-  function recolorInstances(primitive, sequence, selected) {
-    const value = sequenceColor({ selected });
-    for (const instanceId of partIds(sequence)) {
-      try {
-        const attributes = primitive.getGeometryInstanceAttributes(instanceId);
-        if (attributes)
-          attributes.color = Cesium.ColorGeometryInstanceAttribute.toValue(
-            value,
-            attributes.color,
-          );
-      } catch {
-        /* instance not in this primitive */
-      }
-    }
-  }
-
-  /** Every tile on the globe: the current zoom's and the stale zoom's. */
-  function drawnEntries() {
-    return [...state.coverage.tiles.values(), ...state.coverage.stale.values()];
-  }
-
-  /** Recolour one sequence, every part of it, in place (selection highlight). */
-  function recolorSequence(id, selected) {
-    for (const entry of drawnEntries()) {
-      const sequence = entry.sequences.get(id);
-      if (!sequence) continue;
-      for (const record of entry.primitives || []) {
-        // Still building: `syncSelection` catches it up once it is ready.
-        if (!record.primitive.ready) continue;
-        recolorInstances(record.primitive, sequence, selected);
-        if (selected) record.selectedId = id;
-        else if (record.selectedId === id) record.selectedId = null;
-      }
-    }
-    requestRender();
-  }
-
-  /**
-   * Bring a ready primitive's highlight up to the current selection, when
-   * it was built with another one (or none). True when it changed.
-   */
-  function syncSelection(entry, record) {
-    const current = state.sequence.selectedId ?? null;
-    if (record.selectedId === current || !record.primitive.ready) return false;
-    const previous =
-      record.selectedId && entry.sequences.get(record.selectedId);
-    if (previous) recolorInstances(record.primitive, previous, false);
-    const next = current && entry.sequences.get(current);
-    if (next) recolorInstances(record.primitive, next, true);
-    record.selectedId = current;
-    return true;
-  }
-
-  /**
-   * A primitive cannot be recoloured until it is ready, so while any is
-   * building, catch each one up with the selection as it becomes ready.
-   */
-  function watchSelection() {
-    const scene = state.viewer?.scene;
-    if (state.coverage.stopSelectionWatch || !scene?.postRender) return;
-    const stop = scene.postRender.addEventListener(() => {
-      let building = false;
-      let changed = false;
-      for (const entry of drawnEntries()) {
-        for (const record of entry.primitives || []) {
-          if (!record.primitive.ready) building = true;
-          else if (syncSelection(entry, record)) changed = true;
-        }
-      }
-      if (changed) requestRender();
-      if (!building) stopSelectionWatch();
-    });
-    state.coverage.stopSelectionWatch = stop;
-  }
-
-  function stopSelectionWatch() {
-    state.coverage.stopSelectionWatch?.();
-    state.coverage.stopSelectionWatch = null;
-  }
-
   /**
    * Sequences drawn. A sequence that crosses a tile edge is in both tiles'
    * lists, so sequences count once by id.
@@ -533,7 +429,7 @@ export function createCoverage({ state, source }) {
     unblock,
     setKeyStatus,
     rebuild,
-    recolorSequence,
+    highlight,
     sequenceCount,
     stats,
   };

src/layers/streetLevel/providers/mapillary/coverage.test.mjs

@@ -6,7 +6,6 @@ import { freshCoverage } from '../../state.js';
 import { encodeCoverageTile } from './coverageFixture.mjs';
 import { rayCamera } from '../../../../testSupport/streetLevelFakes.mjs';
 import {
-  COLORS,
   COVERAGE_MAX_SEQUENCES,
   COVERAGE_MAX_TILES,
 } from './policy.js';
@@ -48,29 +47,13 @@ function tileCentre(lon, lat) {
 
 /** A viewer looking straight down on a 0.004° square around `view`. */
 function fakeViewer(view) {
-  const postRender = new Set();
-  const preRender = new Set();
   return {
     view,
-    postRender,
-    preRender,
     scene: {
       canvas: { clientWidth: 100, clientHeight: 100 },
       globe: { show: false, ellipsoid: Cesium.Ellipsoid.WGS84 },
       groundPrimitives: collection(),
       primitives: collection(),
-      postRender: {
-        addEventListener(listener) {
-          postRender.add(listener);
-          return () => postRender.delete(listener);
-        },
-      },
-      preRender: {
-        addEventListener(listener) {
-          preRender.add(listener);
-          return () => preRender.delete(listener);
-        },
-      },
     },
     camera: {
       get positionCartographic() {
@@ -144,11 +127,6 @@ function setup() {
   return { viewer, source, state, coverage, bytes, tileKey, onGlobe, centre };
 }
 
-/** Run one frame's listeners, as Cesium's render loop would. */
-function frame(listeners) {
-  for (const listener of [...listeners]) listener();
-}
-
 test('a superseded tile request cannot strand lines on the globe', async () => {
   const { viewer, source, state, coverage, bytes, tileKey, onGlobe } = setup();
   const forTile = () => source.calls.filter((call) => call.key === tileKey);
@@ -345,7 +323,7 @@ test('the per-tile cap applies after the imagery filter, so a dense tile keeps i
   const cap = Math.floor(COVERAGE_MAX_SEQUENCES / COVERAGE_MAX_TILES);
   assert.equal(entry.count, Math.min(300, cap), 'every 360° line is drawn');
   assert.equal(coverage.sequenceCount(), Math.min(300, cap));
-  // Picking and recolouring look sequences up among the drawn lines.
+  // Picking and the highlight look sequences up among the drawn lines.
   assert.ok(entry.sequences.has('pano-0'), 'drawn lines can be looked up');
   assert.equal(entry.sequences.has('flat-699'), false);
   state.filter = { pano: 'all', sinceDays: 0 };
@@ -356,56 +334,6 @@ test('the per-tile cap applies after the imagery filter, so a dense tile keeps i
   coverage.clear();
 });
 
-/** The colour attribute value of a line, selected or not. */
-function colourValue(selected) {
-  return Array.from(
-    Cesium.ColorGeometryInstanceAttribute.toValue(
-      selected
-        ? Cesium.Color.fromCssColorString(COLORS.selected)
-        : Cesium.Color.fromCssColorString(COLORS.coverage).withAlpha(0.92),
-    ),
-  );
-}
-
-/** Take over a drawn primitive's readiness and seq-1's colour attribute. */
-function controlled(record, ready) {
-  const control = { ready, attributes: { color: undefined } };
-  Object.defineProperty(record.primitive, 'ready', {
-    get: () => control.ready,
-  });
-  record.primitive.getGeometryInstanceAttributes = (id) =>
-    id === 'mly:seq:seq-1' ? control.attributes : undefined;
-  return control;
-}
-
-test('a selection made or cleared while a tile builds is applied once it is ready', async () => {
-  const { viewer, source, state, coverage, bytes } = setup();
-  coverage.refresh();
-  source.calls[0].resolve(bytes);
-  await settle();
-  const [entry] = state.coverage.tiles.values();
-  // Selected while its line is still building: nothing to recolour yet...
-  const first = controlled(entry.primitives[0], false);
-  state.sequence.selectedId = 'seq-1';
-  coverage.recolorSequence('seq-1', true);
-  assert.equal(first.attributes.color, undefined);
-  // ...so the highlight lands once it is ready.
-  first.ready = true;
-  frame(viewer.postRender);
-  assert.deepEqual(Array.from(first.attributes.color), colourValue(true));
-
-  // Rebuilt with the highlight baked in, then cleared mid-build: not stuck.
-  coverage.rebuild();
-  const second = controlled(entry.primitives[0], false);
-  coverage.recolorSequence('seq-1', false);
-  state.sequence.selectedId = null;
-  second.ready = true;
-  frame(viewer.postRender);
-  assert.deepEqual(Array.from(second.attributes.color), colourValue(false));
-  coverage.clear();
-  assert.equal(viewer.postRender.size, 0, 'the selection watch is gone');
-});
-
 test('a sequence that crosses a tile edge is counted once', async () => {
   const { viewer, source, coverage, centre } = setup();
   // Look straight down on the edge between this tile and its east neighbour.
@@ -517,56 +445,39 @@ test('a street view toward the horizon asks only for the ground within range', (
   coverage.clear();
 });
 
-test('a selection cleared while the old zoom is still shown uncolours its lines', async () => {
+test('the selected sequence is drawn over the coverage, and goes with the selection', async () => {
   const { viewer, source, state, coverage, bytes } = setup();
   coverage.refresh();
   source.calls[0].resolve(bytes);
   await settle();
-  const [entry] = state.coverage.tiles.values();
-  const line = controlled(entry.primitives[0], true);
-  state.sequence.selectedId = 'seq-1';
-  coverage.recolorSequence('seq-1', true);
-  assert.deepEqual(Array.from(line.attributes.color), colourValue(true));
-  // Zoom out: the street tile stays on screen while the new zoom loads...
-  viewer.view.height = 3000;
-  coverage.refresh();
-  assert.equal(state.coverage.stale.size, 1, 'the old zoom is kept');
-  // ...and the selection is cleared meanwhile.
-  state.sequence.selectedId = null;
-  coverage.recolorSequence('seq-1', false);
-  assert.deepEqual(
-    Array.from(line.attributes.color),
-    colourValue(false),
-    'the retained line is not left cyan',
-  );
+  const lines = () => [...viewer.scene.groundPrimitives.items];
+  assert.equal(lines().length, 1, 'the coverage');
+  coverage.highlight('seq-1');
+  assert.equal(lines().length, 2);
+  const highlight = lines().at(-1);
+  assert.equal(state.coverage.highlight, highlight, 'drawn last, on top');
+  assert.equal(highlight.classificationType, Cesium.ClassificationType.BOTH);
+  coverage.highlight('not-drawn');
+  assert.equal(lines().length, 1, 'nothing to highlight off the map');
+  coverage.highlight(null);
+  assert.equal(state.coverage.highlight, null);
   coverage.clear();
+  assert.equal(lines().length, 0);
 });
 
-test('a selection made while the old zoom is still building is applied once it is ready', async () => {
+test('a tile that lands with the selected sequence draws the highlight again, on top', async () => {
   const { viewer, source, state, coverage, bytes } = setup();
+  state.sequence.selectedId = 'seq-1';
   coverage.refresh();
+  assert.equal(state.coverage.highlight, null, 'nothing loaded yet');
   source.calls[0].resolve(bytes);
   await settle();
-  const [entry] = state.coverage.tiles.values();
-  const line = controlled(entry.primitives[0], false);
-  viewer.view.height = 3000;
-  coverage.refresh();
-  assert.equal(state.coverage.stale.size, 1);
-  frame(viewer.postRender);
-  state.sequence.selectedId = 'seq-1';
-  coverage.recolorSequence('seq-1', true);
-  line.ready = true;
-  frame(viewer.postRender);
-  assert.deepEqual(
-    line.attributes.color && Array.from(line.attributes.color),
-    colourValue(true),
-    'the highlight lands on the retained line',
-  );
+  assert.ok(state.coverage.highlight, 'highlighted once its tile is in');
+  assert.equal([...viewer.scene.groundPrimitives.items].at(-1), state.coverage.highlight);
   coverage.clear();
-  assert.equal(viewer.postRender.size, 0, 'the selection watch is gone');
 });
 
-test('the old zoom goes as soon as the new zoom has loaded, not after the stale wait', async () => {
+test('a zoom change drops the old zoom\'s lines', async () => {
   const { viewer, source, state, coverage, bytes } = setup();
   coverage.refresh();
   source.calls[0].resolve(bytes);
@@ -576,23 +487,8 @@ test('the old zoom goes as soon as the new zoom has loaded, not after the stale
   viewer.view.height = 3000; // zoom out to z13
   coverage.refresh();
   assert.equal(state.coverage.zoom, 13);
-  const fresh = source.calls.slice(1);
-  assert.ok(fresh.length > 0, 'the new zoom is loading');
-  assert.equal(state.coverage.stale.size, 1, 'the old zoom stays meanwhile');
-  assert.ok(viewer.scene.groundPrimitives.items.has(old));
-  for (const call of fresh) {
-    assert.ok(
-      viewer.scene.groundPrimitives.items.has(old),
-      'kept while a new tile is still loading',
-    );
-    call.resolve(new Uint8Array());
-    await settle();
-  }
-  // The last new tile is in: the old lines go now, long before the wait.
-  assert.equal(state.coverage.pending.size, 0);
-  assert.equal(state.coverage.stale.size, 0);
   assert.equal(viewer.scene.groundPrimitives.items.has(old), false);
-  assert.equal(state.coverage.staleTimer, null, 'the stale wait is cancelled');
+  assert.ok(state.coverage.pending.size > 0, 'the new zoom is loading');
   coverage.clear();
 });
 

src/layers/streetLevel/providers/mapillary/sequences.js

@@ -132,11 +132,9 @@ export function createSequences({ state, source, parts }) {
       (state.sequence.images.length || state.sequence.abort)
     )
       return;
-    if (state.sequence.selectedId && state.sequence.selectedId !== sequenceId)
-      parts.coverage.recolorSequence(state.sequence.selectedId, false);
     state.sequence.abort?.abort();
     state.sequence.selectedId = sequenceId;
-    parts.coverage.recolorSequence(sequenceId, true);
+    parts.coverage.highlight(sequenceId);
     const cached = state.sequence.cache.get(sequenceId);
     if (cached) {
       state.sequence.abort = null;
@@ -173,7 +171,7 @@ export function createSequences({ state, source, parts }) {
     } catch (error) {
       if (!controller.signal.aborted) {
         // Nothing to show: drop the highlight, so a click asks again.
-        parts.coverage.recolorSequence(sequenceId, false);
+        parts.coverage.highlight(null);
         state.sequence.selectedId = null;
         state.sequence.error = error?.message || 'Sequence images unavailable';
       }
@@ -189,8 +187,7 @@ export function createSequences({ state, source, parts }) {
   function clearSelection() {
     state.sequence.abort?.abort();
     state.sequence.abort = null;
-    if (state.sequence.selectedId)
-      parts.coverage.recolorSequence(state.sequence.selectedId, false);
+    if (state.sequence.selectedId) parts.coverage.highlight(null);
     state.sequence.selectedId = null;
     state.sequence.loading = false;
     clearCones();

src/layers/streetLevel/providers/mapillary/sequences.test.mjs

@@ -57,7 +57,8 @@ function records(sequenceId, count = 2) {
 
 function setup() {
   const source = deferredSource();
-  const colours = [];
+  /** Every highlight asked of the coverage: a sequence id, or null for none. */
+  const highlights = [];
   const state = {
     services: {},
     viewer: {},
@@ -75,17 +76,17 @@ function setup() {
   };
   const parts = {
     coverage: {
-      recolorSequence: (id, selected) => colours.push([id, selected]),
+      highlight: (id) => highlights.push(id),
     },
   };
   const sequences = createSequences({ state, source, parts });
   const drawn = () =>
     state.sequence.collection.items.map((cone) => cone.id.split(':').at(-1));
-  return { state, source, sequences, colours, drawn };
+  return { state, source, sequences, highlights, drawn };
 }
 
 test('a failed sequence load leaves no stale cones and can be retried', async () => {
-  const { state, source, sequences, colours, drawn } = setup();
+  const { state, source, sequences, highlights, drawn } = setup();
   sequences.select('A');
   source.last('A').resolve(records('A'));
   await settle();
@@ -98,7 +99,7 @@ test('a failed sequence load leaves no stale cones and can be retried', async ()
   assert.deepEqual(drawn(), [], 'nothing of A is left to click');
   assert.equal(state.sequence.loading, false);
   assert.equal(state.sequence.selectedId, null, 'B is not left highlighted');
-  assert.deepEqual(colours.at(-1), ['B', false]);
+  assert.equal(highlights.at(-1), null);
   assert.equal(state.sequence.error, 'Sequence images unavailable');
 
   // Clicking B again asks again.
@@ -149,15 +150,12 @@ test('a cached sequence is re-selected without a lookup', async () => {
   assert.equal(state.sequence.selectedId, 'A');
 });
 
-test('clearSelection cancels the lookup and uncolours the sequence', async () => {
-  const { state, source, sequences, colours, drawn } = setup();
+test('clearSelection cancels the lookup and drops the highlight', async () => {
+  const { state, source, sequences, highlights, drawn } = setup();
   sequences.select('A');
   sequences.clearSelection();
   assert.equal(source.last('A').signal.aborted, true);
-  assert.deepEqual(colours, [
-    ['A', true],
-    ['A', false],
-  ]);
+  assert.deepEqual(highlights, ['A', null]);
   assert.equal(state.sequence.selectedId, null);
   assert.equal(state.sequence.loading, false);
   assert.equal(state.sequence.error, null, 'an error about it goes too');

src/layers/streetLevel/state.js

@@ -27,9 +27,8 @@ export function freshCoverage() {
     zoom: null,
     /** Current zoom's tiles by `z/x/y` key. */
     tiles: new Map(),
-    /** Previous zoom's tiles, kept on screen until replacements land. */
-    stale: new Map(),
-    staleTimer: null,
+    /** The selected sequence drawn over the coverage, or null. */
+    highlight: null,
     /** Tile key → its request's controller; any entry means LOADING. */
     pending: new Map(),
     lastError: null,