— Indicate how much of the processing task has been completed and reports on any abort status.
- effectInstance - the instance of the plugin this progress bar is
associated with. It cannot be NULL.
- progress - a number between 0.0 and 1.0 indicating what proportion of the current task has been processed.
- the progress object was successfully updated and the task should continue
- the progress object was successfully updated and the task should abort
- the progress handle was invalid,