path: root/tools/xmlpatterns/qcoloroutput.cpp

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#include <QFile>
#include <QHash>
#include <QTextCodec>

#include "qcoloroutput_p.h"

// TODO: rename insertMapping() to insertColorMapping()
// TODO: Use a smart pointer for managing ColorOutputPrivate *d;
// TODO: break out the C++ example into a snippet file

/* This include must appear here, because if it appears at the beginning of the file for
 * instance, it breaks build -- "qglobal.h:628: error: template with
 * C linkage" -- on Mac OS X 10.4. */
#ifndef Q_OS_WIN
#include <unistd.h>
#endif

QT_BEGIN_NAMESPACE

using namespace QPatternist;

namespace QPatternist
{
    class ColorOutputPrivate
    {
    public:
        ColorOutputPrivate() : currentColorID(-1)

        {
            /* - QIODevice::Unbuffered because we want it to appear when the user actually calls, performance
             *   is considered of lower priority.
             */
            m_out.open(stderr, QIODevice::WriteOnly | QIODevice::Unbuffered);

            coloringEnabled = isColoringPossible();
        }

        ColorOutput::ColorMapping   colorMapping;
        int                         currentColorID;
        bool                        coloringEnabled;

        static const char *const foregrounds[];
        static const char *const backgrounds[];

        inline void write(const QString &msg)
        {
            m_out.write(msg.toLocal8Bit());
        }

        static QString escapeCode(const QString &in)
        {
            QString result;
            result.append(QChar(0x1B));
            result.append(QLatin1Char('['));
            result.append(in);
            result.append(QLatin1Char('m'));
            return result;
        }

    private:
        QFile                       m_out;

        /*!
         Returns true if it's suitable to send colored output to \c stderr.
         */
        inline bool isColoringPossible() const
        {
#           if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
                /* Windows doesn't at all support ANSI escape codes, unless
                 * the user install a "device driver". See the Wikipedia links in the
                 * class documentation for details. */
                return false;
#           else
                /* We use QFile::handle() to get the file descriptor. It's a bit unsure
                 * whether it's 2 on all platforms and in all cases, so hopefully this layer
                 * of abstraction helps handle such cases. */
                return isatty(m_out.handle());
#           endif
        }
    };
}

const char *const ColorOutputPrivate::foregrounds[] =
{
    "0;30",
    "0;34",
    "0;32",
    "0;36",
    "0;31",
    "0;35",
    "0;33",
    "0;37",
    "1;30",
    "1;34",
    "1;32",
    "1;36",
    "1;31",
    "1;35",
    "1;33",
    "1;37"
};

const char *const ColorOutputPrivate::backgrounds[] =
{
    "0;40",
    "0;44",
    "0;42",
    "0;46",
    "0;41",
    "0;45",
    "0;43"
};

/*!
 \since 4.4
 \nonreentrant
 \brief Outputs colored messages to \c stderr.
 \internal

 ColorOutput is a convenience class for outputting messages to \c stderr
 using color escape codes, as mandated in ECMA-48. ColorOutput will only
 color output when it is detected to be suitable. For instance, if \c stderr is
 detected to be attached to a file instead of a TTY, no coloring will be done.

 ColorOutput does its best attempt. but it is generally undefined what coloring
 or effect the various coloring flags has. It depends strongly on what terminal
 software that is being used.

 When using `echo -e 'my escape sequence'`, \033 works as an initiator but not
 when printing from a C++ program, despite having escaped the backslash.
 That's why we below use characters with value 0x1B.

 It can be convenient to subclass ColorOutput with a private scope, such that the
 functions are directly available in the class using it.

 \section1 Usage

 To output messages, call write() or writeUncolored(). write() takes as second
 argument an integer, which ColorOutput uses as a lookup key to find the color
 it should color the text in. The mapping from keys to colors is done using
 insertMapping(). Typically this is used by having enums for the various kinds
 of messages, which subsequently are registered.

 \code
 enum MyMessage
 {
    Error,
    Important
 };

 ColorOutput output;
 output.insertMapping(Error, ColorOutput::RedForeground);
 output.insertMapping(Import, ColorOutput::BlueForeground);

 output.write("This is important", Important);
 output.write("Jack, I'm only the selected official!", Error);
 \endcode

 \sa {http://tldp.org/HOWTO/Bash-Prompt-HOWTO/x329.html}                        {Bash Prompt HOWTO, 6.1. Colours}
     {http://linuxgazette.net/issue51/livingston-blade.html}                    {Linux Gazette, Tweaking Eterm, Edward Livingston-Blade}
     {http://www.ecma-international.org/publications/standards/Ecma-048.htm}    {Standard ECMA-48, Control Functions for Coded Character Sets, ECMA International},
     {http://en.wikipedia.org/wiki/ANSI_escape_code}                            {Wikipedia, ANSI escape code}
     {http://linuxgazette.net/issue65/padala.html}                              {Linux Gazette, So You Like Color!, Pradeep Padala}
 */

/*!
 \enum ColorOutput::ColorCode

 \value DefaultColor ColorOutput performs no coloring. This typically means black on white
                     or white on black, depending on the settings of the user's terminal.
 */

/*!
 Sets the color mapping to be \a cMapping.

 Negative values are disallowed.

 \sa colorMapping(), insertMapping()
 */
void ColorOutput::setColorMapping(const ColorMapping &cMapping)
{
    d->colorMapping = cMapping;
}

/*!
 Returns the color mappings in use.

 \sa setColorMapping(), insertMapping()
 */
ColorOutput::ColorMapping ColorOutput::colorMapping() const
{
    return d->colorMapping;
}

/*!
  Constructs a ColorOutput instance, ready for use.
 */
ColorOutput::ColorOutput() : d(new ColorOutputPrivate())
{
}

/*!
 Destructs this ColorOutput instance.
 */
ColorOutput::~ColorOutput()
{
    delete d;
}

/*!
 Sends \a message to \c stderr, using the color looked up in colorMapping() using \a colorID.

 If \a color isn't available in colorMapping(), result and behavior is undefined.

 If \a colorID is 0, which is the default value, the previously used coloring is used. ColorOutput
 is initialized to not color at all.

 If \a message is empty, effects are undefined.

 \a message will be printed as is. For instance, no line endings will be inserted.
 */
void ColorOutput::write(const QString &message, int colorID)
{
    d->write(colorify(message, colorID));
}

/*!
 Writes \a message to \c stderr as if for instance
 QTextStream would have been used, and adds a line ending at the end.

 This function can be practical to use such that one can use ColorOutput for all forms of writing.
 */
void ColorOutput::writeUncolored(const QString &message)
{
    d->write(message + QLatin1Char('\n'));
}

/*!
 Treats \a message and \a colorID identically to write(), but instead of writing
 \a message to \c stderr, it is prepared for being written to \c stderr, but is then
 returned.

 This is useful when the colored string is inserted into a translated string(dividing
 the string into several small strings prevents proper translation).
 */
QString ColorOutput::colorify(const QString &message, int colorID) const
{
    Q_ASSERT_X(colorID == -1 || d->colorMapping.contains(colorID), Q_FUNC_INFO,
               qPrintable(QString::fromLatin1("There is no color registered by id %1").arg(colorID)));
    Q_ASSERT_X(!message.isEmpty(), Q_FUNC_INFO, "It makes no sense to attempt to print an empty string.");

    if(colorID != -1)
        d->currentColorID = colorID;

    if(d->coloringEnabled && colorID != -1)
    {
        const int color(d->colorMapping.value(colorID));

        /* If DefaultColor is set, we don't want to color it. */
        if(color & DefaultColor)
            return message;

        const int foregroundCode = (int(color) & ForegroundMask) >> ForegroundShift;
        const int backgroundCode = (int(color) & BackgroundMask) >> BackgroundShift;
        QString finalMessage;
        bool closureNeeded = false;

        if(foregroundCode)
        {
            finalMessage.append(ColorOutputPrivate::escapeCode(QLatin1String(ColorOutputPrivate::foregrounds[foregroundCode - 1])));
            closureNeeded = true;
        }

        if(backgroundCode)
        {
            finalMessage.append(ColorOutputPrivate::escapeCode(QLatin1String(ColorOutputPrivate::backgrounds[backgroundCode - 1])));
            closureNeeded = true;
        }

        finalMessage.append(message);

        if(closureNeeded)
        {
            finalMessage.append(QChar(0x1B));
            finalMessage.append(QLatin1String("[0m"));
        }

        return finalMessage;
    }
    else
        return message;
}

/*!
  Adds a color mapping from \a colorID to \a colorCode, for this ColorOutput instance.

  This is a convenience function for creating a ColorOutput::ColorMapping instance and
  calling setColorMapping().

  \sa colorMapping(), setColorMapping()
 */
void ColorOutput::insertMapping(int colorID, const ColorCode colorCode)
{
    d->colorMapping.insert(colorID, colorCode);
}

QT_END_NAMESPACE