benhutchison / gesture

Purely functional recognition of Drag and Click gestures over a W3C Pointer Event -compatible API in Scala/Scala.js

GitHub

gesture

Purely functional recognition of Drag and Click gestures over a W3C Pointer Event -compatible API, for Scala/Scala.js

Built on top of the State monad provided by the Cats library.

gesture core

Contains the library code:

  • GestureProcessor converts a series of PointerEvents into a series of GestureEvents, while updating a Finite State Machine represented by PointerState.

  • Optionally, GestureAndRegionProcessor[R] can extend the functionality to tracking the region R where the gesture began and completed, if any. The region itself is provided by the user of the library an can be any type, so long a there is a search function (Double, Double) => Option[R] to find the region R at a coordinate, if any.

  • Coordinates are modeled as (Double, Double)

Published for both Scala.jvm and Scala.js.

SBT: "com.github.benhutchison" %%% "gesture" % "0.3"

Changelog

Version When Changes
0.1 Jan 16 Initial release
0.2 Oct 16 Upgrade libs, cats to 0.7.2, scalajs-dom to 0.9
0.3 Nov 16 Scala 2.12, cats to 0.8.1

gesture demo

Shows a working demo of the recognition system, implemented over an HTML canvas. Colored rectangles can be created and dragged around the screen.

To try it out, clone the project, run sbt demo/fullOptJS, and then load file demo/demo-opt.html in a browser.

The demo uses the reliable Points polyfill developed by Rich Harris to provide Pointer Events across browsers/devices.