Flag in drag event to signal reaching clickDistance threshold

[Herst]

In my application I want to do certain things only after I am certain that the user intents to do a drag, e.g.:

• Adding the styles for dragged elements. If I would do it on the drag start event then it the style would be added on every mousedown which is not what I want.

• .raise() the element being dragged. If I would do it right away it might cause the click event to not be triggered (at least in some browsers) if the element got removed from the DOM.

The way I solved it is to simply use the delta x and y inside the drag event handler to calculate whether the click stance threshold has been breached or not.

Now d3 already does the same calculation already, I wondered whether it couldn't just simply tell me about whether the distance has been overstepped in the drag event, e.g. using d3.event.isOutsideClickDistance.

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On a side note, an alternative idea would be a .dragDistance() which would cause the start events to only appear after a certain distance. This would cause the elements to appear a bit sticky though and it depends on the specific use case whether that's what you want or not.

[Herst]

Oops, wrong project. I'm sorry. 😭

Reposted at d3/d3-drag#48.