setText() is about adding the label for button itself- anyway it would not affect probably the Qtextedit area as it is the another widget. Anyway I need to use non-static variable of some class (in that case the Lister, or any other) that should be instatiated. If instantiated in some thread -- it will be out of non-GUI thread that lead to error.
What signal could do - just trigger slot reaction- or how it put textstream to created Lister textview if it needs to put inside another thread first. Could your provide workable example of it, I think it should not be difficult?