Track drags and touches on an element, a bit like a touchpad or trackpad
npm install touch-padTrack drags and touches on an element, a bit like a touchpad or trackpad.
The best way to understand how touch-pad works is to [try it]. But the GIF below may give
you a quick idea.
[try it]: https://limulus.net/penumbra/journal/005-ray-sphere-interactions/#demo
!demo
``sh`
npm install touch-pad
This package provides a web component and an event processor class. In both cases
TouchPadMoveEvents are emitted when the user drags or touches the element. The eventdetail property contains an x and y property with the current position of the touch or
drag relative to the top left corner of the element as a fraction of the element's width and
height.
`javascript`
import 'touch-pad/define'
The touch-pad/define module automatically registers the touch-pad custom element. You
can now use it in your HTML.
`html`
If you prefer to do your own registration, you can instead import { TouchPad } from
'touch-pad' to get the class.
Now you can listen for touchpadmove events on the touch-pad element (or on its
ancestors).
`javascript`
document.querySelector('touch-pad').addEventListener('touchpadmove', (event) => {
console.log(event.detail)
})
`javascript`
import { TouchPadEventProcessor } from 'touch-pad'
`javascript`
const eventProcessor = new TouchPadEventProcessor(
document.querySelector('interactive-element')
)
eventProcessor.listen()
The will now emit touchpadmove events when the user drags or
touches it.
`javascript`
document.querySelector('interactive-element').addEventListener('touchpadmove', (event) => {
console.log(event.detail)
})
If do not want your element to emit touchpadmove events into the DOM, you can specify an EventTarget as the second argument to the constructor.
`javascript
const touchMoveTarget = new EventTarget()
touchMoveTarget.addEventListener('touchpadmove', (event) => {
console.log(event.detail)
})
const eventProcessor = new TouchPadEventProcessor(
document.querySelector('interactive-element'),
touchMoveTarget
)
eventProcessor.listen()
`
#### Cleanup
If the source element is removed from the DOM, you should call eventProcessor.unlisten()`
to stop listening for events. Failure to do so may result in memory leaks, since it adds
event listeners to the element’s document. This is not necessary for the web component usage
pattern where this is handled for you.