How to get the forwarded ref in an async loaded child component

[geohuz]

My case is that I have a base map in svg format, this base map can be changed by user and loaded from server, once the map is loaded I need to get the svg's bbox to have width and height of the component. I've thought this may be implmented with using ref and passing down to the base map component from parent, and using the ref.getBBox(). But the onMount function in parent component doesn't seems to get the ref at the time of child being mounted.

parent component:

function App() {
  let svgRef
  onMount(()=> {
    console.log(svgRef) /* always undefined */
  })

  return <DynaSvg name="basemap" ref={svgRef} />
}

the dynamically created asynic child component:

import { createResource } from "solid-js";

export const DynaSvg = (props) => {
  const fetchSvg = async ({ name, parentRef }) => {
    /* the passed ref is being assigned with a value now */
    let componentObject = (await import(/* @vite-ignore */ `./${name}.svg`))
      .default;
    componentObject.ref = parentRef;
    return componentObject;
  };
  const [SvgComp] = createResource(
    { name: props.name, parentRef: props.ref },
    fetchSvg,
  );
  return (
    <>
      <span> {SvgComp.loading && "loading..."} </span>
      {SvgComp()}
    </>
  );
};

Now my question is, is there a way to grab the forwared ref in a asynic created component? Or just using store/signal to get the child dimensions?