1 /*
2  * Copyright 2021 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package androidx.compose.runtime.snapshots
18 
19 import androidx.compose.runtime.Composable
20 import androidx.compose.runtime.MutableState
21 import androidx.compose.runtime.RecomposeScope
22 import androidx.compose.runtime.SnapshotMutationPolicy
23 import androidx.compose.runtime.State
24 import androidx.compose.runtime.mutableStateOf
25 
26 /**
27  * A mutable value holder where reads to the [value] property during the execution of a [Composable]
28  * function, the current [RecomposeScope] will be subscribed to changes of that value. When the
29  * [value] property is written to and changed, a recomposition of any subscribed [RecomposeScope]s
30  * will be scheduled. Writes to it are transacted as part of the [Snapshot] system.
31  *
32  * In general for correctness: Anything that is mutable, that is read during composition or written
33  * to during composition, should be a [SnapshotMutableState].
34  *
35  * @see [State]
36  * @see [MutableState]
37  * @see [mutableStateOf]
38  */
39 interface SnapshotMutableState<T> : MutableState<T> {
40     /** A policy to control how changes are handled in a mutable snapshot. */
41     val policy: SnapshotMutationPolicy<T>
42 }
43