Focus

⚠️ This library is deprecated; please use https://github.com/jamesplease/lrud instead

A React library for managing focus in TV apps.

✓ Controls LRUD navigation for you – automatically
✓ Hooks-first declarative API

Motivation

Users of TV apps most often use LRUD controls to navigate within the app. Consequently, the focused element on the page is of particular importance.

It is not always the case that your runtime environment includes a built-in system for managing focus. Environments that do include such a system, like the browser, often have a simple focus system that doesn't align with the complex needs of LRUD environments.

Because of this, it is up to the application to manage its own focus state. This library helps you to do that.

Installation

Install using npm:

npm install @xdproto/focus

or yarn:

yarn add @xdproto/focus

This library has the following peer dependencies:

• react@^16.8.0

Table of Contents

• Guides
  • Getting started
  • FAQ
• API
  • <FocusRoot/>
  • <FocusNode/>
  • useIsFocused()
  • useFocusTree()
  • useFocusHierarchy()
• Prior Art
• Limitations

Guides

Getting Started

Render the FocusRoot somewhere high up in your application's component tree. This is the root node of the focus tree.

import { FocusRoot } from '@xdproto/focus';

export default function App() {
  return (
    <FocusRoot>
      <AppContents />
    </FocusRoot>
  );
}

Next, use the FocusNode component to create a focusable node on the page.

import { FocusNode } from '@xdproto/focus';

export default function Profile() {
  return <FocusNode className="profile">Profile</FocusNode>;
}

This library manages moving focus between the FocusNode nodes as the user inputs LRUD commands.

Configuring this behavior is managed entirely through props of the FocusNode components. To learn more about those props, refer to the API documentation below.

FAQ

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.

Is this library right for me?

The limitations described below may help you to determine that.

API

This library has three named exports: FocusRoot, FocusNode, and useFocus.

<FocusRoot />

Serves as the root node of a new focus hierarchy.

All props are optional.

Prop	Type	Default value	Description
orientation	string	'horizontal'	Whether the children of the root node are arranged horizontally or vertically.
wrapping	boolean	'false'	Set to true for the navigation to wrap when the user reaches the start or end of the root's children.

import { FocusRoot } from '@xdproto/focus';

export default function App() {
  return (
    <FocusRoot orientation="vertical">
      <AppContents />
    </FocusRoot>
  );
}

<FocusNode />

A Component that represents a FocusNode node in the focus tree.

All props are optional.

Prop	Type	Default value	Description
className	string		A class name to apply to this element.
focusedClass	string	"isFocused"	A class name that is applied when this element is focused.
focusedExactClass	string	"isFocusedExact"	A class name that is applied this element is exactly focused.
disabledClass	string	"focusDisabled"	A class name that is applied this element is disabled.
nodeType	string	'div'	The element to render. For leaf nodes, you will likely want to use "button".
focusId	string	{unique_id}	A unique identifier for this node. Specify this yourself for debugging purposes, or when you will need to manually set focus to the node.
focusOnMount	boolean	false	Whether or not to focus this node when the component mounts.
orientation	string	'horizontal'	Whether the children of this node are arranged horizontally or vertically.
wrapping	boolean	'false'	Set to true for the navigation to wrap when the user reaches the start or end of the children list.
disabled	boolean	'false'	This node will not receive focus when true.
defaultChildFocusIndex	number	0	The index of the child to move focus to when this element receives focused. Only applies for nodes with children.
onFocus	function		A function that is called when the node receives focus.
onBlur	function		A function that is called when the node loses focus.
onKey	function		A function that is called when the user presses any TV remote key while this element has focus.
onArrow	function		A function that is called when the user presses a directional button.
onLeft	function		A function that is called when the user presses the left button.
onUp	function		A function that is called when the user presses the up button.
onDown	function		A function that is called when the user presses the down button.
onRight	function		A function that is called when the user presses the right button.
onSelect	function		A function that is called when the user pressed the select button.
onBack	function		A function that is called when the user presses the back button.
onMove	function		A function that is called when the focused child index of this node changes. Only called for nodes with children.
...rest	any		All other props are applied to the underlying DOM node.

import { FocusNode } from '@xdproto/focus';

export default function Profile() {
  return (
    <FocusNode
      nodeType="button"
      className="profileBtn"
      onSelect={({ node }) => {
        console.log('The user just selected this profile', node);
      }}>
      Profile
    </FocusNode>
  );
}

useFocusTree()

A Hook that returns the focus tree object.

import { useFocusTree } from '@xdproto/focus';

export default function MyComponent() {
  const focusTree = useFocusTree();

  useEffect(() => {
    console.log('the current state', focusTree.getState());

    focusTree.setFocus('my-node');
  }, []);
}

useIsFocused( focusId, [options] )

A Hook that returns a boolean representing whether or not the node with an ID of focusId is focused.

import { useIsFocused } from '@xdproto/focus';

export default function MyComponent() {
  const buttonIsFocused = useIsFocused('button');
  const buttonIsExactlyFocused = useIsFocused('button', { exact: true });
}

The properties of the object returned from the hook are:

Property	Type	Description
isFocused( focusId )	function	Returns true if focusId is focused.
isFocusedExact( focusId )	function	Returns true if focusId is exactly focused.
setFocus( focusId )	function	Move focus to focusId.

useFocusHierarchy()

A Hook that returns an array representing the focus hierarchy, which are the nodes that are focused in the node tree. Each entry in the array is a focus node. The last node in the hierarchy is the node that is exactly focused.

import { useFocusHierarchy } from '@xdproto/focus';

export default function MyComponent() {
  const focusHierarchy = useFocusHierarchy('button');
  console.log(focusHierarchy);
  // => [
  //   { nodeId: 'root', ... },
  //   { nodeId: 'homePage', ... },
  //   { nodeId: 'mainNav', ... },
  // ]
}

Prior Art

• "Pass the Remote" on the Netflix Tech Blog
• bbc/lrud
• react-tv

Limitations

• No support for pointer (mouse) inputs
• No spatial navigation