我放个问题在这儿吧，如题，我问了好多地方了，呵呵：P　　　　　　

好像KDE有半透明的界面哦。　　　　　　

qt当然可以做

不过好象是靠软件

xfree好象还不支持硬件半透明（据说有扩展支持，但是好象不稳定，默认没有支持）　　　　　　

这个问题在那个官方网站上问了一下,回答也不是很明了,唉　　　　　　

OK,这样回的:
You can use QWidget::setWindowOpacity, but it will only work under Mac OS X and windows 2000 or worse (ie. XP and so on).　　　　　　

我很想知道哦！看了[url="http://www.yotor.com/wiki/zh/am/Amarok%20(%BC%C6%CB%E3).htm"]Amarok [/url]有个窗口　就是透明的！
刚才又搜了搜　好象qt4支持半透明窗口！　　　　　　

windowOpacity : double
This property holds the level of opacity for the window.
The valid range of opacity is from 1.0 (completely opaque) to 0.0 (completely transparent).
By default the value of this property is 1.0.
This feature is available on Mac OS X, X11 platforms that support the Composite extension, and Windows 2000 and later.
Note that under X11 you need to have a composite manager running, and the X11 specific _NET_WM_WINDOW_OPACITY atom needs to be supported by the window manager you are using.
Warning: Changing this property from opaque to transparent might issue a paint event that needs to be processed before the window is displayed correctly. This affects mainly the use of QPixmap::grabWindow(). Also note that semi-transparent windows update and resize significantly slower than opaque windows.
Access functions:
qreal windowOpacity () const
void setWindowOpacity ( qreal level )