/* * Copyright (C) 2019-2021 Yomichan Authors * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <https://www.gnu.org/licenses/>. */ class ScrollElement { constructor(node) { this._node = node; this._animationRequestId = null; this._animationStartTime = 0; this._animationStartX = 0; this._animationStartY = 0; this._animationEndTime = 0; this._animationEndX = 0; this._animationEndY = 0; this._requestAnimationFrameCallback = this._onAnimationFrame.bind(this); } get x() { return this._node !== null ? this._node.scrollLeft : window.scrollX || window.pageXOffset; } get y() { return this._node !== null ? this._node.scrollTop : window.scrollY || window.pageYOffset; } toY(y) { this.to(this.x, y); } toX(x) { this.to(x, this.y); } to(x, y) { this.stop(); this._scroll(x, y); } animate(x, y, time) { this._animationStartX = this.x; this._animationStartY = this.y; this._animationStartTime = window.performance.now(); this._animationEndX = x; this._animationEndY = y; this._animationEndTime = this._animationStartTime + time; this._animationRequestId = window.requestAnimationFrame(this._requestAnimationFrameCallback); } stop() { if (this._animationRequestId === null) { return; } window.cancelAnimationFrame(this._animationRequestId); this._animationRequestId = null; } // Private _onAnimationFrame(time) { if (time >= this._animationEndTime) { this._scroll(this._animationEndX, this._animationEndY); this._animationRequestId = null; return; } const t = this._easeInOutCubic((time - this._animationStartTime) / (this._animationEndTime - this._animationStartTime)); this._scroll( this._lerp(this._animationStartX, this._animationEndX, t), this._lerp(this._animationStartY, this._animationEndY, t) ); this._animationRequestId = window.requestAnimationFrame(this._requestAnimationFrameCallback); } _easeInOutCubic(t) { if (t < 0.5) { return (4.0 * t * t * t); } else { t = 1.0 - t; return 1.0 - (4.0 * t * t * t); } } _lerp(start, end, percent) { return (end - start) * percent + start; } _scroll(x, y) { if (this._node !== null) { this._node.scrollLeft = x; this._node.scrollTop = y; } else { window.scroll(x, y); } } }