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-rw-r--r--ext/js/dom/window-scroll.js110
1 files changed, 110 insertions, 0 deletions
diff --git a/ext/js/dom/window-scroll.js b/ext/js/dom/window-scroll.js
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+++ b/ext/js/dom/window-scroll.js
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+/*
+ * 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 WindowScroll {
+ 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);
+ }
+ }
+}