DelegatingNode.kt
/*
* Copyright 2022 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.node
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
@ExperimentalComposeUiApi
abstract class DelegatingNode : Modifier.Node() {
override fun updateCoordinator(coordinator: NodeCoordinator?) {
super.updateCoordinator(coordinator)
forEachDelegate {
it.updateCoordinator(coordinator)
}
}
private var delegate: Modifier.Node? = null
fun <T : Modifier.Node> delegated(fn: () -> T): T {
val owner = node
val delegate = fn()
delegate.setAsDelegateTo(owner)
if (isAttached) {
updateCoordinator(owner.coordinator)
delegate.attach()
}
addDelegate(delegate)
return delegate
}
private fun addDelegate(node: Modifier.Node) {
val tail = delegate
if (tail != null) {
node.parent = tail
}
delegate = node
}
fun <T : Modifier.Node> lazyDelegated(fn: () -> T): Lazy<T> = lazy(LazyThreadSafetyMode.NONE) {
delegated(fn)
}
private inline fun forEachDelegate(block: (Modifier.Node) -> Unit) {
var node: Modifier.Node? = delegate
while (node != null) {
block(node)
node = node.parent
}
}
override fun onAttach() {
super.onAttach()
forEachDelegate {
updateCoordinator(coordinator)
it.attach()
}
}
override fun onDetach() {
forEachDelegate { it.detach() }
super.onDetach()
}
}