LayoutModifierNode

interface LayoutModifierNode : DelegatableNode

A Modifier.Node that changes how its wrapped content is measured and laid out. It has the same measurement and layout functionality as the androidx.compose.ui.layout.Layout component, while wrapping exactly one layout due to it being a modifier. In contrast, the androidx.compose.ui.layout.Layout component is used to define the layout behavior of multiple children.

This is the androidx.compose.ui.Modifier.Node equivalent of androidx.compose.ui.layout.LayoutModifier

Functions

fun MeasureScope.measure(measurable: Measurable, constraints: Constraints): MeasureResult

The function used to measure the modifier. The measurable corresponds to the wrapped content, and it can be measured with the desired constraints according to the logic of the LayoutModifierNode. The modifier needs to choose its own size, which can depend on the size chosen by the wrapped content (the obtained Placeable), if the wrapped content was measured. The size needs to be returned as part of a MeasureResult, alongside the placement logic of the Placeable, which defines how the wrapped content should be positioned inside the LayoutModifierNode. A convenient way to create the MeasureResult is to use the MeasureScope.layout factory function.

A LayoutModifierNode uses the same measurement and layout concepts and principles as a androidx.compose.ui.layout.Layout, the only difference is that they apply to exactly one child. For a more detailed explanation of measurement and layout, see androidx.compose.ui.layout.MeasurePolicy.

fun IntrinsicMeasureScope.minIntrinsicWidth(measurable: IntrinsicMeasurable, height: Int): Int

The function used to calculate IntrinsicMeasurable.minIntrinsicWidth.

fun IntrinsicMeasureScope.minIntrinsicHeight(measurable: IntrinsicMeasurable, width: Int): Int

The lambda used to calculate IntrinsicMeasurable.minIntrinsicHeight.

fun IntrinsicMeasureScope.maxIntrinsicWidth(measurable: IntrinsicMeasurable, height: Int): Int

The function used to calculate IntrinsicMeasurable.maxIntrinsicWidth.

fun IntrinsicMeasureScope.maxIntrinsicHeight(measurable: IntrinsicMeasurable, width: Int): Int

The lambda used to calculate IntrinsicMeasurable.maxIntrinsicHeight.

Code Examples

LayoutModifierNodeSample

@Composable
fun LayoutModifierNodeSample() {
    class VerticalPadding(var padding: Dp) : LayoutModifierNode, Modifier.Node() {
        override fun MeasureScope.measure(
            measurable: Measurable,
            constraints: Constraints,
        ): MeasureResult {
            val paddingPx = padding.roundToPx()
            val placeable = measurable.measure(constraints.offset(vertical = -paddingPx))
            return layout(placeable.width, placeable.height + paddingPx) {
                placeable.placeRelative(0, paddingPx)
            }
        }
    }
    data class VerticalPaddingElement(val padding: Dp) : ModifierNodeElement<VerticalPadding>() {
        override fun create() = VerticalPadding(padding)
        override fun update(node: VerticalPadding) {
            node.padding = padding
        }
        override fun InspectorInfo.inspectableProperties() {
            name = "verticalPadding"
            properties["padding"] = padding
        }
    }
    fun Modifier.verticalPadding(padding: Dp) = this then VerticalPaddingElement(padding)
    Box(Modifier.background(Color.Gray).verticalPadding(50.dp)) {
        Box(Modifier.fillMaxSize().background(Color.DarkGray))
    }
}