Scrollbars

Scrollbars enable tracking a user's position in the list and fast scrolling through it.

For lazy containers, the easiest way to use them is via the scrollbarState extension method:

@Composable
fun Lazy_State.scrollbarState(
    itemsAvailable: Int,
    itemIndex: (Lazy_ItemInfo) -> Int = Lazy_ItemInfo::index,
): ScrollbarState {
    ...
}

Use of the scroll bar follows the following pattern:

@Composable
fun FastScrollbar(
    modifier: Modifier = Modifier,
    state: ScrollbarState,
    scrollInProgress: Boolean,
    orientation: Orientation,
    onThumbMoved: (Float) -> Unit,
) {
    val interactionSource = remember { MutableInteractionSource() }
    Scrollbar(
        modifier = modifier,
        orientation = orientation,
        interactionSource = interactionSource,
        state = state,
        thumb = {
            FastScrollbarThumb(
                scrollInProgress = scrollInProgress,
                interactionSource = interactionSource,
                orientation = orientation,
            )
        },
        onThumbMoved = onThumbMoved,
    )
}

They are implemented for scrollable containers with [ScrollState], lists, grids and staggered grids.

Composable
Collapsing Headers and Scrollbars