How to apply validation on cells in a QTableWidget?

[mrjj]

@Guerrian
Hi
you cannot connect external QLineEdit.
You must do as in example and make delegate.
http://doc.qt.io/qt-5/qtwidgets-itemviews-spinboxdelegate-example.html
However, instead of spin box, you returns you LineEdit with validator ( as code is now)
in CreateEditor.
Its important to read about how delegates works.
http://doc.qt.io/qt-5/qstyleditemdelegate.html

[Guerrian]

@mrjj Do I have to use a model / view based architecture (QTableView) to go down this path?

[mrjj]

@Guerrian
no, it works the same via setItemDelegateForColumn and friends.
The *Widgets version are also views, but comes wrapped up with own internal model and
its meant for convenience.
However, in the long run, you might be more happy with *Views.

[SGaist]

To add to @mrjj, use QRegularExpression and not QRegExp, that one is deprecated.

[Guerrian]

When I add the delegate to the QTableWidget the cells disappear i.e. there is no text editor in the table. I assume this is because I have not implemented a paint method for the delegate. I do no know how to do this:

class TextDelegate : public QStyledItemDelegate
{
    Q_OBJECT
public:
    TextDelegate(QObject *parent = 0);
    QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &, const QModelIndex &index) const override;
    void setEditorData(QWidget *editor, const QModelIndex &index) const override;
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const override;
    void updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
};

TextDelegate::TextDelegate(QObject *parent): QStyledItemDelegate(parent)
{
}

QWidget *TextDelegate::createEditor(QWidget *parent,
    const QStyleOptionViewItem &,
    const QModelIndex &) const
{
    QLineEdit *editor = new QLineEdit(parent);
    editor->setFrame(false);
    QRegularExpression regExp("/^[^'\"]*$/");
    auto *validator = new QRegularExpressionValidator(regExp, parent);
    editor->setValidator(validator);
    return editor;
}

void TextDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    QLineEdit *lineEdit = static_cast<QLineEdit*>(editor);
    lineEdit->setText("test value");
}

void TextDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
}

void TextDelegate::updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    editor->setGeometry(option.rect);
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->tableWidget->setHorizontalHeaderLabels(QStringList() << tr("Name"));
    TextDelegate delegate;
    ui->tableWidget->setItemDelegate(&delegate);
}

[mrjj]

Hi
Do you mean when not in edit mode ?

[Guerrian]

@mrjj I mean the cells have disappeared from the screen in all modes. There is nothing in the table except for the column and row text.

[mrjj]

@Guerrian
Hi
There is a natural explanation to that.
You delegate runs out of scope and gets deleted. :)

TextDelegate delegate; // local var, wont survive the constructor
ui->tableWidget->setItemDelegate(&delegate);

do like this
ui->tableWidget->setItemDelegate(new TextDelegate(this));

and it will draw as expected.

[Guerrian]

@mrjj Nice one. I got further with this, but two problems still remain:

1. The editor still allows quotes in the input.
2. The text in the QTableWidget is not being updated when I leave the cell.

In the case of 2 I added a debug line, but the function doesn't get called:

void TextDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
    QLineEdit *lineEdit = static_cast<QLineEdit*>(editor);
    QString value = lineEdit->text();
    qDebug() << "value: " << value;
    model->setData(index, value, Qt::EditRole);
}

This is what my createEditor function looks like now:

QWidget *TextDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &, const QModelIndex &) const
{
    QLineEdit *lineEdit = new QLineEdit(parent);
    lineEdit->setFrame(false);
    QRegularExpression regExp("/^[^'\"]*$/");
    QRegularExpressionValidator *validator = new QRegularExpressionValidator(regExp, parent);
    lineEdit->setValidator(validator);
    QSignalMapper *mapper = new QSignalMapper(lineEdit);
    mapper->setMapping(lineEdit, 0);
    QObject::connect(lineEdit, SIGNAL(textEdited(bool)), mapper, SLOT(map()));
    QObject::connect(mapper, SIGNAL(mapped(QWidget *)), this, SIGNAL(commitData(QWidget *)));
    return lineEdit;
}

I'm not sure about the id parameter in the mapping.

[SGaist]

What are you doing with that QSignalMapper ?

By the way, use qobject_cast and not static_case with QObject based classes.

[Guerrian]

@SGaist said in How to apply validation on cells in a QTableWidget?:

What are you doing with that QSignalMapper ?

I'm not sure, this is all new to me.

By the way, use qobject_cast and not static_case with QObject based classes.

Thanks

[SGaist]

In that case, don't use it. Follow the SpinBox Delegate example as suggested and just replace the QSpinBox editor by the QLineEdit + QRegularExpressionValidator. And IIRC, you even just have to re-implement only the createEditor method

[Guerrian]

@SGaist
OK, but why is my setModelData not being executed?

[SGaist]

Did you remove the mapper ?
Are you sure that your editor is used in the first place ?

[Guerrian]

@SGaist said in How to apply validation on cells in a QTableWidget?:

Did you remove the mapper ?

Yes.

Are you sure that your editor is used in the first place ?

Well yes, because createEditor is called when I click on the QTableWidget to edit a cell.

[SGaist]

Can you show your current call and a minimal QTableWidget setup that uses it ?

[VRonin]

@Guerrian said in How to apply validation on cells in a QTableWidget?:

The editor still allows quotes in the input.

That's because your regular expression is wrongly escaped, raw string literals are a blessing in cases like this one: QRegularExpression regExp(QStringLiteral(R"**(^[^'\"]*$)**"));

The text in the QTableWidget is not being updated when I leave the cell.

Make sure you use override in the declaration of setModelData to avoid the usual pitfall.

[Guerrian]

@VRonin
After I corrected the regular expression, my code worked.