From 4beac696c09d6828ce927602eb25e91d8efc5601 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Karl=20Yngve=20Lerv=C3=A5g?= <karl.yngve+git@gmail.com>
Date: Tue, 10 Dec 2013 17:42:25 +0100
Subject: [PATCH] Better support for multi-file documents #6

---
 autoload/latex.vim | 70 ++++++++++++++++++++++++++++++++++++----------
 doc/latex.txt      | 17 +++++++++++
 2 files changed, 72 insertions(+), 15 deletions(-)

diff --git a/autoload/latex.vim b/autoload/latex.vim
index 499a159..bd9de31 100644
--- a/autoload/latex.vim
+++ b/autoload/latex.vim
@@ -112,7 +112,7 @@ function! s:init_environment()
   "
   " Create new or link to old blob
   "
-  let main = s:get_main_tex()
+  let main = s:get_main()
   let id   = s:get_id(main)
   if id >= 0
     let b:latex.id = id
@@ -204,22 +204,62 @@ function! s:get_id(main)
   return -1
 endfunction
 
-" {{{1 s:get_main_tex
-function! s:get_main_tex()
-  let re_begin = '\C\\begin\_\s*{document}'
-  let re_input = '\v\\(input|include)\{' . expand('%:t:r') . '(\.tex)?'
-
-  if search(re_begin, 'nw')
-    return expand('%:p')
-  else
-    for l:file in glob('*.tex', 0, 1) + glob('../*.tex', 0, 1)
-      let lines = readfile(l:file)
-      if len(filter(copy(lines), 'v:val =~ re_input')) > 0
-            \ && len(filter(lines, 'v:val =~ re_begin')) > 0
-        return fnamemodify(l:file, ':p')
+" {{{1 s:get_main
+function! s:get_main()
+  "
+  " Search for main file specifier at the beginning of file.  This is similar
+  " to the method used by several other plugins and editors, such as vim with
+  " LaTeX-Box, TextMate, TexWorks, and texmaker.
+  "
+  for line in getline(1, 5)
+    let candidate = matchstr(line,
+          \ '^\s*%\s*!\s*[tT][eE][xX]\s\+root\s*=\s*\zs.*\ze\s*$')
+    if len(candidate) > 0
+      let main = fnamemodify(candidate, ':p')
+      if filereadable(main)
+        return main
       endif
-    endfor
+    endif
+  endfor
+
+  "
+  " Search for main file recursively through \input and \include specifiers
+  "
+  let main = s:get_main_recurse(expand('%:p'))
+  if filereadable(main)
+    return main
   endif
+
+  "
+  " If not found, use current file
+  "
+  return expand('%:p')
+endfunction
+
+" {{{1 s:get_main_recurse
+function! s:get_main_recurse(file)
+  "
+  " Check if current file is a main file
+  "
+  if len(filter(readfile(a:file),
+        \ 'v:val =~ ''\C\\begin\_\s*{document}''')) > 0
+    return fnamemodify(a:file, ':p')
+  endif
+
+  "
+  " Search for files that include the current file
+  "
+  for l:file in glob('*.tex', 0, 1) + glob('../*.tex', 0, 1)
+    if len(filter(readfile(l:file), 'v:val =~ ''\v\\(input|include)\{'
+          \ . fnamemodify(a:file, ':t:r') . '(\.tex)?''')) > 0
+      return s:get_main_recurse(l:file)
+    endif
+  endfor
+
+  "
+  " If not found, return 0
+  "
+  return 0
 endfunction
 
 " {{{1 s:get_main_ext
diff --git a/doc/latex.txt b/doc/latex.txt
index acf3c0f..c5ae927 100644
--- a/doc/latex.txt
+++ b/doc/latex.txt
@@ -126,6 +126,23 @@ Functions:
         |latex#reinit|
         |latex#view|
 
+------------------------------------------------------------------------------
+Support for multi-file projects:~
+                                                        *vim-latex-multi-file*
+                                                                    *tex-root*
+
+|vim-latex| supports multi-file documents in the sense that the plugin
+automatically detects the root file of the project.  This detection is based
+on a recursive search for files that include the current tex file, but it is
+naive in the sense that it assumes unique file names.  It also assumes that
+the main `tex` file lives in the same folder or the parent folder of the
+current file.  The method is simple, but it should work in most cases.
+
+It is also possible to specify the main TeX file with a comment in one of the
+first five lines of the current file similar to this: >
+
+  %! TEX root = my-main.tex
+
 ==============================================================================
 DEFAULT MAPPINGS                                          *vim-latex-mappings*