Insert and read Image in QLable using QDataWidgetMapper

[ChrisW67]

Not really a lot. Something like this (compiles but untested):

class PicLoadingDelegate: public QItemDelegate
{
    Q_OBJECT
public:
    PicLoadingDelegate(QObject * parent = 0 ): QItemDelegate(parent) { }
 
    void setEditorData( QWidget *editor, const QModelIndex &index ) const
    {
        QLabel *label = qobject_cast<QLabel *>(editor);
        if (label) {
            QByteArray imageData = index.data(Qt::EditRole).toByteArray(); 
            QPixmap pixmap;
            if (pixmap.loadFromData(imageData))
                label->setPixmap(pixmap);
        }
    }
 
    void setModelData( QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
    {
        QLabel *label = qobject_cast<QLabel *>(editor);
        if (label) {
            QBuffer buf;
            buf.open(QIODevice::WriteOnly);
            if (label->pixmap()->save(&buf))
                model->setData(index, buf.data(), Qt::EditRole);
        }
    }
};

class PicLoadingDelegate: public QItemDelegate
{
    Q_OBJECT
public:
    PicLoadingDelegate(QObject * parent = 0 ): QItemDelegate(parent) { }

    void setEditorData( QWidget *editor, const QModelIndex &index ) const
    {
        QLabel *label = qobject_cast<QLabel *>(editor);
        if (label) {
            QByteArray imageData = index.data(Qt::EditRole).toByteArray(); 
            QPixmap pixmap;
            if (pixmap.loadFromData(imageData))
                label->setPixmap(pixmap);
        }
    }

    void setModelData( QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
    {
        QLabel *label = qobject_cast<QLabel *>(editor);
        if (label) {
            QBuffer buf;
            buf.open(QIODevice::WriteOnly);
            if (label->pixmap()->save(&buf))
                model->setData(index, buf.data(), Qt::EditRole);
        }
    }
};

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[hsm13]

wow that's great; Thank you so much.
Is PDF file is different than image ? and can I display it in hyperlink label to open it with outside application ? Many thanks again.

[ChrisW67]

Is PDF file is different than image ?

Yes.

and can I display it in hyperlink label to open it with outside application ?

Yes.

[hsm13]

ummm, sample code if found please

[hsm13]

Let's take a deep breath; In fact I found you post here

http://www.qtcentre.org/threads/4499...light=pdf+blob

It's a bit different; so where I want some tricky help. sorry for any disturb.

[cia.michele]

Good Morning to all,
I've the same problem, but in a QSqlRelationalModel, so, how I should use this delegate?
I've got a table with severals column so, now I use a QSqlRelationalDelegate (I've also 3 QCombobox at 3 relations), so how can I switch from one delegate to other? Or I can subclass QSqlRelationalDelegate to obtain this? And your code affect only the QLabel behavior? The other columns will work as before?

Thanks for your time!

Michele

[ChrisW67]

The delegate code I posted is an example. It assumes that if the editor is a QLabel that the corresponding column in the model is a blob containing an image. It also shows how the current image in the label can be written back to the model. If the editor widget, this was for mapped widgets not a table view, was not a label then no data would be transferred in either direction.

Delegates are attached to a view, not model or table, either as a whole or to a column/ row of the the view (see QAbstractItemView::setItemDelegate(), setItemDelegateForColumn, setItemDelegateForRow). If you use one delegate for the whole view then your delegate usually needs to differentiate between columns using index.column() and do something different for each in the setEditorData() and setModelData() functions. If you use a delegate on a single column then the example is the sort of thing you need.

The default relational delegate should look after creating an populating combo box editors for established relationships and do the default for other columns. You can put separate delegates on columns if you wish or write a combined delegate by subclassing the relational delegate.

What are you trying to achieve?

[cia.michele]

I'm trying to achive the same effect needed by hsm 13 but I'm using a QSqlRelationalTableModel and QDataWidgetMapper, and I don't know how to use your example.
If I assign your delegate to the mapper [mapper->setItemDelegate(new PicLoadingDelegate(this));], I lose the link of other fields of my form.
I use QLabel to show the image stored into Blob file.

Thanks a lot

Michele

[ChrisW67]

You can only attach the delegate to the mapper as a whole so it will affect all the columns and you need to write the delegate to discriminate between columns accordingly. The related columns should be handed off to the superclass to get default combo box treatment. Something like:

class MyDelegate: public QSqlRelationalDelegate {
    Q_OBJECT
public:
    MyDelegate(QObject *p = 0): QSqlRelationalDelegate(p) { }
    void setEditorData(QWidget *editor, const QModelIndex &index) const
    {
        switch(index.column()) {
            case 0: // do nothing special, simple editors
            case 1:
                QSqlRelationalDelegate::setEditorData(editor, index);
                break;
            case 2: // do something special for blob column 2 
                {
                QLabel *label = qobject_cast<QLabel*>(editor);
                Q_ASSERT(label);
                // blob loading code
                break;
                }
            case 3: // the related column gets default treatment
            default:
                QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
    {
        switch(index.column()) {
            case 0: // do nothing special for column 0, 1
            case 1:
                QSqlRelationalDelegate::setEditorData(editor, index);
                break;
            case 2: // do something special for blob column 2 
                {
                QLabel *label = qobject_cast<QLabel*>(editor);
                Q_ASSERT(label);
                // blob saving code
                break;
                }
            case 3: // the related column gets default treatment
            default: // so does anything we've missed
                QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
 
};

class MyDelegate: public QSqlRelationalDelegate {
    Q_OBJECT
public:
    MyDelegate(QObject *p = 0): QSqlRelationalDelegate(p) { }
    void setEditorData(QWidget *editor, const QModelIndex &index) const
    {
        switch(index.column()) {
            case 0: // do nothing special, simple editors
            case 1:
                QSqlRelationalDelegate::setEditorData(editor, index);
                break;
            case 2: // do something special for blob column 2 
                {
                QLabel *label = qobject_cast<QLabel*>(editor);
                Q_ASSERT(label);
                // blob loading code
                break;
                }
            case 3: // the related column gets default treatment
            default:
                QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
    {
        switch(index.column()) {
            case 0: // do nothing special for column 0, 1
            case 1:
                QSqlRelationalDelegate::setEditorData(editor, index);
                break;
            case 2: // do something special for blob column 2 
                {
                QLabel *label = qobject_cast<QLabel*>(editor);
                Q_ASSERT(label);
                // blob saving code
                break;
                }
            case 3: // the related column gets default treatment
            default: // so does anything we've missed
                QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }

};

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[cia.michele]

Hello ChrisW67,
thanks a lot for your help. I've tried something like your code, and I've create my Delegate from your code, but, It seems don't work.
this is my code:

class PicLoadDelegate: public QSqlRelationalDelegate
{
    Q_OBJECT
 
public:
    PicLoadDelegate(QObject * parent = 0 ): QSqlRelationalDelegate(parent) { }
    void setEditorData(QWidget *editor, const QModelIndex &index) const
    {
        switch(index.column()) {
        case 9: // do something special for blob column 2
        {
            QLabel *label = qobject_cast<QLabel*>(editor);
            Q_ASSERT(label);
            if (label) {
                QByteArray imageData = index.data(Qt::EditRole).toByteArray();
                QPixmap pixmap;
                if (pixmap.loadFromData(imageData))
                    label->setPixmap(pixmap);
            }
            break;
        }
        default:
            QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
    {
        switch(index.column()) {
        case 9: // do something special for blob column 2
        {
            QLabel *label = qobject_cast<QLabel*>(editor);
            Q_ASSERT(label);
            if (label) {
                QBuffer buf;
                buf.open(QIODevice::WriteOnly);
                if (label->pixmap()->save(&buf))
                    model->setData(index, buf.data(), Qt::EditRole);
            }
            break;
        }
        default: // so does anything we've missed
            QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
};

class PicLoadDelegate: public QSqlRelationalDelegate
{
    Q_OBJECT

public:
    PicLoadDelegate(QObject * parent = 0 ): QSqlRelationalDelegate(parent) { }
    void setEditorData(QWidget *editor, const QModelIndex &index) const
    {
        switch(index.column()) {
        case 9: // do something special for blob column 2
        {
            QLabel *label = qobject_cast<QLabel*>(editor);
            Q_ASSERT(label);
            if (label) {
                QByteArray imageData = index.data(Qt::EditRole).toByteArray();
                QPixmap pixmap;
                if (pixmap.loadFromData(imageData))
                    label->setPixmap(pixmap);
            }
            break;
        }
        default:
            QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index ) const
    {
        switch(index.column()) {
        case 9: // do something special for blob column 2
        {
            QLabel *label = qobject_cast<QLabel*>(editor);
            Q_ASSERT(label);
            if (label) {
                QBuffer buf;
                buf.open(QIODevice::WriteOnly);
                if (label->pixmap()->save(&buf))
                    model->setData(index, buf.data(), Qt::EditRole);
            }
            break;
        }
        default: // so does anything we've missed
            QSqlRelationalDelegate::setEditorData(editor, index);
        }
    }
};

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What do you think is the mistake?

Thanks a lot for your time

Michele

[ChrisW67]

Which bit doesn't work? Doesn't compile? Doesn't update the QLabel mapped to column 9 (that's the tenth column)? Doesn't save a label image? Have you single stepped it? Is there valid data in the tenth column of the model?