@morgs32/react-use-gesture

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react-use-gesture

Ever thought about doing that sidebar pull-out, a view pager, some slider, any gesture on the web basically, and dropped the idea because it's too hard? In that case, this is your lib.

React-use-gesture is a React hook that lets you bind richer mouse and touch events to any component or view. With the data you receive, it becomes trivial to set up gestures, and often takes no more than a few lines of code.

You can use it stand-alone, but to make the most of it you should combine it with an animation library like react-spring, though you can most certainly use any other.

Installation

npm install react-use-gesture

Api

import { useGesture } from 'react-use-gesture'

// in your component
const bind = useGesture(actions, config)

The api is straight forward. You bind handlers to your view, specify the actions you want to respond to (drag, pinch, hover, move, scroll or wheel) and you will receive events when you interact with the component. These events include the source dom event, but also carry additional kinematics such as velocity, distance, delta, etc.

Hooks allow gestures to be re-used for more than one view (you can use the same bind() function multiple times!).

// Rough example that makes a div respond to drag and scroll gestures
function myComponent() {
  const bind = useGesture(
    {
      onDrag: dragState => doStuffOnDrag,
      onScroll: scrollState => doStuffOnScroll
    },
    { event: { passive: false } }
  )
  return <div {...bind(optionalArgs)} />
}

Making things move

function myComponent() {
  const [[x, y], set] = React.useState([0, 0])
  const bind = useGesture({ onDrag: ({ local }) => set(local) })
  return <div {...bind()} style={{ transform: `translate3d(${x}px,${y}px,0)` }} />
}

When the user drags the div that receives the {...bind()} prop, useGesture updates the state of the component and the div gets positioned accordingly.

In this case we fetch local off the gesture event, which keeps track of delta positions after release. Deltas are especially important in this lib, because they make it possible to use transitions for positioning, instead of doing complex getBoundingClientRect() calculations to figure out where a node went on the screen.

Avoid re-rendering (preferred)

In the example we’ve just seen, the component gets re-rendered every time useGesture drag handler fires, which can be taxing. To avoid re-rendering you may want to use libraries such as react-spring that allow animating dom elements without setting state, and therefore without triggering new renders.

import { useSpring, animated } from 'react-spring'

function myComponent() {
  const [{ local }, set] = useSpring(() => ({ local: [0, 0] }))
  const bind = useGesture({ onDrag: ({ local }) => set({ local }) })

  return <animated.div {...bind()} style={{ transform: local.interpolate((x, y) => `translate3d(${x}px,${y}px,0)`) }} />
}

Because we’re now using animated.div, we’re able to make the element draggable without provoking new renders every time its position should update.

Supported gestures

In addition to drag, react-use-gesture also supports scroll gesture, and mouse-specific gestures such as move, wheel and hover (entering and leaving an element), and touch-specific pinch.

Every gesture has a handler that should be passed to useGesture, and you can pass multiple handlers to the same element for it to respond to different gestures.

const bind = useGesture({
  onDrag: state => {...},     // fires on drag
  onPinch: state => {...},     // fires on pinch
  onScroll: state => {...},   // fires on scroll
  onHover: state => {...},    // fires on mouse enter, mouse leave
  onMove: state => {...},     // fires on mouse move over the element
  onWheel: state => {...}     // fires on mouse wheel over the eleement
})

on[Gesture]Start and on[Gesture]End

Drag, pinch, move, scroll and wheel gestures also have two additional handlers that let you perform actions when they start or end. For example, onScrollEnd fires when the user finished scrolling.

Note #1: on[Gesture]Start and on[Gesture]End methods are provided as a commodity. on[Gesture] handlers also receive first and last properties that indicate if the event fired is the first (i.e. gesture has started) or the last one (i.e. gesture has ended).

// this:
useGesture({ onDragStart: doStuffOnStart, onDragEnd:doStuffOnEnd })

// is equivalent to this:
useGesture({
  onDrag: ({first, last}) {
    if(first) doStuffOnStart()
    if (last) doStuffOnEnd()
  }
})

Note #2: since browsers don't have native event listeners for when scroll, move or wheel ends, react-use-gesture debounces these events to estimate when they stopped. One of the consequence of debouncing is trying to access properties from the source event when a gesture has ended will probably result in a warning: React does event pooling, meaning a React event can only be queried synchronously.

Adding gestures to dom nodes

React-use-gesture also supports adding handlers to dom nodes directly (or the window or document objects). In that case, you shouldn't spread the bind() object returned by useGesture as a prop, but use the React.useEffect hook as below.

// this will add a scroll listener to the window
const bind = useGesture({ onScroll: state => doStuff }, { domTarget: window })
React.useEffect(bind, [bind])

You can also directly pass a ref to domTarget:

const myRef = React.useRef(null)
// this will add a scroll listener the div
const bind = useGesture({ onScroll: state => doStuff }, { domTarget: myRef })
React.useEffect(bind, [bind])
/*...*/
return <div ref={myRef} />

Note that using useEffect will also take care of removing event listeners when the component is unmounted.

Shortcut to the drag event handler

Although React-use-gesture was initially developed to support drag events only (press, move and release), this library now supports pinch, hover, move, scroll and wheel events.

To ensure retro-compatibility with v4.x, v5.x still gives you a shortcut to the onDrag and pass directly the handler function as the sole argument of useGesture.

// this:
const bind = useGesture(state => doStuff)
// is equivalent to this:
const bind = useGesture({ onDrag: state => doStuff })

useGesture event state

Every time a handler is called, it will get passed the current event state for its corresponding gesture. An event state is an object that includes the source event and adds multiple attributes listed below.

Shared State

The following attributes are provided to the handler for all gestures.

Name	Type	Description
event	object	source event
time	Number	timestamp of the current gesture
first	Boolean	marks the first event
last	Boolean	marks the last event
active	Boolean	true when the gesture is active, false otherwise
temp	Any	serves as a cache storing any value returned by your handler during its previous run. See below for an example.
cancel	Function	you can call cancel to interrupt the drag or pinch gestures. cancelis only relevant for onDrag and onPinch handlers.
down	Boolean	mouse / touch down
touches	Number	number of touches pressing the screen
shiftKey altKey ctrlKey metaKey	Boolean	modifier keys are pressed
dragging	Boolean	true when the user is dragging
moving	Boolean	true when the user is moving the mouse
hovering	Boolean	true when the mouse hovers the element
scrolling	Boolean	true when the user is scrolling
wheeling	Boolean	true when the user is wheeling
args	Any	arguments you passed to bind

Specific state attributes for X/Y Coordinates Gestures [drag, scroll, wheel, hover]

The following attributes are provided to the handler for gestures that deal with x/y coordinates.

Name	Type	Description
xy	Vec2 ([x,y])	for touch/mouse events, xy returns the position of the pointer on the screen. For scroll/wheel events xy returns how much the element has been scrolled on x and y axis.
previous	Vec2	previous xy
initial	Vec2	xy value when the gesture has started
delta	Vec2	delta offset (xy - initial)
local	Vec2	delta with book-keeping (remembers the xy value throughout gestures)
lastLocal	Vec2	previous local
vxvy	Vec2	momentum / speed of the gesture (x and y axis separated)
velocity	Number	momentum / speed of the gesture (x and y axis combined)
distance	Number	delta distance

Specific state attributes for Distance Angle Gestures [pinch]

Pinch is generally about scaling and rotating. The scale depends on the distance between the two fingers, while the rotation depends on the direction / angle of the vector formed by the two fingers or pointers.

More specifically, both scale and rotation depends on the delta of distance and angle, so you will probably end up using local or delta in most cases.

Name	Type	Description
da	Vec2	absolute distance and angle of the two pointers/fingers.
previous	Vec2	previous da
initial	Vec2	da value when the gesture has started
delta	Vec2	delta offset (da - initial)
local	Vec2	delta with book-keeping (remembers the da value throughout gestures)
lastLocal	Vec2	previous local
vdva	Vec2	momentum / speed of the gesture for distance and angle
turns	Number	keeps track of the number of turns (don't rely on turns to count the number of rotations)

useGesture config

You can pass a config object as an optional second argument to useGesture to customize its behavior.

Name	Default Value	Description
domTarget	undefined	lets you specify a dom node you want to attach gestures to (body, window, document...). You can also pass a ref created with the useRef hook.
event	{passive: true, capture: false}	the event config attribute lets you configure passive and capture options passed to event listeners.
transform	{x: x => x, y =>y }	transform functions you can pass to modify x and y values.
window	window	lets you specify which window element useGesture should use. See this thread for a relevant use case.
enabled	true	enables or disables all gestures
drag pinch scroll wheel hover move	true	enables or disables gestures individually

Examples

Example with temp and react-spring

Codesandbox

This demo reads out further data like velocity and direction to calculate decay. temp in this case is a simple storage that picks up whatever value you (optionally) return inside the event handler. It's valid as long as the gesture is active. Without this you would need to store the initial xy value somewhere else and conditionally update it when the gesture begins.

const [{ xy }, set] = useSpring(() => ({ xy: [0, 0] }))
const bind = useGesture({
  onDrag: ({ active, delta, velocity, direction, temp = xy.getValue() }) => {
    set({
      xy: add(delta, temp),
      immediate: active,
      config: { velocity: scale(direction, velocity), decay: true }
    })
    return temp
  }
})
return <animated.div {...bind()} style={{ transform: xy.interpolate((x, y) => `translate3d(${x}px,${y}px,0)`) }} />

Frequently asked questions

What are the differences between using useGesture and adding listeners manually?

Not a lot! Essentially useGesture simplifies the implementation of the drag and pinch gestures, calculates kinematics values you wouldn't get out of the box from the listeners, and debounces move scroll and wheel events to let you know when they end.

Why onMove when onDrag already exists?

onDrag only fires while you touch or press the element. You just need to hover your mouse above the element to trigger onMove.

Why onWheel and onScroll?

Scrolling and wheeling are structurally different events although they produce similar results (i.e. scrolling a page). First of all, wheel is a mouse-only event. Then, for onScroll to be fired, the element you're scrolling needs to actually scroll, therefore have content overflowing, while you just need to wheel over an element to trigger onWheel. If you use react-three-fiber, onWheel might prove useful to simulate scroll on canvas elements.

Accessing source event triggers a warning in the console!

You're probably trying to access an event in onScroll, onMove or onWheel handlers. The last event is debounced, and therefore not accessible asynchronously because of how React pools events. A possible solution would be to make sure the event is not part of the last state:

useGesture({
  onScroll: ({ event, last }) => {
    !last && event.preventDefault() // <-- event will not be accessed in the last event
  }
})