latex.py

# -*- coding:utf-8 -*-
## src/common/latex.py
##
## Copyright (C) 2005 Norman Rasmussen <norman AT rasmussen.co.za>
## Copyright (C) 2005-2006 Alex Mauer <hawke AT hawkesnest.net>
##                         Travis Shirk <travis AT pobox.com>
## Copyright (C) 2005-2007 Nikos Kouremenos <kourem AT gmail.com>
## Copyright (C) 2005-2012 Yann Leboulanger <asterix AT lagaule.org>
## Copyright (C) 2006 Dimitur Kirov <dkirov AT gmail.com>
## Copyright (C) 2006-2008 Jean-Marie Traissard <jim AT lapin.org>
## Copyright (C) 2008 Jonathan Schleifer <js-gajim AT webkeks.org>
##                    Julien Pivotto <roidelapluie AT gmail.com>
##                    Stephan Erb <steve-e AT h3c.de>
##
## This file is part of Gajim.
##
## Gajim is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published
## by the Free Software Foundation; version 3 only.
##
## Gajim is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Gajim. If not, see <http://www.gnu.org/licenses/>.
##

import os
import random
from tempfile import mkstemp, mkdtemp
from subprocess import Popen, PIPE

import logging
log = logging.getLogger('gajim.c.latex')

import gajim
from exceptions import LatexError
import helpers

# some latex commands are really bad
blacklist = ['\\def', '\\let', '\\futurelet',
        '\\newcommand', '\\renewcomment', '\\else', '\\fi', '\\write',
        '\\input', '\\include', '\\chardef', '\\catcode', '\\makeatletter',
        '\\noexpand', '\\toksdef', '\\every', '\\errhelp', '\\errorstopmode',
        '\\scrollmode', '\\nonstopmode', '\\batchmode', '\\read', '\\csname',
        '\\newhelp', '\\relax', '\\afterground', '\\afterassignment',
        '\\expandafter', '\\noexpand', '\\special', '\\command', '\\loop',
        '\\repeat', '\\toks', '\\output', '\\line', '\\mathcode', '\\name',
        '\\item', '\\section', '\\mbox', '\\DeclareRobustCommand', '\\[',
        '\\]']
# True if the string matches the blacklist
def check_blacklist(str_):
    for word in blacklist:
        if word in str_:
            return True
    return False

def write_latex(filename, str_):
    texstr = '\\documentclass[12pt]{article}\\usepackage[dvips]{graphicx}'
    texstr += '\\usepackage{amsmath}\\usepackage{amssymb}'
    texstr += '\\pagestyle{empty}'
    texstr += '\\begin{document}\\begin{large}\\begin{gather*}'
    texstr += str_
    texstr += '\\end{gather*}\\end{large}\\end{document}'

    file_ = open(filename, "w+")
    file_.write(texstr)
    file_.flush()
    file_.close()

# a wrapper for Popen so that no window gets opened on Windows
# (i think this is the reason we're using Popen rather than just system())
# stdout goes to a pipe so that it can be read
def popen_nt_friendly(command, directory):
    if os.name == 'nt':
        # CREATE_NO_WINDOW
        return Popen(command, creationflags=0x08000000, cwd=directory,
            stdout=PIPE)
    else:
        return Popen(command, cwd=directory, stdout=PIPE)

def check_for_latex_support():
    """
    Check if latex is available and if it can create a picture
    """
    try:
        filename = latex_to_image("test")
        if filename:
            # we have a file, conversion succeeded
            os.remove(filename)
            return True
        return False
    except LatexError:
        return False

def try_run(argv, directory):
    try:
        p = popen_nt_friendly(argv, directory)
        out = p.communicate()[0]
        log.info(out)
        return p.wait()
    except Exception, e:
        return _('Error executing "%(command)s": %(error)s') % {
            'command': " ".join(argv),
            'error': helpers.decode_string(str(e))}


def latex_to_image(str_):
    result = None
    exitcode = 0

    def fg_str(fmt):
        try:
            return [{'hex' : '+level-colors', 'tex' : '-fg'}[fmt],
                gajim.interface.get_fg_color(fmt)]
        except KeyError:
            # interface may not be available when we test latex at startup
            return []
        except AttributeError:
            # interface may not be available when we test latext at startup
            return {'hex': ['+level-colors', '0x000000'],
                'tex': ['-fg', 'rgb 0.0 0.0 0.0']}[fmt]

    # filter latex code with bad commands
    if check_blacklist(str_):
        # we triggered the blacklist, immediately return None
        return None

    try:
        tmpdir = mkdtemp(prefix='gajimtex')
        tmppng = mkstemp(prefix='gajim_tex', suffix='.png')[1]
    except Exception:
        raise LatexError('could not securely create one or more temporary files'
            ' for LaTeX conversion')

    tmpfile = os.path.join(tmpdir, 'gajim_tex')

    # build latex string
    write_latex(tmpfile + '.tex', str_)

    # convert TeX to dvi
    exitcode = try_run(['latex', '--interaction=nonstopmode', tmpfile + '.tex'],
        tmpdir)

    if exitcode == 0:
        # convert dvi to png
        latex_png_dpi = gajim.config.get('latex_png_dpi')
        exitcode = try_run(['dvipng'] + fg_str('tex') + ['-T', 'tight', '-D',
            latex_png_dpi, tmpfile + '.dvi', '-o', tmpfile + '.png'], tmpdir)

        if exitcode:
            # dvipng failed, try convert
            exitcode = try_run(['convert'] + fg_str('hex') + ['-trim',
                '-density', latex_png_dpi, tmpfile + '.dvi', tmpfile + '.png'],
                tmpdir)

    # remove temp files created by us and TeX
    extensions = ['.tex', '.log', '.aux', '.dvi']
    for ext in extensions:
        try:
            os.remove(tmpfile + ext)
        except Exception:
            pass

    if exitcode == 0:
        os.rename(tmpfile + '.png', tmppng)

    os.rmdir(tmpdir)

    if isinstance(exitcode, (unicode, str)):
        raise LatexError(exitcode)

    if exitcode == 0:
        result = tmppng

    return result