Convert CFStringRef to QString

Question

cross platform c++ header file. separate c++ file for each platform: windows, linux, mac. Deals with platform specific implementation of enumerating windows.

on the mac side: I have a CFStringRef populated. the header file defines a QString object. I need to pass the contents of the CFStringRef to the QString.

How can this be achieved?

Answer 1

This is the static function used internally by Qt (from src/corelib/kernel/qcore_mac.cpp):

QString QCFString::toQString(CFStringRef str)
{
    if (!str)
        return QString();

    CFIndex length = CFStringGetLength(str);
    if (length == 0)
        return QString();

    QString string(length, Qt::Uninitialized);
    CFStringGetCharacters(str, CFRangeMake(0, length), reinterpret_cast<UniChar *> 
        (const_cast<QChar *>(string.unicode())));
    return string;
}

Update (2020): nowadays use QString::fromCFString() as @ehopperdietzel suggested in his answer.

Answer 2

You can use the fromCFString() method included in the QString class:

CFStringRef str = CFSTR("Hello World!");
QString convertedStr = QString::fromCFString(str);

Answer 3

I didn't try it but I would do something like this:

QVector<UniChar> uniChars(CFStringGetLength(cfStr));
CFStringGetCharacters(cfStr, CFRangeMake(0, CFStringGetLength(cfStr), uniChars.data());
QString qString = QString::fromUtf16(uniChars.data(), uniChars.size());

To avoid allocation of the UniChar buffer, you can try CFStringGetCharactersPtr() first and use the buffer one as a fall back.