Re: Triple modifier combinations and extra keys

[Thomas Dickey]

On Wed, Oct 28, 2020 at 08:11:30AM +0100, michal@kast.net.pl wrote:
> Greetings!
> 
> Lately I have read some sections of NCurses FAQ and XTerm FAQ in search
> of knowledge about key modifiers. Learned that XTerm can and does emit
> sequences for ctrl + alt + shift + (key), like for what could be kDC8.
> Telling NCurses about those with define_key() works as expected. If this
> is documented why neither NCurses nor XTerm carry the definitions in
> terminfo?

There's more than one reason.  Offhand:

a) until ncurses 6.1, ncurses would limit (for compatibility) terminfo
   entries to 4096 bytes.

b) for compatibility, the preferred scheme for representing the modified
   function-keys has been by assigning them to the predefined numbered
   kf1 through kf63 (should have been kf0, but again, compatibility...).

   That's usually
        kf1-kf12 (no modifiers)
        kf13-kf24 (shift)
        kf25-kf36 (control)
        kf37-kf48 (shift+control)
        kf49-kf60 (alt)
        kf61-kf63 (shift+alt)

   So that runs out before getting to three modifiers.

c) I could just generate (whatever would fit in 64kb), but that has a few
   drawbacks:

   a) it would be slower to load

   b) very few people would use (and benefit by) it

   c) half of the xterm-alikes don't really work for that anyway

Given the drawbacks, I'd make a terminal description with a different
name, for the people who might use it.
 
> The other discovery is about so called multimedia keys. I have several
> of those in my keyboard. Some like calculator or www key are straight
> eaten by terminal emulators and nothing is offered in return.
> 
> My problem is with those that do send sequences. For example menu key
> is consistently emitted as F16 but ways to get F16 are not so. In XTerm
> F16 is obtainable by shift + F4 while in URxvt this is shift + F6. In
> practice giving user option to use menu key for a function means I need
> to have both shift + F4 and shift + F6 unbound to avoid collisions.
> I would like to learn about other such possible conflicts. Is there a
> list of supported multimedia keys available anywhere? I could not find
> anything relevant in NCurses or XTerm FAQ.

no - it's dependent upon the keyboard configuration,
and the people who develop that stuff don't produce useful documentation.

A few configurations are enough alike to make the terminal descriptions useful.

-- 
Thomas E. Dickey <dickey@invisible-island.net>
https://invisible-island.net
ftp://ftp.invisible-island.net

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