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From: thomson@cs.utah.edu (Rich Thomson)
Newsgroups: comp.graphics
Subject: Re: PHIGS display priorities
Summary: use INQUIRE NUMBER OF DISPLAY PRIORITIES SUPPORTED
Keywords: PHIGS, PPOST, display, view, priority
Message-ID: <1990Jul19.132055.19475@hellgate.utah.edu>
Date: 19 Jul 90 19:20:55 GMT
References: <6722@vax1.acs.udel.EDU>
Distribution: usa
Organization: Design Systems Division, Evans & Sutherland Computer Corporation
Lines: 31
X-Local-Date: 19 Jul 90 12:20:55 PDT
Disclaimer: We use PEX on the ESV workstation, but I do not speak for E&S.

In article <6722@vax1.acs.udel.EDU> gilmore@vax1.udel.edu
    (Scott Gilmore) writes:
>Does anyone know what the PHIGS standard defines as the structure display 
>priority range (last argument to PPOST in Fortran binding)?
>through the official ANSI functional description, as well as the October 1987
>draft ANSI Fortran-PHIGS binding document, and cannot find any mention of the
>valid range.

The routine INQUIRE NUMBER OF DISPLAY PRIORITIES SUPPORTED returns an
integer indicating the number of display priorities supported.  If the
integer is zero, the workstation can support an arbitrary number of display
priorities.  If the integer is non-zero, then that is the number of display
priorities supported by the workstation.

Now of course, this doesn't tell you the accepted range for the floating
point argument to POST STRUCTURE.  This may be a shortcoming of the
standard document in that this is not clearly defined.  My understanding
(which could be flawed ;-) is that the values  of the floating point
parameter are unconstrained, but the *number* of different priority values
you can post a structure with are returned by INQUIRE NUMBER OF DISPLAY
PRIORITIES.  It could very well be that this is the case and the PHIGS
implementations you mention in your post are not strictly adhering to the
standard in this fashion.

PHIGS as a standard is complex enough that getting all the nooks and
crannies filled is quite a task, so these kind of deviations from the
'standard' are not to be interpreted as sloppy work of the implementor.

						-- Rich
Rich Thomson	thomson@cs.utah.edu  {bellcore,hplabs,uunet}!utah-cs!thomson
``If everybody is thinking the same thing, is anybody thinking?'' --Bob Johnson