add threshold setting

[UziTech]

Add threshold setting to move only if mouse moves farther than
threshold. Threshold setting can be a function.
fixes #83

[davetayls]

Hi, a couple of thoughts on this.

I'd prefer the threshold to work by keeping track of Start position and measuring against that at each step I think.

Also, I know that sqrt isn't a particularly fast calculation. Whilst it's definitely more accurate it would be interesting to try and see if the experience works as well by just checking Y distance or X distance is greater than threshold relative to start position.

Let me know your thoughts

[davetayls]

Alternatively if just counting down the threshold works better the property should probably be moveThresholdRemaining

[davetayls]

Please can you also update the read me and include a test with the threshold setting. Cheers

[davetayls]

Just add the test to the end of https://github.com/davetayls/jquery.kinetic/blob/master/test/specs/basic.spec.js 👌

[UziTech]

https://jsperf.com/sqrt-vs-abs

I don't think Math.sqrt will affect the performance especially since it is being used before the scrolling occurs .

I agree it should be from starting position. I will fix that and create the tests.

[UziTech]

Not sure why the build fails. The tests pass when viewing them in any browser.
https://rawgit.com/UziTech/jquery.kinetic/master/test/specs/basic.html

[davetayls]

I'll take a look later this morning

[davetayls]

Just had a quick look on my phone and they aren't passing, is this because of the changes you have made to how the threshold works?

[UziTech]

found the bug in the dragOver() function for the tests. the touch move event was moving to x,x instead of x,y and the threshold wasn't being crossed

[davetayls]

thanks @UziTech nice work, i'll merge this in and do a release 👍