Kotlin 垂直滚动条下拉菜单的桌面组合

我在目前公开的第Scrollbar doesn't work for DropdownMenu #587期中找到了答案.

这就是我如何让我的滚动条在桌面版本的下拉菜单中工作.

1. 将此版本的DesktopMenu.desktop.kt复制到您的项目中.
2. 将此版本的Menu.kt复制到您的项目中.
3. 将这Card添加到您的MenU.S.kt中，围绕显示内容的Column.
4. 按照问题中的this comment，从第3点开始将这一点添加到Card中.

Box(
    modifier = modifier
        .width(IntrinsicSize.Max)
) {
    val scrollState = rememberScrollState()
    var columnSize by remember { mutableStateOf<IntSize?>(null) }
    Column(
        modifier = Modifier
            .padding(vertical = DropdownMenuVerticalPadding)
            .verticalScroll(scrollState)
            .onSizeChanged { size ->
                columnSize = size
            },
        content = content
    )
    columnSize?.let { size ->
        VerticalScrollbar(
            modifier = Modifier
                .align(Alignment.CenterEnd)
                .height(with(LocalDensity.current) { size.height.toDp() }),
            scrollState = scrollState
        )
    }
}

5. 最后一点是，这将溢出我的屏幕，所以我返回到当前版本的DesktopMenu.desktop.kt，将这个版本的DesktopDropdownMenuPositionProvider放回到我的DesktopMenu.desktop.kt中.

/**
 * Positions a dropdown relative to another widget (its anchor).
 */
@Immutable
internal data class DesktopDropdownMenuPositionProvider(
    val contentOffset: DpOffset,
    val density: Density,
    val onPositionCalculated: (IntRect, IntRect) -> Unit = { _, _ -> }
) : PopupPositionProvider {
    override fun calculatePosition(
        anchorBounds: IntRect,
        windowSize: IntSize,
        layoutDirection: LayoutDirection,
        popupContentSize: IntSize
    ): IntOffset {

        val isLtr = layoutDirection == LayoutDirection.Ltr

        // Coerce such that this..this+size fits into min..max; if impossible, align with min
        fun Int.coerceWithSizeIntoRangePreferMin(size: Int, min: Int, max: Int) = when {
            this < min -> min
            this + size > max -> max - size
            else -> this
        }

        // Coerce such that this..this+size fits into min..max; if impossible, align with max
        fun Int.coerceWithSizeIntoRangePreferMax(size: Int, min: Int, max: Int) = when {
            this + size > max -> max - size
            this < min -> min
            else -> this
        }

        fun Int.coerceWithSizeIntoRange(size: Int, min: Int, max: Int) = when {
            isLtr -> coerceWithSizeIntoRangePreferMin(size, min, max)
            else -> coerceWithSizeIntoRangePreferMax(size, min, max)
        }

        // The min margin above and below the menu, relative to the screen.
        val verticalMargin = with(density) { MenuVerticalMargin.roundToPx() }
        // The content offset specified using the dropdown offset parameter.
        val contentOffsetX = with(density) { contentOffset.x.roundToPx() }
        val contentOffsetY = with(density) { contentOffset.y.roundToPx() }

        // Compute horizontal position.
        val preferredX = if (isLtr) {
            anchorBounds.left + contentOffsetX
        }
        else {
            anchorBounds.right - contentOffsetX - popupContentSize.width
        }
        val x = preferredX.coerceWithSizeIntoRange(
            size = popupContentSize.width,
            min = 0,
            max = windowSize.width
        )

        // Compute vertical position.
        val toBottom = maxOf(anchorBounds.bottom + contentOffsetY, verticalMargin)
        val toTop = anchorBounds.top - contentOffsetY - popupContentSize.height
        val toCenter = anchorBounds.top - popupContentSize.height / 2
        val toWindowBottom = windowSize.height - popupContentSize.height - verticalMargin
        var y = sequenceOf(toBottom, toTop, toCenter, toWindowBottom).firstOrNull {
            it >= verticalMargin &&
                it + popupContentSize.height <= windowSize.height - verticalMargin
        } ?: toTop

        // Desktop specific vertical position checking
        val aboveAnchor = anchorBounds.top + contentOffsetY
        val belowAnchor = windowSize.height - anchorBounds.bottom - contentOffsetY

        if (belowAnchor >= aboveAnchor) {
            y = anchorBounds.bottom + contentOffsetY
        }

        if (y + popupContentSize.height > windowSize.height) {
            y = windowSize.height - popupContentSize.height
        }

        y = y.coerceAtLeast(0)

        onPositionCalculated(
            anchorBounds,
            IntRect(x, y, x + popupContentSize.width, y + popupContentSize.height)
        )
        return IntOffset(x, y)
    }
}