Re: wsvt25 backspace key should match terminfo definition

[Valery Ushakov <uwe%stderr.spb.ru@localhost>]

On Tue, Nov 23, 2021 at 18:37:19 -0500, Greg Troxel wrote:

> Valery Ushakov <uwe%stderr.spb.ru@localhost> writes:
> 
> > vt52 is different.  I never used a real vt52 or a clone, but the
> > manual at vt100.net gives the following picture:
> >
> >   https://vt100.net/docs/vt52-mm/figure3-1.html
> >
> > and the description
> >
> >   https://vt100.net/docs/vt52-mm/chapter3.html#S3.1.2.3
> >
> >   Key               Code    Action Taken if Codes Are Echoed
> >   BACK SPACE        010     Backspace (Cursor Left) function
> >   DELETE            177     Nothing
> 
> That is explaining what the terminal does when those codes are sent by
> the computer.  That is a different thing from how the computer
> interprets user input.

No. Or rather not only.  Please, read the sentence before that table.
The "code" column is the code that the terminal transmits when the key
is pressed:

  Table 3-4 lists the function keys, the code they transmit to the
  host, and the terminal action taken if the code is echoed back to
  the terminal.


> When using a VT52 on Seventh Edition, for example one pushed DEL to
> remove the previous character, and the computer woudl send
> "<BS><space><BS>" to make it disappear and leave the cursor left.  One
> basically never pushed BS.

It dawned on me that the terminals I used on the pdp-11 clone were
(not surprisingly) vt clones and managed to find a picture of the
keyboard, which jogged my memory:

  http://www.leningrad.su/museum/show_big.php?n=1539

so yeah, you would use DEL key on those to correct your typing
mistakes.


> > But vt200 and later use a different keyboard, lk201 (and i did use a
> > real vt220 a lot)
> >
> >   https://vt100.net/docs/vt220-rm/figure3-1.html
> >
> > that picture is not very good, the one from the vt320 manual is better
> >
> >   https://vt100.net/docs/vt320-uu/chapter3.html
> >
> > vt220 does NOT have a configuration option that selects the code that
> > the <X] key at the upper right corner sends.  It's always ^? (\177).
> 
> So that is the "DEL" key, not the BS key.

See, this is exactly why I said "<X] key" - because DEL and BS are
loaded names that are also used as the names of ascii codes and then
there's codes generated by the keys and what terminal does when it
receives them.  Hence all the confusion.

Let's say: "kbs" is the code sent by the <- key, whatever the keycap
looks like.

-uwe