IndexedSnapScroller

IndexedSnapScroller is a compound component built on SnapScroller for virtualized, index-windowed paging.

Root Props

Prop	Type	Default
`start`	`number`	`-2`
Starting index used to generate the initial sequence of pages. Acts as the logical origin for the sliding index window.
`startDir`	`-1 \| 1`	`1`
Direction in which the initial index sequence expands. `1` — indexes increase to the right (0, 1, 2…); `-1` — indexes decrease to the right (0, -1, -2…). Controls the growth pattern of the initial index array.
`size`	`number`	`5`
Number of index segments rendered at once. Defines the size of the virtual “window” that the scroller slides over when navigating left or right.
`shift`	`number`	`2`
Number of pages appended when a scroll reaches the end of the window, so a fast swipe keeps going. Once the scroll settles, the window is re-centered on the snapped page.
`index`	`number`	—
Controls the currently active logical index. When provided, the scroller keeps the given index in view, scrolling to it if possible or rebuilding the window if needed.
`preserveScroll`	`boolean`	`true`
Preserve the currently snapped item after content changes (e.g., when pages are prepended/appended). If `true`, the scroller will restore the same snapped index using an immediate `scrollIntoView`.
`apiRef`	`Ref<IndexedSnapScrollerApiRef>`	—
Exposes the imperative API of the scroller. Allows programmatic control such as scrolling to an index or resetting the virtual window.
`onOffset`	`(value: number) => void`	—
Fires when the window grows at an edge. `-1` — the scroll settled on the first page (left/top edge); `+1` — the scroll reached the end (right/bottom edge). Useful for infinite loading: append/prepend pages based on the direction.
`ref`	`Ref<HTMLDivElement>`	—
Ref to the scroller’s element.
`defaultIndex`	`number`	—
Initial index of the item to snap to on mount.
`onScrollSnapChange`	`(element: HTMLElement, index: number) => void`	—
Fired when a scroll snap operation has fully completed and the scroller has settled on a new snap index. This callback is invoked after all scrolling and snapping animations have finished and the active snap position is considered stable.
`onScrollSnapChanging`	`(element: HTMLElement, index: number) => void`	—
Fired while a scroll snap operation is in progress and the active snap index is still changing. This callback may be invoked multiple times during a single scroll or swipe interaction as the scroller approaches its final snap position. Useful for optimistic UI updates, previews, or synchronizing transient state during scrolling.

Also accepts all <div> attributes.

Child Parts

IndexedSnapScrollerContent: content template bound to the current virtual index.

`IndexedSnapScrollerContent`

Prop	Type	Default
`ref`	`Ref<HTMLDivElement>`	—
External ref to the item's root element. Will be merged with internal `itemRef(index)` to participate in snapping logic.
`asChild`	`boolean`	—
Render the content as a child (via `Slot`) instead of a native `<div>`. Keeps attributes/refs bound to the passed child element.

Also accepts all <div> attributes.

Types

IndexedSnapScrollerProps
IndexedSnapScrollerContentProps
IndexedSnapScrollerApiRef

State Model

The root manages a sliding window of logical indexes.
Controlled index can either scroll to an existing item or trigger a window reset.
While a scroll reaches the end, pages are appended so it can keep going; once the scroll settles, the window is re-centered on the snapped page.
next() / prev() count from the page the scroll is already heading to and grow the window first when the target is outside it.