QTableView display data in millimeter or inch

addebito

Hi at all,

do you know the "best way" to display data in millimeters or inch inside a QTableView and QLineEdit mapped to a database table?

As usual, any suggestion will be appreciated.

SGaist

Hi,

What version of the value are you storing in the database ?

addebito

Hi @SGaist,
inside the database all datas are stored in millimeters.

SGaist

In that case, a QStyledItemDelegate for the QTableView.

For the QLineEdit, are you sure you will not be better served by a QSpinBox ?

addebito

@SGaist said in QTableView display data in millimeter or inch:

In that case, a QStyledItemDelegate for the QTableView.

I forgot to specify that the QTableView is in "read-only mode", to edit or insert a new row the user write the data inside the QLineEdits mapped by QDataWidgetMapper.
I've about 15 column to convert on the fly between mm / inch depending of the user choice.

The qtwidgets-itemviews-stardelegate-example could be a good starting point?

QSpinBox... I don't know why, there is no real reason, but I don't like much the "spin box" widget. Not only in QT, but in general. Anyway, I'll give it a chance :-)

addebito

Hi @SGaist ,

I've created my QStyledItemDelegate...

#pragma once

#include <QStyledItemDelegate>

class VTMmInchItemDelegate : public QStyledItemDelegate
{
  public:
    explicit VTMmInchItemDelegate(QObject *parent = nullptr);
    virtual QString displayText(const QVariant &value, const QLocale &locale) const;

  public slots:
    void slotMeasChanged(bool mm);

  private:
    /// unit measure (mm = 1.0, inch = 25.4)
    double m_unitMeas = 1.0;

    /// decimal precision mm = 3, inch = 5
    int m_decimalPrecision = 3;
};

#include "vtmminchitemdelegate.h"

VTMmInchItemDelegate::VTMmInchItemDelegate(QObject *parent) : QStyledItemDelegate(parent)
{
    //
}

QString VTMmInchItemDelegate::displayText(const QVariant &value, const QLocale &locale) const
{
    // unit measure (mm = 1.0, inch = 25.4)
    // decimal precision (mm = 3, inch = 5)
    return QString::number(value.toDouble() / m_unitMeas, 'f', m_decimalPrecision);
}

void VTMmInchItemDelegate::slotMeasChanged(bool mm)
{
    if (mm)
    {
        m_unitMeas         = 1.0;
        m_decimalPrecision = 3;
    }
    else
    {
        m_unitMeas         = 25.4;
        m_decimalPrecision = 5;
    }
}

...and I can use it with a QTableView in this way:

ui->tableView->setItemDelegateForColumn(2, new VTMmInchItemDelegate(this));
ui->tableView->setItemDelegateForColumn(3, new VTMmInchItemDelegate(this));

But now I don't know how to achieve the same behavior with the widgets mapped by QDataWidgetMapper.

I have about 30 widgets (QlineEdit or QComboBox) and I'd like to map some QLineEdits to display as the QTableView, the data correctly according to the setting mm / inch.

Do you have any suggestion please?
Thank you so much.

PS: I've try another way, subclassing the QSqlTableModel and reimplementing the function:

QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;

...but I obtain the same result, the QTableView works fine, the widgets mapped by QDataWidgetMapper not.

SGaist

You can create a widget that contains a QLineEdit and serves as proxy.

addebito

Hi @SGaist ,

thank you for your suggestions, follow my implementation.

QSqlTableModel subclass
QItemDelegate subclass

vtsqltablemodel.h

#pragma once

#include <QSqlTableModel>

class VTSqlTableModel : public QSqlTableModel
{
  public:
    VTSqlTableModel(const QVector<int> &column, QObject *parent = nullptr, QSqlDatabase db = QSqlDatabase());
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;

  public slots:
    void slotMeasChanged(bool mm);

  private:
    /// list of columns to format in mm or inch
    QVector<int> m_column;

    /// unit measure (mm = 1.0, inch = 25.4)
    double m_unitMeas = 1.0;

    /// decimal precision mm = 3, inch = 5
    int m_decimalPrecision = 3;
};

vtsqltablemodel.cpp

#include "vtsqltablemodel.h"

VTSqlTableModel::VTSqlTableModel(const QVector<int> &column, QObject *parent, QSqlDatabase db) : QSqlTableModel(parent, db), m_column(column)
{
    //
}

QVariant VTSqlTableModel::data(const QModelIndex &index, int role) const
{
    if (role == Qt::DisplayRole)
    {
        if (m_column.contains(index.column()))
            return QVariant(QString::number(QSqlTableModel::data(index, role).toDouble() / m_unitMeas, 'f', m_decimalPrecision));
    }

    return QSqlTableModel::data(index, role);
}

void VTSqlTableModel::slotMeasChanged(bool mm)
{
    if (mm)
    {
        m_unitMeas         = 1.0;
        m_decimalPrecision = 3;
    }
    else
    {
        m_unitMeas         = 25.4;
        m_decimalPrecision = 5;
    }
    select();
}

vtmminchitemdelegate.h

#pragma once

#include <QItemDelegate>

class VTMmInchItemDelegate : public QItemDelegate
{
    Q_OBJECT
  public:
    explicit VTMmInchItemDelegate(const QVector<int> &column, QObject *parent = nullptr);
    void setEditorData(QWidget *editor, const QModelIndex &index) const;
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const;

  public slots:
    void slotMeasChanged(bool mm);

  private:
    /// list of columns to format in mm or inch
    QVector<int> m_column;

    /// unit measure (mm = 1.0, inch = 25.4)
    double m_unitMeas = 1.0;

    /// decimal precision mm = 3, inch = 5
    int m_decimalPrecision = 3;
};

vtmminchitemdelegate.cpp

#include "vtmminchitemdelegate.h"

#include <QDebug>
#include <QLineEdit>
#include <QVariant>

VTMmInchItemDelegate::VTMmInchItemDelegate(const QVector<int> &column, QObject *parent) : QItemDelegate(parent), m_column(column)
{
    //
}

void VTMmInchItemDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    QLineEdit *edt = (dynamic_cast<QLineEdit *>(editor));

    if ((m_column.contains(index.column())) && (edt))
    {
        // I have only to display data because is already formatted as QString by my SqlTableModel
        edt->setText(index.data().toString());
    }
    else
        QItemDelegate::setEditorData(editor, index);
}

void VTMmInchItemDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
    QLineEdit *edt = (dynamic_cast<QLineEdit *>(editor));

    if ((m_column.contains(index.column())) && (edt))
    {
        // I have to convert the user input data regarding to the "unit measure" private variable
        QVariant value = edt->text().toDouble() * m_unitMeas;
        model->setData(index, value);
    }
    else
        QItemDelegate::setModelData(editor, model, index);
}

void VTMmInchItemDelegate::slotMeasChanged(bool mm)
{
    if (mm)
    {
        m_unitMeas         = 1.0;
        m_decimalPrecision = 3;
    }
    else
    {
        m_unitMeas         = 25.4;
        m_decimalPrecision = 5;
    }
}

...and you can use it as follow.

    QVector<int> cols;
    cols << 2 << 3 << 4;
    m_model = new VTSqlTableModel(cols);
...
    m_mapper = new QDataWidgetMapper;
    m_mapper->setModel(m_model);
    m_mapper->setItemDelegate(new VTMmInchItemDelegate(cols, this));