Template function

[UnitScan]

In .cpp file I have this template function:

template <typename M, typename N> void MainWindow::showMenu(M m, N n)
{
    QSize size = m->sizeHint();
    m->popup(n->mapToGlobal(QPoint(0,0-size.height())));
}

where
· m = QMenu
· n = QPushPutton

In what form I should declare this function in the header file?

Thanks in advanve

[mrjj]

@UnitScan

What about MainWindow.h ?

Also since all QWidgets are QObjects, you dont need templates for most GUI operations.

[UnitScan]

connect(sel, SIGNAL(released()), this, SLOT(showMenu(QMenu, QPushButton)));

void MainWindow::showMenu(QMenu *m, QPushButton *pb)
{
    QSize size = m->sizeHint();
    m->popup(pb->mapToGlobal(QPoint(0,0-size.height())));
}

Doesn't work

[mrjj]

@UnitScan said in Template function:

Hi
That is because the released() signal DO NOT have QMenu* and QPushButton * parameters.

You cannot invent new parameters for a signal.
You can define new signals though.

http://doc.qt.io/qt-5/signalsandslots.html

also note that connect returns true if connect works.

so

qDebug() << "tcheck:" << connect(xxx) to see if they work.

[UnitScan]

SOLVED

void MainWindow::showMenu()
{
    QPushButton *pb = qobject_cast<QPushButton*>(sender());
    QMenu* m = qobject_cast<QMenu*>(pb->children().at(0));
    QSize size = m->sizeHint();
    m->popup(pb->mapToGlobal(QPoint(0,0-size.height())));
}

[mrjj]

@UnitScan

Hi you should check both pb an m for not being null :)

[VRonin]

since I hate sender() and pb->children().at(0) is even less robust I suggest (assuming you declared QMenu* MainWindow::m):

connect(sel, &QPushButton::released, [=]()->void{
const QSize size = m->sizeHint();
m->popup(sel->mapToGlobal(QPoint(0,-size.height())));
});

---

P.S.
Looking at this functionality, are you sure QToolButton is not a better choice? see QToolButton::setMenu