57 lines
1.7 KiB
Plaintext
57 lines
1.7 KiB
Plaintext
/*
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* Copyright 2020 Adobe. All rights reserved.
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* This file is licensed to you under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License. You may obtain a copy
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* of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under
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* the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
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* OF ANY KIND, either express or implied. See the License for the specific language
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* governing permissions and limitations under the License.
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*/
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import {Point} from './Point';
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import {Rect} from './Rect';
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export class OverscanManager {
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private startTime = 0;
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private velocity = new Point(0, 0);
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private visibleRect = new Rect();
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setVisibleRect(rect: Rect): void {
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let time = performance.now() - this.startTime;
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if (time < 500) {
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if (rect.x !== this.visibleRect.x && time > 0) {
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this.velocity.x = (rect.x - this.visibleRect.x) / time;
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}
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if (rect.y !== this.visibleRect.y && time > 0) {
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this.velocity.y = (rect.y - this.visibleRect.y) / time;
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}
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}
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this.startTime = performance.now();
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this.visibleRect = rect;
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}
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getOverscannedRect(): Rect {
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let overscanned = this.visibleRect.copy();
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let overscanY = this.visibleRect.height / 3;
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overscanned.height += overscanY;
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if (this.velocity.y < 0) {
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overscanned.y -= overscanY;
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}
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if (this.velocity.x !== 0) {
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let overscanX = this.visibleRect.width / 3;
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overscanned.width += overscanX;
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if (this.velocity.x < 0) {
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overscanned.x -= overscanX;
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}
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}
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return overscanned;
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}
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}
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