update event fires for all handles when one is changed with a key press

[eoghanmurray]

With multiple handles, moving one of them using the keyboard causes an update event to fire on all 3 handles.

noUiSlider.create(slider_el, {
    start: [30, 60, 90],
    behaviour: 'drag',
    connect: true,
    tooltips: [true, true, true],
    range: {
	'min': 0,
	'max': 100
    }
});
slider_el.noUiSlider.on('update', 
    function(v, h, u, t, p) { if (!t) { console.log('update:', h); }});
slider_el.noUiSlider.on('set', 
    function(v, h, u, t, p) { if (!t) { console.log('set:', h); }}

Expected output upon moving handle number 2 with keyboard:

update: 1
set: 1

Actual output:

update: 0
update: 1
set: 1
update: 2

This causes a bug with my solution in #957 when trying to move handle number 2 back past the margin of handle number 1; the event handler for handle number 1 gets executed first and modifies the position of handle number 2 such that when the update event for handle number 2 subsequently fires, there's nothing to do.

[eoghanmurray]

Looks like the rationale for the multiple updates was already questioned here:
#579 (comment)
I know there's gonna be a good reason but I can't figure it out.
Could a solution be to check whether a given handles' value has actually changed before firing that event?

[leongersen]

This is a mistake on my end, update should only fire for the handle being, you know, updated.

[leongersen]

As per the rationale behind firing update events:

The idea is that calling set allows handles to "push" each other forward. Say you have a slider with range 0 - 10, step 3, start 0 - 6. Calling set([9, null]) causes handle 0 to move to 9, forcing handle 1 to move to 9 as well, even though no update of handle 1 was requested. If there would be no update event for handle 1, possible listeners would be out of sync.

Thanks for pointing this out, because I'm now realizing that keyboard interaction allows for this same effect: handle 0 can push handle 1 forward, but it shouldn't!

[leongersen]

This is fixed in noUiSlider 13.1.3. Many thanks for contributing, @eoghanmurray! Much appreciated.

[eoghanmurray]

Chuffed to have turned out to be useful!

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