How does the "PREVIEW" option in Qt Designer work?

[Charvi]

You are wrong. You can add signals and slots to the form object and to promoted widgets from the context menu.

In Designer? I am sorry, from the post (http://www.qtcentre.org/threads/2195...ts-in-Designer) I perceived that we cannot "define" (write code for) custom signal and slots in Qt Designer. If its possible then can you show me how? Sorry for my ignorance, but if this makes it my problem gets simplified to a huge extent.