| /* |
| * Copyright 2020 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 |
| |
| import androidx.compose.runtime.dispatch.MonotonicFrameClock |
| import kotlinx.coroutines.suspendCancellableCoroutine |
| import kotlin.coroutines.Continuation |
| |
| /** |
| * A simple frame clock used by [Recomposer]. |
| * |
| * This implementation is intended for low-contention environments involving |
| * low total numbers of threads in a pool on the order of ~number of CPU cores available for UI |
| * recomposition work, while avoiding additional allocation where possible. |
| * |
| * [onNewAwaiters] will be invoked whenever the number of awaiters has changed from 0 to 1. |
| */ |
| internal class BroadcastFrameClock( |
| private val onNewAwaiters: (() -> Unit)? = null |
| ) : MonotonicFrameClock { |
| |
| private data class FrameAwaiter<R>(val onFrame: (Long) -> R, val continuation: Continuation<R>) |
| |
| private val lock = Any() |
| private var awaiters = mutableListOf<FrameAwaiter<*>>() |
| private var spareList = mutableListOf<FrameAwaiter<*>>() |
| |
| val hasAwaiters: Boolean get() = synchronized(lock) { awaiters.isNotEmpty() } |
| |
| @Suppress("UNCHECKED_CAST") |
| fun sendFrame(timeNanos: Long) { |
| synchronized(lock) { |
| // Rotate the lists so that if a resumed continuation on an immediate dispatcher |
| // bound to the thread calling sendFrame immediately awaits again we don't disrupt |
| // iteration of resuming the rest. |
| val toResume = awaiters |
| awaiters = spareList |
| spareList = toResume |
| |
| for (i in 0 until toResume.size) { |
| val (onFrame, co) = toResume[i] as FrameAwaiter<Any?> |
| co.resumeWith(runCatching { onFrame(timeNanos) }) |
| } |
| toResume.clear() |
| } |
| } |
| |
| override suspend fun <R> withFrameNanos( |
| onFrame: (Long) -> R |
| ): R = suspendCancellableCoroutine { co -> |
| val awaiter = FrameAwaiter(onFrame, co) |
| val hasNewAwaiters = synchronized(lock) { |
| val hadAwaiters = awaiters.isNotEmpty() |
| awaiters.add(awaiter) |
| !hadAwaiters |
| } |
| |
| co.invokeOnCancellation { |
| synchronized(lock) { |
| awaiters.remove(awaiter) |
| } |
| } |
| |
| // Wake up anything that was waiting for someone to schedule a frame |
| if (hasNewAwaiters) onNewAwaiters?.invoke() |
| } |
| } |