How to detect scroll on QtextEdit

I dont know how to connect or use the scrollbar events for a QtextEdit.
By now I use at paintevent this:

Code:

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((QAbstractScrollArea*)txt_editor)->verticalScrollBar()->value()<<"";
  QTextCursor first_clock = txt_editor->cursorForPosition(QPoint(0,0));

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Is there any other way ? Am I doing something strange ?
Thanks

What do you want to do? You don't have to cast in line #1, that's for sure.