Using a QCombobox to select which coloum to display i QListView

[salcin]

I have a custom model subclassing QAbstractTableModel. The model contain 4 column of data and in the 5:th column I merge all the data from the other 4 columns.
I want to display one column at a time in a QListView. To select which column to display I want to use a QComboBox. Is there a way to automatically display the available columns in the QComboBox by using the same model as in the QListView?

My thoughts:

• Using a qproxymodel to read the headerdata and return it in data(index). Set the proxy model in the QComboBox
• Using two separate models

Any other ideas?

Thanks!

[ChrisW67]

Does tableView->horizontalHeader()->model() give you a suitable model to use as the list model?

[salcin]

Maybe. Do you mean that should set the horizontalHeaderModel as the model for the QListView?
I can set the table model as the model for the QListView and select which column to display with ; setModelColumn(0). But I need to extract the headers in some way to display them in a QComboBox. I think I need to use the same model in both views to be sure that they will be updated whenever data is changed in the model.

[salcin]

Is there a way to change QListView to use the model's headerData() and coulmnCount() instead of data() and rowCount()?

[Santosh Reddy]

You can use proxy model

class HeaderProxy : public QAbstractProxyModel
{
public:
    explicit HeaderProxy(QObject * parent = 0)
        : QAbstractProxyModel(parent)
    {
        ;
    }
 
    QModelIndex index(int row, int column, const QModelIndex & parent = QModelIndex()) const
    {
        if(!parent.isValid())
            return createIndex(row, column);
        return QModelIndex();
    }
 
    QModelIndex parent(const QModelIndex & /*child*/) const
    {
        return QModelIndex();
    }
 
    QModelIndex mapToSource(const QModelIndex & proxyIndex) const
    {
        if(!proxyIndex.isValid())
            return QModelIndex();
 
        return createIndex(proxyIndex.row(), proxyIndex.column());
    }
 
    QModelIndex mapFromSource(const QModelIndex & sourceIndex) const
    {
        if(!sourceIndex.isValid())
            return QModelIndex();
 
        return index(sourceIndex.row(), sourceIndex.column() );
    }
 
    int rowCount(const QModelIndex &parent) const
    {
        return sourceModel()->columnCount(parent);
    }
 
    int columnCount(const QModelIndex &/*parent*/) const
    {
        return 1;
    }
 
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const
    {
        return sourceModel()->headerData(index.row(), Qt::Horizontal, role);
    }
};
 
//elsewhere
TableWidget tableWidget;
tableWidget.show();
// Populate rows, columns and other data.
 
QListView listView;
listView.show();
 
QComboBox comboBox;
comboBox.show();
 
HeaderProxy m;
m.setSourceModel(tableWidget.model());
listView.setModel(&m);
comboBox.setModel(&m);
 
//connect the required signal of comboBox to listView

class HeaderProxy : public QAbstractProxyModel
{
public:
    explicit HeaderProxy(QObject * parent = 0)
        : QAbstractProxyModel(parent)
    {
        ;
    }

    QModelIndex index(int row, int column, const QModelIndex & parent = QModelIndex()) const
    {
        if(!parent.isValid())
            return createIndex(row, column);
        return QModelIndex();
    }

    QModelIndex parent(const QModelIndex & /*child*/) const
    {
        return QModelIndex();
    }

    QModelIndex mapToSource(const QModelIndex & proxyIndex) const
    {
        if(!proxyIndex.isValid())
            return QModelIndex();

        return createIndex(proxyIndex.row(), proxyIndex.column());
    }

    QModelIndex mapFromSource(const QModelIndex & sourceIndex) const
    {
        if(!sourceIndex.isValid())
            return QModelIndex();

        return index(sourceIndex.row(), sourceIndex.column() );
    }

    int rowCount(const QModelIndex &parent) const
    {
        return sourceModel()->columnCount(parent);
    }

    int columnCount(const QModelIndex &/*parent*/) const
    {
        return 1;
    }

    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const
    {
        return sourceModel()->headerData(index.row(), Qt::Horizontal, role);
    }
};

//elsewhere
TableWidget tableWidget;
tableWidget.show();
// Populate rows, columns and other data.

QListView listView;
listView.show();

QComboBox comboBox;
comboBox.show();

HeaderProxy m;
m.setSourceModel(tableWidget.model());
listView.setModel(&m);
comboBox.setModel(&m);

//connect the required signal of comboBox to listView

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[salcin]

Thanks!

It is almost what I want. When I use the proxy model in the combobox the items are not selectable. do I have to implement mapSelectionFromSource and mapSelectionToSource for them to be selectable?

[Santosh Reddy]

If you are using the proxy in the example which I posted you should be able to select items in QComboBox.

BTW selectable option depends on Qt::ItemFlags HeaderProxy::flags(const QModelIndex &index) const; that too if you implement it, else the base class QAbstractProxyModel implementation should enable you to select by default

[salcin]

For some reason, the combobox still displays grayed out items.
I tried to implement
Qt::ItemFlags flags(const QModelIndex & index) const
{
return Qt::ItemIsSelectable;
}

but the combobox didn't respond to that.

[Santosh Reddy]

1. Don't implement the flags() function
or
2. return Qt::ItemSeletable | Qt::ItemEnabaled

[salcin]

Thanks
Adding Qt::ItemIsEnabled did the trick!

[aShook]

This seems to only work if the row and column count are static and not changing. When Columns are inserted and removed I get empty feilds everywhere.
What do we need to reimpliment to get the proxy to track the source as it changes size?

Thanks