How to set alignment of QTableWidget columns

JonB

@VRonin
The one I really like is given in https://stackoverflow.com/a/4959104/489865. That does it by column instead of by cell. However, comments there state (so I did not reference it):

return QAbstractTableModel::data(index,role) is not possible I think.
This answer was given in a simpler time, when grass was greener and sky was clearer. Please feel free to edit this answer

Could you give us the corrected code for this in Qt now, kindly?

VRonin

@JonB said in How to set alignment of QTableWidget columns:

Could you give us the corrected code for this in Qt now, kindly?

My answer is still valid. that SO answer suggests subclassing the delegate and reimplement data, that's not what I'm doing

But how to set alignment of QWidget in cell ?

How are you setting this QWidget and why are you using a QWidget at all to simply display an image?!

JonB

@VRonin said in How to set alignment of QTableWidget columns:

@JonB said in How to set alignment of QTableWidget columns:

Could you give us the corrected code for this in Qt now, kindly?

My answer is still valid. that SO answer suggests subclassing the delegate and reimplement data, that's not what I'm doing

Sorry, yes, I know your answer is valid. My question to you (as an expert!) is: I much prefer setting something on the column once over setting on each item. So how would you rewrite the way he does it such that it is legal again in Qt5?

VRonin

@JonB said in How to set alignment of QTableWidget columns:

So how would you rewrite the way he does it such that it is legal again in Qt5?

I'd subclass the delegate and reimplement paint changing 1 line

class AlignDelegate : public QStyledItemDelegate{
Q_OBJECT
Q_DISABLE_COPY(AlignDelegate)
public:
explicit AlignDelegate(Qobject* parent = Q_NULLPTR) : QStyledItemDelegate(parent), m_alignment(Qt::AlignLeft){}
void paint(QPainter *painter,const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    Q_ASSERT(index.isValid());
    QStyleOptionViewItem opt = option;
    initStyleOption(&opt, index);
opt.displayAlignment = m_alignment; // only line changed from default
    const QWidget *widget = option.widget;
    QStyle *style = widget ? widget->style() : QApplication::style();
    style->drawControl(QStyle::CE_ItemViewItem, &opt, painter, widget);
}
Qt::Alignment alignment() const {return m_alignment;}
void setAlignment(Qt::Alignment align) {m_alignment=align;}
private:
Qt::Alignment m_alignment;
};

JonB

@VRonin
Oh my word! OK, fair enough, far too much for me to want to do in Python! I liked the guy's "one-liner" to set column alignment.... It was just the replacement for line:

return QAbstractTableModel::data(index, role);

(which a comment says "no longer works", and possibly to do with a QVariant) that I was looking for.

VRonin

@JonB Let's try this one if it's easier:

class AlignProxy : public QIdentityProxyModel{
Q_OBJECT
Q_DISABLE_COPY(AlignProxy)
public:
explicit AlignProxy(QObject* parent = Q_NULLPTR)  : QIdentityProxyModel(parent) , m_alignment(Qt::AlignLeft), m_alignColumn(0){}
Qt::Alignment alignment() const {return m_alignment;}
void setAlignment(Qt::Alignment align) {
if(align==m_alignment) return;
m_alignment=align;
alignmentChanged(m_alignment);
if(sourceModel())
dataChanged(index(0,m_alignColumn),index(rowCount(),m_alignColumn));
}
Q_SIGNAL void alignmentChanged(Qt::Alignment align);
Q_SIGNAL void alignedColumnChanged(int col);
int alignedColumn() const {return m_alignColumn;}
void setAlignedColumn(int col){
if(col==m_alignColumn) return;
const int oldCol=m_alignColumn;
m_alignColumn=col;
alignedColumnChanged(m_alignColumn);
if(sourceModel()){
dataChanged(index(0,m_alignColumn),index(rowCount(),m_alignColumn));
dataChanged(index(0,oldCol),index(rowCount(),oldCol));
}
}
QVariant data(const QModelIndex& index, int role = Qt::DisplayRole) const Q_DECL_OVERRIDE{
if(sourceModel() && role==Qt::TextAlignmentRole && index.column() == m_alignColumn) return m_alignment;
return QIdentityProxyModel::data(index,role);
}
private:
int m_alignColumn;
Qt::Alignment m_alignment;
};

JonB

@VRonin
Thank you so much for your efforts to convince me, but nope! Unless it's a one-line rewrite of return QAbstractTableModel::data(index, role); such that it works in Qt5 ('coz from the comment that no longer works compared to "old" Qt), I'll stick to setting each QTableWidgetItem individually :)

VRonin

@JonB The change is really just two lines:

QVariant data(const QModelIndex& index, int role = Qt::DisplayRole) const Q_DECL_OVERRIDE{
if(sourceModel() && role==Qt::TextAlignmentRole && index.column() == m_alignColumn) return m_alignment;
return QIdentityProxyModel::data(index,role);
}

the rest is there to make it pretty and work dinamically

JonB

@VRonin
Ah ha! That's more like it, to my taste!

To be clear (excuse my ignorance, I'm a Qt learner! the docs page does not show how the QIdentityProxy is originally created), do you have to originally set up the QTableWidgets model to be a QIdentityProxyModel-wrapper around the originally-desired model? Like:

model = ...;
identityModel = QIdentityProxyModel();
identityModel->setSourceModel(model);
tableWidget = QTableWidget();
tableWidget->setSourceModel(identityModel);

?

VRonin

QAbstractItemModel* model = new QStandardItemProxyModel(/*parent*/);
QTableView* tableView = new QTableView(/*parent*/);
QAbstractProxyModel* identityModel = new QIdentityModel(/*parent*/);
identityModel->setSourceModel(model);
tableView->setModel(identityModel);