Re: Add five new escape sequences to wscons

[Crystal Kolipe <kolipe.c%exoticsilicon.com@localhost>]

On Mon, Jan 16, 2023 at 08:20:35PM +0300, Valery Ushakov wrote:
> On Mon, Jan 16, 2023 at 09:18:53 -0300, Crystal Kolipe wrote:
> 
> > It's useful, because these sequences correspond to the terminfo
> > capabilities rin, indn, vpa, hpa, and cbt as defined in the xterm
> > terminfo entry.  With these sequences implemented, it becomes
> > slightly more practical to set TERM=xterm when connecting to remote
> > systems that don't have a comprehensive terminfo database.
> 
> Why is is desirable to set specifically TERM=xterm instead of, say,
> vt220, or whichever vt entry describes wscons the closest?

The xterm entry supports colour, which vt220 does not.

Remote systems vary in the entries they have available in their terminfo
database.  In the vast majority of cases it can be expected that they
will have an accurate entry for xterm.  Wscons is already almost usable
with the xterm control sequences, and the five I've added are enough to
make many curses based programs just work.

> For multi-line scroll the patch just calls scrollup/scrolldown, but
> that's not what the single-line scroll commands do (see
> wsemul_vt100.c)

The single-line scroll commands are concerned with moving the cursor.

The multi-line scroll commands, as far as I understand, are supposed to
scroll the entire screen, (or the scrolling region).

With my patch, the behaviour of wscons matches that of xterm for these
sequences.

> I'm actually not entirely convinced that it's even correct to describe
> vt220 as having sf/ind scrolling capabilities, b/c the vt220 scrolling
> sequences take the scrolling region into account and the terminfo
> capabilities for scrolling are defined to operate on the whole screen
> as far as I can tell.

Again, xterm does take into account the scrolling region when interpreting
these sequences, so I patched wscons to do the same.

> So in its current form I don't think this patch is suitable and I'm
> not convinced it's needed at all.

If there is really no interest then I'll drop further work on this.  I've
got other patches in progress for wscons so it would be nice to know.

But I don't think that your arguments are very convincing, unless you are
saying that xterm is also wrong in it's emulation, or there is a bug in my
patch that I am not aware of.