Wrong enum value from QSettings using Qt 6

Cobra91151

Hello!

I have found an issue with my program using Qt 6. For example, I created this method to read the QSettings ini file.

#define APP_SETTINGS_PATH QDir::toNativeSeparators(QString("%1/settings/%2.ini").arg(QApplication::applicationDirPath(), QString(APP_NAME).remove(QRegularExpression("\\s"))))

QVariant ManageProgram::loadSettings(QString group, QString property, QVariant defaultValue)
{
    QSettings appSettings(APP_SETTINGS_PATH, QSettings::IniFormat);
    appSettings.beginGroup(group);
    QVariant valueVariant = appSettings.value(property, defaultValue);
    appSettings.endGroup();
    return valueVariant;
}

Then, I want to get the value from my enum: Connection::State

Connection::State wlanConnectionState = ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown).value<Connection::State>();

INI file:

[AppSettings]
WlanState=2

The stored value is: 2 but it returns as 0 on Qt 6.3.2, Qt 6.4.1, Qt 6.4.2, which breaks some of the features in my program. On Qt 5 this works well and returns the correct enum value: 2. Any ideas? Thank you.

Christian Ehrlicher

Ok, looks like an enum now need Q_ENUM() (even though I think it may be a subtle bug):

struct Connection {
    Q_GADGET
public:
        enum State {
        NotConnected = 0,
        Connecting = 1,
        Connected = 2,
        Canceled = 3,
        Unknown = 4
    };
    Q_ENUM(State)
};

This also allows this in your ini file:

[AppSettings]
WlanState=Connected

Will investigate it later on

// see https://bugreports.qt.io/browse/QTBUG-109744

Christian Ehrlicher

Please print a debug output of your QVariant to see if it's a QVariant conversion problem or QSettings.

qDebug() << ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown);

JonB

@Cobra91151 said in Wrong enum value from QSettings using Qt 6:

Connection::State

Where is this enum in the docs, please? I can find enum QAbstractSocket::SocketState?

Try reading your saved value as an int, do you get the right value? Try converting that to your desired enum, does that work?

Cobra91151

@Christian-Ehrlicher

Ok. I have recompiled the program:

qDebug() << ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown);
It returns: QVariant(QString, "2")

So, it seems it's QVariant conversion issue.

J.Hilk

@Cobra91151 are you sure the Enum is correctly registered with the meta system ?

I think Variant falls back on that.

Besides that, simply read it as int:

value<int>()

and cast the result to the enum.

Cobra91151

@JonB

No, it's my custom enum.

namespace Connection {
    enum State {
        NotConnected = 0,
        Connecting = 1,
        Connected = 2,
        Canceled = 3,
        Unknown = 4
    };
}

Yes, it works only when converting using toInt() method.

int wlanState = ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown).toInt();
wlanConnectionState = static_cast<Connection::State>(wlanState);
qDebug() << "wlanConnectionState: " << wlanConnectionState;

wlanConnectionState: 2

Why it fails to convert to enum: wlanConnectionState = ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown).value<Connection::State>();? That's the question.

Christian Ehrlicher

@Cobra91151 said in Wrong enum value from QSettings using Qt 6:

Why it fails to convert to enum

@J-Hilk

are you sure the Enum is correctly registered with the meta system ?

Cobra91151

@J-Hilk
@Christian-Ehrlicher
@JonB

I think, it is already registered: Q_DECLARE_METATYPE(Connection::State).
Or Qt 6 uses different method of registering types?

J.Hilk

@Cobra91151 did you also use Q_ENUM_NS or Q_ENUM if your declaration is inside a QObject class?

Cobra91151

@J-Hilk

This enum declaration is in constants.h (header file). I use it as a helper file to create some enums/structs/defines there and use it in my program. There is no class in this file.
So, it's outside of a QObject class.

Cobra91151

I think that I need to use something like this in my program.

#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
    int wlanState = ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown).toInt();
    wlanConnectionState = static_cast<Connection::State>(wlanState);
#else
    wlanConnectionState = ManageProgram::loadSettings("AppSettings", "WlanState", Connection::State::Unknown).value<Connection::State>();
#endif

The output for both cases: wlanConnectionState: 2

I should use the .value<Connection::State>(); in Qt 5 as always. And use .toInt() and then cast the result to the enum in Qt 6 until QVariant conversion problem is fixed.

Christian Ehrlicher

Works fine for me with Qt6.head + MSVC

namespace Connection {
    enum State {
        NotConnected = 0,
        Connecting = 1,
        Connected = 2,
        Canceled = 3,
        Unknown = 4
    };
}
Q_DECLARE_METATYPE(Connection::State);  // not even needed for the testcase

int main(int argc, char* argv[])
{
    QCoreApplication app(argc, argv);
    QVariant v(2);
    Connection::State s = v.value<Connection::State>();
    if (s == Connection::Connected) 
        qDebug() << "Connected";
    else 
        qDebug() << "Not connected";
}

Cobra91151

@Christian-Ehrlicher

Yes, it works. So, the enum must be overwritten somewhere in my program which changes the value to 0.
I will check it and fix it. Thank you very much for checking it.

Cobra91151

@Christian-Ehrlicher
@JonB
@J-Hilk

I have commented all wlanConnectionState code in my program where it could be overwritten, recompiled it (clean/run qmake/build) but it still returns as 0. So, I have used @Christian-Ehrlicher example and added my code there.

#include <QCoreApplication>
#include <QVariant>
#include <QSettings>
#include <QDir>
#include <QRegularExpression>

#define APP_NAME "ConsoleApp"
#define APP_SETTINGS_PATH QDir::toNativeSeparators(QString("%1/settings/%2.ini").arg(QCoreApplication::applicationDirPath(), QString(APP_NAME).remove(QRegularExpression("\\s"))))

namespace Connection {
    enum State {
        NotConnected = 0,
        Connecting = 1,
        Connected = 2,
        Canceled = 3,
        Unknown = 4
    };
}

Q_DECLARE_METATYPE(Connection::State);  // not even needed for the testcase
QVariant loadSettings(QString group, QString property, QVariant defaultValue);

int main(int argc, char* argv[])
{
    QCoreApplication app(argc, argv);
    //QVariant v(2);
    Connection::State s = loadSettings("AppSettings", "WlanState", Connection::State::Unknown).value<Connection::State>();

    //int wlanState = loadSettings("AppSettings", "WlanState", Connection::State::Unknown).toInt();
    //Connection::State s = static_cast<Connection::State>(wlanState);

    if (s == Connection::Connected) {
        qDebug() << "Connected";
    } else {
        qDebug() << "Not connected";
    }

    qDebug() << "s: " << s;
}

QVariant loadSettings(QString group, QString property, QVariant defaultValue)
{
    QSettings appSettings(APP_SETTINGS_PATH, QSettings::IniFormat);
    appSettings.beginGroup(group);
    QVariant valueVariant = appSettings.value(property, defaultValue);
    appSettings.endGroup();
    return valueVariant;
}

It also returns:

Not connected
s:  0

When I use this code:

int wlanState = loadSettings("AppSettings", "WlanState", Connection::State::Unknown).toInt();
Connection::State s = static_cast<Connection::State>(wlanState);

The output is the following:

Connected
s:  2

So, it seems that issue with QVariant conversion still exists.
Can you confirm (reproduce) it using updated code? Also, you will need the settings directory with .ini file: https://mega.nz/file/EVRwWI5b#4MXbcgqE1aCm_YKEk0leZnMnEGMWw1yuLHL61UlIi54

Or create one called ConsoleApp.ini with the following content:

[AppSettings]
WlanState=2

Thank you.

JoeCFD

@Cobra91151 said in Wrong enum value from QSettings using Qt 6:

namespace Connection {
enum State {
NotConnected = 0,
Connecting = 1,
Connected = 2,
Canceled = 3,
Unknown = 4
};
}

why not use enum class?

namespace Connection {
    enum class State {
        NotConnected = 0,
        Connecting = 1,
        Connected = 2,
        Canceled = 3,
        Unknown = 4
    };
}

Cobra91151

@JoeCFD

Hello!

I do not think it will work in my case, since I need to store enum value as integer in the .ini file and get it later as enum. On Qt 5 it works as expected. So, I think there is an issue with enum convertion in Qt 6. You can try out my example above to see what the issue is.
Anyway, thank you for your reply :)

Christian Ehrlicher

Ok, looks like an enum now need Q_ENUM() (even though I think it may be a subtle bug):

struct Connection {
    Q_GADGET
public:
        enum State {
        NotConnected = 0,
        Connecting = 1,
        Connected = 2,
        Canceled = 3,
        Unknown = 4
    };
    Q_ENUM(State)
};

This also allows this in your ini file: