GtkDrawingArea) or a GdkDrawable
(like a GdkPixmap) to a Cairo graphics
device, so that R plot commands draw to the widget/drawable.asCairoDevice(widget, pointsize = 10)GdkPixmap is useful for
buffering and transforming R graphics.
For example, one could copy the pixmap to a GdkPixbuf
and add a watermark before saving as a gif, png, jpg, etc.