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QSqlQueryModel::data() not called with Qt::TextAlignmentRole?



  • I have QSqlQueryModel (and other SQL model types) with QTableView to view it.

    Because I am already overriding http://doc.qt.io/qt-5/qsqlquerymodel.html#data, I was expecting to find that called at some point with ItemDataRole of Qt::TextAlignmentRole for aligning the data in the table column. Then I could return Qt::AlignmentFlag::AlignRight to align my numbers right.

    I have seen this suggested & accepted as simplest solution at least for Qt 4. But under my Qt 5.7 I can only say that QSqlQueryModel::data() never does seem to get called for Qt::TextAlignmentRole.

    Is that right? Is that because it's a QSqlQueryModel and not some other model? Does QTableView simply not do it that way? Or what? :)


  • Lifetime Qt Champion

    Since QSqlQueryModel is just a QAbstractItemModel, data() will also be called with Qt::TextAlignmentRole when an item is drawn. Therefore you must be doing something wrong. Please show us some compileable code.



  • @Christian-Ehrlicher

    will also be called with Qt::TextAlignmentRole when an item is drawn

    And that will definitely apply when a QTableView attached to the model is doing the drawing, right? Just for example, for all I know it might be that QTableView handles any alignment in cells itself, and hence would never need to call with the alignment role....

    My proof is that, as I say, I have overridden the virtual QSqlQueryModel::data() and examined calls in debugger/debug output. I see many, many calls to that method which must be coming from the drawer/tableview, with a variety of roles passed in requesting various attributes for the data. However, Qt::TextAlignmentRole is not one of the roles I ever see. Hence the question.

    I shall have to think about what code to post here, as obviously this is all one part of a complete project. I do not mind doing further investigating myself before doing so. Hence my question to discover what the behaviour should be, before I spend my time.


  • Lifetime Qt Champion

    See QStyledItemDelegate::initStyleOption(): https://code.woboq.org/qt5/qtbase/src/widgets/itemviews/qstyleditemdelegate.cpp.html#287
    So you must be doing something wrong.



  • @Christian-Ehrlicher Thanks v. much, I will investigate and report back.



  • @Christian-Ehrlicher
    For my sins, I have to develop in Python/PyQt. I use the (excellent) PyCharm IDE/debugger.

    To test it would be called before writing the actual code, I had:

    def data(self, index: QtCore.QModelIndex, role: QtCore.Qt.ItemDataRole = QtCore.Qt.DisplayRole) -> typing.Any:
        if role == QtCore.Qt.TextAlignmentRole:
            pass
        return super().data(index, role)
    

    and I placed a breakpoint on the pass statement.

    Turns out, that pass breakpoint is never hit! :( I think I have broken on pass in other circumstances, and it was. Anyway, I shall not be using that for breakpoints any more!

    So you are correct, and I have no problem now :)


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