fix: correct typing for itemSize

Closes #724
Reverts #688 - the PR was incorrect, and I misled the contributor.

src/components.tsx

@@ -21,6 +21,7 @@ import {
   GridRootProps,
   FlatIndexLocationWithAlign,
   FlatScrollIntoViewLocation,
+  SizeFunction,
 } from './interfaces'
 import { List } from './List'
 import { Grid } from './Grid'
@@ -121,7 +122,7 @@ export interface VirtuosoProps<D, C> extends ListRootProps {
    *
    * The default implementation reads `el.getBoundingClientRect().height` and `el.getBoundingClientRect().width`.
    */
-  itemSize?: (el: HTMLElement, dimension: 'height' | 'width') => number
+  itemSize?: SizeFunction
 
   /**
    * Can be used to improve performance if the rendered items are of known size.
@@ -349,7 +350,7 @@ export interface TableVirtuosoProps<D, C> extends Omit<VirtuosoProps<D, C>, 'com
    *
    * The default implementation reads `el.getBoundingClientRect().height` and `el.getBoundingClientRect().width`.
    */
-  itemSize?: (el: HTMLElement, dimension: 'height' | 'width') => number
+  itemSize?: SizeFunction
 
   /**
    * Can be used to improve performance if the rendered items are of known size.

src/hooks/useChangedChildSizes.ts

@@ -1,7 +1,7 @@
 import { Log, LogLevel } from '../loggerSystem'
-import { SizeFunction, SizeRange } from '../sizeSystem'
+import { SizeRange } from '../sizeSystem'
 import { useSizeWithElRef } from './useSize'
-import { ScrollContainerState } from '../interfaces'
+import { SizeFunction, ScrollContainerState } from '../interfaces'
 export default function useChangedListContentsSizes(
   callback: (ranges: SizeRange[]) => void,
   itemSize: SizeFunction,

src/interfaces.ts

@@ -327,3 +327,6 @@ export interface ScrollContainerState {
   scrollTop: number
   viewportHeight: number
 }
+
+/** Calculates the height of `el`, which will be the `Item` element in the DOM. */
+export type SizeFunction = (el: HTMLElement, field: 'offsetHeight' | 'offsetWidth') => number

src/sizeSystem.ts

@@ -4,6 +4,7 @@ import * as arrayBinarySearch from './utils/binaryArraySearch'
 import { correctItemSize } from './utils/correctItemSize'
 import { loggerSystem, Log, LogLevel } from './loggerSystem'
 import { recalcSystem } from './recalcSystem'
+import { SizeFunction } from './interfaces'
 
 export interface SizeRange {
   startIndex: number
@@ -273,9 +274,6 @@ const SIZE_MAP = {
   offsetWidth: 'width',
 } as const
 
-/** Calculates the height of `el`, which will be the `Item` element in the DOM. */
-export type SizeFunction = (el: HTMLElement, field: 'offsetHeight' | 'offsetWidth') => number
-
 export const sizeSystem = u.system(
   ([{ log }, { recalcInProgress }]) => {
     const sizeRanges = u.stream<SizeRange[]>()