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Descendant styles dependent on ancestor state

Consider the case where the content within a sidebar needs to have conditional styles applied when the sidebar as whole is hovered.

Using CSS variables, you can style descendants based on a parent's state, such as :hover.

Step 1

Define one or more variables using stylex.defineVars:

// variables.stylex.ts
import * as stylex from '@stylexjs/stylex';

export const vars = stylex.defineVars({
  childColor: 'black',
});

Step 2

Define conditional styles setting the value for the variable in the ancestor component.

import * as stylex from '@stylexjs/stylex';
import { vars } from './variables.stylex';

const styles = stylex.create({
  parent: {
    [vars.childColor]: {
      default: 'black',
      ':hover': 'blue',
    },
  },
});

function ParentWithHover({children}) {
  return (
    <div {...stylex.props(styles.parent)}>
      {children}
    </div>
  );
}

Step 3

Use the variable to style the child component

import * as stylex from '@stylexjs/stylex';
import { vars } from './variables.stylex';

const styles = stylex.create({
  row: {
    color: vars.childColor,
  }
});

function ParentWithHover() {
  return (
      <span {...stylex.props(styles.child)}><Icon />A Row</span>
  );
}

Example: Sidebar