feat(useInfiniteScroll): new options (#1354)

Co-authored-by: Anthony Fu <anthonyfu117@hotmail.com>

packages/core/useInfiniteScroll/index.ts

@@ -1,5 +1,5 @@
 import type { UnwrapNestedRefs } from 'vue-demi'
-import { reactive, watch } from 'vue-demi'
+import { nextTick, reactive, unref, watch } from 'vue-demi'
 import type { MaybeRef } from '@vueuse/shared'
 import type { UseScrollOptions } from '../useScroll'
 import { useScroll } from '../useScroll'
@@ -11,6 +11,20 @@ export interface UseInfiniteScrollOptions extends UseScrollOptions {
    * @default 0
    */
   distance?: number
+
+  /**
+   * The direction in which to listen the scroll.
+   *
+   * @default 'bottom'
+   */
+  direction?: 'top' | 'bottom'
+
+  /**
+   * Whether to preserve the current scroll position when loading more items.
+   *
+   * @default false
+   */
+  preserveScrollPosition?: boolean
 }
 
 /**
@@ -20,25 +34,42 @@ export interface UseInfiniteScrollOptions extends UseScrollOptions {
  */
 export function useInfiniteScroll(
   element: MaybeRef<HTMLElement | SVGElement | Window | Document | null | undefined>,
-  onLoadMore: (state: UnwrapNestedRefs<ReturnType<typeof useScroll>>) => void,
+  onLoadMore: (state: UnwrapNestedRefs<ReturnType<typeof useScroll>>) => void | Promise<void>,
   options: UseInfiniteScrollOptions = {},
 ) {
+  const direction = options.direction ?? 'bottom'
   const state = reactive(useScroll(
     element,
     {
       ...options,
       offset: {
-        bottom: options.distance ?? 0,
+        [direction]: options.distance ?? 0,
         ...options.offset,
       },
     },
   ))
 
   watch(
-    () => state.arrivedState.bottom,
-    (v) => {
-      if (v)
-        onLoadMore(state)
+    () => state.arrivedState[direction],
+    async(v) => {
+      if (v) {
+        const elem = unref(element) as Element
+        const previous = {
+          height: elem?.scrollHeight ?? 0,
+          width: elem?.scrollWidth ?? 0,
+        }
+
+        await onLoadMore(state)
+
+        if (options.preserveScrollPosition && elem) {
+          nextTick(() => {
+            elem.scrollTo({
+              top: elem.scrollHeight - previous.height,
+              left: elem.scrollWidth - previous.width,
+            })
+          })
+        }
+      }
     },
   )
 }