Removing behaviors

[tmcw]

While it's possible to specifically unbind a behavior's handlers, I'm not seeing any clear way to easily remove the behavior itself, in v2 or v3 - if you want an element to be draggable most of the time, but disable the drag handler later.

[mbostock]

Right, currently you’d need to remove the listeners yourself, which is a bit of a pain:

selection
    .on("mousedown.zoom", null)
    .on("mousewheel.zoom", null)
    .on("mousemove.zoom", null)
    .on("DOMMouseScroll.zoom", null)
    .on("dblclick.zoom", null)
    .on("touchstart.zoom", null)
    .on("touchmove.zoom", null)
    .on("touchend.zoom", null);

I think either we’d need a way to remove an entire namespace, say selection.on("*.zoom", null), or the behavior should expose a method for unbinding from a selection and do the same.

[jfirebaugh]

selection.on("*.zoom", null) would be useful in its own right. I would spell it selection.on(".zoom", null) though, per jQuery's convention.

[mbostock]

Ah, sure, that sounds fine. Related #880.

And if you say selection.on(".zoom", listener), it overwrites any current listener in the zoom namespace, but has no effect if there are no existing listeners with that namespace?

[mbostock]

Not sure if we need another way to unbind a behavior now that selection.on(".zoom", null) has been supported since #1140 in 3.1.

[dannyko]

Sorry to ask a possibly dumb question here, but what about the use-case where the user would like to clear all "on" functions that may (or may not) have been bound to any elements over the entire document/DOM, e.g. by some user-generated code? Since the external code might bind the "on" functions to tags like html or body which you don't want to remove, removing them from the DOM would not be a good option as a method for also removing their associated/bound callbacks. Out of blind hope, I tried something naive like d3.on("*", null) and got an error (TypeError: undefined is not a function). Is there a better way, other than explicitly enumerating each type of listener (e.g. click, drag, mouseover, etc.) and doing a ...d3.selectall("*").on(listener_type, null)... type of iteration?

[jasondavies]

Removing all listeners in all namespaces is not supported at the moment, but would be simple enough to add. Removing all namespaced listeners for a particular event type is also not supported, e.g. mousedown.*, but that’s probably not common enough to warrant inclusion.

[jasondavies]

We can discuss further in #1855.