Norigin Spatial Navigation: An open-source library that enables navigating between focusable elements built with ReactJS

by React

Norigin Spatial Navigation

Norigin Spatial Navigation is an open-source library that enables navigating between focusable elements built with ReactJS based application software. To be used while developing applications that require key navigation (directional navigation) on Web-browser Apps and other Browser based Smart TVs and Connected TVs. Our goal is to make navigation on websites & apps easy, using React Javascript Framework and React Hooks. Navigation can be controlled by your keyboard (browsers) or Remote Controls (Smart TV or Connected TV). Software developers only need to initialise the service, add the Hook to components that are meant to be focusable and set the initial focus. The Spatial Navigation library will automatically determine which components to focus next while navigating with the directional keys. We keep the library light, simple, and with minimal third-party dependencies.

Illustrative Demo

Norigin Spatial Navigation can be used while working with Key Navigation and React JS. This library allows you to navigate across or focus on all navigable components while browsing. For example: hyperlinks, buttons, menu items or any interactible part of the User Interface according to the spatial location on the screen.

Example Source

Supported Devices

The Norigin Spatial Navigation library is theoretically intended to work on any web-based platform such as Browsers and Smart TVs. For as long as the UI/UX is built with the React Framework, it works on the Samsung Tizen TVs, LG WebOS TVs, Hisense Vidaa TVs and a range of other Connected TVs. It can also be used in React Native apps on Android TV and Apple TV, however functionality will be limited. This library is actively used and continuously tested on many devices and updated periodically in the table below:

Platform Name
Web Browsers Chrome, Firefox, etc.
Smart TVs Samsung Tizen, LG WebOS, Hisense
Other Connected TV devices Browser Based settop boxes with Chromium, Ekioh or Webkit browsers
AndroidTV, AppleTV Only React Native apps, limited functionality

Related Blogs

  1. Use & benefits of using the Norigin Spatial Navigation library on Smart TVs here.

Changelog

A list of changes for all the versions for the Norigin Spatial Navigation: CHANGELOG.md

Table of Contents

Installation

npm i @noriginmedia/norigin-spatial-navigation --save

Usage

Initialization

Init options

// Called once somewhere in the root of the app

import { init } from '@noriginmedia/norigin-spatial-navigation';

init({
  // options
});

Making your component focusable

Most commonly you will have Leaf Focusable components. (See Tree Hierarchy) Leaf component is the one that doesn’t have focusable children. ref is required to link the DOM element with the hook. (to measure its coordinates, size etc.)

import { useFocusable } from '@noriginmedia/norigin-spatial-navigation';

function Button() {
  const { ref, focused } = useFocusable();

  return (<div ref={ref} className={focused ? 'button-focused' : 'button'}>
    Press me
  </div>);
}

Wrapping Leaf components with a Focusable Container

Focusable Container is the one that has other focusable children. (i.e. a scrollable list) (See Tree Hierarchy) ref is required to link the DOM element with the hook. (to measure its coordinates, size etc.) FocusContext.Provider is required in order to provide all children components with the focusKey of the Container, which serves as a Parent Focus Key for them. This way your focusable children components can be deep in the DOM tree while still being able to know who is their Focusable Parent. Focusable Container cannot have focused state, but instead propagates focus down to appropriate Child component. You can nest multiple Focusable Containers. When focusing the top level Container, it will propagate focus down until it encounters the first Leaf component. I.e. if you set focus to the Page, the focus could propagate as following: Page -> ContentWrapper -> ContentList -> ListItem.

import { useFocusable, FocusContext } from '@noriginmedia/norigin-spatial-navigation';
import ListItem from './ListItem';

function ContentList() {
  const { ref, focusKey } = useFocusable();

  return (<FocusContext.Provider value={focusKey}>
    <div ref={ref}>
      <ListItem />
      <ListItem />
      <ListItem />
    </div>
  </FocusContext.Provider>);
}

Manually setting the focus

You can manually set the focus either to the current component (focusSelf), or to any other component providing its focusKey to setFocus. It is useful when you first open the page, or i.e. when your modal Popup gets mounted.

import React, { useEffect } from 'react';
import { useFocusable, FocusContext } from '@noriginmedia/norigin-spatial-navigation';

function Popup() {
  const { ref, focusKey, focusSelf, setFocus } = useFocusable();

  // Focusing self will focus the Popup, which will pass the focus down to the first Child (ButtonPrimary)
  // Alternatively you can manually focus any other component by its 'focusKey'
  useEffect(() => {
    focusSelf();

    // alternatively
    // setFocus('BUTTON_PRIMARY');
  }, [focusSelf]);

  return (<FocusContext.Provider value={focusKey}>
    <div ref={ref}>
      <ButtonPrimary focusKey={'BUTTON_PRIMARY'} />
      <ButtonSecondary />
    </div>
  </FocusContext.Provider>);
}

Tracking children components

Any Focusable Container can track whether it has any Child focused or not. This feature is disabled by default, but it can be controlled by the trackChildren flag passed to the useFocusable hook. When enabled, the hook will return a hasFocusedChild flag indicating when a Container component is having focused Child down in the focusable Tree. It is useful for example when you want to style a container differently based on whether it has focused Child or not.

import { useFocusable, FocusContext } from '@noriginmedia/norigin-spatial-navigation';
import MenuItem from './MenuItem';

function Menu() {
  const { ref, focusKey, hasFocusedChild } = useFocusable({trackChildren: true});

  return (<FocusContext.Provider value={focusKey}>
    <div ref={ref} className={hasFocusedChild ? 'menu-expanded' : 'menu-collapsed'}>
      <MenuItem />
      <MenuItem />
      <MenuItem />
    </div>
  </FocusContext.Provider>);
}

Restricting focus to a certain component boundaries

Sometimes you don’t want the focus to leave your component, for example when displaying a Popup, you don’t want the focus to go to a component underneath the Popup. This can be enabled with isFocusBoundary flag passed to the useFocusable hook.

import React, { useEffect } from 'react';
import { useFocusable, FocusContext } from '@noriginmedia/norigin-spatial-navigation';

function Popup() {
  const { ref, focusKey, focusSelf } = useFocusable({isFocusBoundary: true});

  useEffect(() => {
    focusSelf();
  }, [focusSelf]);

  return (<FocusContext.Provider value={focusKey}>
    <div ref={ref}>
      <ButtonPrimary />
      <ButtonSecondary />
    </div>
  </FocusContext.Provider>);
}

Using the library in React Native environment

In React Native environment the navigation between focusable (Touchable) components is happening under the hood by the native focusable engine. This library is NOT doing any coordinates measurements or navigation decisions in the native environment. But it can still be used to keep the currently focused element node reference and its focused state, which can be used to highlight components based on the focused or hasFocusedChild flags. IMPORTANT: in order to “sync” the focus events coming from the native focus engine to the hook, you have to link onFocus callback with the focusSelf method. This way, the hook will know that the component became focused, and will set the focused flag accordingly.

import { TouchableOpacity, Text } from 'react-native';
import { useFocusable } from '@noriginmedia/norigin-spatial-navigation';

function Button() {
  const { ref, focused, focusSelf } = useFocusable();

  return (<TouchableOpacity
    ref={ref}
    onFocus={focusSelf}
    style={focused ? styles.buttonFocused : styles.button}
  >
    <Text>Press me</Text>
  </TouchableOpacity>);
}

API

Top Level exports

init

Init options

debug: boolean (default: false)

Enables console debugging.

visualDebug: boolean (default: false)

Enables visual debugging (all layouts, reference points and siblings reference points are printed on canvases).

nativeMode: boolean (default: false)

Enables Native mode. It will disable certain web-only functionality:

  • adding window key listeners
  • measuring DOM layout
  • onFocus and onBlur callbacks don’t return coordinates, but still return node ref which can be used to measure layout if needed
  • coordinates calculations when navigating (smartNavigate in SpatialNavigation.ts)
  • navigateByDirection
  • focus propagation down the Tree
  • last focused child feature
  • preferred focus key feature

In other words, in the Native mode this library DOES NOT set the native focus anywhere via the native focus engine. Native mode should be only used to keep the Tree of focusable components and to set the focused and hasFocusedChild flags to enable styling for focused components and containers. In Native mode you can only call focusSelf in the component that gets native focus (via onFocus callback of the Touchable components) to flag it as focused. Manual setFocus method is blocked because it will not propagate to the native focus engine and won’t do anything.

throttle: integer (default: 0)

Enables throttling of the key event listener.

throttleKeypresses: boolean (default: false)

Works only in combination with throttle > 0. By default, throttle only throttles key down events (i.e. when you press and hold the button). When this feature is enabled, it will also throttle rapidly fired key presses (rapid “key down + key up” events).

setKeyMap

Method to set custom key codes. I.e. when the device key codes differ from a standard browser arrow key codes.

setKeyMap({
  'left': 9001,
  'up': 9002,
  'right': 9003,
  'down': 9004,
  'enter': 9005
});

destroy

Resets all the settings and the storage of focusable components. Disables the navigation service.

useFocusable hook

This hook is the main link between the React component (its DOM element) and the navigation service. It is used to register the component in the service, get its focusKey, focused state etc.

const {/* hook output */ } = useFocusable({/* hook params */ });

Hook params

focusable (default: true)

This flag indicates that the component can be focused via directional navigation. Even if the component is not focusable, it still can be focused with the manual setFocus. This flag is useful when i.e. you have a Disabled Button that should not be focusable in the disabled state.

saveLastFocusedChild (default: true)

By default, when the focus leaves a Focusable Container, the last focused child of that container is saved. So the next time when you go back to that Container, the last focused child will get the focus. If this feature is disabled, the focus will be always on the first available child of the Container.

trackChildren (default: false)

This flag controls the feature of updating the hasFocusedChild flag returned to the hook output. Since you don’t always need hasFocusedChild value, this feature is disabled by default for optimization purposes.

autoRestoreFocus (default: true)

By default, when the currently focused component is unmounted (deleted), navigation service will try to restore the focus on the nearest available sibling of that component. If this behavior is undesirable, you can disable it by setting this flag to false.

isFocusBoundary (default: false)

This flag makes the Focusable Container keep the focus inside its boundaries. It will only block the focus from leaving the Container via directional navigation. You can still set the focus manually anywhere via setFocus. Useful when i.e. you have a modal Popup and you don’t want the focus to leave it.

focusKey (optional)

If you want your component to have a persistent focus key, it can be set via this property. Otherwise, it will be auto generated. Useful when you want to manually set the focus to this component via setFocus.

preferredChildFocusKey (optional)

Useful when you have a Focusable Container and you want it to propagate the focus to a specific child component. I.e. when you have a Popup and you want some specific button to be focused instead of the first available.

onEnterPress (function)

Callback that is called when the component is focused and Enter key is pressed. Receives extraProps (see below) and KeyPressDetails as arguments.

onEnterRelease (function)

Callback that is called when the component is focused and Enter key is released. Receives extraProps (see below) as argument.

onArrowPress (function)

Callback that is called when component is focused and any Arrow key is pressed. Receives direction (left, right, up, down), extraProps (see below) and KeyPressDetails as arguments.

onFocus (function)

Callback that is called when component gets focus. Receives FocusableComponentLayout, extraProps and FocusDetails as arguments.

onBlur (function)

Callback that is called when component loses focus. Receives FocusableComponentLayout, extraProps and FocusDetails as arguments.

extraProps (optional)

An object that can be passed to the hook in order to be passed back to certain callbacks (see above). I.e. you can pass all the props of the component here, and get them all back in those callbacks.

Hook output

ref (required)

Reference object created by the useRef inside the hook. Should be assigned to the DOM element representing a focused area for this component. Usually it’s a root DOM element of the component.

function Button() {
  const { ref } = useFocusable();

  return (<div ref={ref}>
    Press me
  </div>);
}
focusSelf (function)

Method to set the focus on the current component. I.e. to set the focus to the Page (Container) when it is mounted, or the Popup component when it is displayed.

setFocus (function) (focusKey: string) => void

Method to manually set the focus to a component providing its focusKey.

focused (boolean)

Flag that indicates that the current component is focused.

hasFocusedChild (boolean)

Flag that indicates that the current component has a focused child somewhere down the Focusable Tree. Only works when trackChildren is enabled!

focusKey (string)

String that contains the focus key for the component. It is either the same as focusKey passed to the hook params, or an automatically generated one.

navigateByDirection (function) (direction: string, focusDetails: FocusDetails) => void

Method to manually navigation to a certain direction. I.e. you can assign a mouse-wheel to navigate Up and Down. Also useful when you have some “Arrow-like” UI in the app that is meant to navigate in certain direction when pressed with the mouse or a “magic remote” on some TVs.

pause (function)

Pauses all the key event handlers.

resume (function)

Resumes all the key event handlers.

updateAllLayouts (function)

Manually recalculate all the layouts. Rarely used.

FocusContext (required for Focusable Containers)

Used to provide the focusKey of the current Focusable Container down the Tree to the next child level. See Example

Types exported for development

FocusableComponentLayout

interface FocusableComponentLayout {
  left: number; // absolute coordinate on the screen
  top: number; // absolute coordinate on the screen
  width: number;
  height: number;
  x: number; // relative to the parent DOM element
  y: number; // relative to the parent DOM element
  node: HTMLElement; // or the reference to the native component in React Native
}

KeyPressDetails

interface KeyPressDetails {
  pressedKeys: PressedKeys;
}

PressedKeys

type PressedKeys = { [index: string]: number };

FocusDetails

interface FocusDetails {
  event?: KeyboardEvent;
}

Other Types exported

These types are exported, but not necessarily needed for development.

KeyMap

Interface for the keyMap sent to the setKeyMap method.

UseFocusableConfig

Interface for the useFocusable params object.

UseFocusableResult

Interface for the useFocusable result object.

Technical details and concepts

Tree Hierarchy of focusable components

As mentioned in the Usage section, all focusable components are organized in a Tree structure. Much like a DOM tree, the Focusable Tree represents a focusable components’ organization in your application. Tree Structure helps to organize all the focusable areas in the application, measure them and determine the best paths of navigation between these focusable areas. Without the Tree Structure (assuming all components would be simple Leaf focusable components) it would be extremely hard to measure relative and absolute coordinates of the elements inside the scrolling lists, as well as to restrict the focus from jumping outside certain areas. Technically the Focusable Tree structure is achieved by passing a focus key of the parent component down via the FocusContext. Since React Context can be nested, you can have multiple layers of focusable Containers, each passing their own focusKey down the Tree via FocusContext.Provider as shown in this example.

Navigation Service

Navigation Service is a “brain” of the library. It is responsible for registering each focusable component in its internal database, storing the node references to measure their coordinates and sizes, and listening to the key press events in order to perform the navigation between these components. The calculation is performed according to the proprietary algorithm, which measures the coordinate of the current component and all components in the direction of the navigation, and determines the best path to pass the focus to the next component.

Migration from v2 (HOC based) to v3 (Hook based)

Reasons

The main reason to finally migrate to Hooks is the deprecation of the recompose library that was a backbone for the old HOC implementation. As well as the deprecation of the findDOMNode API. It’s been quite a while since Hooks were first introduced in React, but we were hesitating of migrating to Hooks since it would make the library usage a bit more verbose. However, recently there has been even more security reasons to migrate away from recompose, so we decided that it is time to say goodbye to HOC and accept certain drawbacks of the Hook implementation. Here are some of the challenges encountered during the migration process:

Getting node reference

HOC implementation used a findDOMNode API to find a reference to a current DOM element wrapped with the HOC:

const node = SpatialNavigation.isNativeMode() ? this : findDOMNode(this);

Note that this was pointing to an actual component instance even when it was called inside lifecycle HOC from recompose allowing to always find the top-level DOM element, without any additional code required to point to a specific DOM node. It was a nice “magic” side effect of the HOC implementation, which is now getting deprecated.

In the new Hook implementation we are using the recommended ref API. It makes a usage of the library a bit more verbose since now you always have to specify which DOM element is considered a “focusable” area, because this reference is used by the library to calculate the node’s coordinates and size. Example above

Passing parentFocusKey down the tree

Another big challenge was to find a good way of passing the parentFocusKey down the Focusable Tree, so every focusable child component would always know its parent component key, in order to enable certain “tree-based” features described here. In the old HOC implementation it was achieved via a combination of getContext and withContext HOCs. Former one was receiving the parentFocusKey from its parent no matter how deep it was in the component tree, and the latter one was providing its own focusKey as parentFocusKey for its children components.

In modern React, the only recommended Context API is using Context Providers and Consumers (or useContext hook). While you can easily receive the Context value via useContext, the only way to provide the Context down the tree is via a JSX component Context.Provider. This requires some additional code in case you have a Focusable Container component. In order to provide the parentFocusKey down the tree, you have to wrap your children components with a FocusContext.Provider and provide a current focusKey as the context value. Example here

Examples

Migrating a leaf focusable component

HOC Props and Config vs Hook Params

import {withFocusable} from '@noriginmedia/norigin-spatial-navigation';

// Component ...

const FocusableComponent = withFocusable({
  trackChildren: true,
  forgetLastFocusedChild: true
})(Component);

const ParentComponent = (props) => (<View>
  ...
  <FocusableComponent
    trackChildren
    forgetLastFocusedChild
    focusKey={'FOCUSABLE_COMPONENT'}
    onEnterPress={props.onItemPress}
    autoRestoreFocus={false}
  />
  ...
</View>);

Please note that most of the features/props could have been passed as either direct JSX props to the Focusable Component or as an config object passed to the withFocusable HOC. It provided certain level of flexibility, while also adding some confusion as to what takes priority if you pass the same option to both the prop and a HOC config.

In the new Hook implementation options can only be passed as a Hook Params:

const {/* hook output */ } = useFocusable({
  trackChildren: true,
  saveLastFocusedChild: false,
  onEnterPress: () => {},
  focusKey: 'FOCUSABLE_COMPONENT'
});

HOC props passed to the wrapped component vs Hook output values

HOC was enhancing the wrapped component with certain new props such as focused etc.:

import {withFocusable} from '@noriginmedia/norigin-spatial-navigation';

const Component = ({focused}) => (<View>
  <View style={focused ? styles.focusedStyle : styles.defaultStyle} />
</View>);

const FocusableComponent = withFocusable()(Component);

Hook will provide all these values as the return object of the hook:

const { focused, focusSelf, ref, ...etc } = useFocusable({/* hook params */ });

The only additional step when migrating from HOC to Hook (apart from changing withFocusable to useFocusable implementation) is to link the DOM element with the ref from the Hook as seen in this example. While it requires a bit of extra code compared to the HOC version, it also provides a certain level of flexibility if you want to make only a certain part of your UI component to act as a “focusable” area.

Please also note that some params and output values has been renamed. CHANGELOG

Migrating a container focusable component

In the old HOC implementation there was no additional requirements for the Focusable Container to provide its own focusKey down the Tree as a parentFocusKey for its children components. In the Hook implementation it is required to wrap your children components with a FocusContext.Provider as seen in this example.

Development

npm i
npm start

Contributing

Please follow the Contribution Guide

License

MIT Licensed

GitHub

View Github