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Rezi / svelte-gestures

MIT License
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svelte-gestures

3 KB gzipped (you can use just part of those 3 KB) - a collection of gesture recognizers for Svelte. It can be actually used in any framework or native JS as it does not use any specific Svelte syntax at all ;)

New in svelte-gestures 1.5:

installation

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.

Language tools types installation (optional)

If you use Svelte language tools (Svelte for VS Code for instance) and you would appreciate seeing return types from svelte-gestures actions <div on:swipe={fn} > in your markup,and running on svelte version 4.2 or below add the following line to your global.d.ts or sililar definition ts file :

/// <reference types="svelte-gestures" />

if you use older version of Svelte kit, you already have a global.d.ts in src folder. Just add this line after

/// <reference types="@sveltejs/kit" />

It must be done this way as language tools use global types and a regular npm package cannot expose global types as long as it is used by another package. In case global.d.ts does not exist in your project and you run svelte version 4.1 or below, you need to create such a file and add it to yout tsconfig.json file inside include:[].

About

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

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 actions with custom event emitters. Any number of different recognizers can be used on one element, but it is recommended to use composedGesture for combined gestures.

API events

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

For example pan action has for example panup, pandown, panmove. It dispatches event.detail with the following property

{ 
  event: PointerEvent, 
  pointersCount: number , 
  target:HTMLElement,
  x: number,
  y: number,
} 
<script lang="ts">
  import { pan, type PanCustomEvent, type GestureCustomEvent } from 'svelte-gestures';
  let x: number;
  let y: number;
  let target: EventTarget;

  function handler(event: PanCustomEvent) {
    x = event.detail.x;
    y = event.detail.y;
    target = event.detail.target;
    }

  function panDown(gestureEvent: GestureCustomEvent) {
    const { event, pointersCount, target, x, y } = gestureEvent.detail;
  }

  function panMove(gestureEvent: GestureCustomEvent) {
    console.log(gestureEvent.detail);
  }
</script>

<div
  use:pan
  on:pan={handler}
  on:pandown={panDown}
  on:panmove={panMove}
  style="width:500px;height:500px;border:1px solid black;"
></div>

You can import this event type as GestureCustomEvent. First is a native pointer event; the second is the number of active pointers; third 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.

Pan

Pan action (on:pan) fires pan event:

The pan accepts the following options

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

> repl Pan demo

<script lang="ts">
  import { pan, type PanCustomEvent } from 'svelte-gestures';
  let x;
  let y;
  let target;
  let pointerType;

  function handler(event: PanCustomEvent) {
    x = event.detail.x;
    y = event.detail.y;
    target = event.detail.target;
    pointerType = event.detail.pointerType;

  }
</script>

<div
  use:pan="{{delay:300}}"
  on:pan="{handler}"
  style="width:500px;height:500px;border:1px solid black;"
>
  pan: {x} {y}
</div>

Pinch

Pinch action (on:pinch) fires pinch event:

The pinch accepts the following options

> repl Pinch demo

<script lang="ts">
  import { pinch, type PinchCustomEvent } from 'svelte-gestures';
  let scale;
  let x;
  let y;
  let pointerType;

  function handler(event: PinchCustomEvent) {
    scale = event.detail.scale;
    x = event.detail.center.x;
    y = event.detail.center.y;
    pointerType = event.detail.pointerType;
  }
</script>

<div
  use:pinch
  on:pinch="{handler}"
  style="width:500px;height:500px;border:1px solid black;"
>
  pinch scale: {scale} <br />
  center: x {x}, y {y}
</div>

Rotate

Rotate action (on:rotate) fires rotate event:

The rotate accepts the following options

> repl Rotation demo

<script lang="ts">
  import { rotate, type RotateCustomEvent } from 'svelte-gestures';
  let rotation;
  let x;
  let y;
  let pointerType;

  function handler(event: RotateCustomEvent) {
    rotation = event.detail.rotation;
    x = event.detail.center.x;
    y = event.detail.center.y;
    pointerType = event.detail.pointerType;
  }
</script>
<div
  use:rotate
  on:rotate="{handler}"
  style="width:500px;height:500px;border:1px solid black;"
>
  rotation: {rotation} <br />
  center: x {x}, y {y}
</div>

Swipe

Swipe action (on:swipe) fires swipe event:

The swipe accepts the following options

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

<script lang="ts">
import { swipe, type SwipeCustomEvent } from 'svelte-gestures';
let direction;
let target;
let pointerType;

function handler(event: SwipeCustomEvent) {
  direction = event.detail.direction;
  target = event.detail.target;
  pointerType = event.detail.pointerType;
}
</script>

<div use:swipe={{ timeframe: 300, minSwipeDistance: 60 }} on:swipe={handler} style="width:500px;height:500px;border:1px solid black;">
  direction: {direction}
</div>

Tap

Tap action (on:tap) fires tap event:

The tap accepts the following options

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

> repl Tap demo

<script lang="ts">
import { tap, type TapCustomEvent } from 'svelte-gestures';

let x;
let y;
let target;
let pointerType;

function handler(event: TapCustomEvent) {
  x = event.detail.x;
  y = event.detail.y;
  target = event.detail.target;
  pointerType = event.detail.pointerType;
}

</script>
<div use:tap={{ timeframe: 300 }} on:tap={handler} style="width:500px;height:500px;border:1px solid black;">
  tap: {x} {y}
</div>

Press

Press action (on:press) fires press event:

The press accepts the following options

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

<script lang="ts">
import { press, type PressCustomEvent } from 'svelte-gestures';
let x;
let y;
let target;

function handler(event: PressCustomEvent) {
x = event.detail.x;
y = event.detail.y;
target = event.detail.target
}
</script>
<div use:press={{ timeframe: 300, triggerBeforeFinished: false }} on:press={handler} style="width:500px;height:500px;border:1px solid black;">
  press: {x} {y}
</div>

Shape gesture

ShapeGesture action (on:shapeGesture) fires shapeGesture event:

The shapeGesture accepts the following options

shapeGesture action 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 coordinants 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 automaticaly for gesture/shape comparison.
  4. When bothDirections is set to false, order of points matters, even if the shape is closed (circle, suare, etc)

> repl ShapeGesture demo

<script lang="ts">
  import { shapeGesture, type ShapeCustomEvent } from 'svelte-gestures';
  const shapeOptions = {
    threshold: 0.5,
    shapes: [
      {
        name: 'triangle',
        allowRotation: true,
        points: [
          { x: 0, y: 0 },
          { x: 50, y: 100 },
          { x: 100, y: 0 },
          { x: 0, y: 0 },
        ],
      },
      {
        name: 'right-down',
        points: [
          { x: 0, y: 0 },
          { x: 100, y: 0 },
          { x: 100, y: 100 },
        ],
      },
      {
        name: 'up-right',
        bothDirections: false,
        points: [
          { x: 0, y: 100 },
          { x: 0, y: 0 },
          { x: 100, y: 0 },
        ],
      },
    ],
  };

  let result;

  function handler(event: ShapeCustomEvent) {
    result = event.detail;
  }
</script>

<div
  use:shapeGesture="{shapeOptions}"
  on:shapeGesture="{handler}"
  style="width:500px;height:500px;background:#ddd;"
>
  {#if result?.score} There is <b>{(result.score * 100).toFixed(0)}%</b> chance
  you have drawn a <b>{result.pattern}</b> shape {/if}
</div>

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 use:composedGesture. The function definition should have the following signature:

The register parameter is a callback function provided by composedGesture, and it has the following signature:

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.

> repl ComposedGesture demo

<script lang="ts">
  import {
    press,
    pan,
    scroll,
    composedGesture,
    type RegisterGestureType,
    type GestureCallback,
  } from 'svelte-gestures';

  let x;
  let y;

  const scrollPan: GestureCallback = (register: RegisterGestureType) => {
    const pressFns = register(press, {
      triggerBeforeFinished: true,
      spread: 10,
      timeframe: 100,
    });
    const scrollFns = register(scroll, { delay: 0 });
    const panFns = register(pan, { delay: 0 });

    return (activeEvents: PointerEvent[], event: PointerEvent) => {
      pressFns.onMove(activeEvents, event) || event.pointerType !== 'touch'
        ? panFns.onMove(activeEvents, event)
        : scrollFns.onMove(activeEvents, event);
    };
  };

  function handler(event) {
    x = event.detail.x;
    y = event.detail.y;
  }
</script>
<div
  use:composedGesture="{scrollPan}"
  on:pan="{handler}"
  style="width:500px;height:500px;border:1px solid black;"
>
  press: {x} {y}
</div>

Your own gestures

You are encouraged to define your own custom gestures. There is a setPointerControls function exposed by the svelte-gestures. It handles all the events registration/deregistration needed for handling gestures; you just need to pass callbacks in it.

function setPointerControls(
  gestureName: string,
  node: HTMLElement,
  onMoveCallback: (activeEvents: PointerEvent[], event: PointerEvent) => void,
  onDownCallback: (activeEvents: PointerEvent[], event: PointerEvent) => void,
  onUpCallback: (activeEvents: PointerEvent[], event: PointerEvent) => void
);

You can pass null instead of a callback 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 a doubletap custom gesture is implemented:

> repl Custom gesture (doubletap) demo

<script lang="ts">
  import { setPointerControls, DEFAULT_DELAY } from 'svelte-gestures';

  let dx;
  let dy;

  function doubletapHandler(event) {
    dx = event.detail.x;
    dy = event.detail.y;
  }

  function doubletap(
    node: HTMLElement,
    parameters: { timeframe: number } = { timeframe: DEFAULT_DELAY }
  ): { destroy: () => void } {
    const gestureName = 'doubletap';
    const spread = 20;

    let startTime: number;
    let clientX: number;
    let clientY: number;
    let tapCount = 0;
    let timeout;

    function onUp(activeEvents: PointerEvent[], event: PointerEvent) {
      if (
        Math.abs(event.clientX - clientX) < spread &&
        Math.abs(event.clientY - clientY) < spread &&
        Date.now() - startTime < parameters.timeframe
      ) {
        if (!tapCount) {
          tapCount++;
        } else {
          const rect = node.getBoundingClientRect();
          const x = Math.round(event.clientX - rect.left);
          const y = Math.round(event.clientY - rect.top);

          node.dispatchEvent(
            new CustomEvent(gestureName, {
              detail: { x, y },
            })
          );

          clearTimeout(timeout);
          tapCount = 0;
        }
      }
    }

    function onDown(activeEvents: PointerEvent[], event: PointerEvent) {
      if (!tapCount) {
        clientX = event.clientX;
        clientY = event.clientY;
        startTime = Date.now();
      }

      timeout = setTimeout(() => {
        tapCount = 0;
      }, parameters.timeframe);
    }
    return setPointerControls(gestureName, node, null, onDown, onUp);
  }
</script>
<div
  use:doubletap
  on:doubletap="{doubletapHandler}"
  style="width:500px;height:500px;border:1px solid black;"
>
  double tap me {dx} {dy}
</div>

License

MIT