1. Open a long text in a small QPlainTextEdit:

   #include <QApplication>
   #include <QPlainTextEdit>
   
   int main(int argc, char *argv[])
   {
       QApplication a(argc, argv);
       QPlainTextEdit w;
       w.show();
   
       return a.exec();
   }
   

2. Leave the text cursor at the top of the text and scroll the edit down towards the end.
3. Remove the focus from the application e.g. by switching to a different application.
   Earlier on, the edit would have scrolled all the way up to the position of the cursor. Fortunately we don't have that problem anymore because QTBUG-40755 was fixed.
4. Give focus back to the application, e.g. by clicking its title bar by pressing Alt+Tab.
   The edit scrolls all the way up to the position of the cursor.

The edit should not move at all when losing or getting focus.