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23 lines
1.1 KiB
JavaScript
23 lines
1.1 KiB
JavaScript
/*
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* Normalize scroll wheel events.
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*
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* It seems like there's no consent as to how mouse wheel events are presented in the javascript API. The standard
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* states that a MouseEvent has a deltaY property that contains the scroll distances, together with a deltaMode
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* property that state the "unit" that deltaY has been measured in. The deltaMode can be either pixels, lines or
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* pages. The latter is seldomly used in practise.
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*
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* The troublesome part is that there is no standard on how to correlate the two at this point.
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*
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* The basic idea is that one tick of a mouse wheel results in a total return value of +/- 1 from this method.
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* It's important to keep in mind that one tick of a wheel may result in multiple events in the browser. The aim
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* of this method is to scale the sum of deltaY over
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*/
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function wheelDelta(evt) {
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if ('deltaMode' in evt && evt.deltaMode === WheelEvent.DOM_DELTA_PIXEL) {
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// chrome and webkit-based browsers seem to correlate one tick of the wheel to 120 pixels.
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return evt.deltaY / 120;
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}
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// firefox seems to scroll at an interval of 6 lines per wheel tick
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return evt.deltaY / 6;
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}
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