Re: [groff] 04/05: {g, n}roff.1.man: Give assistance to pager users.

[Ingo Schwarze]

Hi Branden,

G. Branden Robinson wrote on Sun, Jun 30, 2019 at 05:11:48AM +1000:
> At 2019-06-29T18:13:57+0200, Ingo Schwarze wrote:

>> On top of the above, i consider that
> [telling pagers to interpret ISO 6429 escape sequences]
>> bad advice.  If you think people need to be told about roff's bad
>> habit of defaulting to SGR escapes, then let's recommend groff(1) -c
>> rather than less(1) -R.
> [...]
>> Same point again: please recommend groff(1) -c rather than less(1) -R.

> I could not disagree with you more about this.
> 
> Video display terminals simply are not paper teletypes.  They just
> aren't.  The technology is radically different.  You can't
> constructively overstrike, for one thing.

Sure, paper teletypes is what backspace encoding historically comes
from.  But that doesn't mean its usefulness is restricted to
paper teletypes.  In fact, modern pagers handle it just fine.

> (Not without special support, hence supplementary attributes on
> character cells that indicate bold and/or underlining).
> 
> By your reasoning, there's no point supporting UTF-8 because there is no
> teletype device in the entire world with a typeball large enough to
> strike all the defined code points in Basic Multilingual Plane.

That's a non sequitur because i didn't say "use backspace encoding
because nothing except paper teletypes matters"; i intended to say
"use backspace encoding because it does the job for most use cases
and avoids the risks involved in allowing terminal escape sequences
in your pager".  Additional risks from using UTF-8 exist, too, but
they are relatively minor.

And yes, if you desire coloured output or true italics, then of
course you do need SGR escapes and live with the risk *and* somehow
make sure your input to the pager is properly sanitized, just like
you do need UTF-8 when you want to use non-ASCII characters.


All that said, and given that SGR encoding was already made the
default in groff at some point in the past, there may not be
consensus in the groff community for recommending -c more strongly,
so just describing both modes neutrally, as you did, is probably
OK after all.

Yours,
  Ingo