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<script lang="ts">
import { onMount, onDestroy } from "svelte";
export let top = 0;
export let bottom = 0;
export let left = 0;
export let right = 0;
export let steps = 100;
export let threshold = 0.01;
export let once = false;
let element: Element;
let percent = 0;
let visible = false;
let observer: IntersectionObserver;
const intersectPercent = (
entries: IntersectionObserverEntry[],
observer: IntersectionObserver,
) => {
for (let entry of entries)
if (entry.target === element) {
percent = Math.round(entry.intersectionRatio * 100);
visible = entry.intersectionRatio >= threshold;
if (visible && once) observer.unobserve(element);
break;
}
};
onMount(() => {
if ("IntersectionObserver" in window) {
let options = {
rootMargin: `${top}px ${right}px ${bottom}px ${left}px`,
threshold: Array.from({ length: steps }, (_, i) => i / (steps - 1)),
};
observer = new IntersectionObserver(intersectPercent, options);
observer.observe(element);
}
});
onDestroy(() => observer?.unobserve(element));
</script>
<div bind:this={element}>
<slot {visible} {percent} />
</div>
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