fix(globe): a Navara click never takes a stale GPU pick of a neighbour

Navara 0.2.1 can answer a click with the previous gesture's pick. The
check let that answer through when its instance was drawn within twice its
pick radius of the click — the followed aircraft at the centre beside the
clicked one (the 20/24 flights checklist run: a click selected the
previously followed aircraft). A GPU answer for a sprite or point set now
has to be drawn under the click (no slack) and be the instance the CPU
pick finds on top there (lines left out: they are not in the GPU pick);
otherwise the CPU pick answers. Models, which the CPU pick does not see,
are still taken as answered. The CPU drill takes `includeLines`.

Test: 20 gestures alternating a click on A and a click on its neighbour B
answered with A's stale pick — B every time. In the app, 40 scripted
click/follow/release gestures on Navara selected the clicked aircraft
every time with and without the fix (the stale answer is rare).

src/globe/cpuPicks.js

@@ -156,10 +156,14 @@ export function createCpuPicker({ projector, camera, movers, lines }) {
     }
   }
 
-  const drill = (at, limit = Infinity, { includeMovers = true } = {}) => {
+  const drill = (
+    at,
+    limit = Infinity,
+    { includeMovers = true, includeLines = true } = {},
+  ) => {
     const hits = [];
     if (includeMovers) moverHits(at, hits);
-    lineHits(at, hits);
+    if (includeLines) lineHits(at, hits);
     hits.sort((a, b) => a.depth - b.depth);
     return hits.slice(0, limit).map(({ result }) => result);
   };

src/globe/navara/picking.js

@@ -38,6 +38,10 @@ export function createNavaraPicking({
   now = () => performance.now(),
 }) {
   const drillPick = createCpuPicker({ projector, camera, movers, lines });
+  const isModelSet = (id) =>
+    movers().some(
+      ({ options }) => options.id === id && options.kind === 'model',
+    );
 
   // Clicks waiting for Navara's GPU answer, oldest first.
   const waiting = [];
@@ -55,11 +59,26 @@ export function createNavaraPicking({
   // frame): a set that changes its instances after it still names the
   // instance that was under the pointer.
   const resolveInfo = (info) => (info ? resolveBatch(info.batchId) : null);
+  // A GPU answer is checked against the CPU pick at the click: an instance
+  // the CPU sees must be drawn under the click (its pick radius, no slack)
+  // and be the one the CPU finds on top. A stale answer from the previous
+  // gesture (the followed aircraft at the centre) lay within twice its
+  // radius of a neighbour's click and won (10b/11b flake). Models, which
+  // the CPU pick does not see, are still taken as answered.
   const answerFrom = (hit, at) => {
-    if (hit && !drillPick.near(hit.set, hit.instance, at)) {
+    if (hit) {
+      // The instance the CPU sees on top (lines are not in the GPU pick).
+      const top = drillPick(at, 1, { includeLines: false })[0];
+      const stale =
+        !drillPick.near(hit.set, hit.instance, at, 1) ||
+        (top !== undefined &&
+          !(top.owner === hit.set && top.instance === hit.instance) &&
+          !isModelSet(hit.set));
+      if (stale) {
         stats.stale++;
         return drillPick(at, 1)[0];
       }
+    }
     return hit
       ? { id: hit.pickId, owner: hit.set, instance: hit.instance }
       : drillPick(at, 1, { includeMovers: false })[0];

src/globe/navara/picking.test.mjs

@@ -296,3 +296,37 @@ test('the pick id is the one the instance had when Navara answered', async () =>
   time += 1;
   assert.equal((await picking.clickPick({ x: 10, y: 10 })).id, 'before');
 });
+
+test('a stale GPU answer for a neighbour of the click never wins over the instance under it (20 gestures)', async () => {
+  // The followed aircraft A sits at the centre; B is drawn 15 px from it.
+  // Navara answers B's click with the previous gesture's pick (A): within
+  // twice A's pick radius, but the instance under the click is B.
+  const view = fakeView();
+  const sets = [
+    moverSet('flights', [
+      [100, 100, 5, 'a'],
+      [115, 100, 5, 'b'],
+    ]),
+  ];
+  const picking = createNavaraPicking({
+    view,
+    projector,
+    camera,
+    movers: () => sets,
+    lines: () => [],
+    resolveBatch: (batchId) =>
+      batchId === 1
+        ? { set: 'flights', instance: 0, pickId: 'a' }
+        : { set: 'flights', instance: 1, pickId: 'b' },
+    ...timers(),
+  });
+  for (let gesture = 0; gesture < 20; gesture++) {
+    const onA = picking.clickPick({ x: 100, y: 100 });
+    view.emit('featureClick', { batchId: 1 });
+    assert.equal((await onA).id, 'a', `gesture ${gesture}: a`);
+    const onB = picking.clickPick({ x: 115, y: 100 });
+    view.emit('featureClick', { batchId: 1 }); // stale: A again
+    assert.equal((await onB).id, 'b', `gesture ${gesture}: b, not the stale a`);
+  }
+  assert.equal(picking.clickStats().stale, 20);
+});