Function initBackend

packages/react-devtools-shared/src/backend/index.js:16–102

(
  hook: DevToolsHook,
  agent: Agent,
  global: Object,
  isReloadAndProfileSupported: boolean,
)

export type InitBackend = typeof initBackend;

export function initBackend(
  hook: DevToolsHook,
  agent: Agent,
  global: Object,
  isReloadAndProfileSupported: boolean,
): () => void {
  if (hook == null) {
    // DevTools didn't get injected into this page (maybe b'c of the contentType).
    return () => {};
  }

  function registerRendererInterface(
    id: RendererID,
    rendererInterface: RendererInterface,
  ) {
    agent.registerRendererInterface(id, rendererInterface);

    // Now that the Store and the renderer interface are connected,
    // it's time to flush the pending operation codes to the frontend.
    rendererInterface.flushInitialOperations();
  }

  const subs = [
    hook.sub(
      'renderer-attached',
      ({
        id,
        rendererInterface,
      }: {
        id: number,
        rendererInterface: RendererInterface,
      }) => {
        registerRendererInterface(id, rendererInterface);
      },
    ),
    hook.sub('unsupported-renderer-version', () => {
      agent.onUnsupportedRenderer();
    }),

    hook.sub('fastRefreshScheduled', agent.onFastRefreshScheduled),
    hook.sub('operations', agent.onHookOperations),
    hook.sub('traceUpdates', agent.onTraceUpdates),
    hook.sub('settingsInitialized', agent.onHookSettings),

    // TODO Add additional subscriptions required for profiling mode
  ];

  agent.addListener('getIfHasUnsupportedRendererVersion', () => {
    if (hook.hasUnsupportedRendererAttached) {
      agent.onUnsupportedRenderer();
    }
  });

  hook.rendererInterfaces.forEach((rendererInterface, id) => {
    registerRendererInterface(id, rendererInterface);
  });

  hook.emit('react-devtools', agent);