the remaining font-sub issue

[Lofton Henderson <lofton@rockynet.com>]

BACKGROUND:
=====

Airbus asked for font-sub capability that is equivalent to a priority
list of fallbacks.  Essentially:
1st-choice, 2nd-choice, ...., last-choice.

So for example, using the terminology of Ch.9 of WebCGM 2.1 CD01:
<cgmFont>Helvetica</cgmFont>
<displayFont>Arial, Swiss, san-serif</displayFont>

If Arial is present, use it; else use Swiss; else use any san-serif
font.  (Note that "Helvetica" could in fact be the first
name in the list.)  This has the characteristic of building some OS
independence into the font-sub.

This is equivalent to (taken from?) the CSS syntax, including the sort of
generic specification like "san-serif".  (WebCGM has not
yet endorsed that concept on the font-sub file.  Though such
generics are part of the required support of the CGM:1999 Font Properties
element.) 

On Wednesday, after much discussion, we could agree ONLY on the minimal
font-sub capability that is the intersection of all vendors' private
font-sub support:  a single unconditional displayFont name, with a
default in case that failed.  This has the characteristic of
increasing the OS dependence of the font-sub file.  I.e., with the
same viewer on different operating systems, one would typically have
different font-sub directives.

Today we resolved a number of details of the syntax, such as the
normalization rules for <cgmFont> and <displayFont>
names.  

The ISSUE(s):

Then this question came up:

Suppose the CGM FONT LIST element contains Helvetica, and font-sub file
contains:

<cgmFont>Helvetica</cgmFont>
<displayFont>Arial</displayFont>
<cgmFont>Helvetica</cgmFont>
<displayFont>Swiss</displayFont>

How should this be processed?  CD02 does not say.  Two
choices:
a.) first match wins.  In other words, the font-sub engine stops
looking for a match for Helvetica as soon as it finds the first match,
and substitutes "Arial" for display.
b.) last match wins.  In other words, the font-sub engine processes
the entire file, and in this case substitutes 
"Swiss".

#a is functionally equivalent to the CSS syntax and the Airbus
request.  Discussion ended without a decision.  But there did
seem (correct me if this is wrong) to be some vendor willingness to
implement #a if that's what the group wants.

ISSUE 1:  Which of the effects, #a or #b, should WebCGM 2.1 font sub
syntax support?

ISSUE 2:  If #a is chosen, then should WebCGM instead just specify
the list syntax for the displayFont element, for example:
<displayFont>Arial, Swiss</displayFont>
(It is more direct and obvious what is being requested.)

As agreed today, this is to be addressed and resolved (vote or strawpoll)
first thing Friday morning.

Regards,
-Lofton