Re: LYNX-DEV text/html;q=0.000: some implementation doc

[David Combs]

KLAUS -- you're "chosen"!

This is just about the FIRST documentation of how program works,
something about data-structures, etc, that I have seen on the list
(other than good stuff by Fote, I think I'd better add. <smiley>).

Seems like you have an ability with the written word re documentation.

Maybe (maybe not) you have time to do more (much more).

At any rate, THIS email that you sent should get it's subject
line relabeled "... implementationDoc" or "IDoc" or some such
that can be found easily in archive.

Maybe some others (who also KNOW the program) can write up
some stuff too.  Especially that ties what the user sees & does
& can do to how lynx implements it.

History would also be good, for those who know it.  Would give
an understanding to why variable/func names DO make sense -- for
an earlier version, that is -- leading to better understanding NOW.

NICE DOC, klaus!

---------------------------------------------------

> From address@hidden Sun Dec  1 20:36:31 1996
> Date: Sun, 1 Dec 1996 22:13:32 -0600 (CST)
> From: Klaus Weide <address@hidden>
> To: Rob Hartill <address@hidden>
> cc: address@hidden
> Subject: Re: LYNX-DEV text/html;q=0.000
> In-Reply-To: <199612020101.BAA19451>
> MIME-Version: 1.0
> Content-Type: TEXT/PLAIN; charset=US-ASCII
> Sender: address@hidden
> Errors-To: address@hidden
> Precedence: bulk
> Reply-To: address@hidden
> 
> On Mon, 2 Dec 1996, Rob Hartill wrote:
> 
> > Klaus Weide wrote:
> > 
> > >On Sun, 1 Dec 1996, Rob Hartill wrote:
> > >
> > >> Hi,
> > >> 
> > >> why do so many Lynx users have it set to send "text/html;q=0.000" ?
> > >
> > >Ah, have they?  This is the first time I hear about that.
> > 
> > I've seen ~5 in as many days. Always Lynx.
> > 
> > One location found that they'd send that string with Lynx 2.6 but not 2.5
> 
> >[...] 
> > my 2.6 behaves.
> 
> So do mine :)
>  
> > > - Lynx does it by mistake a.k.a. bug
> > 
> > possible. It might be pulling in extra Accept info from other source
> > on the user system ?
> [...] 
> > I think 2.6 is perhaps grabbing more user info from somewhere.
> 
> The places from where it "grabs" info about media types:
> 
> (1) some are hardwired in src/HTInit.c (and some of those depend on whether
>    Lynx is running under X, i.e. DISPLAY variable set at startup, or not)
> (2) the lynx.cfg file
> (3) a global (system wide) mailcap file 
> (4) a personal .mailcap file
> The names for the last two can be configured in lynx.cfg or userdefs.h.
> 
> Lynx internally constructs a list of all media types that it knows about.
> Actually, to be more exact, a list of possible conversions from one
> media type to a target media type, where the target type most often
> is an internal one like "www/present".  "converting" e.g. "text/html"
> to "www/present" means parsing the HTML and presenting to the user.
> 
> Those conversion also have a quality factor defined - normally it is 1.0.
> 
> When constructing a HTTP request, Lynx walks through that list and
> creates an Accept header from those entries that have a conversion to
> "www/present".  Each entry in the Accept header will also have the ";q=..."
> _IF_ the quality factor is < 1.0.  A catch-all "*/*;q=0.001" is appended 
> at the end.
> 
> The quality factor stuff was added between Lynx2.5 and Lynx2.6.
> It is not possible to specify one for viewers defined in lynx.cfg.
> It is posssible to do it for viewers (helper apps) defined in one of
> the mailcap files, and it is documented in the sample mailcap file
> distributed with Lynx.
> 
> But now to the mystery: there is no way that a user could specify a
> quality factor of 0.000 for text/html via one of the mailcap files.
> First of all, Lynx tries to completely skip extries for text/plain and
> text/html from those files.  There is also the following test:
> 
>                 mc->quality = atof(eq);
>                 if (mc->quality < 0.001)
>                     mc->quality = 0.001;
> 
> (This is both implemented in src/HTInit.c.)  Third, the header lines
> you gave show that the media types with a bogus ";q=0.000" appended
> are from the settings done internally, i.e. (1) from the (1)-(4) listed
> above.
> 
> Here is one of those lines (from src/HTInit.c) that add an entry to the list:
>  HTSetConversion("text/html", "www/present", HTMLPresent,    1.0, 0.0, 0.0, 
> 0);
> That one somehow gets a bogus ";q=0.000" setting in your examples.  But
> the 1.0 is the argument setting the quality factor.  So, big mystery.
> 
> Do those client sites where Lynx2.6 emits such headers have something 
> in common?  Platform or compiler etc.  
> Is it the official Lynx2.6 they are using?
> 
>     Klaus
> 
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