[rfc-i] The <tt> train wreck

Martin Thomson mt at lowentropy.net
Mon Aug 16 14:59:15 PDT 2021

On Mon, Aug 16, 2021, at 19:09, Carsten Bormann wrote:
> I find a zero-width space (U+200B) on 0x0100-​0x01ff 

Ah, I forgot which it was, you are right.

> So you would prefer 0x0100-<preferentially-break-here/>0x01ff or some such?

Neither.  The table layout should handle hyphens as it would in regular flow, with an override needed to suppress that behaviour.  It appears as though hyphen/punctuation breaks are not considered when doing an initial pass on column width calculations.  That said, I appreciate just how challenging it is to do this sort of thing and don't see a fix as high priority, so I can tolerate the hack.

> (Do you mean the Phrase “BCP 14”, which should have an nbsp in it, or 
> do you mean <bcp14>MUST NOT</bcp14>?)

I meant the phrase "BCP 14".  In LaTeX source we would have "BCP~14".  I am ambivalent on whether to discourage breaking within bcp14 elements.  They seem OK with their current implementation.

> The boilerplate says “BCP 78” without no-break as well.


> Note that RFC 9087 has six occurrences of “AS path”, only one of which 
> is nbsp-protected (but the example pathes after three of them are).

> Note that there are several aspects of horizontal no-breaking:
> — turn blank space into no-break spaces etc.
> — don’t allow breaking after characters such as / @ & | - + # % :
> (— hyphenation no-breaking, which we don’t need as we don’t do 
> hyphenation - or should we?)

I would settle for a control that discouraged breaking at the usual places (spaces and punctuation).  I would use that for URLs, RFC numbers (like "RFC 9000", for which breaking should be avoided), and Section references ("Section 7.1" is often cause for   if constructed manually).

As for the rest, I generally only want the font change.  It appears as though you usually want a default of font+decoration.  That suggests a global switch in authoring tools might be worthwhile.  The XML can do whatever it likes.

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