commonMain.androidx.compose.ui.layout.RootMeasurePolicy.kt Maven / Gradle / Ivy

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/*
 * Copyright 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.compose.ui.layout

import androidx.compose.ui.node.LayoutNode
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.constrainHeight
import androidx.compose.ui.unit.constrainWidth
import androidx.compose.ui.util.fastForEach
import androidx.compose.ui.util.fastMap

internal object RootMeasurePolicy :
    LayoutNode.NoIntrinsicsMeasurePolicy("Undefined intrinsics block and it is required") {
    override fun MeasureScope.measure(
        measurables: List,
        constraints: Constraints
    ): MeasureResult {
        return when (measurables.size) {
            0 -> {
                layout(constraints.minWidth, constraints.minHeight) {}
            }
            1 -> {
                val placeable = measurables[0].measure(constraints)
                layout(
                    constraints.constrainWidth(placeable.width),
                    constraints.constrainHeight(placeable.height)
                ) {
                    placeable.placeRelativeWithLayer(0, 0)
                }
            }
            else -> {
                var maxWidth = 0
                var maxHeight = 0
                val placeables =
                    measurables.fastMap {
                        it.measure(constraints).apply {
                            maxWidth = maxOf(width, maxWidth)
                            maxHeight = maxOf(height, maxHeight)
                        }
                    }
                layout(
                    constraints.constrainWidth(maxWidth),
                    constraints.constrainHeight(maxHeight)
                ) {
                    placeables.fastForEach { placeable -> placeable.placeRelativeWithLayer(0, 0) }
                }
            }
        }
    }
}