Function staysInFrame

packages/cli/src/utils/motionAudit.ts:138–162

(frames: MotionFrame[], selector: string, canvas: Canvas)

// the first-appear anchor uses APPEAR_OPACITY (0.5). Elements fading in between those
// thresholds are tracked for position but don't start the window — intentional.
function staysInFrame(frames: MotionFrame[], selector: string, canvas: Canvas): LayoutIssue[] {
  if (!everMatched(frames, selector)) return [missingIssue(selector, 0)];
  const appear = firstAppear(frames, selector);
  if (!appear) return [];

  for (const frame of frames) {
    const sample = frame.data[selector];
    if (frame.time < appear.time || !sample || !sample.visible) continue;
    if (!isOffFrame(sample.rect, canvas)) continue;
    const r = sample.rect;
    return [
      {
        code: "motion_off_frame",
        severity: "error",
        time: frame.time,
        selector,
        message: `${selector} drifts off the ${canvas.width}×${canvas.height} canvas at ${round(frame.time)}s (box ${r.left},${r.top}→${r.right},${r.bottom})`,
        rect: r,
        fixHint:
          "Clamp the element's motion so its box stays within the canvas for the whole shot.",
      },
    ];
  }
  return [];
}

function keepsMoving(
  frames: MotionFrame[],