Path: utzoo!yunexus!torsqnt!dptcdc!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!pasteur!ames!oliveb!apple!casseres
From: casseres@Apple.COM (David Casseres)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Need for PrGeneral in printer drivers.
Message-ID: <880@internal.Apple.COM>
Date: 8 Mar 89 18:48:04 GMT
Article-I.D.: internal.880
References: <12534@dartvax.Dartmouth.EDU> <873@internal.Apple.COM>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 30

In article <873@internal.Apple.COM> IanHendry@apple.com (Ian Hendry) writes:

>You are correct, I should have said, it "sometimes will refuse."  I don't 
>know exactly what the circumstances are myself.  Just for fun, take the 
>imagewriter driver and remover PDEF 7 (PrGeneral) with ResEdit.  Now try 
>to print in HyperCard.  It will give you an error message about "version 
>2.5 or later."  This printer driver is otherwise totally functional (try 
>printing from the finder for example).  Now for fun try "ImageSaver" which 
>is part of SuperGlue.  You get a different error, same problem.  Now put 
>the PDEF 7 from the ImageWriter into the ImageSaver which does not have a 
>PDEF 7 (this is not for use, just to see what HyperCard will do) and 
>HyperCard no longer objects.

Here's what's going on.  The system glue that handles printing calls attempts
to load PDEF 7 and fails, so it returns an error to the application (I forget
which error, but it's documented).  At this point the application is just
required to not crash or do anything real dumb.  Some applications will just
go ahead and print, but others (like HyperCard) may decide that it just has
to have PrGeneral.  Some applications may make this a printer-dependent
requirement, e.g. "if the printer is an ImageWriter it has to have PrGeneral,
but if it's a LaserWriter it doesn't have to."

><PrGeneral were a necessary part of the printer resource file.  Since
><there has been no official word on this as yet, I assume for now that
><it is not necessary, however.

Printer drivers do not have to implement PrGeneral; that's why the error-
message return is documented.

David Casseres