Why QStyle dosen't changes the standard font?

[Dark_Tower]

Hi all, I want to know how to set to the standard font of a specified style (winxp, win, platique,...). I change the style of my app in this way:

QApplication::setStyle(QStyleFactory::create("plastique"));
	QApplication::setPalette(QApplication::style() -> standardPalette());

QApplication::setStyle(QStyleFactory::create("plastique"));
	QApplication::setPalette(QApplication::style() -> standardPalette());

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but it only changes the colors to the standard palette of the style (the font is always the windows xp font). I attach an image from Qt docs that shows how is the standard font of each style. I specially want to know the font of the 'plastique' style

Thanks.