Compile a region in auctex with import package

Question

Consider the three following (see below) files: test.tex is in the main directory, test1.tex is in the subdirectory ./test1/ and test11.tex is in the subsubdirectory ./test1/test11/ (see the directory structure below).

When I compile with auctex (C-c C-c) from the buffer where I read test11.tex, the file is compiled correctly: no problem. However, if I want to compile only the region (see screenshot below) where the figure environement is (C-c C-r), it fails. The _region_.tex produced by auctex in the directory where the master-file is is reproduced at the end of the question. This happens because no import-related command is issued in the _region_.tex file: thus the graphicspath is not adjusted. Is there a workaround?

Note: I can add the directory of the imported and subimported files in the Local Variables section it if can help.

├── _region_.aux
├── _region_.log
├── _region_.pdf
├── _region_.tex
├── test1
│   ├── test11
│   │   ├── KnuthAtOpenContentAlliance.jpg
│   │   ├── test11.log
│   │   └── test11.tex
│   └── test1.tex
├── test.aux
├── test.log
├── test.pdf
├── test-pics.pdf
└── test.tex

---

% This is ./test.tex
\documentclass{article}
\usepackage{graphics}
\usepackage{import}
\begin{document}

\import{./test1/}{test1.tex}

\end{document}

---

% This is ./test1/test1.tex
\subimport{test11/}{test11.tex}

% Local Variables:
% TeX-master: "../test.tex"
% End:

---

% This is ./test1/test11/test11.tex
% http://commons.wikimedia.org/wiki/File:KnuthAtOpenContentAlliance.jpg

\begin{figure}
\includegraphics{KnuthAtOpenContentAlliance}
\end{figure}

Test...

% Local Variables:
% TeX-master: "../../test.tex"
% End:

---

This is the file _region_.tex produced by auctex.

\message{ !name(../../test.tex)}% This is ./test.tex
\documentclass{article}
\usepackage{graphics}
\usepackage{import}
\begin{document}

\message{ !name(test1/test11/test11.tex) !offset(-4) }
\begin{figure}
\includegraphics{KnuthAtOpenContentAlliance}
\end{figure}

Test...

\message{ !name(../../test.tex) !offset(-7) }

\end{document}

Answer 1

Inspection of _region_.tex shows that it contains the information which file the region came from.

\message{ !name(test1/test11/test11.tex) !offset(-38) }

All we have to do is extract the path and fake it for \includegraphics. Thus, the plan:

1. Temporarily redefine \message.
2. Extract the path. (This is actually the hardest part ... I couldn't find any package doing it, so I used pgfkeys.)
3. Set whatever current-path macros import sets.
4. Make sure all this happens only if we're compiling a region. We don't want to end up with a redefined \message!

Point 4 is accomplished by setting AUCTeX's variable TeX Command -> TeX Region Extra to \let\message\regioncompilationfix.

And here's the code accomplishing the real work. (Only the master file needs to be changed.)

% This is ./test.tex
\documentclass{article}
\usepackage{graphics}
\usepackage{import}

\makeatletter
% 1. Temporarily redefine `\message`.
\let\regioncompilationfix@orig@message\message
\def\regioncompilationfix#1{%
  \let\message\regioncompilationfix@orig@message
  \message{#1}%
  \regioncompilationfix@parsemessage#1%
}
\expandafter\def\expandafter\regioncompilationfix@parsemessage\space!name(#1) !offset(#2) {%
  \getpath{#1}%
  % 3. Set whatever the `import` package sets.
  \edef\import@path{\getpathresult/}%
  \edef\Ginput@path{{\getpathresult/}{./}}%
  \edef\input@path{{\getpathresult/}{./}}%
}
% 2. Define a macro which extracts the path from path+filename.
\usepackage{pgfkeys}
\def\getpath#1{%
  {%
    %\pgfkeyslet{/getpath/#1}\relax
    %\pgfkeyslet{/getpath/#1/.@cmd}\relax
    % to be really sure this worked, we'd also need to delete
    % key "/getpath/path/.unknown" ... but since we're searching for
    % the "path", we just hope nothing's there ...
    \pgfkeys{%
      /handlers/.unknown/.code={%
        \xdef\getpathresult{\pgfkeyscurrentpath}%(
        \expandafter\getpath@stripprefix\getpathresult)%
      },
      /getpath/#1,
    }%
  }%
}
\def\getpath@stripprefix/getpath/#1){\gdef\getpathresult{#1}}
\makeatother

\begin{document}
\import{./test1/}{test1.tex}
\end{document}

UPDATE: A purely AUCTeX way

AUXTeX provides hook TeX-region-hook which is run just after the region buffer is constructed. This is the Elisp code that inserts the TeX code that adjusts import's paths:

(add-hook 
 'TeX-region-hook 
 (lambda ()
   (goto-char (point-min))
   (search-forward "\\begin{document}")
   (insert
    "\\makeatletter"
    "\\def\\import@path{"
    (TeX-quote-filename (file-name-directory original))
    "}"
    "\\edef\\Ginput@path{{\\import@path}{./}}"
    "\\edef\\input@path{{\\import@path}{./}}"
    "\\makeatother"
    )
   )
 )

Put this code in your .emacs file.