A proposed scheme for parsing preformatted alt text

[mbays at sdf.org]

* Monday, 2020-09-07 at 22:15 +0200 - Sandra Snan <sandra.snan at idiomdrottning.org>:

>This feels like the "hot comment" antipattern. Codifying a part of the
>language that was meant for humans.
>http://wiki.c2.com/?HotComments

Yes. IIUC, gemtext deliberately avoided having a comment line type in 
order to avoid this problem. It was designed to be non-extensible. But 
preformatting toggle lines -- both the opening ones we're talking about 
here, and (to my mind even more worryingly) the closing ones -- seem to 
have ended up as potential extensibility hooks anyway, because most 
clients ignore any data there. (I haven't researched this properly, but 
I checked that at least Amfora, AV-98, and Bombadillo ignore it by 
default.)

So, with apologies for hijacking this thread with something totally 
opposed to its original idea, I'd like to encourage client authors to 
close this extensibility hole by not suppressing text after the "```" in 
preformatting toggle lines.

For the opening line that means displaying the alt text by default 
somehow. Even if the alt text is primarily intended for screenreaders, 
it could well be interesting to visual readers.

For the closing line, the spec says
> Any text following the leading "```" of a preformat toggle line which 
> toggles preformatted mode off MUST be ignored by clients.
I believe the intention is that having text there is an error (though 
this could definitely be made clearer). So I suggest that when a client 
encounters some text there, it displays some sort of (unobtrusive, but 
not too unobtrusive) warning indicating that there is an error in the 
gemtext. I know that with html it's traditional for renderers to be 
forgiving about syntax errors, but since this and invalid uris are the 
only ways gemtext can be invalid, I think it makes sense to be strict. 
If most clients just ignore the error and suppress the extra text, one 
day people will start using it as an extension mechanism, e.g. embedding 
base64-encoded images.
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