1// Copyright (C) 2018 The Android Open Source Project 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14 15import {globals} from './globals'; 16 17export class Animation { 18 private startMs = 0; 19 private endMs = 0; 20 private boundOnAnimationFrame = this.onAnimationFrame.bind(this); 21 22 constructor(private onAnimationStep: (timeSinceStartMs: number) => void) {} 23 24 start(durationMs: number) { 25 const nowMs = performance.now(); 26 27 // If the animation is already happening, just update its end time. 28 if (nowMs <= this.endMs) { 29 this.endMs = nowMs + durationMs; 30 return; 31 } 32 this.startMs = nowMs; 33 this.endMs = nowMs + durationMs; 34 globals.rafScheduler.start(this.boundOnAnimationFrame); 35 } 36 37 stop() { 38 this.endMs = 0; 39 globals.rafScheduler.stop(this.boundOnAnimationFrame); 40 } 41 42 get startTimeMs(): number { 43 return this.startMs; 44 } 45 46 private onAnimationFrame(nowMs: number) { 47 if (nowMs >= this.endMs) { 48 globals.rafScheduler.stop(this.boundOnAnimationFrame); 49 return; 50 } 51 this.onAnimationStep(Math.max(Math.round(nowMs - this.startMs), 0)); 52 } 53} 54