1 | import { Lambda, once, untrackedEnd, untrackedStart } from "../internal"
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2 |
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3 | export interface IListenable {
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4 | changeListeners_: Function[] | undefined
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5 | }
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6 |
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7 | export function hasListeners(listenable: IListenable) {
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8 | return listenable.changeListeners_ !== undefined && listenable.changeListeners_.length > 0
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9 | }
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10 |
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11 | export function registerListener(listenable: IListenable, handler: Function): Lambda {
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12 | const listeners = listenable.changeListeners_ || (listenable.changeListeners_ = [])
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13 | listeners.push(handler)
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14 | return once(() => {
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15 | const idx = listeners.indexOf(handler)
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16 | if (idx !== -1) listeners.splice(idx, 1)
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17 | })
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18 | }
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19 |
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20 | export function notifyListeners<T>(listenable: IListenable, change: T) {
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21 | const prevU = untrackedStart()
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22 | let listeners = listenable.changeListeners_
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23 | if (!listeners) return
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24 | listeners = listeners.slice()
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25 | for (let i = 0, l = listeners.length; i < l; i++) {
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26 | listeners[i](change)
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27 | }
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28 | untrackedEnd(prevU)
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29 | }
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