attaching css to shadow dom with nextjs and geistui

[yifan]

Hi,

I am trying to apply css to shadow dom for my browser extension. I tried:

let shadowRoot = hostElement.attachShadow({ mode: "open" });

let styleElement = document.createElement("style");
styleElement.textContent = CssBaseline.flushToHTML();
shadowRoot.appendChild(styleElement);

render(app, shadowRoot);

The CssBaseline.flushToHTML is empty. CssBaseline.flush also returns an empty array. What am I doing wrong here? Thanks in advance.