QTableView & CheckBox delegate alignmnent

[hsfougaris]

I have a QSqlTableModel that I am trying to use with a QTableView.
As I have some columns that contain 1/0 which means true/false in my case, I need to display check boxes instead of the numbers.

I created a delegate, but I'm having an alignment problem: when it is displayed it is centered as intended, but when editing it is displayed to the left (with another checkbox visible in the center).

Here is my code:
@
BooleanItemDelegate::BooleanItemDelegate(QObject *parent) :
QStyledItemDelegate(parent)
{
}

QWidget *BooleanItemDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const {
if (index.isValid()) {
QCheckBox *cb =new QCheckBox(parent);
return cb;
} else {
return QStyledItemDelegate::createEditor(parent, option, index);
}
}

void BooleanItemDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const {
if(index.isValid())
{
int value = index.model()->data(index, Qt::DisplayRole).toInt();
QCheckBox checkBox = static_cast<QCheckBox>(editor);
if(value == 1) {
checkBox->setCheckState(Qt::Checked);
} else {
checkBox->setCheckState(Qt::Unchecked);
}
}
else
{
QStyledItemDelegate::setEditorData(editor, index);
}

}

void BooleanItemDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const {
if(index.isValid())
{
QCheckBox checkBox = static_cast<QCheckBox>(editor);
int value;
if(checkBox->checkState() == Qt::Checked)
value = 1;
else
value = 0;

    model->setData(index, value);
}
else
{
    QStyledItemDelegate::setModelData(editor, model, index);
}

}

QRect BooleanItemDelegate::CheckBoxRect(const QStyleOptionViewItem &view_item_style_options) {
QStyleOptionButton check_box_style_option;
QRect check_box_rect = QApplication::style()->subElementRect( QStyle::SE_CheckBoxIndicator, &check_box_style_option);
QPoint check_box_point(view_item_style_options.rect.x() + view_item_style_options.rect.width() / 2 - check_box_rect.width() / 2,
view_item_style_options.rect.y() + view_item_style_options.rect.height() / 2 -
check_box_rect.height() / 2);
return QRect(check_box_point, check_box_rect.size());
}

void BooleanItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {

 int value = index.model()->data(index, Qt::DisplayRole).toInt();

 QStyleOptionButton check_box_style_option;
 check_box_style_option.state |= QStyle::State_Enabled;
 if (value == 1) {
     check_box_style_option.state |= QStyle::State_On;
 } else {
     check_box_style_option.state |= QStyle::State_Off;
 }
 check_box_style_option.rect = BooleanItemDelegate::CheckBoxRect(option);

 QApplication::style()->drawControl(QStyle::CE_CheckBox, &check_box_style_option, painter);

}
@

Can somone please tell me what I am doing wrong?

Thanks,
Harry

[giesbert]

perhaps you should not use the checkbox itself, try to make the cell itself checkable.
As you want to use a QSqlTableModel, you could use a custom proxy model, derived from QSortFilterProxyModel and add the flag there. then editing is not done via a real combo box :-)

[andre]

Indeed. A proxy model is the way to go here. You only need to reimplement the data(), setData() and the flags() methods to make the column user checkable with a checkbox. That is much simpler than using a custom delegate.

[giesbert]

If the check sign should be centered, the delegate is in fact needed...
Otherwise it's in the front of the cell

[hsfougaris]

But that would mean I'd need a custom proxy model for every table I use, doesn't it?
I've been trying to avoid that.

If I had to do that, would it make more sense QSqlTableModel for every table?
What would be the benefits in each case?

[andre]

No, you can make a generic proxy model that can make any column checkable, and simply reuse that.

[hsfougaris]

Do you have a link of an example handy? I would think I'd have to tweak ony the flags() functions....
Thanks, Harry

[giesbert]

If you only tweak flags, you will never show a checked state.

That's why you have to also implement data and setData.

[hsfougaris]

Ok I found something that seems to work.
(based on this http://www.qtcentre.org/archive/index.php/t-18675.html)

I'm putting the code here, in case it helps someone else:

The basic idea is that there is something like a QList that holds the indexes of the columns that you want to have checkboxes (I'm already thinking of adding another QList for readonly columns).
Actual usage would be
@
CheckableSortFilterProxyModel *cfpm = new CheckableSortFilterProxyModel(this);
QList<int> boolCols;
boolCols.append( usrModel->fieldIndex("isActive") );
boolCols.append( usrModel->fieldIndex("isOk") );
cfpm->setParameters(boolCols);
cfpm->setSourceModel( mySqlTableModel );
myTableView->setModel(cfpm);
@

Here is the code:

checkablesortfilterproxymodel.h:
@
#ifndef CHECKABLESORTFILTERPROXYMODEL_H
#define CHECKABLESORTFILTERPROXYMODEL_H

#include <QSortFilterProxyModel>

class CheckableSortFilterProxyModel : public QSortFilterProxyModel
{
Q_OBJECT
public:
explicit CheckableSortFilterProxyModel(QObject *parent = 0);

void setParameters(QList<int> boolCols);

protected:
QVariant data(const QModelIndex &index, int role) const;
bool setData(const QModelIndex &index, const QVariant &value, int role);
Qt::ItemFlags flags ( const QModelIndex & index ) const;

signals:

public slots:

private:
QList<int> booleanSet;

};

#endif // CHECKABLESORTFILTERPROXYMODEL_H
@

checkablesortfilterproxymodel.cpp:
@
#include "checkablesortfilterproxymodel.h"

CheckableSortFilterProxyModel::CheckableSortFilterProxyModel(QObject *parent) :
QSortFilterProxyModel(parent)
{
}

void CheckableSortFilterProxyModel::setParameters(QList<int> boolCols) {
booleanSet.clear();
if (!boolCols.isEmpty()) {
foreach(int column , boolCols)
{
booleanSet.append(column);
}
}
}

QVariant CheckableSortFilterProxyModel::data(const QModelIndex &index, int role) const {
if(!index.isValid())
return QVariant();

if(booleanSet.contains(index.column()) && (role == Qt::CheckStateRole || role == Qt::DisplayRole)) {
    if (role == Qt::CheckStateRole)
        return index.data(Qt::EditRole).toBool() ? QVariant(Qt::Checked) : QVariant(Qt::Unchecked);
    else if (role == Qt::DisplayRole)
        return QVariant();
}
else
    return QSortFilterProxyModel::data(index,role);

}

bool CheckableSortFilterProxyModel::setData(const QModelIndex &index, const QVariant &value, int role) {
if(!index.isValid())
return false;

if(booleanSet.contains(index.column()) && role==Qt::CheckStateRole)
{
    QVariant data = (value.toInt()==Qt::Checked) ? QVariant(1) : QVariant (0);
    return QSortFilterProxyModel::setData(index, data, Qt::EditRole);
}
else
    return QSortFilterProxyModel::setData(index,value,role);

}

Qt::ItemFlags CheckableSortFilterProxyModel::flags ( const QModelIndex & index ) const {
if(!index.isValid())
return Qt::ItemIsEnabled;

if(booleanSet.contains(index.column()))
    return Qt::ItemIsUserCheckable | Qt::ItemIsSelectable | Qt::ItemIsEnabled;
else
    return QSortFilterProxyModel::flags(index);

}
@

[hsfougaris]

I can easily (I think) make a column readonly with the same logic.

If I wanted to have password fields (in the sense where the actual data is not displayed), would I need to use a delegate, or can it somehow be done with the proxy model?

[giesbert]

The pure display can be done in the same way, just return some stars and not the text.
But to enable password like editing, you need a delegate.

[hsfougaris]

Readonly works fine.
If I add another list (eg. readonlySet)

in the flags function, all I need to add is
@
else if (readonlySet.contains(index.column()))
return Qt::ItemIsSelectable;
@

For the password thing, all I've been able to do is return '***' when the columns is in the passwordSet list. When the user clicks on it, the actual text is shown.

[hsfougaris]

One thing still not working is that the checkboxes are not aligned in the center.
How should I handle that?

[hsfougaris]

Another issue:
it doesn't work with a QSqlRelationalTableModel (I've been using a QSqlTableModel).

The lookup value is displayed correctly, but it is an editable text box, instead of a combo box.
I am using
@
myTableVw->setItemDelegate(new QSqlRelationalDelegate(myTableVw));
@
Any ideas?

[giesbert]

For moving the check box to the center, a custom delegate is needed.
Also for editing the Password stuff with a password edit.

by the way, you should make a code sniuppet of this and add it to the wiki :-)

[hsfougaris]

I guess the checkbox can stay to the left if it will save me a delegate :)
The issue with the SqlRelationalTableModel however is much more serious, and a deal breaker if it can't be resolved.

[hsfougaris]

I can't resist the urge to complain:
It looks like another issue that will never be resolved (like other questions I've asked here and in the mailing list)...
I mean are my questions that stupid? Most things desktop related and especially SQL stuff, seem to be so underdeveloped, you'd think it was developed by a different company.
I've learnt to live with that, but the fact that noone from the Nokia developers (that read these message) bothers to acknowledge, concern or help with desktop issues, is very frustrating.

I see pointless, endless discussions about the best way to draw a pixel, or the ill-fated mobile stuff, which would be all good, if such major gaps didn't exist.

Look at this simple class I've almost done here: why doesn't it exist as part of Qt? There are hundreds (if not thousands) of messages/questions of people asking how to do checkboxes in a tableView.
Each implements it differently, depending on Google's mood on the day they search for info.

[giesbert]

Hey hsfougaris,

a checkable cell is described in the docs with the Qt::ItemIsUserCheckable flag. This is also described in the docs and perhaps in the examples. What else should they do? They have a standard way.

And as a side note: this is a community forum, not a nokia developers forum. If spome of the Trolls hang around here, it's in their free time.

[hsfougaris]

Well, how can you easily use it when using any QSql** models (which is a very common case one would think)? You have to subclass every time...

I also know this is a community forum, that people like you devote a lot of resources to, and manage to help many people.
What annoys me is they seem to respond to many questions about almost everything, except desktop and database related stuff.

thanks,
harry

[hsfougaris]

Back to the main issue, I found this post http://lists.qt.nokia.com/pipermail/qt-interest/2009-January/001833.html which is pretty much about the same thing.

It seems to be a bug in QSqlRelationalDelegate , and a workaround for the createEditor is discussed.
But I can't seem to find the code.
In src\sql\models\qsqlrelationaldelegate.cpp there is only the following
@
/*!
\fn QWidget *QSqlRelationalDelegate::createEditor(QWidget *parent,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
\reimp
*/
@
Does anyone know where the actual implementation is?