okular/part/latexrenderer.cpp

/*
    SPDX-FileCopyrightText: 2004 Duncan Mac-Vicar Prett <duncan@kde.org>
    SPDX-FileCopyrightText: 2004-2005 Olivier Goffart <ogoffart@kde.org>
    SPDX-FileCopyrightText: 2011 Niels Ole Salscheider
    <niels_ole@salscheider-online.de>

    SPDX-License-Identifier: GPL-2.0-or-later
*/

#include "latexrenderer.h"

#include <QDebug>

#include <KProcess>

#include <QColor>
#include <QDir>
#include <QFileInfo>
#include <QImage>
#include <QRegularExpression>
#include <QStandardPaths>
#include <QTemporaryFile>
#include <QTextStream>

#include "gui/debug_ui.h"

namespace GuiUtils
{
LatexRenderer::LatexRenderer()
{
}

LatexRenderer::~LatexRenderer()
{
    for (const QString &file : qAsConst(m_fileList)) {
        QFile::remove(file);
    }
}

LatexRenderer::Error LatexRenderer::renderLatexInHtml(QString &html, const QColor &textColor, int fontSize, int resolution, QString &latexOutput)
{
    if (!html.contains(QStringLiteral("$$"))) {
        return NoError;
    }

    // this searches for $$formula$$
    QRegularExpression rg(QStringLiteral("\\$\\$.+?\\$\\$"));
    QRegularExpressionMatchIterator it = rg.globalMatch(html);

    QMap<QString, QString> replaceMap;
    while (it.hasNext()) {
        QRegularExpressionMatch match = it.next();
        const QString matchedString = match.captured(0);

        QString formul = matchedString;
        // first remove the $$ delimiters on start and end
        formul.remove(QStringLiteral("$$"));
        // then trim the result, so we can skip totally empty/whitespace-only formulas
        formul = formul.trimmed();
        if (formul.isEmpty() || !securityCheck(formul)) {
            continue;
        }

        // unescape formula
        formul.replace(QLatin1String("&gt;"), QLatin1String(">"));
        formul.replace(QLatin1String("&lt;"), QLatin1String("<"));
        formul.replace(QLatin1String("&amp;"), QLatin1String("&"));
        formul.replace(QLatin1String("&quot;"), QLatin1String("\""));
        formul.replace(QLatin1String("&apos;"), QLatin1String("\'"));
        formul.replace(QLatin1String("<br>"), QLatin1String(" "));

        QString fileName;
        Error returnCode = handleLatex(fileName, formul, textColor, fontSize, resolution, latexOutput);
        if (returnCode != NoError) {
            return returnCode;
        }

        replaceMap[matchedString] = fileName;
    }

    if (replaceMap.isEmpty()) { // we haven't found any LaTeX strings
        return NoError;
    }

    int imagePxWidth, imagePxHeight;
    for (QMap<QString, QString>::ConstIterator it = replaceMap.constBegin(); it != replaceMap.constEnd(); ++it) {
        QImage theImage(*it);
        if (theImage.isNull()) {
            continue;
        }
        imagePxWidth = theImage.width();
        imagePxHeight = theImage.height();
        QString escapedLATEX = it.key().toHtmlEscaped().replace(QLatin1Char('"'), QLatin1String("&quot;")); // we need  the escape quotes because that string will be in a title="" argument, but not the \n
        html.replace(it.key(),
                     QStringLiteral(" <img width=\"") + QString::number(imagePxWidth) + QStringLiteral("\" height=\"") + QString::number(imagePxHeight) + QStringLiteral("\" align=\"middle\" src=\"") + (*it) + QStringLiteral("\"  alt=\"") +
                         escapedLATEX + QStringLiteral("\" title=\"") + escapedLATEX + QStringLiteral("\"  /> "));
    }
    return NoError;
}

bool LatexRenderer::mightContainLatex(const QString &text)
{
    if (!text.contains(QStringLiteral("$$"))) {
        return false;
    }

    // this searches for $$formula$$
    QRegularExpression rg(QStringLiteral("\\$\\$.+?\\$\\$"));
    if (!rg.match(text).hasMatch()) {
        return false;
    }

    return true;
}

LatexRenderer::Error LatexRenderer::handleLatex(QString &fileName, const QString &latexFormula, const QColor &textColor, int fontSize, int resolution, QString &latexOutput)
{
    KProcess latexProc;
    KProcess dvipngProc;

    QTemporaryFile *tempFile = new QTemporaryFile(QDir::tempPath() + QLatin1String("/okular_kdelatex-XXXXXX.tex"));
    tempFile->open();
    QString tempFileName = tempFile->fileName();
    QFileInfo *tempFileInfo = new QFileInfo(tempFileName);
    QString tempFileNameNS = tempFileInfo->absolutePath() + '/' + tempFileInfo->baseName();
    QString tempFilePath = tempFileInfo->absolutePath();
    delete tempFileInfo;
    QTextStream tempStream(tempFile);

    tempStream << "\
\\documentclass["
               << fontSize << "pt]{article} \
\\usepackage{color} \
\\usepackage{amsmath,latexsym,amsfonts,amssymb,ulem} \
\\pagestyle{empty} \
\\begin{document} \
{\\color[rgb]{" << textColor.redF()
               << "," << textColor.greenF() << "," << textColor.blueF() << "} \
\\begin{eqnarray*} \
" << latexFormula
               << " \
\\end{eqnarray*}} \
\\end{document}";

    tempFile->close();
    QString latexExecutable = QStandardPaths::findExecutable(QStringLiteral("latex"));
    if (latexExecutable.isEmpty()) {
        qCDebug(OkularUiDebug) << "Could not find latex!";
        delete tempFile;
        fileName = QString();
        return LatexNotFound;
    }
    latexProc << latexExecutable << QStringLiteral("-interaction=nonstopmode") << QStringLiteral("-halt-on-error") << QStringLiteral("-output-directory=%1").arg(tempFilePath) << tempFile->fileName();
    latexProc.setOutputChannelMode(KProcess::MergedChannels);
    latexProc.execute();
    latexOutput = QString::fromLocal8Bit(latexProc.readAll());
    tempFile->remove();

    QFile::remove(tempFileNameNS + QStringLiteral(".log"));
    QFile::remove(tempFileNameNS + QStringLiteral(".aux"));
    delete tempFile;

    if (!QFile::exists(tempFileNameNS + QStringLiteral(".dvi"))) {
        fileName = QString();
        return LatexFailed;
    }

    QString dvipngExecutable = QStandardPaths::findExecutable(QStringLiteral("dvipng"));
    if (dvipngExecutable.isEmpty()) {
        qCDebug(OkularUiDebug) << "Could not find dvipng!";
        fileName = QString();
        return DvipngNotFound;
    }

    dvipngProc << dvipngExecutable << QStringLiteral("-o%1").arg(tempFileNameNS + QStringLiteral(".png")) << QStringLiteral("-Ttight") << QStringLiteral("-bgTransparent") << QStringLiteral("-D %1").arg(resolution)
               << QStringLiteral("%1").arg(tempFileNameNS + QStringLiteral(".dvi"));
    dvipngProc.setOutputChannelMode(KProcess::MergedChannels);
    dvipngProc.execute();

    QFile::remove(tempFileNameNS + QStringLiteral(".dvi"));

    if (!QFile::exists(tempFileNameNS + QStringLiteral(".png"))) {
        fileName = QString();
        return DvipngFailed;
    }

    fileName = tempFileNameNS + QStringLiteral(".png");
    m_fileList << fileName;
    return NoError;
}

bool LatexRenderer::securityCheck(const QString &latexFormula)
{
    return !latexFormula.contains(
        QRegularExpression(QString::fromLatin1("\\\\(def|let|futurelet|newcommand|renewcommand|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)[^a-zA-Z]")));
}

}