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ant-design-vue/components/vc-virtual-list/hooks/useHeights.tsx

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import type { VNodeProps, Ref, ShallowRef } from 'vue';
import { watch, ref } from 'vue';
import type { GetKey } from '../interface';
export type CacheMap = Map<any, number>;
export default function useHeights<T>(
mergedData: ShallowRef<any[]>,
getKey: GetKey<T>,
onItemAdd?: ((item: T) => void) | null,
onItemRemove?: ((item: T) => void) | null,
): [(item: T, instance: HTMLElement) => void, () => void, CacheMap, Ref<Symbol>] {
const instance = new Map<VNodeProps['key'], HTMLElement>();
const heights = new Map();
const updatedMark = ref(Symbol('update'));
watch(mergedData, () => {
updatedMark.value = Symbol('update');
});
let heightUpdateId = 0;
function collectHeight() {
heightUpdateId += 1;
const currentId = heightUpdateId;
Promise.resolve().then(() => {
// Only collect when it's latest call
if (currentId !== heightUpdateId) return;
// let changed = false;
instance.forEach((element, key) => {
if (element && element.offsetParent) {
const { offsetHeight } = element;
if (heights.get(key) !== offsetHeight) {
//changed = true;
updatedMark.value = Symbol('update');
heights.set(key, element.offsetHeight);
}
}
});
});
}
function setInstance(item: T, ins: HTMLElement) {
const key = getKey(item);
const origin = instance.get(key);
if (ins) {
instance.set(key, (ins as any).$el || ins);
collectHeight();
} else {
instance.delete(key);
}
// Instance changed
if (!origin !== !ins) {
if (ins) {
onItemAdd?.(item);
} else {
onItemRemove?.(item);
}
}
}
return [setInstance, collectHeight, heights, updatedMark];
}