Re: Tabstop width not reset by reset command, or hardcoded to wrong width

[Vincent Huisman]

On 26-05-2019 16:39, Thomas Dickey wrote:
> Offhand, using hard-resets in rs1/rs2 would reinforce that assumption,
> and eliminate the overhead of constructing tab-stops to make "it" match
> the user's expectations.  You see, the documentation says that "it" matches
> the power-up behavior.  It doesn't tell ncurses to initialize it to that
> value.

This is in reset_cmd, I assumed that that's not called on whatever 
initialisation, but only on actual calls to the reset utility? I have 
little experience with the inner workings of ncurses so I'm not up to 
speed on the "init sequence". Reading the man page on reset, I see that 
reset does nothing with tabs because tset does the initialisation, even 
though it says that it should reset the terminal modes to "sane" values, 
so I guess that should include clearing any messed-up tabstops. I'd say 
that if you're seeing it as two different things, reset should do 
reinitialisation of tabs as a separate action from whatever it is that 
tset might do later on. That way you can still avoid the tabstop 
construction in tset but restore the original power-up behaviour (as per 
terminfo) on reset. At least, that's what I'd expect from reset.

> The one example with "it" to a value other than 8 is interesting, in part
> because it won't work as documented above since it lacks the set/clear
> capabilities for tab stops.  (If the entry were for something that people
> _use_, I'd investigate and fix, but since the system's defunct, it's only
> of academic interest).

But what I'm mostly trying to focus on is that the tab initialisation 
code only runs for init_tabs!=8. The vast majority of terminals in the 
standard terminfo database have init_tabs=8 so for those terminals it 
basically means that you could replace the entire function body by 
"return FALSE;". So that's on terminals that people _use_, like xterm 
and linux:

Actual behaviour on clean TERM=linux:
$ tabs 2 > accidental_binary_file; echo -e "\ta"
        a
$ cat accidental_binary_file; echo -e "\ta"
  a
$ reset; echo -e "\ta"
  a

Expected behaviour:
$ reset; echo -e "\ta"
        a

Seeing that you seem to say that the reset_tabstops() call is supposed 
to be a tset-only thing and not a reset-thing, that would imply that 
reset needs its own reset_tabstops function (independent from tset) that 
is always executed as long as the terminal supports ct/st.

Regarding reset_tabstops in tset, the value of init_tabs on its own says 
nothing about the terminal capabilities as far as I can tell, so if 
you're trying to avoid running code on terminals that have specific 
features then you should check for those specific features rather than 
this unrelated variable.

Am I making sense, or am I misunderstanding this completely?

Sincerely,

Vincent Huisman