QSlider valueChanged connection not working

[SPlatten]

I have written a widget which I use in two places:

At the right of the display there are three controls, two spinners and a pushbutton. The spinners are used to set common attributes for the widgets, the maximum and minimum values to show.

In the class I have defined static pointers so that each graphic can access the values of the controls, in the constructor I have code like:

        truth::mspSpinMax = new QSpinBox(pParent);
        truth::mspSpinMax->setSingleStep(truth::mscuint16StepSize - 1);
        truth::mspSpinMax->setMaximum(truth::msintMaximum);
        truth::mspSpinMax->setValue(truth::msintMaximum);
        truth::mscnSpinMaxValueChanged =
            QObject::connect(truth::mspSpinMax,
                QOverload<int>::of(&QSpinBox::valueChanged),
            [this](int intValue)
            {
                if ( truth::mspBtnUpdate != nullptr )
                {
                    truth::mspBtnUpdate->setEnabled(truth::msintLastMax != intValue);
                }
            }
        );

The problem is that the signals are not making it to the slots, in that the lambda slots I am using never get called. What could be wrong?

[SPlatten]

@SPlatten , What I found that works:

QObject::connect(truth::mspSpinMax,
                QOverload<int>::of(&QSpinBox::valueChanged),
            [this](int intValue)
            {
               emit maximumChanged(intValue);
            }
        );

[jsulm]

@SPlatten said in QSlider valueChanged connection not working:

in that the lambda slots I am using never get called

How did you prove that?

[J.Hilk]

@SPlatten

are you mixing something up here ?

truth::mscnSpinMaxValueChanged =
            QObject::connect(truth::mspSpinMax,
                QOverload<int>::of(&QSpinBox::valueChanged),
            [this](int intValue)
            {
                if ( truth::mspBtnUpdate != nullptr )
                {
                    truth::mspBtnUpdate->setEnabled(truth::msintLastMax != intValue);
                }
            }
        );

the return type of QObject::connect is a QMetaObject::Connection that allows for a implicit conversion to bool and therefore int.

You seem to want to assign it to a int value mscnSpinMaxValueChanged ?

[SPlatten]

@jsulm , Whilst debugging in Qt Creator with breakpoint in slot.

[SPlatten]

@J-Hilk , mscnSpinMaxValueChanged is defined in the class as:

static QMetaObject::Connection mscnSpinMaxValueChanged;

[Nan Feng]

This post is deleted!

[SPlatten]

@Nan-Feng , what has this got to do with the subject????

[jsulm]

@Nan-Feng Please post your questions in your own threads!

[SPlatten]

@J-Hilk , @jsulm , something very strange is happening, I thought I would try adding another connection:

truth::mscnSpinMaxValueChanged =
            QObject::connect(truth::mspSpinMax,
                QOverload<int>::of(&QSpinBox::valueChanged),
            [this](int intValue)
            {
                if ( truth::mspBtnUpdate != nullptr )
                {
                    truth::mspBtnUpdate->setEnabled(truth::msintLastMax != intValue);
                }
            }
        );
truth::mscnSpinMaxValueChanged =
            QObject::connect(truth::mspSpinMax,
                QOverload<int>::of(&QSpinBox::valueChanged),
            [this](int intValue)
            {
qDebug() << intValue;
            }
        );

Now the first connection is working and the debugger stops in the slot...the second connection doesn't work and no debug output appears.

It has to be a bug because with both connections the first connection works, if I comment out the second it doesn't work.

Qt Creator 4.4.1
Based on Qt 5.9.2 (MSVC 2015, 32 bit)

Unfortunately I cannot upgrade Qt or MSVC, these are the versions I have to work with. Could it be something to do with the static member references in the first slot?

[SPlatten]

@SPlatten , What I found that works:

QObject::connect(truth::mspSpinMax,
                QOverload<int>::of(&QSpinBox::valueChanged),
            [this](int intValue)
            {
               emit maximumChanged(intValue);
            }
        );