Need help from QT Experts ( Model / View for QDateTimeEdit widget)

[SGaist]

Hi and welcome to devnet,

You can create a custom widget with 6 properties matching your model content. The you can use the QDataWidgetMapper::addMapping overload that takes a property name.

Sadly my suggestion is not possible with the current implementation of QDataWidgetMapper.

[edit: SGaist]

[JonB]

@SGaist
As I understand it, the OP has 6 properties. You will call addMapping() 6 times to map each of these to the same widget? I thought (haven't used it) QDataWidgetMapper gave you one distinct widget per distinct property? Won't something go wrong with multiple properties mapped to a single widget?

[chakry]

Hi SGaist,JonB thank you very much , This is my first question happy to see people replying . I am new to QT development as well.

I tried that as well , sorry didint mention that . I have created a custom widget(extending existing) with six more properties and then used addMapping to map each property. This didnt work , it was working only for the last property . Looks like As JonB mentioned QDataWidgetMapper will only work with one property per one widget.

[JonB]

@chakry
That's kind of what I thought (or it would error). However, be aware that @SGaist is an expert: unless he mis-read your question, he usually knows what he is talking about!

[SGaist]

@JonB said in Need help from QT Experts ( Model / View for QDateTimeEdit widget):

@chakry
That's kind of what I thought (or it would error). However, be aware that @SGaist is an expert: unless he mis-read your question, he usually knows what he is talking about!

Thanks for the flowers, but I can be wrong and that's one occurrence. I had the same assumption you have but taking a look at the current QDataWidgetMapper implementation, it doesn't handle mapping of several properties on the same widget. However, I don't know whether it's on purpose in which case the documentation should be updated to reflect that or if it just a case of "use case did not happen before" in which case it could be considered a bug. From the looks of the API, I think the original design was really one different widget per section but that is pure speculation.

[JonB]

@SGaist

Thanks for the flowers

Since I believe you are Swiss, I send you some "Leontopodium" ("lion's paw", Edelweiss), your national flower ;-)

[chakry]

Thank you for your suggestions :). This in general gets me into a new question , suppose i have a database of multiple cells that i want to show them in a single widget then i have the same problem right ? i cannot do that , are there any other ways ?

isn't it a use case which might be coming in working environments or am i the only one landed there as i don't see much people talking about it :).

for example i have custom widget with 10 sliders on it where i want to have a database model that updates 10 cells(value) it should be vice versa (if the cells are updated ( background by some one else) and in turn the sliders change automatically ). I know with signals and slots its possible but if i have many of these scenarios like this in a project then it will be a lot of signal/slots and updates right, difficult to track in case of errors ? any other options todo such things .

@I may be wrong in thinking ( writing whatever on my mind :))

[SGaist]

You'll likely have these 10 sliders in one custom widget so you would have the mapper within that widget and then map each slider independently.

[SGaist]

As for your single widget with multiple properties, here's a workaround taking advantage of Qt's dynamic properties. Note that I don't find it elegant because it requires one widget per property but at least you can have your single QDateTimeEdit used.

class QDWMProxy : public QWidget
{
public:
    /*!
        Set which property should be set on the target
    */
    void setMapping(QWidget *target, const QByteArray& propertyName)
    {
        _target = target;
        _propertyName = propertyName;
    }

    bool event(QEvent *event) override
    {
        if (event->type() == QEvent::DynamicPropertyChange) {
            QDynamicPropertyChangeEvent *pe = static_cast<QDynamicPropertyChangeEvent *>(event);
            if (pe->propertyName() == _propertyName) {
                _target->setProperty(_propertyName, property(_propertyName));
                event->accept();
                return true;
            }
        }
        return QWidget::event(event);
    }

private:
    QWidget *_target;
    QByteArray _propertyName;
};

You'll create one proxy per properties and use it for the QDataWidgetMapper mapping function. Don't forget to handle their deletion appropriately.

Dummy main.cpp example:

    MyCustomWidget widget;
    QDWMProxy proxyHours;
    proxy1.setMapping(&widget, "hours");
    QDWMProxy proxyMinutes;
    proxy2.setMapping(&widget, "minutes");
    QDataWidgetMapper mapper;
    mapper.setModel(model);
    mapper.addMapping(&proxyHours, 0, "hours");
    mapper.addMapping(&proxyMinutes, 1, "minutes");
    mapper.toFirst();
    widget.show();

I'll let you replace your model and widget.

[chakry]

@SGaist Thank you. you are right , that works. This may be a wrong example.

[chakry]

@SGaist Thank you. Good trick, it worked . Mapping works , if the model data is updated then the widget is updated . But when the widget is updated then the model is not updated automatically . I am still looking a reason for this. Probably missing something , will post once it is completely working.

[VRonin]

Just trying to understand. An example always helps me.
So your model looks like:

• Parent A
  • 2019-12-25
  • 13:58:15
  • Wednesday
  • 13
  • 58
  • 15
• Parent B
  • 2019-05-30
  • 20:30:55
  • Thursday
  • 20
  • 30
  • 55

And you want it displayed as a list that appears

• 2019-12-25 13:58:15
• 2019-05-30 20:30:55

And when one item of that list gets modified then the children of the tree get modified accordingly.
Is the above an accurate representation? (if so there is a solution that requires a proxy).

Or do you want a widget completely external to the representation of the data?

[chakry]

HI @VRonin ,

Model is almost correct small difference is ( date is also broken to a separate child as below)

Parent A

2019
12
25
13
58
15
Wednesday ( this one is not must)

And you want it displayed as a list that appears ( not as a list but i want to display and edit using a QDateTimeEdit widget or similar)

2019-12-25 13:58:15
2019-05-30 20:30:55

if it is a tree widget or tree view then it is no problem it works directly.( element wise )

proxy , i have read about this and tried to implement but did not succeed( it is easier in a table widget or Tree i think). do you have a example of this to a seperate widget?

[chakry]

@SGaist Dear SGaist, I could not make it 100 % working , so posting here the widget code. I have tried a simple version to check functionality.

problem: widget mapper mapping to property . updates property when model changed , does not update model when property changed. I didn't understand how widget mapper gets property change info.

here is code

class QmDateTimeEdit : public QDateTimeEdit {
Q_OBJECT

Q_PROPERTY(uint16_t dateYear READ dateYear WRITE setDateYear NOTIFY dateYearChanged USER true)
Q_PROPERTY(uint16_t dateMonth READ dateMonth WRITE setDateMonth NOTIFY dateMonthChanged USER true)
Q_PROPERTY(uint16_t dateDay READ dateDay WRITE setDateDay NOTIFY dateDayChanged USER true)

public:
explicit QmDateTimeEdit(QWidget* parent = nullptr);

uint16_t dateYear() const { return mYear; }
uint16_t dateMonth() const { return mMonth; }
uint16_t dateDay() const { return mDay; }

QDateTime dateTime() const;

signals:

void dateYearChanged(const uint16_t& dateYear);
void dateMonthChanged(const uint16_t& dateMonth);
void dateDayChanged(const uint16_t& dateDay);

private slots:

void valueChanged(const QDateTime& dateTime);
void setDateTime(const QDateTime& dateTime);
void setDateDay(uint16_t dateDay);
void setDateYear(uint16_t dateYear);
void setDateMonth(uint16_t dateMonth);

private:

uint16_t mYear;
uint16_t mMonth;
uint16_t mDay;

};

// when ever valueChanged() occurs i just set 3 values (mYear , mMonth and mDay) and emit 3 signals . I expected this should update the model data but it doesn't.

QmDateTimeEdit::QmDateTimeEdit(QWidget* parent)
: QDateTimeEdit(parent)
{
connect(this, &QDateTimeEdit::dateTimeChanged, this, &QmDateTimeEdit::valueChanged);
}

void QmDateTimeEdit::setDateYear(uint16_t dateYear)
{

mYear = dateYear;
qDebug() << "Year changed" << mYear;	

}

void QmDateTimeEdit::setDateMonth(uint16_t dateMonth)
{

mMonth = dateMonth;
qDebug() << "Month changed" << mMonth;	

}

void QmDateTimeEdit::setDateDay(uint16_t dateDay)
{

mDay = dateDay;
qDebug() << "Day changed" << mDay << this->parent();	

}

void QmDateTimeEdit::valueChanged(const QDateTime& dateTime)
{

setDateYear(dateTime.date().year());
setDateMonth(dateTime.date().month());
setDateDay(dateTime.date().day());

emit dateYearChanged(dateTime.date().year());
emit dateMonthChanged(dateTime.date().month());	
emit dateDayChanged(dateTime.date().day());

}

[tajny_agent]

You can use QDataWidgetMapper with custom delegate.

void MyDelegate::setEditorData(QWidget* parent, const QModelIndex& index) const
{
  if (auto dte = qobject_cast<QDateTimeEdit*>(editor); dte) {
    auto* model = index.model();
    const auto& year = model->index(0, 0, index.parent()).data().toString();
    const auto& month = model->index(1, 0, index.parent()).data().toString();
    // ...
    QDateTime dt = QDateTime::fromString(/*combine above to QDateTime*/);
    dte->setDateTime(dt);
  }
}

Then map your QDateTimeEdit with QDataWidgetMapper, set delegate. and voila

[VRonin]

Something like this minimal example is what you want or did I miss something?

#include <QApplication>
#include <QTreeWidget>
#include <QVBoxLayout>
#include <QDateTimeEdit>
#include <QStandardItemModel>
class ExampleWid : public QWidget{
    //Q_OBJECT
    Q_DISABLE_COPY(ExampleWid)
public:
    explicit ExampleWid(QWidget *parent = Q_NULLPTR)
        :QWidget(parent)
        ,view(new QTreeView(this))
        ,editor(new QDateTimeEdit(this))
    {
        QAbstractItemModel* model = new QStandardItemModel(this);
        model->insertColumn(0);
        model->insertRows(0,2);
        QModelIndex parIdx= model->index(0,0);
        model->setData(parIdx,QStringLiteral("Parent A"));
        model->insertColumn(0,parIdx);
        model->insertRows(0,7,parIdx);
        model->setData(model->index(0,0,parIdx),2019);
        model->setData(model->index(1,0,parIdx),12);
        model->setData(model->index(2,0,parIdx),25);
        model->setData(model->index(3,0,parIdx),13);
        model->setData(model->index(4,0,parIdx),58);
        model->setData(model->index(5,0,parIdx),15);
        model->setData(model->index(6,0,parIdx),QStringLiteral("Wednesday"));
        parIdx= model->index(1,0);
        model->setData(parIdx,QStringLiteral("Parent B"));
        model->insertColumn(0,parIdx);
        model->insertRows(0,7,parIdx);
        model->setData(model->index(0,0,parIdx),2019);
        model->setData(model->index(1,0,parIdx),5);
        model->setData(model->index(2,0,parIdx),30);
        model->setData(model->index(3,0,parIdx),20);
        model->setData(model->index(4,0,parIdx),30);
        model->setData(model->index(5,0,parIdx),55);
        model->setData(model->index(6,0,parIdx),QStringLiteral("Thursday"));

        view->setModel(model);
        QVBoxLayout* minLay = new QVBoxLayout(this);
        minLay->addWidget(editor);
        minLay->addWidget(view);
        QObject::connect(view->selectionModel(),&QItemSelectionModel::currentChanged,this,[this](QModelIndex idx)->void{
            if(!idx.isValid())
                return;
            while(idx.parent().isValid())
                idx =idx.parent();
            lastIdx = QPersistentModelIndex();
            editor->setDateTime(QDateTime(
                QDate(
                    idx.model()->index(0,0,idx).data().toInt()
                    ,idx.model()->index(1,0,idx).data().toInt()
                    ,idx.model()->index(2,0,idx).data().toInt()
                )
                , QTime(
                    idx.model()->index(3,0,idx).data().toInt()
                    ,idx.model()->index(4,0,idx).data().toInt()
                    ,idx.model()->index(5,0,idx).data().toInt()
                )
            ));
            lastIdx = idx;
        });
        QObject::connect(editor,&QDateTimeEdit::dateTimeChanged,this,[this](const QDateTime &datetime)->void {
            if(!lastIdx.isValid())
                return;
            QAbstractItemModel * model = view->model();
            model->setData(model->index(0,0,lastIdx),datetime.date().year());
            model->setData(model->index(1,0,lastIdx),datetime.date().month());
            model->setData(model->index(2,0,lastIdx),datetime.date().day());
            model->setData(model->index(3,0,lastIdx),datetime.time().hour());
            model->setData(model->index(4,0,lastIdx),datetime.time().minute());
            model->setData(model->index(5,0,lastIdx),datetime.time().second());
            model->setData(model->index(6,0,lastIdx),view->locale().toString(datetime.date(),QStringLiteral("dddd")));
        });
    }
private:
    QTreeView* view;
    QDateTimeEdit *editor;
    QPersistentModelIndex lastIdx;
};

int main(int argc, char **argv)
{
    QApplication app(argc,argv);
    ExampleWid wid;
    wid.show();
    return app.exec();
}

[chakry]

@VRonin said in Need help from QT Experts ( Model / View for QDateTimeEdit widget):

view

HI VRonin,

Thank you for your reply. This would work but my model is not a local one , it is set from a different class using a set-model function(example). I need it because the model might change during run time. in this case i need dynamic signal slot right ?. I have a requirement of sessions in my program if a session is changed then the model changes which i have to set it externally.

Thanks and regards

[VRonin]

Nothing difficult, mine was just an example, just remove everything in the constructor before QVBoxLayout* minLay = new QVBoxLayout(this); and add a public void setModel(QAbstractItemModel* model){view->setModel(model);} that you can use to set a new model from outside this class. Everything else is all the same

[chakry]

Yes i tried that but when the model data is changed then the signal is not fired , it never comes to this function . why is that ?

QObject::connect(lView->selectionModel(), &QItemSelectionModel::currentChanged, this, [this](QModelIndex idx) -> void {
	qDebug() << "modelchanged " << idx;
    }

[JonB]

@chakry

I need it because the model might change during run time

Do you mean the whole model is changed, or just one item? If it's the former:
https://doc.qt.io/qt-5/qitemselectionmodel.html#currentChanged

Note that this signal will not be emitted when the item model is reset.

and you might mean:
https://doc.qt.io/qt-5/qitemselectionmodel.html#modelChanged

This signal is emitted when the model is successfully set with setModel().

or am I grasping the wrong end of the stick for what you are saying?