| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | */ |
| 7 | |
| 8 | /** |
| 9 | * These variables store information about text content of a target node, |
| 10 | * allowing comparison of content before and after a given event. |
| 11 | * |
| 12 | * Identify the node where selection currently begins, then observe |
| 13 | * both its text content and its current position in the DOM. Since the |
| 14 | * browser may natively replace the target node during composition, we can |
| 15 | * use its position to find its replacement. |
| 16 | * |
| 17 | * |
| 18 | */ |
| 19 | |
| 20 | let root = null; |
| 21 | let startText = null; |
| 22 | let fallbackText = null; |
| 23 | |
| 24 | export function initialize(nativeEventTarget) { |
| 25 | root = nativeEventTarget; |
| 26 | startText = getText(); |
| 27 | return true; |
| 28 | } |
| 29 | |
| 30 | export function reset() { |
| 31 | root = null; |
| 32 | startText = null; |
| 33 | fallbackText = null; |
| 34 | } |
| 35 | |
| 36 | export function getData() { |
| 37 | if (fallbackText) { |
| 38 | return fallbackText; |
| 39 | } |
| 40 | |
| 41 | let start; |
| 42 | const startValue = startText; |
| 43 | const startLength = startValue.length; |
| 44 | let end; |
| 45 | const endValue = getText(); |
| 46 | const endLength = endValue.length; |
| 47 | |
| 48 | for (start = 0; start < startLength; start++) { |
| 49 | if (startValue[start] !== endValue[start]) { |
| 50 | break; |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | const minEnd = startLength - start; |
| 55 | for (end = 1; end <= minEnd; end++) { |
| 56 | if (startValue[startLength - end] !== endValue[endLength - end]) { |
| 57 | break; |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | const sliceTail = end > 1 ? 1 - end : undefined; |
| 62 | fallbackText = endValue.slice(start, sliceTail); |
| 63 | return fallbackText; |
| 64 | } |
| 65 | |
| 66 | export function getText() { |
| 67 | if ('value' in root) { |
| 68 | return root.value; |
| 69 | } |
| 70 | return root.textContent; |
| 71 | } |