Change Qt theme while running

[Macok]

I saw an application which permit user to change Qt theme of this application while it's running.
I know that it's possible to change Qt theme for whole system, but how to do it for one application only?

If you don't understand what i mean, here's screen from "Kadu":

[talk2amulya]

by using setStyleSheet() ?

[jpn]

QApplication::setStyle()

[Macok]

Thanks, and one more question:
How to get list of styles that are available in system?

[jpn]

See QStyleFactory::keys().

[Macok]

Thanks for the answer, but why this code doesn't work?

QStyle *style=QStyleFactory::create("motif");
setStyle(style);

QStyle *style=QStyleFactory::create("motif");
setStyle(style);

To copy to clipboard, switch view to plain text mode 

I added it to the mainwindow constructor, but application theme is still the same.

@Edit
Ok, I had to write

QApplication::setStyle

QApplication::setStyle

To copy to clipboard, switch view to plain text mode 

instead of

setStyle

setStyle

To copy to clipboard, switch view to plain text mode 

[jpn]

Oh, QWidget::setStyle() seems to be somehow broken at least in Qt 4.5.0-beta1. Yeah, QApplication::setStyle() still works.

[Macok]

Ok, thanks jpn!