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/*
* SPDX-FileCopyrightText: syuilo and misskey-project
* SPDX-License-Identifier: AGPL-3.0-only
*/
import { throttle } from 'throttle-debounce';
import { nextTick, onActivated, onDeactivated, onUnmounted, watch } from 'vue';
import type { Ref } from 'vue';
// note render skippingがオンだとズレるため、遷移直前にスクロール範囲に表示されているdata-scroll-anchor要素を特定して、復元時に当該要素までスクロールするようにする
// TODO: data-scroll-anchor がひとつも存在しない場合、または手動で useAnchor みたいなフラグをfalseで呼ばれた場合、単純にスクロール位置を使用する処理にフォールバックするようにする
export function useScrollPositionKeeper(scrollContainerRef: Ref<HTMLElement | null | undefined>): void {
let anchorId: string | null = null;
let ready = true;
watch(scrollContainerRef, (el) => {
if (!el) return;
const onScroll = () => {
if (!el) return;
if (!ready) return;
const scrollContainerRect = el.getBoundingClientRect();
const viewPosition = scrollContainerRect.height / 2;
const anchorEls = el.querySelectorAll('[data-scroll-anchor]');
for (let i = anchorEls.length - 1; i > -1; i--) { // 下から見た方が速い
const anchorEl = anchorEls[i] as HTMLElement;
const anchorRect = anchorEl.getBoundingClientRect();
const anchorTop = anchorRect.top;
const anchorBottom = anchorRect.bottom;
if (anchorTop <= viewPosition && anchorBottom >= viewPosition) {
anchorId = anchorEl.getAttribute('data-scroll-anchor');
break;
}
}
};
// ほんとはscrollイベントじゃなくてonBeforeDeactivatedでやりたい
// https://github.com/vuejs/vue/issues/9454
// https://github.com/vuejs/rfcs/pull/284
el.addEventListener('scroll', throttle(1000, onScroll), { passive: true });
}, {
immediate: true,
});
const restore = () => {
if (!anchorId) return;
const scrollContainer = scrollContainerRef.value;
if (!scrollContainer) return;
const scrollAnchorEl = scrollContainer.querySelector(`[data-scroll-anchor="${anchorId}"]`);
if (!scrollAnchorEl) return;
scrollAnchorEl.scrollIntoView({
behavior: 'instant',
block: 'center',
inline: 'center',
});
};
onDeactivated(() => {
ready = false;
});
onActivated(() => {
restore();
nextTick(() => {
restore();
window.setTimeout(() => {
restore();
ready = true;
}, 100);
});
});
}
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