Header override requires grid CSS

[chrisvxd]

Overriding the header requires specifying grid CSS. The user shouldn't need to know about the parent CSS in order to override the header.

[henrycjchen]

Yes, currently we can only add style={{ gridArea: 'header' }} to support the one line through header. And it is not mentioned in the document.

The demo code should be:

const overrides = {
  header: ({ actions }) => (
    <header style={{ gridArea: 'header' }}>
      <span>My header</span>
      <div>{actions}</div>
    </header>
  ),
};