React hook for receiving gestures
$ npm install react-use-gesture
React-use-gesture is a 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.
The demos are real click them!
import { useSpring, animated } from 'react-spring'
import { useDrag } from 'react-use-gesture'
function PullRelease() {
const [{ xy }, set] = useSpring(() => ({ xy: [0, 0] }))
// 1. Define the gesture
const bind = useDrag(({ down, movement }) => set({ xy: down ? movement : [0, 0] }))
return (
<animated.div
// 2. Bind it to a component
{...bind()}
style={{ transform: xy.interpolate((x, y) => `translate3D(${x}px, ${y}px, 0)`) }} />
The example above makes a div
draggable so that it follows your mouse on drag, and returns to its initial position on release.
➡️ Why using react-spring
instead of React.useState
?
React-use-gesture exports several hooks that can handle different gestures.
Hook | Description |
---|---|
useDrag |
Handles the drag gesture |
useMove |
Handles mouse move events (touch devices not supported) |
useHover |
Handles mouse over events (touch devices not supported) |
useScroll |
Handles scroll events |
useWheel |
Handles wheel events |
usePinch |
Handles pinch events |
useGesture |
Handles multiple gestures in one hook (read more here) |
Every time a handler is called, it will get passed a gesture state that includes the source event and adds multiple attributes such as speed, previous value, and much mroe.
const bind = useDrag(({
event, // * the source event
xy, // [x,y] position of the pointer or scroll value for useScroll or useWheel
previous, // * previous xy
initial, // * xy value when the gesture has started
delta, // * delta between current and previous values (xy - previous)
movement, // * last gesture offset (xy - initial)
offset, // * offset since the first gesture (movement with book-keeping)
vxvy, // [vx, vy] momentum / speed of the gesture
velocity, // combined moment / speed of the gesture
distance, // offset distance
direction, // * [dirx, diry] direction per axis
time, // * timestamp of the current gesture
first, // * true when it's the first event
last, // * true when it's the last event
active, // * true when the gesture is active
memo, // * stores the value returned by your handler during its previous run
cancel, // * function you can call to interrupt relevant gestures
down, // * true when a mouse button or touch is down
buttons, // * buttons pressed (see https://developer.mozilla.org/fr/docs/Web/API/MouseEvent/button)
touches // * numbers of touches pressing the screen
shiftKey, altKey, ctrlKey, metaKey, // * true when modifier keys are pressed
args // * arguments you passed to bind
} => {
/* gesture logic */
})
)
Pinch is about scaling and rotating, therefore the keys xy
and vxvy
are renamed da
(for distance and angle) and vdva
respectively.
const bind = usePinch(({
da, // [d,a] absolute distance and angle of the two pointers
vdva, // momentum / speed of the distance and rotation
origin, // coordinates of the center between the two touch event
} => {
/* gesture logic */
})
)
You can pass a an object as an optional second argument to use[Gesture]
hooks to customize their behavior.
const bind = useScroll(handler, {
// lets you specify a dom node or ref you want to attach the gesture to
domTarget: undefined,
// the event config attribute lets you configure `passive` and `capture` options passed to event listeners
event: { passive: true, capture: false },
// transform functions you can pass to modify `x` and `y` values
transform: { x: x => x, y => y },
// lets you specify which window element the gesture should use.
window: window,
// enables or disables gestures
enabled: true,
// enables or disables gestures individually (relevant for the useGesture hook)
drag: true,
pinch: true,
scroll: true,
wheel: true,
move: true
})
➡️ See this thread for a relevant use case of window
.
If you want your component to support multiple gestures at once, it is preferred that you use the useGesture
hook as below.
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 element
})
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:
useDrag(({first, last}) {
if (first) { /* do stuff on drag start */ }
if (last) { /* do stuff on drag end */ }
})
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 use[Gesture]
hooks as a prop, but use the React.useEffect
hook as below.
// this will add a scroll listener to the window
const bind = useScroll(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 = useScroll(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.
This demo reads out further data like velocity and direction to calculate decay. memo
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 pos
value somewhere else and conditionally update it when the gesture begins.
const [{ pos }, set] = useSpring(() => ({ pos: [0, 0] }))
const bind = useDrag(({ active, movement, velocity, direction, memo = pos.getValue() }) => {
set({
pos: addV(movement, memo),
immediate: active,
config: { velocity: scale(direction, velocity), decay: true },
})
return memo
})
return <animated.div {...bind()} style={{ transform: pos.interpolate((x, y) => `translate3d(${x}px,${y}px,0)`) }} />
React-use-gesture also exports two methods that add or substract vectors formed as arrays. They might be handy in the case you need to manipulate positions.
import { addV, subV } from 'react-use-gesture'
const sum = addV([10, 10], [5, 5])
const sub = subV([10, 10], [5, 5])
react-spring
instead of React.useState
?Simply because setting state in the gesture handler would re-render the component on each gesture frame, which isn't always good for performance. react-spring
lets us animate components without triggering renders. You could still use useState
if you'd like though!
use[Gesture]
hooks and adding listeners manually?Not a lot! Essentially these use[Gesture]
hooks simplify the implementation of the drag and pinch gestures, calculate kinematics values you wouldn't get out of the box from the listeners, and debounce move, scroll and wheel events to let you know when they end.
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
.
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.
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 update:
useScroll(({ event, last }) => {
!last && event.preventDefault() // <-- event will not be accessed in the last event
})
memo
?As you've seen in some examples, whenever memo
is used, it is imperatively returned in the handler function. Essentially memo
is a gesture state attribute that is undefined when the gesture starts, but then takes the return value of the handler function.
In many use cases, we want memo
to hold the original value of our element position when the gesture starts so that it becomes our point of reference when adding the gesture movement
. So we set memo
to the value of our position when memo
is undefined, which is in fact when the gesture starts. Usually it looks like so:
const [{ x }, set] = useSpring(() => ({ x: 0 }))
const bind = useDrag(({ movement: [mx], memo = x.getValue() }) => {
set({ x: ox + memo })
return memo
})
If we don’t return memo
, then memo
will remain undefined and in the next drag frame memo
will take again the value of x, which will have updated in the meantime (therefore not being the point of reference when the gesture starts anymore).
It may sound silly but returning memo
makes sure that we continue holding a reference to the initial value of memo
, ie the original value of x when the gesture started.
preventDefault()
after I pass { passive: false }
The basic use of <Component {...bind()) />
passes the task of attaching listeners to React. React does not (yet) support binding passive listeners via props. To have useGesture
attach the listeners, you must also use a domTarget. This is only required if you plan to preventDefault
or cancel the event.
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