public Pixbuf? wait_for_image ()
Requests the contents of the clipboard as image and converts the result to a Pixbuf .
This function waits for the data to be received using the main loop, so events, timeouts, etc, may be dispatched during the wait.
a newly-allocated Pixbuf object which must be disposed with unref, or null if retrieving the selection data failed. (This could happen for various reasons, in particular if the clipboard was empty or if the contents of the clipboard could not be converted into an image.)