Multitouch

Tracks multitouch input and outputs a list of active touches, plus scale and rotation delta between the first two touch points.

For single-point input, generally pointer is more appropriate as it provides a simple, cross-platform interface.

Import

import { multitouch } from 'popmotion';

Usage

multitouch({
  preventDefault?: boolean = true,
  scale?: number,
  rotate?: number
})
multitouch().start(({ touches, scale, rotate }) => {
  touches.forEach(({ x, y }) => console.log(x, y))
});

multitouch provides:

  • touches: { x: number, y: number }[]: An array of x/y coordinates representing each active finger.
  • scale: number: The distance between the first two fingers since start, represented as a multiplier of the original distance. scale starts from 1.0, or the initially provided scale.
  • rotate: number: The angle rotation of the first two fingers as a delta of the original rotation. rotate starts from 0.0, or the initially provided rotate.

Commonly-used properties

If you often use, for instance, rotate, you can easily create a new action that returns only that value:

const touchRotation = (initialRotate = 0) => multitouch({ rotate: initialRotate })
  .pipe(({ rotate }) => rotate);

touchRotation(45).start((rotate) => console.log(rotate));

Props

  • preventDefault?: boolean = true
  • scale?: number = 1.0
  • rotate?: number = 0.0

Methods

Action methods

multitouch() returns:

  • filter((v: any) => boolean): Returns a new action that filters out values when the provided function returns false.
  • pipe(...funcs: Array<(v) => v): Returns a new action that will run update values through this sequence of functions.
  • start(update | { update, complete }): Starts the action and returns a subscription.
  • while((v: any) => boolean): Returns a new action that will complete when the provided function returns false.

Subscription methods

multitouch().start() returns:

  • stop(): void

Example

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