use-focus-path

A React Hook for managing focus in TV apps.

Motivation

Users of TV apps typically use LRUD for navigation. Accordingly, the element on the page that has focus is of particular importance.

It is not always the case that your runtime environment includes a system for managing focus. Environments that do include such a system, like the browser, typically have support for a one dimensional navigation system (i.e.; Tab and Shift + Tab), rather than two dimensional navigation (LRUD).

For these reasons, it is up to the app to manage its own focus state. This hook helps you to do that.

Installation

Install using npm:

npm install use-focus-path

or yarn:

yarn add use-focus-path

Guides

What is LRUD?

LRUD is an acronym that stands for left-right-up-down, and it refers to the directional buttons typically found on remotes. In LRUD systems, input devices usually also have some kind of "submit" button, and, less commonly, a back button.

What is a Focus Path?

A focus path is a string that represents an element on the page that has focus. For instance, you may have a focus path of "profilePage", representing that the profile page of your app has focus.

Focus paths can be hierarchical, too. A period is used to separate pieces of the path. In the focus path profilePage.0, the focus is on the 0th item within the profile page.

If you have used a modern JavaScript router, such as React Router, you may notice the similarity between routes and focus paths. Focus paths are very similar to routes. The difference is that routes represent the user's location within the app, whereas focus paths represent what has focus within the app.

Is this library right for me?

The limitations described below may help you to determine that.

Getting Started

Configure the Provider somewhere high up in your application's component tree. You may optionally specify an initial focus path.

import { FocusProvider } from 'use-focus-path';

export default function App() {
  return (
    <FocusProvider initialFocusPath="app.profile.settings.0">
      <AppContents />
    </FocusProvider>
  );
}

Next, use the hook in your components.

import { useFocusPath } from 'use-focus-path';

export default function Profile() {
  const { isFocused } = useFocusPath('profile');

  // ...use `isFocused`, or any of the other things returned by `useFocusPath`

  return <div className="profile">Profile</div>;
}

To learn more about the different properties of the return value of the hook, refer to the API documentation below.

API

This library has two named exports: FocusProvider and useFocusPath.

`<FocusProvider />`

A Context Provider that you must place at the root of your application.

import { FocusProvider } from 'use-focus-path';

export default function App() {
  return (
    <FocusProvider initialFocusPath="app.profile.settings.0">
      <AppContents />
    </FocusProvider>
  );
}

Prop	Default value	Description
`initialFocusPath`	`""`	The focus path to use when the app is initialized.

`useFocusPath( targetFocusPath )`

A Hook that returns information about whether or not targetFocusPath is focused, as well as functions to update the focus path.

Arguments	Type	Default value	Description
`targetFocusPath`	string	`""`	The focus path you are interested in knowing more about.

The return value of the hook has the following properties:

Arguments	Type	Description
`isFocused`	boolean	`true` when the `targetFocusPath`, or a child path, is focused.
`isFocusedExact`	boolean	`true` when the `targetFocusPath` is focused exactly.
`child`	string\|number	The direct child of `targetFocusPath`. Will be a number if the child is a number.
`focusPath`	string	The full focus path.
`setFocusPath`	function	Set a new focus path.
`setFocusedChild`	function	Update the focused child of `targetFocusPath`.
`setFocusedSibling`	function	Update the focus path with a sibling of `targetFocusPath`.

import { useFocusPath } from 'use-focus-path';

export default function Profile() {
  const { isFocused } = useFocusPath('profile');

  useEffect(() => {
    console.log('The focus state changed', isFocused);
  }, [isFocused]);

  return <div className="profile">Profile</div>;
}

Prior Art

Limitations

No support for pointer (mouse) inputs
No spatial navigation; all transitions must be manually specified

jasonmit / use-focus-path