XT Rear Derailleur Alignment with chain

David

My front XT derailleur got caught on the chain the other night, and
after repositioning and readjusting it, I notice that I get a clicking
noise ever half chain revolution or so from the rear of the bike.

When I turned the bike over I could see the rear derailleur arm (XT)
was not aligned with the direction the chain was running in, and so
every so often the chain jumped from its guide wheel. It happens with
the large front cog and the larger rear cogs selected.

I know little about bike mechanics, but any advice would be useful. I
cant tell whether the whole housing is moved, bent , or whether just
the arm is bent.

Can anyone point me to some diagrams/pictures that show correct
alignment and how it measured ?

Any help appreciated
Dave