Qt 6 way of saving a Unicode string to QSettings – Is this a bug or a feature?!

l3u_

Hi all :-)

I save one single char as a symbol in a QSettings key. Apparently, the way Qt 6 saves such a string is different from Qt 5:

The default symbol I use is QStringLiteral("\u25CF"), "BLACK CIRCLE". When I save this using Qt 5 (by using setValue(s_symbol, text)), the following appears in my config file:

symbol=\x25cf

When I build my program using Qt 6, this is – without calling the respective save method, silently! – changed to it's literal Unicode representation, and I get:

symbol=●

When using the same config again with a Qt 5 build, this is read and displayed as (using symbol = value(s_symbol, DefaultValues::symbol).toString()):

â

(an â followed by two boxes). And again, without calling the save method, this is silently changed to

symbol=\xe2\x97\x8f

The problem is that I can't detect if the symbol is what it should be, or if it has been "messed up" by Qt 6.

So: Is this a bug or a feature?! And if it's the latter: Is there any way to force Qt 6 to save the escaped version that can also be read by Qt 5?

Thanks for all help!

Cheers, Tobias!

hskoglund

Hi, I had a similar problem and got around it by using toHex() and fromHex() for QSettings, e.g. setValue(s_symbol, text.toUtf8().toHex()) when saving, and using ...fromHex().fromUtf8() when reading back.

Christian Ehrlicher

Qt6 assumes that the ini-file is utf-8 encoded so a hex encoding is no longer needed. This is not backwards compatible but consistent.

l3u_

Okay, good to know! Thanks for the clarification.

l3u_

@Christian-Ehrlicher Oh, I just realized you said that INI files are assumed to be UTF-8 – does this mean the change does not affect Windows, where the settings are stored in the registry?

Christian Ehrlicher

It should not as the registry should be unicode

l3u_

Okay. Thanks for the info! Let's see :-)