Re: [help-texinfo] underlining a word?

[Gavin Smith]

On 27 November 2016 at 18:23, Alfred M. Szmidt <address@hidden> wrote:
>    >    > Couldnt find anything in the manual, but how do you underline a 
> word?
>    >
>    >    You don't, not in Texinfo.
>    >
>    > I have no idea what that is supposed to mean.
>
>    Sorry, I thought it was clear.
>
> So "can't" (right now), not "don't".  Would it be difficult/possible
> to add something like @underline or @ul?  For TeX and HTML this would
> easy, not sure what would happen in Info, and other formats.
>

Following the example of @b, @sansserif, and so on, if it was
implemented, underline would likely do nothing at all in Info.

It can be implemented if it is desirable; the real problem is whether
it is desirable.

In favour:
* Some authors may find a use for it
* Other commands for text styling exist already

Against:
* Texinfo source is ideally "semantic", specifying the meaning of
texts without specifying details like font, style or layout.
* An extra command is a burden to maintain in anything that processes
Texinfo in the future, for the purpose of maintaining compatibility
with any input that uses this command. (For example, I wish
@definfoenclose had never been invented. It is not a huge burden, but
a waste of time nonetheless, but I can't justify getting rid of it
either.)
* There are complications like what are the interactions between
underline and other commands: like is there such a thing as bold
underline, or bold underline typewriter italic (some combinations are
possible, others aren't).
* Texinfo has in general a lack of customizability and extensibility.
Even if underlining is added, the number of other possible features
that could be added is limitless. Coloured text, for example, or
Fraktur.
* Underlining doesn't really seem necessary in a manual. If it was
something that a lot of people needed, we could add it.

It would be nice to have some kind of extensibility mechanism. One way
of doing this would be to add a command, for example @span, which
could be passed through to the output format in some form, enabling
further processing by tools to add styles to the marked text. For
example, if the LaTeX backend is ever done, this would allow any of
the styling options provided with LaTeX. Similarly for HTML and CSS.
This proposal only covers text styling: someone was asking a few days
ago about vertically centring images, which I can't think how it could
be achieved in a good way: probably by marking the image in a way that
would allow post-processing of the output after the Texinfo tools are
finished.

The idea here is to allow extensibility without implementing all of
that in Texinfo, because that would be painful, probably not done very
well and would always be incomplete.