How can I align the checkboxes in a view?

In order to align the checkboxes in a view, you need to create your own QItemDelegate and reimplement drawCheck() to draw the checkboxes with the alignment that you want.  See the documentation:

In order to do this, QStyle::alignedRect() is used in order to ensure that it is correctly aligned in the center of the rect for the index, then the base implementation is called with the new information so it takes care of rendering the checkbox.

It is also necessary to reimplement editorEvent() to handle the toggling of the checkbox correctly since the checkbox has actually been moved to a different position, and therefore the events for the index need to be handled correctly. See the documentation:

http://doc.trolltech.com/4.3/qabstractitemdelegate.html#editorEvent

The following example demonstrates how this can be done:

#include <QtGui>

class ItemDelegate : public QItemDelegate
{
public:
    ItemDelegate(QObject *parent = 0)
        : QItemDelegate(parent)
    {
    }
    virtual void drawCheck(QPainter *painter, const QStyleOptionViewItem &option,
                           const QRect &, Qt::CheckState state) const
    {
        const int textMargin = QApplication::style()->pixelMetric(QStyle::PM_FocusFrameHMargin) + 1;

        QRect checkRect = QStyle::alignedRect(option.direction, Qt::AlignCenter,
            check(option, option.rect, Qt::Checked).size(),
            QRect(option.rect.x() + textMargin, option.rect.y(),
            option.rect.width() - (textMargin * 2), option.rect.height()));
        QItemDelegate::drawCheck(painter, option, checkRect, state);
    }
    virtual bool editorEvent(QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option,
                             const QModelIndex &index)
    {
        Q_ASSERT(event);
        Q_ASSERT(model);

        // make sure that the item is checkable
        Qt::ItemFlags flags = model->flags(index);
        if (!(flags & Qt::ItemIsUserCheckable) || !(flags & Qt::ItemIsEnabled))
            return false;
        // make sure that we have a check state
        QVariant value = index.data(Qt::CheckStateRole);
        if (!value.isValid())
            return false;
        // make sure that we have the right event type
        if (event->type() == QEvent::MouseButtonRelease) {
            const int textMargin = QApplication::style()->pixelMetric(QStyle::PM_FocusFrameHMargin) + 1;
            QRect checkRect = QStyle::alignedRect(option.direction, Qt::AlignCenter,
                check(option, option.rect, Qt::Checked).size(),
                QRect(option.rect.x() + textMargin, option.rect.y(),
                option.rect.width() - (2 * textMargin), option.rect.height()));
            if (!checkRect.contains(static_cast<QMouseEvent*>(event)->pos()))
                return false;
        } else if (event->type() == QEvent::KeyPress) {
            if (static_cast<QKeyEvent*>(event)->key() != Qt::Key_Space
                && static_cast<QKeyEvent*>(event)->key() != Qt::Key_Select)
                return false;
        } else {
            return false;
        }
        Qt::CheckState state = (static_cast<Qt::CheckState>(value.toInt()) == Qt::Checked
            ? Qt::Unchecked : Qt::Checked);
        return model->setData(index, state, Qt::CheckStateRole);
    }
    virtual void drawFocus(QPainter *painter, const QStyleOptionViewItem &option, const QRect &rect) const
    {
        QItemDelegate::drawFocus(painter, option, option.rect);
    }
};


static int ROWS = 3;
static int COLS = 1;
class Table : public QTableWidget
{
    Q_OBJECT
public:
    Table(QWidget *parent = 0)
        : QTableWidget(ROWS, COLS, parent)
    {
        setItemDelegate(new ItemDelegate(this));
        QTableWidgetItem *item = 0;
        for (int i=0; i<rowCount(); ++i) {
            for (int j=0; j<columnCount(); ++j) {
                setItem(i, j, item = new QTableWidgetItem);
                item->setFlags(Qt::ItemIsEnabled|Qt::ItemIsUserCheckable);
                item->setCheckState((i+j) % 2 == 0 ? Qt::Checked : Qt::Unchecked);
            }
        }
    }
};

#include "main.moc"

int main(int argc, char **argv)
{
    QApplication a(argc, argv);
    Table w;
    w.show();
    return a.exec();
}