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reactjsmaterial-uinext.jscss-modules

Nextjs css flickering

I'm building a react app using material ui and nextjs. I'm using <Autocomplete /> component, provided by material UI and override some its styles with my own like this:

<Autocomplete
  classes={{
    root: `${styles[`search__autocomplete`]} ${
      styles[`search--${variant}__autocomplete`]
    }`,
    inputRoot: `${styles[`search__autocomplete-input`]} ${
      styles[`search--${variant}__autocomplete-input`]
    }`
  }} 
/>

variant is a prop, which gets passed to the component and styles is a variable, which get imported from the css module: import styles from "Search.module.sass".

Now, when I'm working on this locally everything looks great:

expected

But, after I deploy it to production via next build && next export I start experiencing "flickering" effect when for like 1/3 of a second my page looks like this:

enter image description here

My guess is that it might be related to the fact that nextjs export my css to several files on production:

    <link
      rel="preload"
      href="/_next/static/css/4dcd7fa805fb41261f08.css"
      as="style"
    />
    <link
      rel="stylesheet"
      href="/_next/static/css/4dcd7fa805fb41261f08.css"
      data-n-g=""
    />
    <link
      rel="preload"
      href="/_next/static/css/a23cf79bceae4047fddb.css"
      as="style"
    />
    <link
      rel="stylesheet"
      href="/_next/static/css/a23cf79bceae4047fddb.css"
      data-n-p=""
    />

How can I solve that?

Solution

  • The solution was to create a custom pages/_document.js page with:

    import React from 'react';
// Modules
import Document, { Html, Head, Main, NextScript } from 'next/document';
// MUI Core
import { ServerStyleSheets } from '@material-ui/core/styles';

class MyDocument extends Document {
  render() {
    return (
      <Html lang="en">
        <Head>

          <link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Open+Sans:wght@300;400;600;700&display=swap" />
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    );
  }
}

// `getInitialProps` belongs to `_document` (instead of `_app`),
// it's compatible with server-side rendering (SSR).
MyDocument.getInitialProps = async (ctx) => {
  // Resolution order
  //
  // On the server:
  // 1. app.getInitialProps
  // 2. page.getInitialProps
  // 3. document.getInitialProps
  // 4. app.render
  // 5. page.render
  // 6. document.render
  //
  // On the server with error:
  // 1. document.getInitialProps
  // 2. app.render
  // 3. page.render
  // 4. document.render
  //
  // On the client
  // 1. app.getInitialProps
  // 2. page.getInitialProps
  // 3. app.render
  // 4. page.render

  // Render app and page and get the context of the page with collected side effects.
  const sheets = new ServerStyleSheets();
  const originalRenderPage = ctx.renderPage;

  ctx.renderPage = () => originalRenderPage({
    enhanceApp: (App) => (props) => sheets.collect(<App {...props} />),
  });

  const initialProps = await Document.getInitialProps(ctx);

  return {
    ...initialProps,
    // Styles fragment is rendered after the app and page rendering finish.
    styles: [
      ...React.Children.toArray(initialProps.styles),
      sheets.getStyleElement(),
    ],
  };
};

export default MyDocument;