React hook for receiving gestures
$ npm install react-use-gesture
These demos are real, click them!
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.
npm install react-use-gesture
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 => { /* do stuff on drag */ },
onScroll: scrollState => { /* do stuff on scroll */ },
},
{ event: { passive: false } }
)
return <div {...bind(optionalArgs)} />
}
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.
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.
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
andon[Gesture]End
methods are provided as a commodity.on[Gesture]
handlers also receivefirst
andlast
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.
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.
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 stateEvery 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.
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. cancel is only relevant for onDrag and onPinch handlers. |
down |
Boolean |
mouse / touch down |
buttons |
Number |
buttons pressed (see documentation) |
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 |
[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 |
[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
ofdistance
andangle
, so you will probably end up usinglocal
ordelta
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 |
origin |
Number |
center between the two touch event coordinates |
turns |
Number |
keeps track of the number of turns (don't rely on turns to count the number of rotations) |
useGesture
configYou 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 |
temp
and react-springThis 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)`) }} />
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
},
})
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