yawn/vendor/fxnode/test/pointer-lane.test.ts

import assert from "node:assert/strict";
import test from "node:test";
import {
  advancePointerLaneFence,
  createPointerLane,
  pointerLaneFence,
  publishPointerMove,
  readPointerMove,
  type PointerMoveWire,
} from "@lib/browser/pointer-lane.js";

const move = (x: number, y: number): PointerMoveWire => ({
  kind: "pointer",
  phase: "move",
  pointerId: 7,
  pointerType: "pen",
  position: { x, y },
  button: -1,
  buttons: 1,
  modifiers: 8,
});

test("shared pointer lane publishes exact latest coordinates and fences", () => {
  const lane = createPointerLane();
  assert.equal(pointerLaneFence(lane), 0);
  const generation = 0x1_0000_0007;
  const sequence = publishPointerMove(lane, move(-12.25, 987.125), generation);
  assert.equal(sequence, 1);
  assert.deepEqual(readPointerMove(lane), { sequence: 1, hostGeneration: generation, event: move(-12.25, 987.125) });
  assert.equal(advancePointerLaneFence(lane), 1);
  assert.equal(pointerLaneFence(lane), 1);
  assert.equal(publishPointerMove(lane, { ...move(4, 5), pointerType: "unknown" }, generation + 1), undefined);
  assert.deepEqual(readPointerMove(lane), { sequence: 1, hostGeneration: generation, event: move(-12.25, 987.125) });
});

test("shared pointer lane rejects an in-progress publication", () => {
  const lane = createPointerLane();
  publishPointerMove(lane, move(1, 2), 3);
  const words = new Int32Array(lane);
  Atomics.store(words, 0, Atomics.load(words, 0) | 1);
  assert.equal(readPointerMove(lane), undefined);
});