isFinished
A convenience function to find out if the print operation is finished.
a print operation is finished if its status is either %GTK_PRINT_STATUS_FINISHED or %GTK_PRINT_STATUS_FINISHED_ABORTED.
Note: when you enable print status tracking the print operation can be in a non-finished state even after done has been called, as the operation status then tracks the print job status on the printer.
Return
true, if the print operation is finished.