Extension events about core HOT 4 CLOSED

@kriszyp, @neonstalwart, @kitsonk, @csnover Any thoughts?

from core.

i'm currently on medication for a toothache... there's a lot of words to comprehend here 😄

i always thought that extension events were a reasonably elegant mechanism to provide a way to do things which are out of the ordinary but inevitably come up from time to time. as of this moment, i can't think of concrete cases but given that i think it's useful for those things which i don't typically think of i'd be in favor of having this kind of mechanism.

that said, i'm going to take a position i've taken a few times now... is it something that can be added later (either pre-2.0 or 2.0.x) once some concrete use cases arise to guide what it should look like? i think it's easier to leave something out and add it later than it is to get it wrong and have to live with it.

from core.

I think I am struggling like @neonstalwart to understand the use case that would be less confusingly solved by some other pattern. Personally I "get" synthetic events, but I have never "gotten" extension events, other than they were a way to try to "normalise" some things. I haven't ever found myself thinking "oh, I know how to solve this problem, extension events." (Of course, I may not have encountered problems they solve though...)

If we are saying that we believe the biggest use cases that were prevalent in Dojo 1 don't exist anymore and as Ben says, introducing that at a later date would clearly not be a breaking change, why would we tackle them now?

from core.

I almost had a reason to bring these back from the dead when I realized that dojo/mouse in Dojo 1 served a purpose beyond providing support to browsers without native mouseenter and mouseleave - it also provides support for using those events with event delegation. However, if i'm not mistaken, this is ridiculously easy to do manually:

delegate(rootNode, '.selector', 'mouseover', function (event) {
    if (dom.contains(this, event.target) && !dom.contains(this, event.relatedTarget)) {
        ...
    }
});

So, yeah. Still don't have a use case for extension events right now, and at this point we're thinking of going ahead and removing ExtensionEvent from on.ts.

from core.