PositionFocusedItemInLazyLayout.kt

// Copyright 2024 Google LLC.
// SPDX-License-Identifier: Apache-2.0

@OptIn(ExperimentalFoundationApi::class)
@Composable
fun PositionFocusedItemInLazyLayout(
    parentFraction: Float = 0.3f,
    childFraction: Float = 0f,
    content: @Composable () -> Unit,
) {
    // This bring-into-view spec pivots around the center of the scrollable container
    val bringIntoViewSpec = object : BringIntoViewSpec {
        override fun calculateScrollDistance(
            // Initial position of item requesting focus
            offset: Float,
            // Size of item requesting focus
            size: Float,
            // Size of the lazy container
            containerSize: Float
        ): Float {
            val childSmallerThanParent = size <= containerSize
            val initialTargetForLeadingEdge =
                parentFraction * containerSize - (childFraction * size)
            val spaceAvailableToShowItem = containerSize - initialTargetForLeadingEdge

            val targetForLeadingEdge =
                if (childSmallerThanParent && spaceAvailableToShowItem < size) {
                    containerSize - size
                } else {
                    initialTargetForLeadingEdge
                }

            return offset - targetForLeadingEdge
        }
    }

    // LocalBringIntoViewSpec will apply to all scrollables in the hierarchy
    CompositionLocalProvider(
        LocalBringIntoViewSpec provides bringIntoViewSpec,
        content = content,
    )
}

// To implement, provide a LazyRow as the PositionFocusedItemInLazyLayout's content
PositionFocusedItemInLazyLayout(parentFraction = 0.5f) {
    LazyRow {}
}

Will that be added to tv-foundation once TvLazyLists are removed?

@pflammertsma I used this snippet to document migration from TvLazyLists to LazyLists https://medium.com/@dejwidh/lazylist-pivotoffset-without-tvlazylist-7ad24fe439ab. I hope it's fine.

Hi Dawid, well observed; we are in the process of bringing scrollable containers back into componse-foundation and this code snippet replaces the pivotOffset parameter.

I will have more to share once we are closer to updating the TV libraries.