Jetpack Compose VerticalScrollBar for Android

ComposeVerticalScrollBar.kt

// Reference: https://stackoverflow.com/questions/66341823/jetpack-compose-scrollbars/68056586#68056586
// Modify: LazyListState -> ScrollState

fun Modifier.verticalScrollbar(
    scrollState: ScrollState,
    scrollBarWidth: Dp = 4.dp,
    minScrollBarHeight: Dp = 5.dp,
    scrollBarColor: Color = Color.Blue,
    cornerRadius: Dp = 2.dp
): Modifier = composed {
    val targetAlpha = if (scrollState.isScrollInProgress) 1f else 0f
    val duration = if (scrollState.isScrollInProgress) 150 else 500

    val alpha by animateFloatAsState(
        targetValue = targetAlpha,
        animationSpec = tween(durationMillis = duration)
    )

    drawWithContent {
        drawContent()

        val needDrawScrollbar = scrollState.isScrollInProgress || alpha > 0.0f

        if (needDrawScrollbar && scrollState.maxValue > 0) {
            val visibleHeight: Float = this.size.height - scrollState.maxValue
            val scrollBarHeight: Float = max(visibleHeight * (visibleHeight / this.size.height), minScrollBarHeight.toPx())
            val scrollPercent: Float = scrollState.value.toFloat() / scrollState.maxValue
            val scrollBarOffsetY: Float = scrollState.value + (visibleHeight - scrollBarHeight) * scrollPercent

            drawRoundRect(
                color = scrollBarColor,
                topLeft = Offset(this.size.width - scrollBarWidth.toPx(), scrollBarOffsetY),
                size = Size(scrollBarWidth.toPx(), scrollBarHeight),
                alpha = alpha,
                cornerRadius = CornerRadius(cornerRadius.toPx())
            )
        }
    }
}


// Usage
@Compose
fun ScrollText() {
    val scrollState = rememberScrollState()
    Text(
        text = "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30",
        modifier = Modifier
            .fillMaxWidth()
            .padding(horizontal = 8.dp)
            .verticalScroll(scrollState)
            .verticalScrollbar(scrollState)
    )
}