# `lr-intersection-observer` - **Import** `import '@aceshooting/lyra-ui/components/lr-intersection-observer.js';` (stable tag alias; registers the tag) - **Class** `LyraIntersectionObserver`, also available unregistered from `@aceshooting/lyra-ui/components/utility/intersection-observer/intersection-observer.class.js` - **Family** `components/utility/` — see `llms/index.md` for its siblings - **Status** `stable` since `4.0.0` — see the maturity and deprecation policy in `llms/shared.md` - **Release history** [CHANGELOG.md](../../CHANGELOG.md); family-wide breaking-change summaries: [llms-full.txt](../../llms-full.txt) - **Deprecations** none - **Optional peers** none - **Themeable via** 1 part, 0 custom properties — see this component's own `@csspart`/`@cssprop` list below - **Library-wide behavior** (events, form association, `locale`/`strings`, tokens, TS types): `llms/shared.md` --- ## `lr-intersection-observer` Lifecycle-managed wrapper around the native `IntersectionObserver`. It observes all element children in the default slot and emits a composed event, while adding no layout of its own. **Properties:** `disabled: boolean = false` (reflected), `rootMargin: string = '0px'` (attribute `root-margin`), `threshold: number | number[] | string = '0'` (the mapped attribute form accepts space-separated values), `root: Element | string | null = null` (an element or mapped element ID), `intersectClass: string = ''` (attribute `intersect-class`, toggled on each target), and `once: boolean = false` (reflected; unobserves a target after its first intersection). A once-consumed target stays consumed across option-driven observer rebuilds and disconnect/reconnect cycles; setting `once` to false is the explicit reset boundary. The browser capability is optional. A missing or throwing owner-window lookup or unavailable constructor leaves that rebuild inert rather than leaking an exception; an initial construction failure retries once with safe default options. Individual `observe`, `unobserve`, and `disconnect` failures are contained, so later valid targets and later rebuilds can still observe. Callbacks are tied to the current owner document, so a detached or adopted wrapper cannot emit a stale batch. Threshold collections inspect at most their first 10,000 direct data entries. Malformed or accessor-backed entries are skipped; a valid prefix remains active, while an entirely unusable value falls back to threshold `0`. **Events:** mapped `lr-intersect` once per entry with `{ entry }`, plus the existing batch alias `lr-intersection` with a frozen `Readonly<{ entries: readonly IntersectionObserverEntry[] }>` detail. The batch sequence is detached and bounded while each native observer entry retains identity. **Slots:** default observed elements. **CSS parts:** `base`. ---