Responsive Typography

While there are many different approaches to styling responsive typography on the web, the theme.styles API can be used to create rich, responsive typography in MDX documents, with full control over the end result. Used in combination with responsive array values and variants, you can create reusable typographic styles that don't pollute the global CSS scope.

// example theme with responsive typography styles
{
  fontSizes: [
    12, 14, 16, 18, 24, 32, 48, 64, 72,
  ],
  fonts: {
    body: 'system-ui, sans-serif',
    heading: 'Poppins, sans-serif',
  },
  fontWeights: {
    body: 400,
    heading: 900,
    bold: 700,
  },
  lineHeights: {
    body: 1.5,
    heading: 1.125,
  },
  text: {
    heading: {
      fontFamily: 'heading',
      fontWeight: 'heading',
      lineHeight: 'heading',
    },
  },
  styles: {
    root: {
      fontFamily: 'body',
      fontWeight: 'body',
      lineHeight: 'body',
    },
    p: {
      fontSize: [2, 3],
    },
    h1: {
      variant: 'text.heading',
      fontSize: [5, 6, 7],
    },
    h2: {
      variant: 'text.heading',
      fontSize: [4, 5],
    },
  },
}

Caveats

Due to how CSS specificity works, if you've defined responsive styles in theme.styles, overriding styles with the sx prop requires also including styles for the breakpoints set in the theme. For example, with the following, the fontSize style will only apply at the smallest breakpoint, and the theme.styles.h1 responsive styles will apply at other breakpoints.

// example theme
{
  styles: {
    h1: {
      fontSize: [ 4, 5, 6 ],
    }
  }
}

<Themed.h1
  sx={{
    // styles for larger breakpoints will still apply
    // due to CSS specificity in media queries
    fontSize: 3,
  }}
/>

Non-MDX content

The Themed components can be used to pick up responsive styles outside of MDX, but if you'd like to apply styles to other markdown or user generated content, you can use the sx prop with a variant to style child elements. What this does is take the entire theme.styles object, adds a scoped classname to the <div>, and injects CSS with child selectors based on the keys in theme.styles.

export default (props) => (
  <div
    sx={{
      variant: 'styles',
    }}>
    {props.children}
  </div>
)

Optionally, the Themed.root component can be used to set base styles within the <div>.

export default (props) => (
  <div
    sx={{
      variant: 'styles',
    }}>
    <Themed.root>{props.children}</Themed.root>
  </div>
)