| 1 | /*
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| 2 | * Copyright 2020 Adobe. All rights reserved.
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| 3 | * This file is licensed to you under the Apache License, Version 2.0 (the "License");
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| 4 | * you may not use this file except in compliance with the License. You may obtain a copy
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| 5 | * of the License at http://www.apache.org/licenses/LICENSE-2.0
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| 6 | *
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| 7 | * Unless required by applicable law or agreed to in writing, software distributed under
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| 8 | * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
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| 9 | * OF ANY KIND, either express or implied. See the License for the specific language
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| 10 | * governing permissions and limitations under the License.
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| 11 | */
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| 12 |
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| 13 | /**
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| 14 | * Scrolls `scrollView` so that `element` is visible.
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| 15 | * Similar to `element.scrollIntoView({block: 'nearest'})` (not supported in Edge),
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| 16 | * but doesn't affect parents above `scrollView`.
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| 17 | */
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| 18 | export function scrollIntoView(scrollView: HTMLElement, element: HTMLElement) {
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| 19 | let offsetX = relativeOffset(scrollView, element, 'left');
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| 20 | let offsetY = relativeOffset(scrollView, element, 'top');
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| 21 | let width = element.offsetWidth;
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| 22 | let height = element.offsetHeight;
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| 23 | let x = scrollView.scrollLeft;
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| 24 | let y = scrollView.scrollTop;
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| 25 | let maxX = x + scrollView.offsetWidth;
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| 26 | let maxY = y + scrollView.offsetHeight;
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| 27 |
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| 28 | if (offsetX <= x) {
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| 29 | x = offsetX;
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| 30 | } else if (offsetX + width > maxX) {
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| 31 | x += offsetX + width - maxX;
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| 32 | }
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| 33 | if (offsetY <= y) {
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| 34 | y = offsetY;
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| 35 | } else if (offsetY + height > maxY) {
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| 36 | y += offsetY + height - maxY;
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| 37 | }
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| 38 |
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| 39 | scrollView.scrollLeft = x;
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| 40 | scrollView.scrollTop = y;
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| 41 | }
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| 42 |
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| 43 | /**
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| 44 | * Computes the offset left or top from child to ancestor by accumulating
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| 45 | * offsetLeft or offsetTop through intervening offsetParents.
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| 46 | */
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| 47 | function relativeOffset(ancestor: HTMLElement, child: HTMLElement, axis: 'left'|'top') {
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| 48 | const prop = axis === 'left' ? 'offsetLeft' : 'offsetTop';
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| 49 | let sum = 0;
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| 50 | while (child.offsetParent) {
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| 51 | sum += child[prop];
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| 52 | if (child.offsetParent === ancestor) {
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| 53 | // Stop once we have found the ancestor we are interested in.
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| 54 | break;
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| 55 | } else if (child.offsetParent.contains(ancestor)) {
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| 56 | // If the ancestor is not `position:relative`, then we stop at
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| 57 | // _its_ offset parent, and we subtract off _its_ offset, so that
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| 58 | // we end up with the proper offset from child to ancestor.
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| 59 | sum -= ancestor[prop];
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| 60 | break;
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| 61 | }
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| 62 | child = child.offsetParent as HTMLElement;
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| 63 | }
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| 64 | return sum;
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| 65 | }
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