Function positionArrow

tests/popover.test.ts:198–217

(opts: {
    side: Side;
    align?: Alignment;
    element: Partial<DOMRect>;
    popover: Partial<DOMRect>;
  })

  // jsdom doesn't lay anything out, so we feed both the element and the popover
  // their boxes, then refresh to run the positioning against those boxes.
  function positionArrow(opts: {
    side: Side;
    align?: Alignment;
    element: Partial<DOMRect>;
    popover: Partial<DOMRect>;
  }): Promise<void> {
    const el = document.querySelector<HTMLElement>("#intro")!;
    el.getBoundingClientRect = () => rect(opts.element);
    // jsdom has no scrollIntoView; off-screen element boxes would otherwise throw.
    el.scrollIntoView = () => {};

    const d = createDriver({ animate: false });
    d.highlight({ element: "#intro", popover: { title: "Intro", side: opts.side, align: opts.align ?? "start" } });

    const wrapper = popoverEl() as HTMLElement;
    wrapper.getBoundingClientRect = () => rect(opts.popover);

    d.refresh();
    return nextFrame();
  }

  it("points the arrow at the element's vertical center for a left/right placement", async () => {
    // Element sits to the right with its vertical center at y=230; popover box