react/packages/react-devtools-shared/src/devtools/views/Settings/SettingsModalContextToggle.js

// @flow

import React, {useCallback, useContext, useMemo} from 'react';
import {SettingsModalContext} from './SettingsModalContext';
import Button from '../Button';
import ButtonIcon from '../ButtonIcon';
import {StoreContext} from '../context';
import {useSubscription} from '../hooks';

export default function SettingsModalContextToggle() {
  const {setIsModalShowing} = useContext(SettingsModalContext);
  const store = useContext(StoreContext);
  const {profilerStore} = store;

  const showFilterModal = useCallback(() => setIsModalShowing(true), [
    setIsModalShowing,
  ]);

  // Updating preferences while profiling is in progress could break things (e.g. filtering)
  // Explicitly disallow it for now.
  const isProfilingSubscription = useMemo(
    () => ({
      getCurrentValue: () => profilerStore.isProfiling,
      subscribe: (callback: Function) => {
        profilerStore.addListener('isProfiling', callback);
        return () => profilerStore.removeListener('isProfiling', callback);
      },
    }),
    [profilerStore],
  );
  const isProfiling = useSubscription<boolean>(isProfilingSubscription);

  return (
    <Button
      disabled={isProfiling}
      onClick={showFilterModal}
      title="View settings">
      <ButtonIcon type="settings" />
    </Button>
  );
}