diff --git a/README.md b/README.md index c79eec12f5..e64cd5f656 100644 --- a/README.md +++ b/README.md @@ -30,6 +30,24 @@ The old behavior of adding three arguments (`delta`, `deltaX`, and `deltaY`) to event handler is now deprecated and will be removed in later releases. +## The Deltas... + +The combination of Browsers, Operating Systems, and Devices offer a huge range of possible delta values. In fact if the user +uses a trackpad and then a physical mouse wheel the delta values can differ wildly. This plugin normalizes those +values so you get a whole number starting at +-1 and going up in increments of +-1 according to the force or +acceleration that is used. This number has the potential to be in the thousands depending on the device. +Check out some of the data collected from users [here](http://mousewheeldatacollector.herokuapp.com/). + +### Getting the scroll distance + +In some use-cases we prefer to have the normalized delta but in others we want to know how far the browser should +scroll based on the users input. This can be done by multiplying the `deltaFactor` by the `deltaX` or `deltaY` +event property to find the scroll distance the browser reported. + +The `deltaFactor` property was added to the event object in 3.1.5 so that the actual reported delta value can be +extracted. This is a non-standard property. + + ## See it in action [See the tests on Github](http://brandonaaron.github.io/jquery-mousewheel/test).