There's a behavior I find myself always reimplementing : pressing on an object (or touching it), attaching it to the mouse cursor or the finger, and releasing it when I let go the mouse button or the finger.
Everytime I seems to implement it a different way, never too happy with the results and the slight variations.
One of the biggest problem I encounter is the right way to make it "exclusive" (I don't want to attach every instance of the same object when I pass on it when I'm already attached to one).
Does that kind of thing merits its own behavior ?
Is there a quick and efficient way to do that every time ? (something that doesn't break on border cases...)