real time display

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From oechslin@lrc.epfl.ch  Tue May 14 06:24:36 1996
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To: Henrik Frystyk Nielsen <frystyk@w3.org>
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In-Reply-To: Your message of "Mon, 15 Jan 1996 17:03:36 EST."
             <9601152203.AA21989@www20> 
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Date: Tue, 14 May 1996 12:24:26 +0200
From: Philippe Oechslin <oechslin@lrc.epfl.ch>

> Philippe Oechslin writes:

> > Dear Henrik,
> > 
> > I am looking for sources of a web agent to implement some ATM
> > extensions we are developing
> > (http://lrcwww.epfl.ch/WebOverAtmDir/about_woa/bb96.ps)
> > 
> > Is it possible to get the sources of Arena for this purpose? 
> 
> Yes, the Arena sources are now available at
> 
> 	http://www.w3.org/pub/WWW/Arena/beta-1
> 
> Good luck - and of course - we are more than happy for getting diffs back ;-)

Henrik,

Here is a first set of diffs. They implement an extension to arena
which allows to pipe data directly into external viewers instead of
first saving them into a file. 

This is very usefull if you have a server that sends audio or video in
real-time, or even faster as they need to be displayed. 

 (Our ATM extensions will allow to open an ATM connection which
  guarantees that you have the necessary bandwidth to send the document,
  but that patch is expected only in a month.)

You can find the patches (3 little diffs) and the README file at

  http://lrcwww.epfl.ch/WebOverATM/tools/real_time/index.html

You are more than welcome to include them in further releases of
arena.

  cheers,

    Philippe


BUG ALERT: While implementing the extension we have come around the
following bug:

  description: system-wide mailcap files override userdefined ones.

     platform: any platform.

  explanation: In mailcap.c, if no MAILCAPS variable is defined in the
               environment, a list of mailcap file names is built,
               using arenas defaults in the beginning of the
               list. The filename $HOME/.mailcap is appended to the
               _end_ of the list:

mailcap.c, register_mailcaps()
>    s = getenv("MAILCAPS");
>    if (s)
>        mailcaps = strdup(s);
>    else {
>        mailcaps = strdup(MAILCAPS);
> 
>        home = getenv("HOME");
>        if (home) {
>            StrAllocCat(mailcaps, ":");
>            StrAllocCat(mailcaps, home);
>            StrAllocCat(mailcaps, "/.mailcap");
>        }
>    }

               For each filename in the list, the corresponding
               mailcap file is parsed and the corresponding
               conversions are registered if HTCheckPresentation
               returns true.

mailcap.c, register_mailcap(..)
>
> if (HTCheckPresentation(context->conversions,content_type, quality))
>     HTSetPresentation(context->conversions, content_type, 
>                       view_command, test_command, 
>                       quality, 0.0, 0.0);

 
               However, HTCheckPresentation returns false if a
               conversion is already registered with the same
               quality. Thus, if a user had redefined a viewer in his
               $HOME/.mailcap file with the same quality as in the
               system-wide file (eg. no quality, which defaults to
               0.5) then the users definition is not registered.

bridge.c:
> BOOL HTCheckPresentation(HTList * conversions, char * content_type, 
>                          double quality)
>{
>    HTList *l = conversions;
>    HTPresentation *p;
> 
>    while (p = (HTPresentation *)HTList_nextObject(l)) {
>        if (strcmp(content_type, p->rep->name) == 0) {
>            if (p->quality < quality)
>                return TRUE;
>            else {
>                if (MAILCAP_TRACE)
>                    fprintf(stderr,
>                            "HTCheckPresentation returning FALSE for %s\n",
>                             content_type);
>                return FALSE;
>            }
>        }
>    }

 Proposed fix: Either replace 'if (p->quality < quality)' in
               HTCheckPresentation by 'if (p->quality <= quality)'

               or 

               Change register_mailcaps() in such a way that it puts
               the user-defined files before the system-defined files
               in the mailcaps variable.

 
- --
Philippe Oechslin                                    
mailto:oechslin@di.epfl.ch
Laboratoire de Reseaux de Communication (LRC)         Phone:  +41(21) 693 66 
16
Swiss Federal Institute of Technology (EPFL)            Fax:  +41(21) 693 66 
10
CH-1015 Lausanne, Switzerland                   http://lrcwww.epfl.ch/~oechsl
in


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-- 
Henrik Frystyk Nielsen, <frystyk@w3.org>
World-Wide Web Consortium, MIT/LCS NE43-356
545 Technology Square, Cambridge MA 02139, USA

Received on Wednesday, 15 May 1996 11:44:04 UTC