When setting the pageSize on the QTextDocument of a QGraphicsTextItem, the contents of the QGraphicsTextItem is shown as in a document view. However, the last visible lines in the document become non-editable. I can't place the cursor or select that text with the mouse. Also the selection border disappears when clicking on those lines. When moving the textCursor with the keyboard to those lines, the textCursor is no longer shown/redrawn.
After going through the source code it seems to me that the pageSize.height causes the problem.