RootMeasureBlocks.kt
/*
* 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.ExperimentalLayoutNodeApi
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
@OptIn(ExperimentalLayoutNodeApi::class)
internal object RootMeasureBlocks : LayoutNode.NoIntrinsicsMeasureBlocks(
"Undefined intrinsics block and it is required"
) {
override fun measure(
measureScope: MeasureScope,
measurables: List<Measurable>,
constraints: Constraints
): MeasureResult {
return when {
measurables.isEmpty() -> {
measureScope.layout(constraints.minWidth, constraints.minHeight) {}
}
measurables.size == 1 -> {
val placeable = measurables[0].measure(constraints)
measureScope.layout(
constraints.constrainWidth(placeable.width),
constraints.constrainHeight(placeable.height)
) {
placeable.placeRelativeWithLayer(0, 0)
}
}
else -> {
val placeables = measurables.map {
it.measure(constraints)
}
var maxWidth = 0
var maxHeight = 0
placeables.fastForEach { placeable ->
maxWidth = maxOf(placeable.width, maxWidth)
maxHeight = maxOf(placeable.height, maxHeight)
}
measureScope.layout(
constraints.constrainWidth(maxWidth),
constraints.constrainHeight(maxHeight)
) {
placeables.fastForEach { placeable ->
placeable.placeRelativeWithLayer(0, 0)
}
}
}
}
}
}