如何在开罗表面上绘制任何GTK小部件

I would like to save the looks of a GTK window, and all the buttons and other widgets it contains to a PNG or PDF file. Cairo supports drawing on such surfaces. Could I somehow ask a GTK widget to draw itself on Cairo surface? A code sample would be much appreciated, since I am a newcomer to both GTK and Cairo. Python is my language of choice.I would like to save the looks of a GTK window,