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@thi.ng/rstream-gestures

@thi.ng/rstream-gestures

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This project is part of the @thi.ng/umbrella monorepo.

About

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

Status

STABLE - used in production

Breaking changes

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

Installation

yarn add @thi.ng/rstream-gestures

Package sizes (gzipped): ESM: 1.20 KB / CJS: 1.25 KB / UMD: 1.32 KB

Dependencies

Usage examples

Several demos in this repo's /examples directory are using this package.

A selection:

Screenshot Description Live demo Source
Canvas based dial widget Demo Source
Doodle w/ K-nearest neighbor search result visualization 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
Worker based, interactive Mandelbrot visualization Demo Source
Basic rstream-gestures multi-touch demo Demo Source

API

Generated API docs

GestureType

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

  • START - mousedown / touchstart
  • MOVE - movemove
  • 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": 2, // GestureType.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 { GestureType, 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 === GestureType.DRAG),
        map((e) => e.active.map((g) => Math.hypot(...g.delta)))
    )
);

Authors

Maintainer

Contributors

License

© 2018 - 2020 Karsten Schmidt // Apache Software License 2.0

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