Hit-test where the mouse-down event is fired, hit-test where the mouse-up event is fired. What the hell do you need a library for?

> If anyone can dig up an ancient library on GitHub for drag-and-drop back in those days, I'd imagine it would be several thousand lines long,

I bet, the JS devs who do write code overcompensate for the ones who can only stitch together libraries. I suppose because the expectation is that the library consumer is incapable of writing their own code extending it, so the library itself must support every possible combination of use cases for a million different users, even though the code any individual consumer actually needs is more like 100 loc.

▲ gavinray 2 hours ago | parent [-]

  > What the hell do you need a library for?

On the frontend, you have to re-calculate the display state for all the possible drop positions, in-between transitions, and drop-end-snap-back.

Think of a grid of cards, and all the possible drag, hover, and drop state transitions it can be in with any other card, and the animations required to make it look nice

Now also consider that you need to persist the final state on the backend, and handle things like rejection, cancellation, failed updates/errors.

It becomes a massive state chart and web of complexity

	▲	anonymous908213 2 hours ago \| parent [-]
		I mean, maybe we're missing context here. Is that what your boss was actually asking for? 99% of web applications (or, hell, desktop applications) don't have ultra-interactive, fully-responsive-animation drag-and-drop. If he was asking for functional drag-and-drop and the team was implementing top 1% cosmetic drag-and-drop, that's certainly one avenue for a mismatch in expectations.