How to get the position of widgets in QTablewidget

[MasterBlade]

Hello I have a QTableWidget, and I set some widgets in it.

When I right-click that widget, I want to know which row it is in.

I used the following code, but during my debugging, row is always 0. What's the matter?

QComboBox* cb = new QComboBox(this);
connect(cb, &QComboBox::customContextMenuRequested, [=](QPoint pos){ContextMenu(pos);});

void EffectTable::ContextMenu(QPoint &pos)
{
    QModelIndex index = ui->table->indexAt(pos);
    qint32 row = index.row();
}

[Bonnie]

@MasterBlade You need to map pos from comboBox to the tableWidget (maybe it's better to map to the viewport) using

QPoint QWidget::mapTo(const QWidget *parent, const QPoint &pos) const

or mapToGlobal and then mapFromGlobal.

[MasterBlade]

@Bonnie said in How to get the position of widgets in QTablewidget:

@MasterBlade You need to map pos from comboBox to the tableWidget (maybe it's better to map to the viewport) using

QPoint QWidget::mapTo(const QWidget *parent, const QPoint &pos) const

or mapToGlobal and then mapFromGlobal.

Thank you for the reply.

I tried this

QWidget* w = qobject_cast<QWidget*>(sender());
    QPoint p = mapTo(w, pos);
    QModelIndex index = ui->table->indexAt(p);
    qint32 row = index.row();

But row is still 0. I replaced mapTo() with mapFrom(), same result.

[Bonnie]

@MasterBlade No, the mapTo should be called by the comboBox.
Did you see the doc?
The parent should be a parent of the calling widget.
I think it should be

    QPoint p = w->mapTo(ui->table->viewport(), pos);

If you are confused with that, you can try

QPoint global = w->mapToGlobal(pos);
QPoint p = ui->table->viewport()->mapFromGlobal(global);

[MasterBlade]

@Bonnie The program crashed at QModelIndex index = ui->table->indexAt(p);

QWidget* w = qobject_cast<QWidget*>(sender());
    QPoint p = w->mapTo(ui->table->viewport(), pos);
    QModelIndex index = ui->table->indexAt(p);
    qint32 row = index.row();

[Bonnie]

@MasterBlade Wow, I thought the viewport should be a parent of the cell widget. It's not?
Then you should try the "global" ones.

[EDITED]
Is the sender widget set by setCellWidget?
If it is, can you try that if you don't use viewport, will it crash? If not crash, what's the result?

QPoint p = w->mapTo(ui->table, pos);

[MasterBlade]

@Bonnie
I used ui->table->setCellWidget(j, 2, cb); to setup the widget.

After changing to QPoint p = w->mapTo(ui->table, pos);
it still crashed with exactly the same error message.

[EDIT]
I tried

QPoint global = w->mapToGlobal(pos);
QPoint p = ui->table->mapFromGlobal(global);

It didn't crash. But I'm having issues with QtCreator. It's not showing watchlist.
But I'm sure row is a negative value because the program went into

if (row < 0){
//
}

[Bonnie]

@MasterBlade Wait! I found that in your code the ContextMenu is not called as a slot.
So the sender() should not be the comboBox...

[MasterBlade]

@Bonnie It's a lambda function and should work.

Actually I also connected the table with this function.

connect(ui->table, &QTableWidget::customContextMenuRequested, [=](QPoint pos){ContextMenu(pos);});

This is working alright. I can get the correct row number.

[Bonnie]

@MasterBlade But that's not the correct way to use sender()

1. If EffectTable::ContextMenu is declared as a slot, use

connect(cb, &QComboBox::customContextMenuRequested, this, &EffectTable::ContextMenu);

2. If not , try this and don't do any mapping in EffectTable::ContextMenu, leave it same as in the top post

    connect(cb, &QComboBox::customContextMenuRequested, [=](QPoint pos){
        QWidget* w = qobject_cast<QWidget*>(sender());
        ContextMenu(w->mapTo(ui->table->viewport(), pos));
    });

[MasterBlade]

@Bonnie

You are correct. I output sender with

QObject* obj = sender();
qDebug() << obj;

and got

QObject(0x0)

sender is not working in this case.

[MasterBlade]

@Bonnie There is a compile error with ContextMenu(w->mapTo(ui->table->viewport(), pos));

C:\Users\<...>\effecttable.cpp:132: error: non-const lvalue reference to type 'QPoint' cannot bind to a temporary of type 'QPoint'

I changed it to

QPoint p = w->mapTo(ui->table->viewport(), pos);
ContextMenu(p);

and it's running.

But it again crashed with the same error message.

[MasterBlade]

@Bonnie said in How to get the position of widgets in QTablewidget:

connect(cb, &QComboBox::customContextMenuRequested, this, &EffectTable::ContextMenu);

connect(cb, &QComboBox::customContextMenuRequested, this, &EffectTable::ContextMenu);

has a link error.
C:\Qt\5.15.0\msvc2019_64\include\QtCore\qobject.h:255: error: C2338: Signal and slot arguments are not compatible.

[MasterBlade]

@Bonnie It's late at night in China and I need to take some sleep.
Thank you so much for the help.
I will answer your further responses tomorrow.

[Bonnie]

@MasterBlade I've tried myself. sender() is still 0x0.
Seems not a good idea to use it in the lambda. We should use cb instead.
Still in the lambda:

QPoint p = cb->mapTo(ui->table, pos);
ContextMenu(p);

And no mapping in ContextMenu.
I've tried, this works. ;)

[MasterBlade]

@Bonnie Oh god this is working!
Thank you so much!

[MasterBlade]

@Bonnie Well there are still some minor problems.

I have QComboBox and QPushbutton on the same row.

Let's say the first row. Right-clicking the QPushbutton gives row# 0, but QComboBox gives 1.

Also for the last row both give -1.

They are linked the the same ContextMenu() function.

[Bonnie]

@MasterBlade I've tried again, to get the correct row, we need to map to the viewport, as I expected.
So in the lambda

QPoint p = cb->mapTo(ui->table->viewport(), pos);
ContextMenu(p);

I also tried to add a QPushButton, it works fine, too.
How did you connect the button?
Did you change cb to the button's pointer?

[MasterBlade]

@Bonnie
After adding viewport everything works perfect!
I wish I could give you 100 thumbs up!!!