Starts to print job asynchronously. This function will ready the job for
printing and install an idle handler that will render one page at a time.
This function will not return immediately, as only page rendering is done
asynchronously. Text retrieval and paginating happens within this
function. Also, if highlighting is enabled, the whole buffer needs to be
highlighted first.
To get notification when the job has finished, you must connect to the
"finished" signal.
GTK2.SourcePrintJob()->print_range()