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About

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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.

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Installation

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Dependencies

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API

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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);