A rendering filter uses the
IPrintPipelineProgressReport interface to send progress status to a spooler.
A rendering filter should search for the XPS_FP_PROGRESS_REPORT property in a property bag, get the progress, and then remove it from the property bag. If there are no rendering filters, the filter pipeline sends the notifications to the spooler. It is very important for a rendering filter to remove the progress and send progress status to the spooler; if progress status is not handled correctly, the spooler may get conflicting progress reports.
IPrintPipelineProgressReport has one method: