Move PerDisplayRepository from SystemUI to displaylib (77637ac6) · Commits · e / os / android_frameworks_libs_systemui

displaylib/src/com/android/app/displaylib/PerDisplayRepository.kt

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		/*
		* Copyright (C) 2025 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 com.android.app.displaylib

		import android.util.Log
		import android.view.Display
		import com.android.app.tracing.coroutines.launchTraced as launch
		import com.android.app.tracing.traceSection
		import dagger.assisted.Assisted
		import dagger.assisted.AssistedFactory
		import dagger.assisted.AssistedInject
		import java.util.concurrent.ConcurrentHashMap
		import javax.inject.Qualifier
		import kotlinx.coroutines.CoroutineScope
		import kotlinx.coroutines.flow.collectLatest

		/**
		* Used to create instances of type `T` for a specific display.
		*
		* This is useful for resources or objects that need to be managed independently for each connected
		* display (e.g., UI state, rendering contexts, or display-specific configurations).
		*
		* Note that in most cases this can be implemented by a simple `@AssistedFactory` with `displayId`
		* parameter
		*
		* ```kotlin
		* class SomeType @AssistedInject constructor(@Assisted displayId: Int,..)
		* @AssistedFactory
		* interface Factory {
		* fun create(displayId: Int): SomeType
		* }
		* }
		* ```
		*
		* Then it can be used to create a [PerDisplayRepository] as follows:
		* ```kotlin
		* // Injected:
		* val repositoryFactory: PerDisplayRepositoryImpl.Factory
		* val instanceFactory: PerDisplayRepositoryImpl.Factory
		* // repository creation:
		* repositoryFactory.create(instanceFactory::create)
		* ```
		*
		* @see PerDisplayRepository For how to retrieve and manage instances created by this factory.
		*/
		fun interface PerDisplayInstanceProvider<T> {
		/** Creates an instance for a display. */
		fun createInstance(displayId: Int): T?
		}

		/**
		* Extends [PerDisplayInstanceProvider], adding support for destroying the instance.
		*
		* This is useful for releasing resources associated with a display when it is disconnected or when
		* the per-display instance is no longer needed.
		*/
		interface PerDisplayInstanceProviderWithTeardown<T> : PerDisplayInstanceProvider<T> {
		/** Destroys a previously created instance of `T` forever. */
		fun destroyInstance(instance: T)
		}

		/**
		* Provides access to per-display instances of type `T`.
		*
		* Acts as a repository, managing the caching and retrieval of instances created by a
		* [PerDisplayInstanceProvider]. It ensures that only one instance of `T` exists per display ID.
		*/
		interface PerDisplayRepository<T> {
		/** Gets the cached instance or create a new one for a given display. */
		operator fun get(displayId: Int): T?

		/** Debug name for this repository, mainly for tracing and logging. */
		val debugName: String

		/**
		* Callback to run when a given repository is initialized.
		*
		* This allows the caller to perform custom logic when the repository is ready to be used, e.g.
		* register to dumpManager.
		*
		* Note that the instance is leaked outside of this class, so it should only be done when
		* repository is meant to live as long as the caller. In systemUI this is ok because the
		* repository lives as long as the process itself.
		*/
		fun interface InitCallback {
		fun onInit(debugName: String, instance: Any)
		}
		}

		/** Qualifier for [CoroutineScope] used for displaylib background tasks. */
		@Qualifier @Retention(AnnotationRetention.RUNTIME) annotation class DisplayLibBackground

		/**
		* Default implementation of [PerDisplayRepository].
		*
		* This class manages a cache of per-display instances of type `T`, creating them using a provided
		* [PerDisplayInstanceProvider] and optionally tearing them down using a
		* [PerDisplayInstanceProviderWithTeardown] when displays are disconnected.
		*
		* It listens to the [DisplayRepository] to detect when displays are added or removed, and
		* automatically manages the lifecycle of the per-display instances.
		*
		* Note that this is a [PerDisplayStoreImpl] 2.0 that doesn't require [CoreStartable] bindings,
		* providing all args in the constructor.
		*/
		class PerDisplayInstanceRepositoryImpl<T>
		@AssistedInject
		constructor(
		@Assisted override val debugName: String,
		@Assisted private val instanceProvider: PerDisplayInstanceProvider<T>,
		@DisplayLibBackground bgApplicationScope: CoroutineScope,
		private val displayRepository: DisplayRepository,
		private val initCallback: PerDisplayRepository.InitCallback,
		) : PerDisplayRepository<T> {

		private val perDisplayInstances = ConcurrentHashMap<Int, T?>()

		init {
		bgApplicationScope.launch("$debugName#start") { start() }
		}

		private suspend fun start() {
		initCallback.onInit(debugName, this)
		displayRepository.displayIds.collectLatest { displayIds ->
		val toRemove = perDisplayInstances.keys - displayIds
		toRemove.forEach { displayId ->
		Log.d(TAG, "<$debugName> destroying instance for displayId=$displayId.")
		perDisplayInstances.remove(displayId)?.let { instance ->
		(instanceProvider as? PerDisplayInstanceProviderWithTeardown)?.destroyInstance(
		instance
		)
		}
		}
		}
		}

		override fun get(displayId: Int): T? {
		if (displayRepository.getDisplay(displayId) == null) {
		Log.e(TAG, "<$debugName: Display with id $displayId doesn't exist.")
		return null
		}

		// If it doesn't exist, create it and put it in the map.
		return perDisplayInstances.computeIfAbsent(displayId) { key ->
		Log.d(TAG, "<$debugName> creating instance for displayId=$key, as it wasn't available.")
		val instance =
		traceSection({ "creating instance of $debugName for displayId=$key" }) {
		instanceProvider.createInstance(key)
		}
		if (instance == null) {
		Log.e(
		TAG,
		"<$debugName> returning null because createInstance($key) returned null.",
		)
		}
		instance
		}
		}

		@AssistedFactory
		interface Factory<T> {
		fun create(
		debugName: String,
		instanceProvider: PerDisplayInstanceProvider<T>,
		): PerDisplayInstanceRepositoryImpl<T>
		}

		companion object {
		private const val TAG = "PerDisplayInstanceRepo"
		}

		override fun toString(): String {
		return "PerDisplayInstanceRepositoryImpl(" +
		"debugName='$debugName', instances=$perDisplayInstances)"
		}
		}

		/**
		* Provides an instance of a given class only for the default display, even if asked for another
		* display.
		*
		* This is useful in case of flag refactors: it can be provided instead of an instance of
		* [PerDisplayInstanceRepositoryImpl] when a flag related to multi display refactoring is off.
		*
		* Note that this still requires all instances to be provided by a [PerDisplayInstanceProvider]. If
		* you want to provide an existing instance instead for the default display, either implement it in
		* a custom [PerDisplayInstanceProvider] (e.g. inject it in the constructor and return it if the
		* displayId is zero), or use [SingleInstanceRepositoryImpl].
		*/
		class DefaultDisplayOnlyInstanceRepositoryImpl<T>(
		override val debugName: String,
		private val instanceProvider: PerDisplayInstanceProvider<T>,
		) : PerDisplayRepository<T> {
		private val lazyDefaultDisplayInstance by lazy {
		instanceProvider.createInstance(Display.DEFAULT_DISPLAY)
		}

		override fun get(displayId: Int): T? = lazyDefaultDisplayInstance
		}

		/**
		* Always returns [instance] for any display.
		*
		* This can be used to provide a single instance based on a flag value during a refactor. Similar to
		* [DefaultDisplayOnlyInstanceRepositoryImpl], but also avoids creating the
		* [PerDisplayInstanceProvider]. This is useful when you want to provide an existing instance only,
		* without even instantiating a [PerDisplayInstanceProvider].
		*/
		class SingleInstanceRepositoryImpl<T>(override val debugName: String, private val instance: T) :
		PerDisplayRepository<T> {
		override fun get(displayId: Int): T? = instance
		}