bug#33749: 26.1; input-decode-map to empty vector should preserve echo area

[Yuri Khan]

On Sat, Dec 15, 2018 at 1:58 PM Eli Zaretskii <eliz@gnu.org> wrote:

> […] if you want to propose a new feature in this area, I very
> much prefer to trigger such a feature by some (new) variable that is
> bound to a special value, rather than base the feature on decisions
> made by some modified logic.  Doing this by such a variable might be
> slightly less elegant and general, but OTOH it runs a much lower risk
> of causing unintended consequences elsewhere.

Okay. So, amended proposed course:

* Add a variable such as ‘input-decode-preserve-echo’, boolean,
default nil, that controls the following behavior changes.

[any better ideas on the naming?]

* If the above variable is true
> > and ‘read_key_sequence’ detects that the whole key sequence has been
> > rewritten to an empty sequence, return -1.
> >
> > * In ‘command_loop_1’, save the echo area contents before calling
> > ‘read_key_sequence’.
Afterwards, if ‘input-decode-preserve-echo’ is true and the return
value is -1, restore the echo area contents.

* In the future ‘terminal-init-xterm-kitty’ function, set
‘input-decode-preserve-echo’ to true when full keyboard mode is
requested.


An alternative way could be to add hooks at start of
‘read_key_sequence’ and at each each sequence rewrite, but IMO that
would be excessive.