Applier.kt
/*
* Copyright 2021 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.glance
import androidx.annotation.RestrictTo
import androidx.compose.runtime.AbstractApplier
import java.lang.IllegalStateException
/**
* Applier for the Glance composition.
* @suppress
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public class Applier(root: EmittableWithChildren) : AbstractApplier<Emittable>(root) {
private val newRootMaxDepth = root.maxDepth
override fun onClear() {
(root as EmittableWithChildren).children.clear()
}
override fun insertBottomUp(index: Int, instance: Emittable) {
// Ignored, the tree is built top-down.
}
override fun insertTopDown(index: Int, instance: Emittable) {
val parent = current as EmittableWithChildren
require(parent.maxDepth > 0) {
"Too many embedded views for the current surface. The maximum depth is: " +
"${(root as EmittableWithChildren).maxDepth}"
}
if (instance is EmittableWithChildren) {
instance.maxDepth = if (instance.resetsDepthForChildren) {
newRootMaxDepth
} else {
parent.maxDepth - 1
}
}
currentChildren.add(index, instance)
}
override fun move(from: Int, to: Int, count: Int) {
currentChildren.move(from, to, count)
}
override fun remove(index: Int, count: Int) {
currentChildren.remove(index, count)
}
private val currentChildren: MutableList<Emittable>
get() {
current.let {
if (it is EmittableWithChildren) {
return it.children
}
}
throw IllegalStateException("Current node cannot accept children")
}
}