Saving QByteArray to text similar to QSettings' format in ini file?

[lansing]

In QSettings, a saved QByteArray would be like this in text:

@ByteArray(\0\0\0\x2\0\0\0\x3\0\0 #\0\0\0\x2\0\0\0\0\0\0\0)

How do I do this without going through QSettings?

I have a QTextstream writing to a QString, and the string will be saved to a text file at the end. How do I convert the QByteArray so that it's saving in this format?

QString m_storedText;
QTextStream out(&m_storedText);

out << "hi ";
out << QByteArray(QColor(Qt::yellow));

[jsulm]

@lansing Why do you want to store in unreadable binary format? Ini files should be normal text files which can be read by humans.

[lansing]

@lansing

I want to save settings like QFont but storing its values separately seem unnecessary. Because when I load it back I would have to reconstruct it from all those values again before it's ready to use. So I think it would be easier to just wrap it in QByteArray for saving and retrieving.

[jsulm]

@lansing I'm not sure I follow: do you want to store memory dump of an object (like QFont instance) as binary data in ini files?! In my opinion you should rethink this approach:

• This is unreadable for user
• This is unchangeable by user
• This is most probably not going to work because of internal d pointer used by Qt classes to hide internal implementation. Also endianess and memory alignment needs to be considered...

[jsulm]

@lansing You should check documentation: https://doc-snapshots.qt.io/qt5-dev/qfont.html
"If you want to store a user's font preferences you could use QSettings, writing the font information with toString() and reading it back with fromString(). The operator<<() and operator>>() functions are also available, but they work on a data stream."
There is really no need for binary data.

[lansing]

@jsulm

I want to store a list of font as selection. User can add or remove font preference to this file

[theme one]
id_1 ; font-setting ; other stuff
[theme two]
id_2; font-setting; ...

I don't think QSettings is right for this case?

I also tried the operator<<() to store them separately as font family, font size etc but I have to reconstruct them back together when I loaded them, which is tedious.

[jsulm]

@lansing said in Saving QByteArray to text similar to QSettings' format in ini file?:

but I have to reconstruct them back together

Why? fromString() should do it just fine if you stored it before using toString() as described in the documentation.

"I want to store a list of font as selection" - you could construct this list by yourself calling toString() on each font and joining these strings into one using a separator. Later, when loading, just read the string from settings split it using the separator and use fromString() for each font. This is not that much work.

[lansing]

@jsulm said in Saving QByteArray to text similar to QSettings' format in ini file?:

fromString

Oh I don't know that we can do that. What is the syntax of fromString() when reading back from the text?

[jsulm]

@lansing said in Saving QByteArray to text similar to QSettings' format in ini file?:

What is the syntax of fromString() when reading back from the text?

There is documentation: https://doc.qt.io/qt-5/qfont.html#fromString

[lansing]

@jsulm

Yes I read it, this is what I got so far

QFont preferenceFont;               
preferenceFont.fromString(fontString);

Is there a one liner for this? I tried QFont::fromString(fontString) but it doesn't work.

[jsulm]

@lansing said in Saving QByteArray to text similar to QSettings' format in ini file?:

I tried QFont::fromString(fontString) but it doesn't work.

Of course it does not since fromString() is not static.
Why do you need one liner?

[J.Hilk]

@lansing

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QFont defaultFont;
    qDebug() << defaultFont;
    defaultFont.setPixelSize(25);
    defaultFont.setBold(true);
    qDebug() << defaultFont;
    QString stringRepresentation = defaultFont.toString();
    qDebug() << stringRepresentation;
    QFont loadedFont;
    loadedFont.fromString(stringRepresentation);

    qDebug() << defaultFont << loadedFont;
//    return app.exec();
}

output:

QFont( ".AppleSystemUIFont,13,-1,5,50,0,0,0,0,0" )
QFont( ".AppleSystemUIFont,-1,25,5,75,0,0,0,0,0" )
".AppleSystemUIFont,-1,25,5,75,0,0,0,0,0"
QFont( ".AppleSystemUIFont,-1,25,5,75,0,0,0,0,0" ) QFont( ".AppleSystemUIFont,-1,25,5,75,0,0,0,0,0" )

[lansing]

@jsulm

I will be passing it as an argument after the conversion, so it would be shorter to do it in one line instead of three.

QFont preferenceFont;               
preferenceFont.fromString(fontString);
document->setFont(preferenceFont)

[J.Hilk]

@lansing

constexpr auto stringToFont = [](const QString &str)->QFont{
        QFont preferenceFont;               
        preferenceFont.fromString(str);
        return preferenceFont;
    };
 document->setFont(stringToFont(fontString));

made it constexpr to force inline-ness