39 lines
1.4 KiB
TypeScript
39 lines
1.4 KiB
TypeScript
/*
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Copyright 2022 New Vector Ltd
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Licensed 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.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { RoomState, RoomStateEvent } from "matrix-js-sdk/src/models/room-state";
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import { useCallback, useMemo, useState } from "react";
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import type { Room } from "matrix-js-sdk/src/models/room";
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import { useTypedEventEmitter } from "../useEvents";
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/**
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* A React hook for values computed from room state.
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* @param room The room.
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* @param f A mapping from the current room state to the computed value.
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* @returns The computed value.
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*/
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export const useRoomState = <T>(room: Room, f: (state: RoomState) => T): T => {
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const [numUpdates, setNumUpdates] = useState(0);
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useTypedEventEmitter(
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room,
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RoomStateEvent.Update,
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useCallback(() => setNumUpdates((n) => n + 1), [setNumUpdates])
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);
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// We want any change to the update counter to trigger an update here
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// eslint-disable-next-line react-hooks/exhaustive-deps
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return useMemo(() => f(room.currentState), [room, f, numUpdates]);
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};
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