LaTeX composition in (g)vim with live update-as-you-type PDF preview

Question

Ever since I tried the gummi LaTeX editor, I've been intrigued by the idea of having a live-updating PDF preview--i.e., a PDF output panel which updated as I typed. This provides all the good things of WYSIWYG, but without taking away the control I have by editing the source directly. However, apart from its preview panel, I was thoroughly unimpressed with gummi as an editor. It had none of the advanced features I was used to.
Since then, I've been trying various techniques to make it work with my preferred editor, (g)vim. At first, I used latexmk with the -pvc option which recompiles whenever the file changes, along with a PDF editor that refreshes whenever the file changes (like evince); but found it slow and tended to get stuck.
My current method is to use mupdf as my viewer, with a custom LaTeX script which calls xdotool to update mupdf whenever I have a successful compilation. This seems to be working fairly well.
Here's an animated GIF screen capture showing it in action
There is typically still a 1-second delay between typing something and it showing on the PDF preview, but it's not really any worse than it seems to be wih gummi, and I get to use a world-class editor.
I should note that I'm not using the vim-latex suite plugin or anything similar, so I don't know whether or not any of this is compatible.
Anyway, I thought I'd post my method here just in case anyone thought it useful, or more importantly, anyone had any feedback for how it might be improved. I'm not a programmer (--my degrees are in philosophy!--) and don't really have that much experience with vim or bash scripting, so forgive my naive methods.
Anyway, in my ~/.vim/ftplugin/tex.vim I have:
" Function to save, check if already compiling and compile if not
function! KKLtxAction()
" go to right directory
lcd %:p:h
" save the file if need be and it's possible
if filewritable(bufname("%"))
silent update
endif
" see how many kkltx processes there are
" note that there are always 3 when the checking itself happens
" so we need there to be no more than that
let numrunning = system("ps ax | grep kkltx | wc -l")
if numrunning < 4
exec "silent !kkltx " . expand("%") . " &"
endif
endfunction
" Call this function whenever mupdf the cursor moves
" But only in gvim
if has("gui_running")
au CursorMoved *.tex call KKLtxAction()
au CursorMovedI *.tex call KKLtxAction()
endif
So whenever the cursor moves, the file saves and checks if the compilation script is running. If it is not, it runs it. Here's the script, named kkltx. (To make it work, create a ~/.config/kkltx folder. Sorry about the stupid name; I needed it to be uncommon.)
#!/bin/bash
file="$1"
logfile="${file%.tex}.log"
auxfile="${file%.tex}.aux"
# check to see when file was last saved and
# check see what version of file was last compiled
currmodified=$(stat -c %Y "$file")
oldmodified=$(cat $HOME/.config/kkltx/lastprocessedfile)
# if they're the same exit with no change
if [ "$currmodified" == "$oldmodified" ] ; then
echo "nochange"
exit 0
else
# if compilation is necessary, check what program to use
# 'xelatex' should appear in first 5 lines for xelatex docs
if head -n 5 "$file" | grep -i -q 'xelatex' > /dev/null 2>&1 ; then
execprog="xelatex"
else
execprog="pdflatex"
fi
# try to compile
if ${execprog} -interaction=batchmode -file-line-error -synctex=1 "$file" > /dev/null 2>&1 ; then
# if compiling worked check if bibtex needs to run
if cat "$logfile" | grep -i -q 'undefined citations' > /dev/null 2>&1 ; then
if bibtex "$auxfile" > /dev/null 2>&1 ; then
if ! ${execprog} -interaction=batchmode -file-line-error -synctex=1 "$file" > /dev/null 2>&1 ; then
echo "failure"
exit 1
fi
else
echo "bibfail"
exit 2
fi
fi
# check if a rerun is necessary to update cross-references
if cat "$logfile" | grep -i -q 'rerun to get' > /dev/null 2>&1 ; then
if ! ${execprog} -interaction=batchmode -file-line-error -synctex=1 "$file" > /dev/null 2>&1 ; then
echo "failure"
exit 1
fi
fi
# update mupdf by sending the r key to it
xdotool search --class mupdf key --window %@ r > /dev/null 2>&1
echo "success"
# save time of compilation
echo -n "$currmodified" > "$HOME/.config/kkltx/lastprocessedfile" 2>/dev/null
else
echo "failure"
exit 1
fi
fi
exit 0
One thing you miss out on with mupdf is the SyncTeX ability in, e.g., TeXworks that allows you jump from the source to the corresponding part of the PDF and vice-versa. Here's a kludge that at least gets to you to the right page by using xdotool to send the signal to move to a certain page matching the source, or to read what page mupdf is on, and move to the beginning of the source code for that page (or strictly, a couple inches over and down). Again, in my ~/.vim/ftplugin/tex.vim
" \v to open the viewer
nnoremap \v :exec "silent! !mupdf ".expand("%:r").".pdf &"
" forward search with mupdf
function! MuPDFForward()
" make sure I'm in the right directory
lcd %:p:h
let pageforward = 0
" find where I am now; adjust for starting with 0
let searchline = line(".") + 1
let searchcol = col(".") + 1
" use synctex to find the page to jump to
let pageforward = system("synctex view -i " . searchline . ":" . searchcol . ":\"" . expand("%") . "\" -o \"" . expand("%:r") . ".pdf\" | grep -m1 'Page:' | sed 's/Page://'")
" if a page other than 0 is found, send the page number to mupdf
if pageforward > 0
call system("xdotool search --class mupdf type --window %1 \"" . pageforward . "g\"")
endif
endfunction
" inverse search with mypdf
function! MuPDFReverse()
lcd %:p:h
let gotoline = 0
" call a script which returns the line number near start of page shown on mupdf
let gotoline = system("syncreverse-mupdf.sh " . expand("%:p:r"))
if gotoline > 0
exec ":" . gotopage
endif
endfunction
" mappings \f and \r for forward and reverse search
nnoremap <buffer> \f :call MuPDFForward()<CR>
nnoremap <buffer> \r :call MuPDFReverse()<CR>
Here is the script syncreverse-mupdf.sh called by the above:
#!/bin/bash
# syncreverse.sh full-path-of-PDF-minus-extension
pathfn="$1"
# reduce filename to base, add .pdf
pdffile="$(echo "$pathfn" | sed 's@.*/@@g').pdf"
# change to directory containing files
cd "$(echo "$pathfn" | sed 's@\(.*\)/[^/]*@\1@g')"
# read page number in mupdf window title
page=$(xdotool search --class mupdf getwindowname | sed 's:.* - \([0-9]*\)/.*:\1:')
# synctex lookup; remove junk
line=$(synctex edit -o "$page:288:108:$pdffile" | grep -m1 'Line:' | sed 's/Line://' | head -n1)
line=$(echo "$line" | sed -n 's/\([0-9]*\).*/\1/p')
# return line for gvim
echo "$line"
exit 0
I also recommend putting mappings in vim to send keys to mupdf to move around, so you can move around in the preview but without making (g)vim lose focus. These are just examples.
nnoremap <silent> <buffer> <C-PageDown> :silent! call system("xdotool search --class mupdf key --window %@ Page_Down")<CR>
nnoremap <silent> <buffer> <C-PageUp> :silent! call system("xdotool search --class mupdf key --window %@ Page_Up")<CR>
Anyway, these could definitely be improved, by, for example, accommodating master/sub-documents, and so on. Thoughts?
Last edited by frabjous (2010-11-04 22:41:21)

Answer 1

OK, I've uploaded a PKGBUILD to AUR. Since I've changed how it handles recognizing when it's safe to recompile, it no longer needs to have a weird name. The name is now:
vim-live-latex-preview
It comes with a very short vim help file, which I'll copy here.
*live-latex-preview.txt* For Vim version 7.3. Last change: 2010 Oct 27
*live-latex-preview*
A plugin for creating a live-updating PDF
preview for a LaTeX file in MuPDF
Default key bindings:~
\p = Begin auto-compilation and launch MuPDF preview.
\o = End auto-compilation and close MuPDF preview.
\s = Check the result of the last compilation;
jump to first error in case of errors.
\f = Forward search to page in PDF matching cursor
position in source.
\r = Reverse/inverse search to position in source
matching active page in MuPDF. (Very approximate.)
\<PageUp>, \<PageDown>, \<Up>, \<Down>, \<Right>, \<Left>, \G
\m, \t, \-, \+, \= = Send the corresponding keystrokes
to the MuPDF preview without losing focus on vim Window
The '\' can be changed by changing <LocalLeader>.
Be aware that your file is saved whenever the cursor moves. Be sure
to take the appropriate measures to keep back-up saves and undo files
so you can undo changes if need be.
To compile with XeLaTeX rather than PDFLaTeX, include the string
'xelatex' somewhere in the first five lines of your file (e.g., in a
comment). Currently only PDFLaTeX and XeLaTeX are supported. (Support
for LuaLaTeX and/or LaTeX > dvips > ps2pdf may be added in the future,
but they may be too slow for the live updating process anyway.)
The plug-in does not currently support master- and sub-documents
via LaTeX's \input{...} and \include{...} mechanisms. This may be
added in the future.
vim:tw=78:ts=8:ft=help:norl:
This is a new version; pretty much completely rewritten from the above. In particular, I've tried to incorporate keenerd's ideas; in particular some changes:
Rather than grepping the active processes, when it begins a compilation, it records the process ID of the compilation script, and will not begin a new compilation until that process finishes.
When it first launches MuPDF, it records the Window ID and sends it back to vim, so vim knows which instance of MuPDF to refresh or work with.
I've added a \s quick key which provides a one-word summary of the effects of the last compilation and jumps to the line number of the first error, if there were errors.
The script is located in a separate file in the main $VIMRUNTIME/ftplugin folder, rather than a user's tex.vim file.
I'm sure there's still plenty of room for improvement. I'd still like to get it to handle master/sub-documents well, for example. All comments welcome.