QAction setFont doesn't change menu item's font correctly - Mac OS X Cocoa

Build and run the Qt examples/mainwindows/menus/menus.pro project on Windows and on Mac OS X (Cocoa build of Qt).

On Windows the Edit->Format submenu shows bold and italic menu items with a bold and an italic font because of code like this:

boldAct = new QAction(tr("&Bold"), this);

QFont boldFont = boldAct->font();
boldFont.setBold(true);
boldAct->setFont(boldFont);

On Macintosh those items are rendered in a slightly smaller plain font that is neither bold nor italic.