svelte-gestures

3 KB gzipped (you can use just part of those 3 KB) - a collection of gesture recognizers for Svelte ;)

BREAKING CHANGES in svelte-gestures 5.2.1:

• Now works as Svelte Attachments (see new example and documentation)
• Only works with Svelte 5
• Support for plugins (highlight plugin provided in the library for gesture visualization)
• Multi touch gesture added
• Touch point plugin for pointer highlighting added
• Experimental vibrate plugin added
• There are several breaking changes with new API. It changes how parameters are passed to gestures. If you want to follow readme and examples for svelte-gestures 5.1.4 and older please follow the old README_5.1.4.md

Migration

For migration from 5.1.4 or older please follow CHANGELOG.md

installation

Npm npm install svelte-gestures

Npm Installing from JSR npx jsr add @rezi/svelte-gestures

Deno deno add @rezi/svelte-gestures

Svelte 4 projects should use svelte-gestures version 4, while older Svelte projects should use version 1.5.2 and lower.

About

It contains the most popular gestures: pan, pinch, press, rotate, swipe, tap, multitouch. Besides that, it comes with shapeGesture which helps with the recognition of custom shapes declared by a set of x and y coordinates.

Library support additional plugins which can add extra functionality to gestures. Currently there are highlight and touch-point gestures plugins for gesture visualization and experimental vibrate gesture for haptic feedback on mobile devices (works rather badly in most of browsers and phones)

It also exposes a generic event handling core, which can be extended for your specific gesture implementation (see source code on how gestures are implemented). Besides above mentioned gestures, there are two more: composedGesture and scroll gestures:

1. The composedGesture let you combine more gestures while using just one pointer EventListener per element. It also lets users switch active gestures on the fly.
2. scroll is a custom basic implementation of scrolling for touch devices. It is needed, as by default, when a gesture mode is activated on an Element on a touch device, browser scrolling is turned off for that Element. Unfortunately, the gesture mode needs to be set before the first touch/click is done and cannot be changed while there are active pointers. The scroll gesture is made to work with the composedGesture.

It uses pointer events under the hood, to make it cross-platform. Gestures will be recognized if done by mouse, touch, stylus etc.

Recognizers are kept as simple as possible but still provide desired basic functionality. They are made in the form of svelte attachments with custom event emitters. Any number of different recognizers can be used on one element, but it is recommended to use useComposedGesture attachment for combined gestures.

Usage example

<script lang="ts">
    import { useSwipe, type SwipeCustomEvent, type GestureCustomEvent } from 'svelte-gestures';
    let direction: string | null = $state(null);
    let pointerType: string = $state('');;
    let target: HTMLElement | null = $state(null);;

    function handler(event: SwipeCustomEvent) {
        direction = event.detail.direction;
        pointerType = event.detail.pointerType;
        target = event.detail.target as HTMLElement;
    }
</script>
<section
    {...useSwipe(handler, () => ({ timeframe: 300, minSwipeDistance: 50, touchAction: 'none' }))}>
        <div>swipe direction: {direction}</div>
        <div>pointerType {pointerType}</div>
        <div>target: {target?.tagName}</div>
</section>

For complete code example (including up, down and move handlers) see REPL example of swipe gesture

API events

Except for the main event, each recognizer triggers, three more events with names composed of gesture name (pan | pinch | tap | swipe | rotate | shapeGesture | composedGesture) and event type (up | down | move).

For example usePan attachment has for example onpanup, onpandown, onpanmove. It dispatches event.detail with the following property

{
  event: PointerEvent,
  pointersCount: number ,
  target:HTMLElement,
  x: number,
  y: number,
  attachmentNode: HTMLElement;
}

You can import this event type as GestureCustomEvent.

• event a native pointer event; the
• pointersCount is the number of active pointers;
• target is the target Element on which the gesture started (it can be a child of the element on which a gesture is applied).
• x and y refer to coordinates within the gesture element.
• attachmentNode is the element on which the attachment is applied

Gesture arguments

All basic gestures follow the same pattern. A gesture attachment starts with use for instance usePan, it accept 3 arguments:

1. Handler for the gesture main event.Handle is triggered when pan gesture is recognized
2. A function which returns gesture options object. The function wrapper allow the options to be changed on the fly.
3. Object with three extra event handles. In case of pan gesture Object with onpanup, onpandown, onpanmove properties which hold handler functions for those events.
4. isRaw boolean. Defaults to false. If set to true, the usePan function returns the main pan function in form under property name pan instead of regular attachment key (createAttachmentKey()). It is useful when @attach syntax i needed like on svelte:body element on which spread properties are not allowed. Also can be handy for attaching handler programmatically by addEventListener().

Example for isRaw true.

<script lang="ts">
...

const { swipe, onswipe, onswipedown, onswipemove, onswipeup } = useSwipe(
  handler,
  () => ({ timeframe: 300, minSwipeDistance: 50, touchAction: 'none' }),
  {
    onswipemove: moveHandler,
    onswipeup: upHandler,
    onswipedown: downHandler
  },
  true
);
</script>

<svelte:body {@attach swipe} {onswipe} {onswipedown} {onswipemove} {onswipeup} />

Pan

Pan attachment (usePan) fires PanCustomEvent event:

• event.detail object has the following properties
  • x, y (x,y stand for position within the `element`` on which the action is used)
  • target is an EventTarget (HTMLElement) of the pan. The target is recorded when the pan starts.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The usePan accepts the following options

• delay (default value is 300ms)
• touchAction (defaults value is none) Apply css touch-action style, to leave handling of some touch actions to the browser; see touch-action on MDN. You can pass an array, the values will be joined with spaces.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

pan gesture is triggered on the pointer (mouse, touch, etc.) move. But not earlier than delay parameter.

> REPL Pan demo

Pinch

Pinch attachment (usePinch) fires pinch event:

• event.detail object has following properties
  • center: {x:number; y:number;}
    • x and y represent coordinates in px of an imaginary center of the pinch gesture. They originate in the top left corner of the element on which pinch is used.
  • scale: number. The initial scale after the first two registered points is 1, then it either decreases toward zero as the points get nearer, or grow up as their distance grows.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The pinch accepts the following options

• touchAction (defaults value is none) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

> REPL Pinch demo

Rotate

Rotate attachment (useRotate) fires rotate event:

• event.detail object has the following properties
  • center: {x:number; y:number;}
    • x and y represent coordinates in px of an imaginary center of the rotation gesture. They originate in the top left corner of the element on which rotation is used.
  • rotation: number. Initial rotation after the first two registered points is 0, then it either decreases to -180 as the points rotate anti-clockwise or grows up to 180 as they rotate clockwise.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The rotate accepts the following options

• touchAction (defaults value is none) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

> REPL Rotation demo

Swipe

Swipe attachment (useSwipe) fires swipe event:

• event.detail object has following properties
  • direction: 'top' | 'right' | 'bottom' | 'left'
  • target: HTMLElement. The target is recorded when swipe starts.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The swipe accepts the following options

• timeframe:number (default value is 300ms )
• minSwipeDistance: number (default value is 60px)
• touchAction (defaults value is none) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

Swipe is fired if the preset distance in the proper direction is done in the preset time.

You can use the touchAction parameter to control the default behavior of the browser.

For example, if you only use left/right swipe and want to keep the default browser behavior (scrolling) for up/down swipe use touchAction: 'pan-y'.

> REPL Swipe demo

Tap

Tap is activated once pointer is released withing a timeframe

Tap attachment (useTap) fires tap event:

• event.detail object has the following properties
  • x: number. X coordinate
  • y: number. Y coordinate
  • target: HTMLElement.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The tap accepts the following options

• timeframe:number (default value is 300ms )
• touchAction (defaults value is auto) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

Tap action is fired only when the click/touch is finished within the given timeframe.

> REPL Tap demo

Press

Press event is activated once pointer is down for certain time

Press attachment (usePress) fires press event:

• event.detail object has the following properties
  • x: number. X coordinate
  • y: number. Y coordinate
  • target: HTMLElement.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The press accepts the following options

• triggerBeforeFinished: boolean (default value is false). If set to true, the press event is triggered after the given timeframe, even if a user still keeps pressing (event hasn't finished).
• timeframe:number (default value is 300ms )
• spread: number; (default value is 4px). If a user moves farther than the spread value from the initial touch point, the event is never triggered.
• touchAction (defaults value is auto) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

Press action is fired only when the click/touch is released after the given timeframe. Or when triggerBeforeFinished is set to true, after given timeframe even when click/touch continues.

> REPL Press demo

Multitouch

Press attachment (useMultiTouch) fires multiTouch event:

• event.detail object has the following properties
  • x: number. X coordinate (center of the multitouch)
  • y: number. Y coordinate (center of the multitouch)
  • target: HTMLElement.
  • pointerType: 'touch' | 'mouse' | 'pen'.
  • coords: Array<{x:number; y:number;}>
    • x and y coordinates in px of all touch points. They originate in the top left corner of the element on which multiTouch is used.

The multiTouch accepts the following options

• touchCount:number (defaults to 2) How many pointer events are needed to trigger the multiTouch event
• touchAction (defaults value is auto) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

> REPL Multitouch

Shape gesture

ShapeGesture attachment (useShapeGesture) fires shapeGesture event:

• event.detail object has the following properties
  • score: number. A number between 0 and 1. The higher the number is, the bigger chance that shape has been recognized.
  • pattern: string | null. name of pattern with best match. null in case there is no match
  • target: HTMLElement.
  • pointerType: 'touch' | 'mouse' | 'pen'.

The shapeGesture accepts the following options

• shapes: { name: string; points: { x: number; y: number }[]; allowRotation?: boolean (default false) bothDirections?: boolean (default true) }[]
• timeframe:number (default value is 1000ms ). Time within which the gesture need to be done.
• threshold:number (default value is 0.9 ). Possible values are between 0 and 1; The higher the threshold is the more precise the gesture needs to be drawn, to trigger the shapeGesture action.
• nbOfSamplePoints: number (default 64). The number of points the gesture is converted to before the match is done.
• touchAction (defaults value is auto) Apply css touch-action style, letting the browser know which type of gesture is controlled by the browser and your program respectively.
• composed is only applicable when used inside composedGesture.
• plugins os an array of plugins to be applied

shapeGesture event is fired only when the click/touch is finished within the given timeframe and gesture similarity is above the threshold

Tips and hints

1. When defining points in a shape, beware that the coordinates system is same as for SVG. x increases toward right and y increases toward bottom !!
2. shapeGesture can accept more shapes at once. It's not only handy to recognize more gestures, but can be used to define more similar shapes with same name. For instance if you need to recognize a triangle shape, it is preferable to define several slightly different triangles with same name, rather than defining one triangle shape and lowering the threshold.
3. You don't need to care about scale of your shapes, they are always scaled automatically for gesture/shape comparison.
4. When bothDirections is set to false, order of points matters, even if the shape is closed (circle, square, etc)

> REPL ShapeGesture demo

Composed Gesture

composedGesture is a special gesture, which does not listen to any gesture of its own. It rather gives you the power of composing gestures together or switching gestures while a gesture is recorded.

Usage

To use composedGesture, you need to pass a function definition to the useComposedGesture. The function definition should have the following signature:

• (register: RegisterFnType) => (activeEvents: PointerEvent[], event: PointerEvent) => boolean

The register parameter is a callback function provided by composedGesture

Within the function body, you can call the register function to add different gestures to the composed gestures. The register function accepts two arguments: the first argument is the gesture you want to register, and the second argument is an options object for the gesture.

You can register multiple gestures using the register function, and each call to register returns an object with onDown, onMove, and onUp properties. The onDown and onUp functions are automatically executed by composedGesture, while the onMove function needs to be explicitly triggered by returning a callback function from the option function. This callback function should run all the necessary onMove functions for the gestures. You can implement your logic to determine which gesture to execute under which conditions.

Example: panning combined with scrolling

Let's use pan gesture, but only after the press gesture has been successfully triggered; otherwise, we will trigger the special scroll gesture which mimics the default scroll behavior (it is needed, because default scrolling need to be disabled on elements where any kind of swiping gesture is done). The result will be, that a fast swipe over the element will let the user scroll thru as normal, while a move initiated with 100ms press, will end up with panning.

You can see in the repl that there are registered 3 basic gestures and their onMove function is called based on our defined logic. The trick is that every base gesture returns true from its onMove function when the gesture's main event has been triggered (most of gestures trigger main event after onUp, but for instance press gesture can trigger before release. We are leveraging that fact in the composed gesture example)

> REPL ComposedGesture demo

Plugins

You can pass plugin as parameter to a build in gesture to enhance the gesture functionality. Currently svelte-gestures library provides highlight and touch-point gestures plugins for gesture visualization and experimental vibrate gesture for haptic feedback on mobile devices (works rather badly in most of browsers and phones).

Plugin is kind of a side effect to a gesture. You cannot modify a gesture by plugin. Plugin is meant for visual/audio/haptic enhancement of a gesture.

You are encouraged to create your own plugins. Just follow the source code of the highlight gesture.

Plugin is a function which accepts options as only argument and returns object with following signature:

{
    onMove: PluginEventCallback;
    onDown: PluginEventCallback;
    onUp: PluginEventCallback;
    onDestroy?: () => void;
    onInit?: (activeEvents: PointerEvent[]) => void;
}

Highlight plugin

Leaves fading out trace after pointers. If multiple pointers are highlighted they are all connected by lines

In the following example the plugin options are used in form of $state which enable them to change after each use. On pan up event we simply change the highlighter color to random one.

Highlight plugin options:

{
  color?: string;
  fadeTime?: number;
  zIndex?: number;
  lineWidth?: number;
}

> REPL Highlight plugins demo

Touch points plugin

Show colored circles around touch points.

Touch points plugin options:

{
  color?: string;
  zIndex?: number;
  size?: number;
}

> REPL Touch points plugins demo

Vibrate plugin (experimental)

Vibrate a haptic sequence while gesture is executed

Vibrate plugin options:

{
  vibrationSequence: number[];
}

Vibration sequence is the same as the argument of navigator.vibrate function.

> REPL Vibrate plugins demo

Your own gestures

You are encouraged to define your own custom gestures. There is a createPointerControls function exposed by the svelte-gestures. It handles all the events registration/deregistration needed for handling gestures. It is a closure which returns a setPointerControls function.

Your custom attachment needs to return this setPointerControls function. You need to pass your own callbacks to it, which makes it your unique gesture. See source code of basic gestures to better understand how to create your won one.

function setPointerControls: (
  gestureName: string,
  node: HTMLElement,
  onMoveCallback: PointerEventCallback<boolean>,
  onDownCallback: PointerEventCallback<void>,
  onUpCallback: PointerEventCallback<void>,
  touchAction?: TouchAction | TouchAction[],
  pluginsArg?: GesturePlugin[]
) => {
  destroy: () => void;
};

You can pass null instead of a PointerEventCallback if you don't need to call it in that event. In a double tap example below you do not need any events related to move, as they are irrelevant for tapping.

See how an example doubletap gesture is implemented:

> REPL Custom gesture (doubletap) demo

License

MIT