I was working on my "SmartOpen" script, and thought of an issue that I came back to check on in your bash script...

# you find the correct instance of mvim if several are running, 
# and find one that contains a loaded buffer of the file you're 
# looking for ($foundfile)
mvim --servername $server --remote-expr "foreground()"
mvim --servername $server --remote-send ":exec \"tabnext $foundfile\" <CR>"
mvim --servername $server --remote-send ":$line <CR>"

OK, so you select the correct tab, then jump to the desired line. The problem is that tabs can have multiple split windows inside them, and this technique is just going to give focus to whichever window was last used on that tab by mvim when it switches to it with :tabnext.

To reproduce:

1. open the doc in Skim.app
2. open the source in mvim
3. in that same tab in mvim, create another window with :new whatever
4. make another tab in mvim (not necessary, but helps to demonstrate)
5. go back and invoke your bash script from within Skim.app (shift-command-click?)

This should switch to the correct tab, but not the correct window within that tab, and your --remote-send ":$line <CR>" will either jump to the line in the other window's buffer or its last line if $line exceeds its number of lines.

So, you could write another function and instead of making 3 calls to mvim from the shell, just make one call that executes the foreground, tabnext, SelectWindow of some sort, and then :$line. However, I was also thinking.. you probably need to break that loop after you succeed in finding an mvim server with your source file open. If you have multiple mvim servers (gui windows) running, you probably don't want this script playing a game of musical windows on your desktop. ;)

I wrote a vim function that has been working great the past few days of use, although I can't say it's 100% bulletproof. Instead of trying to find the right tab and window, it takes advantage of vim's behavior in the command :sbuffer:

:[N]sb[uffer] [N]                   *:sb* *:sbuffer*
    Split window and edit buffer [N] from the buffer list.  If [N]
    is not given, the current buffer is edited.  Respects the
    "useopen" setting of 'switchbuf' when splitting.  This will
    also edit a buffer that is not in the buffer list, without
    setting the 'buflisted' flag.

So, what I do is capture the user's current settings for &switchbuf, save them, set it to the necessary setting of let &switchbuf = "useopen,usetab", then check if the buffer's loaded somewhere and call exec "sbuffer" bufNo. Vim then switches to the correct tab & window automagically without me having to muck with searching through tabs and windows myself. Then I set the user's original settings back to &switchbuf. Anyway, I modified what I had for you:

function! MVS_Focus(filename, line)
  " See if the given filename is found to be loaded in any tab/window
  " if so, raise window, switch to file's tab, window, and jump line
  let oldSwitchBufOpt = &switchbuf
  let &switchbuf = "useopen,usetab"
  let bufNo = bufnr('\(^\|/\)' . a:filename . '$')
  if (!bufNo || !bufloaded(bufNo))
    return 0
  endif
  call foreground()
  exec "sbuffer" bufNo
  let &switchbuf = oldSwitchBufOpt " restore user's switchbuf option
  exe ":silent! :".a:line
  " see if you like this... could also pass a number of lines down to highlight
  exe ":normal V"
  call REcho(printf("Focused on %s line %d by macvim-skim.", fnamemodify(bufname("%"), ":f"), a:line))
  return 1
endfunction

" Redraw-echo (:he echo-redraw) -- more reliable echo!
function! REcho(msg)
  redraw | echo a:msg
endfunction

Now you can just make a single call to each mvim server...

for server in mvim --serverlist
do
if [[ $debug ]] ; then echo mvim --servername $server --remote-expr "MVS_Focus('$file', '$line')"; fi
finished=mvim --servername $server --remote-expr "MVS_Focus('$file', '$line')"
if [[ $finished > 0 ]]
then
echo Succeeded on servername: $server
break
fi
done

Right now I hard-link to a particular version of Skim.app on sourceforge. It would be better to use the latest version, but I'm not sure how to do that with sourceforge links.

I have Skim.app located at ~/Applications/PDFs, therefore would like to do something like:

let g:macvim_skim_app_path = '~/Applications/PDFs'

in my .vimrc.

According to :help bufname()

bufname({expr}) *bufname()* The result is the name of a buffer, as it is displayed by the ":ls" command. If {expr} is a Number, that buffer number's name is given. Number zero is the alternate buffer for the current window. If {expr} is a String, it is used as a |file-pattern| to match with the buffer names. This is always done like 'magic' is set and 'cpoptions' is empty. When there is more than one match an empty string is returned.

Since the string is used as a pattern, it might match part of another buffer name. The 'magic'-like behavior will save you in a lot of common cases, but there are still some gotchas. To avoid them, instead of calling:
let buffername = bufname(a:filename)
You can call:
let buffername = bufname("^" . a:filename . "$")

i.e., a regex that says the entire buffer must match the filename.

I'm trying to create an environment like this. Do I need VIM-LaTeX for this to work?

I wanna ask if it is okay to do backward search in terminal macvim? seems not working (I use iTerm2)

See bug description here: http://stackoverflow.com/questions/8839846/vim-check-if-a-file-is-open-in-current-tab-window-and-activate-it/14427211#14427211

Vundle is a package manager for Vim that simplifies life. :)