Re: [emacs-wiki-discuss] Re: RFC: verse tag markup and IE

[Vadim Nasardinov]

On Tuesday 04 January 2005 00:44, Sacha Chua wrote:
> >>  2. Include a configurable option to put the "br" tag at the end
> >>     of each line within verse tags, disabled by default.
> >
> > That sounds like a totally useless knob, but that may be just me.
>
> We have a fair number of non-CSS-capable browser users out here,
> myself included. I rarely use the <verse> tag, but occasionally post
> quoted snippets from mail. Does that count as a valid use for such a
> knob?  <grin>

First of all, let me prefix my comments by saying that you guys have
done and are doing a terrific job with emacs-wiki and planner --
way better than anything I could have written myself.

On to your question.

Yes, it's a valid use case.  Is the proposed knob the best way to
address this use case?

If the intention is to provide two distinct output markups -- one for
CSS-enabled and another one for disabled browsers -- then a better
abstraction would be to give users a single switch that does just
that.  Toggle it to "css-on" or "css-off" depending on your target
audience.


Now, I may have misread Michael's original post, but here's what it
sounded like to me: You want to publish for a CSS-challenged browser,
go ahead and toggle these fifty switches over here.  (Because
special-casing the <br> tag is just the first step down a slippery
slope.)

So, if you anticipate having to support many corner cases like <br>,
then providing a single CSS on/off switch might be a good idea.

As long as we're only dealing with this pesky <br> thingy though, an
arguably better idea is to try and output markup that degrades
gracefully.  I'm not convinced yet that this is impossible.  As far as
I can tell, the purpose of the <verse> tag is to produce output markup
that maintains line breaks but doesn't use a fixed-width font.

The following works regardless of CSS:

 | <p>
 | `Twas brillig, and the slithy toves<br/>
 |   Did gyre and gimble in the wabe:<br/>
 | All mimsy were the borogoves,<br/>
 |   And the mome raths outgrabe<br/>
 | </p>

Michael says this is not valid XHTML though.  Ok.

The following works, but doesn't meet the requirement of displaying in
a non-fixed-width font on non-CSS browsers.  As far as I'm concerned,
not a big deal.

 | <pre class="verse">
 | `Twas brillig, and the slithy toves
 |   Did gyre and gimble in the wabe:
 | All mimsy were the borogoves,
 |   And the mome raths outgrabe
 | </pre>

If the non-fixed-width font requirement is crucial for some reason,
then this should work:

 | <blockquote class="verse">
 | <p>`Twas brillig, and the slithy toves</p>
 | <p>  Did gyre and gimble in the wabe:</p>
 | <p>All mimsy were the borogoves,</p>
 | <p>And the mome raths outgrabe</p>
 | </blockquote>

Again, the linespacing would be less than ideal on non-CSS browsers,
but so what.


Speaking more generally, if you are going to support two distinct
outputs, then a more systematic approach is in order, IMHO.  Something
like a two-phase transformation.  Firstly, parse the wiki markup into
an AST.  Secondly, transform the AST into the final output markup,
based on the user's stated preferences.


Let's see if I can summarize this.

Special-casing the <verse> case strikes me as suboptimal.

On the flip side, being able to produce different outputs a la Muse is
a fine goal, but one that would probably require a fairly massive
rewrite of emacs-wiki.


Vadim