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

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?

chakry

@JonB Thank you .
sorry i want to correct few things . Your code is working fine with view and set model i have just verified that. The reason it didnt work was i was not displaying my view.
I must not show view to user . i just have to map the model to widget(QDateTimeEdit) and show that widget to user. I thought with view it might work if i dont show this to user. just set everything but not showing. This dont work right? please correct me.

I meant both cases. in one case , one child value will be changed in another case a new model is set.I can connect these signals as you mentioned but they work with TreeView when visible right?