Typical Printing Process Scenario Using an EMF Spool File

This section illustrates the major relationships between the print spooler components, the printer driver, and GDI during the printing process using an EMF spool file. The presented scenario walks through the sequence of calls between components during the spooling of an EMF spool file and subsequent playback (despooling) of the file on a bidirectional printer.

The spooling and despooling of a raw file is a simpler scenario to walk through than the spooling and despooling of an EMF file, so you may want to read the raw file spooling and despooling scenario before you read this one. The raw spool handling scenario is described in Typical Printing Process Scenario Using a Raw Spool File.

If the raw spool file scenario is simpler, you might ask the question, "Why would an application want to use EMF spool files instead of raw spool files?" A set of EMF files (each EMF file is a logical representation of a printed page) are

• More portable than raw files -- the same EMF file can be printed on any number of printers whereas a particular raw spool file can only be printed to one printer model.
• The set of EMF files that represent all the pages in a print job are typically smaller in size, all together, than a raw file that contains the same print job.

Note that an application may not want to request EMF spooling if it is sending a print job to a PostScript printer because a PostScript raw print job is already condensed compared to a raw print sent to a raster printer.

Also, an EMF file is not always smaller than the comparable raw print file. This may especially be true for pages that are heavily-laden with shaded graphics. An application may want to use EMF spool files even in this case, because the return of the print spooler subsystem to the application will still be quicker in the EMF spool file case than the raw spool file case.