Question

I need to create my own codec, i.e. subclass of QTextCodec. And I’d like to use it via QTextCodec::codecForName("myname");
However, just subclass is not enough. QTextCodec::availableCodecs() does not contain my codec name.

QTextCodec documentation does not cover the area of proper registration of a custom codec:

Creating Your Own Codec Class

Support for new text encodings can be
added to Qt by creating QTextCodec
subclasses.

The pure virtual functions describe
the encoder to the system and the
coder is used as required in the
different text file formats supported
by QTextStream, and under X11, for the
locale-specific character input and
output.

To add support for another encoding to
Qt, make a subclass of QTextCodec and
implement the functions listed in the
table below.
name()
aliases()
mibEnum()
convertToUnicode()
convertFromUnicode()

You may find it more convenient to
make your codec class available as a
plugin; see How to Create Qt Plugins
for details.

So, I’ve tried to dig a little into plugins’ direction. But I don’t want to have a separate project with plugin. Is it possible to declare plugin within the same project?

Or is there a direct way to register my codec into QTextCodec? This is preferable.

Answer 1

according to qtextcodex.cpp any new codec is added to the collection of registered codecs (*static QList all) by its own constructor. So creating an instance of your codec class should do the trick; code below worked fine for me:

QMyCodec myCodec;

foreach (QByteArray codecName,  QTextCodec::availableCodecs())
{
    QString codecNameStr(codecName);
    qDebug() << codecNameStr;
}

QTextCodec* codec = QTextCodec::codecForName("MyNewCodec");
if (codec)
{
    qDebug() << "found ";
    qDebug() << codec->name() << '\n';
}

QTextCodec::availableCodecs returned:

“MyNewCodec”
“System”
“roman8”
“hp-roman8”
“csHPRoman8” …

QTextCodec::codecForName returned a pointer to my codec class

hope this helps, regards