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enhance(client): Better element visible detection

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This commit is contained in:
syuilo 2020-08-19 17:52:11 +09:00
parent c54d5e7040
commit 6870262f8d
2 changed files with 10 additions and 5 deletions
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10
src/client/scripts/scroll.ts
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@ -13,12 +13,18 @@ export function getScrollPosition(el: Element | null): number {
return container == null ? window.scrollY : container.scrollTop;
}
export function isTopVisible(el: Element | null): boolean {
const scrollTop = getScrollPosition(el);
const topPosition = el.offsetTop; // TODO: container内でのelの相対位置を取得できればより正確になる
return scrollTop <= topPosition;
}
export function onScrollTop(el: Element, cb) {
const container = getScrollContainer(el) || window;
const onScroll = ev => {
if (!document.body.contains(el)) return;
const pos = getScrollPosition(el);
if (pos === 0) {
if (isTopVisible(el)) {
cb();
container.removeEventListener('scroll', onScroll);
}