I'm pretty sure htop will not give you any useful information about swap usage by a specific pid. I'm even more sure top will not give you useful swap use info (top has a SWAP column that is useless info and not correlated with swap use).
In /proc/pid/smaps you can find the best detail I know of for memory and swap use by a pid. It is a bit verbose, so you would probably want some kind of program to read that and summarize the data into a more easily understood form.
Last edited by johnsfine; 12-19-2012 at 10:44 AM.