problem with SIGNAL SLOT new notation for QAbstractButton - c++

Question

I am writing a small utility composed by :
1) 4 QToolBar
2) 1 QToolBox
3) 1 QMenu
4) 1 QGraphicsView
I have some buttons on the QToolBox, each button represents a grid with different spacing.
Everytime a user clicks a button on the QToolBox the spacing on the QGraphicsScene` changes.
I use daily the new notation and never had any problems with it until I had to use an "abstract" entity such as the QAbstractButton approach.
the problem I have is that I don't seem to properly set the connection signal/slot of the QAbstractButton:
mainwindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void backgroundButtonClicked(QAbstractButton *button);
private:
void createToolBox();
QButtonGroup *buttonGroup;
QButtonGroup *backgroundButtonGroup;
mainwindow.cpp
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
createToolBox();
scene = new DiagramScene(itemMenu,this);
QHBoxLayout *layout = new QHBoxLayout;
layout->addWidget(toolBox);
view = new QGraphicsView(scene);
QWidget *widget = new QWidget;
widget->setLayout(layout);
setCentralWidget(widget);
}
void MainWindow::backgroundButtonClicked(QAbstractButton *button)
{
QList<QAbstractButton*> buttons = backgroundButtonGroup->buttons();
foreach (QAbstractButton *myButton, buttons) {
if(myButton != button)
button->setChecked(false);
}
QString text = button->text();
if(text == tr("Blue Grid"))
scene->setBackgroundBrush(QPixmap(":/images/background1.png"));
else if(text == tr("White Grid"))
scene->setBackgroundBrush(QPixmap(":/images/background2.png"));
else if(text == tr("Gray Grid"))
scene->setBackgroundBrush(QPixmap(":/images/background3.png"));
else
scene->setBackgroundBrush(QPixmap(":/images/background4.png"));
scene->update();
view->update();
}
void MainWindow::createToolBox()
{
buttonGroup = new QButtonGroup(this);
buttonGroup->setExclusive(false);
QGridLayout *layout = new QGridLayout;
layout->addWidget(createCellWidget(tr("Conditional"), DiagramItem::Conditional), 0, 0);
layout->addWidget(createCellWidget(tr("Process"), DiagramItem::Step), 0, 1);
layout->addWidget(createCellWidget(tr("Input/Output"), DiagramItem::Io), 1, 0);
QToolButton *textButton = new QToolButton;
textButton->setCheckable(true);
buttonGroup->addButton(textButton, InsertTextButton);
textButton->setIcon(QIcon(QPixmap(":/images/textpointer.png")));
textButton->setIconSize(QSize(50, 50));
QWidget *itemWidget = new QWidget;
itemWidget->setLayout(layout);
backgroundButtonGroup = new QButtonGroup(this);
// This is my first attempt but it does not work:
QObject::connect(backgroundButtonGroup, &QAbstractButton::clicked, this, &QAbstractButton::backgroundButtonClicked());
}
Different options I tried are:
1) via static_cast<> trying to cast it into the QAbstractButton as shown below:
QObject::connect(static_cast<QAbstractButton*>(backgroundButtonGroup), this, static_cast<QAbstractButton>(backgroundButtonClicked(void)));
2) Also I tried the following according to official documentation but that also didn't work:
QObject::connect(backgroundButtonGroup, &QAbstractButton::clicked, this, &QAbstractButton::backgroundButtonClicked);
Adding to that I was digressing towards the following structure below (heading to Q_INVOKE) but I am afraid I was over complicating the issue, but just wanted to include the additional solution I was trying to explore:
const bool connected = connect(sender, &Sender::aSignal,
receiver, &Receiver::aSlot);
Q_ASSERT(connected);
Q_UNUSED(connected);
Thanks for pointing to the right direction for solving this issue.

Answer 1

You have the following errors:
QButtonGroup does not have the clicked signal but buttonClicked.
You must not use ().
The syntax in general is: obj, & Class_of_obj, in your case backgroundButtonGroup is QButtonGroup and this is MainWindow so preliminarily the syntax is:
QObject::connect(backgroundButtonGroup, &QButtonGroup::buttonClicked, this, &MainWindow::backgroundButtonClicked);
But buttonClicked is overload then you must use QOverload to indicate the signature.
Considering the above, the solution is:
QObject::connect(backgroundButtonGroup, QOverload<QAbstractButton *>::of(&QButtonGroup::buttonClicked), this, &MainWindow::backgroundButtonClicked);
I recommend you check:
the QButtonGroup docs where it shows the example of how to make the connection.
In addition to New Signal Slot Syntax that indicates the various cases