vue-devtools/packages/app-frontend/src/features/chrome/pane-visibility.ts

import { isChrome } from '@vue-devtools/shared-utils'

let panelShown = !isChrome
let pendingAction: (() => void | Promise<void>) | null = null

if (isChrome) {
  chrome.runtime.onMessage.addListener((request) => {
    if (request === 'vue-panel-shown') {
      onPanelShown()
    }
    else if (request === 'vue-panel-hidden') {
      onPanelHidden()
    }
  })
}

export function ensurePaneShown(cb: () => void | Promise<void>) {
  if (panelShown) {
    cb()
  }
  else {
    pendingAction = cb
  }
}

function onPanelShown() {
  panelShown = true
  if (pendingAction) {
    pendingAction()
    pendingAction = null
  }
}

function onPanelHidden() {
  panelShown = false
}