vue-devtools/packages/app-backend-core/src/flash.ts

import type { DevtoolsBackend } from '@vue-devtools/app-backend-api'
import type { ComponentInstance } from '@vue/devtools-api'

export async function flashComponent(instance: ComponentInstance, backend: DevtoolsBackend) {
  const bounds = await backend.api.getComponentBounds(instance)
  if (bounds) {
    let overlay: HTMLDivElement = instance.__VUE_DEVTOOLS_FLASH
    if (!overlay) {
      overlay = document.createElement('div')
      instance.__VUE_DEVTOOLS_FLASH = overlay
      overlay.style.border = '2px rgba(65, 184, 131, 0.7) solid'
      overlay.style.position = 'fixed'
      overlay.style.zIndex = '99999999999998'
      overlay.style.pointerEvents = 'none'
      overlay.style.borderRadius = '3px'
      overlay.style.boxSizing = 'border-box'
      document.body.appendChild(overlay)
    }
    overlay.style.opacity = '1'
    overlay.style.transition = null
    overlay.style.width = `${Math.round(bounds.width)}px`
    overlay.style.height = `${Math.round(bounds.height)}px`
    overlay.style.left = `${Math.round(bounds.left)}px`
    overlay.style.top = `${Math.round(bounds.top)}px`
    requestAnimationFrame(() => {
      overlay.style.transition = 'opacity 1s'
      overlay.style.opacity = '0'
    })
    clearTimeout((overlay as any)._timer)
    ;(overlay as any)._timer = setTimeout(() => {
      document.body.removeChild(overlay)
      instance.__VUE_DEVTOOLS_FLASH = null
    }, 1000)
  }
}