OptionalonendRelease, cancel (event.type === 'pointercancel'), or the pointer lost, with the final
travel. Not called for a drag still in progress when the element is destroyed.
Every move while pressed, with the travel so far.
OptionalonstartA press on the element. Return false to leave this one alone: it is not tracked, and
nothing else below is called for it. Only the primary button of a mouse reaches here.
What
pointerDragcalls. Travel is always since the press, in the element's own pixels.