Draggable: Only blur the focused element if the event occurs on a handle

[tjvantoll]

I manually verified this works and doesn't regress #4261 in IE 8, 9, 10, 11, and Chrome. I'm having a hell of a time writing a test for this though. The existing test for #4261 passes in all the IEs.

cc @mikesherov

[mikesherov]

Why can't this be unit tested? Seems like a pretty important thing to test.

[mikesherov]

combine this conditional with the one below it to reduce nesting level.

[tjvantoll]

I split them up to make it clear that the Support comment only applied to that check. But if I combine the comments on lines 133 and 134 I think it should be clear enough.

[mikesherov]

Good point about comment. Then perhaps instead you can make the new check be a guard clause even before the try.

[mikesherov]

Ah, I just saw that the test seems hard. I'll like to take a crack at it if you can't get a suitable one going because I think it's important this not regress again.

[mikesherov]

I can confirm that in the test for the blur behavior, if you switch the input to a <div tabindex=-1>, and append it to the draggable, and simulate a drag on it, you can get a red/green test. Didn't test it on ie8 though. Lemme know if that works.

[tjvantoll]

The <div> did make this a lot easier to test. I tested in Chrome and all the IEs, so hopefully this is good to go.

[mikesherov]

@tjvantoll actually, there's another bug! I found it during testing. I'm opening a separate PR with your change and mine. We also needed to prevent focus on mouseup for the same thing.

[mikesherov]

#1315

[mikesherov]

@tjvantoll also, thanks again for sticking with this. I really appreciate your diligence.

[tjvantoll]

Closing in favor of #1315.