Widget request: a "fold form" widget for showing/hiding details

The request is to have "fold form" widget, to hide or show parts of the dialog. It would be a very useful addition to Qt. One option would be to add an option to QGroupBox.

The widget normally looks a bit like this when it's unfolded:

Bla bla bla ---------------------------------------------------------- [-]

[child widgets go here]

i.e. it's basically a flat QGroupBox, but with a [-] button on the right (or an arrow).

It looks like this when it's folded:

Bla bla bla ---------------------------------------------------------- [+]