@thi.ng/rstream-gestures

[!NOTE] This is one of 201 standalone projects, maintained as part of the @thi.ng/umbrella monorepo and anti-framework.

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• About
• Status
  • Breaking changes
    • v3.0.0
    • v2.0.0
• Related packages
• Installation
• Dependencies
• Usage examples
• API
  • GestureType
  • GestureEvent
  • GestureStreamOpts
  • Basic usage
  • Resettable zoom
• Authors
• License

About

Unified mouse, mouse wheel & multi-touch event stream abstraction. This is a support package for @thi.ng/rstream.

Status

STABLE - used in production

Search or submit any issues for this package

Breaking changes

v3.0.0

The gestureStream() now supports external zoom control/resetting via providing a subscription as zoom option. That itself isn't a breaking change, however a result of this is that the GestureEvents emitted by the stream do not always contain the original DOM event anymore (i.e. not in the case when the zoom factor is being reset via attached subscription).

v2.0.0

Multi-touch support has been added in v2.0.0, resulting in a complete rewrite of gestureStream() and new event data formats.

Related packages

• @thi.ng/hdom - Lightweight vanilla ES6 UI component trees with customizable branch-local behaviors
• @thi.ng/rdom - Lightweight, reactive, VDOM-less UI/DOM components with async lifecycle and @thi.ng/hiccup compatible

Installation

yarn add @thi.ng/rstream-gestures

ESM import:

import * as gest from "@thi.ng/rstream-gestures";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/rstream-gestures"></script>

JSDelivr documentation

For Node.js REPL:

const gest = await import("@thi.ng/rstream-gestures");

Package sizes (brotli'd, pre-treeshake): ESM: 1.20 KB

Dependencies

• @thi.ng/api
• @thi.ng/checks
• @thi.ng/math
• @thi.ng/rstream
• @thi.ng/transducers

Note: @thi.ng/api is in most cases a type-only import (not used at runtime)

Usage examples

15 projects in this repo's /examples directory are using this package:

Screenshot	Description	Live demo	Source
	Canvas based dial widget	Demo	Source
	Interactive visualization of closest points on ellipses	Demo	Source
	Interactive inverse FFT toy synth	Demo	Source
	Doodle w/ K-nearest neighbor search result visualization	Demo	Source
	K-nearest neighbor search in an hash grid	Demo	Source
	Mouse gesture / stroke analysis, simplification, corner detection	Demo	Source
	Interactive pattern drawing demo using transducers	Demo	Source
	Canvas based Immediate Mode GUI components	Demo	Source
	Minimal IMGUI usage example	Demo	Source
	Worker based, interactive Mandelbrot visualization	Demo	Source
	Basic rstream-gestures multi-touch demo	Demo	Source
	Minimal rstream dataflow graph	Demo	Source
	Minimal shader graph developed during livestream #2	Demo	Source
	Multi-layer vectorization & dithering of bitmap images	Demo	Source
	rdom & WebGL-based image channel editor	Demo	Source

API

Generated API docs

GestureType

All native events are abstracted into one of the following event types:

• move - movemove
• start - mousedown / touchstart
• drag - mousemove (whilst dragging) / touchmove
• end - mouseup / touchend / touchcancel
• zoom - wheel

GestureEvent

The stream emits GestureEvent objects of:

• type - Current translated/abstracted event type (GestureType)
• event - Original DOM event
• pos - Event position (transformed as per GestureStreamOpts)
• active - Active cursors (i.e. ongoing drag / touch gestures)
• buttons - Mouse button bitmask (same as in standard MouseEvent), or, if isTouch is true, number of active touches.
• zoom - Current zoom factor (as per GestureStreamOpts config)
• zoomDelta - Last WheelEvent's transformed deltaY, wheelDeltaY
• isTouch - True, if original event was a TouchEvent

// example mouse gesture event
{
  "type": "drag"
  "event": MouseEvent,
  "pos": [254, 169],
  "active": [
    {
      "id": 0, // always 0 for mouse gestures
      "start": [443, 37],
      "pos": [254, 169],
      "delta": [-189, 132]
    }
  ],
  "buttons": 2, // right button pressed
  "zoom": 1,
  "zoomDelta": 0,
  "isTouch": false
}

GestureStreamOpts

See the GestureStreamOpts config options for further details.

Basic usage

import { gestureStream } from "@thi.ng/rstream-gestures";
import { trace } from "@thi.ng/rstream";
import { comp, dedupe, filter, map, pluck } from "@thi.ng/transducers";

// create event stream with custom options
const gestures = gestureStream(document.body, { smooth: 0.01 });

// subscription logging zoom value changes
gestures.subscribe(
    // trace is simply logging received values to console
    trace("zoom"),
    // composed transducer, `dedupe` ensures only changed values are received
    comp(pluck("zoom"), dedupe())
);

// another subscription computing & logging drag gesture distance(s)
gestures.subscribe(
    trace("distance"),
    comp(
        filter((e) => e.type === "drag"),
        map((e) => e.active.map((g) => Math.hypot(...g.delta)))
    )
);

Resettable zoom

For some applications (e.g. graphical editors), it can be helpful to reset the zoom value. This can be done by supplying a stream/subscription as part of the config options:

import { reactive } from "@thi.ng/rstream";
import { gestureStream } from "@thi.ng/rstream-gestures";

// create stream for initial zoom value & for resetting
const zoomReset = reactive(1);

// create gesture stream w/ zoom subscription
const gestures = gestureStream(document.body, {
    smooth: 0.01,
    zoom: zoomReset
});

// ... then to reset the zoom at some point (e.g to zoom=2)
zoomReset.next(2);

Authors

• Karsten Schmidt (Main author)
• Arthur Carabott
• Matei Adriel

If this project contributes to an academic publication, please cite it as:

@misc{thing-rstream-gestures,
  title = "@thi.ng/rstream-gestures",
  author = "Karsten Schmidt and others",
  note = "https://thi.ng/rstream-gestures",
  year = 2018
}

License

© 2018 - 2025 Karsten Schmidt // Apache License 2.0