PinnableParent.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.foundation.lazy.layout
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.ui.modifier.modifierLocalOf
// This is a temporary placeholder implementation that prevents the newly focused item from being
// disposed while it is brought into view. We ultimately need a generic solution for this use case
// and to support b/195049010.
/**
* This is a modifier local that is used to implement pinning (Keeping items around even when they
* are beyond visible bounds).
*
* This API is experimental and will change in the future.
*/
@Suppress("OPT_IN_MARKER_ON_WRONG_TARGET")
@get: ExperimentalFoundationApi
@ExperimentalFoundationApi
val ModifierLocalPinnableParent = modifierLocalOf<PinnableParent?> { null }
/**
* Parent modifiers that implement this interface should retain its current children when it
* receives a call to [pinItems] and return a [PinnedItemsHandle]. It should hold on to
* thesechildren until it receives a call to [PinnedItemsHandle.unpin].
*/
@ExperimentalFoundationApi
interface PinnableParent {
/**
* Pin the currently composed items.
*/
fun pinItems(): PinnedItemsHandle
/**
* This is an object returned by [PinnableParent.pinItems] when it pins its
* currently composed items. It provides an [unpin] function to release the pinned children.
*/
@ExperimentalFoundationApi
interface PinnedItemsHandle {
/**
* Un-pin the items associated with this [PinnedItemsHandle].
*/
fun unpin()
}
}