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monome / norns

norns is many sound instruments.
http://monome.org
GNU General Public License v3.0
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add maiden UI libs (ncurses/readline) #15

Closed catfact closed 7 years ago

catfact commented 7 years ago

... obviously, but some questions:

an interesting reference for both design and implementation is actually gdb: http://sourceware.org/git/?p=gdb.git;a=blob;f=gdb/tui/tui-io.c

catfact commented 7 years ago

dc0601ba9926ac55b6356d9d580c1e550a9a86ad

tehn commented 7 years ago

does this work over ssh?

we'll also log in via uart, so 'screen' as well

On Wed, Mar 8, 2017 at 2:30 AM ezra buchla notifications@github.com wrote:

... obviously, but some questions:

an interesting reference for both design and implementation is actually gdb: http://sourceware.org/git/?p=gdb.git;a=blob;f=gdb/tui/tui-io.c

  • how does readline work over an ssh connection? my guess is that arrow keys are probably fine, function keys almost certainly fine, but ctl and meta might be complicated by client terminal / ssh server.

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catfact commented 7 years ago

yes

tehn commented 7 years ago

wonderful!

On Thu, Mar 9, 2017 at 7:25 PM, ezra buchla notifications@github.com wrote:

yes

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catfact commented 7 years ago

a more detailed answer:

in this technique, we use ncurses for all terminal IO. it passes input to readline on a per-character basis, lets readline do its editing stuff, and pulls readline's buffer for display. at the same time it can also handle output from child processes and put it in a separate window. we need this.

"does ncurses work over ssh?" yes. ssh as a network protocol is designed to pass shell signals as well as character data. the question is, will ncurses be well behaved with a given ssh server configuration, host shell configuration, and client shell? of course it depends, but in general i think that using this standard unix stack (ncurses uses terminfo and so on) is the most robust approach - it works for nano and all the other standard unix tools.

that said, there are two general issues:

  1. getting non-ascii characters across a socket (secure or otherwise), especially the meta/alt key, and combos like ctl-left, which the client terminal will often capture for its own use. that's why emacs and nano allow ESC as an alternate meta key, and stuff. this could be exacerbated on a serial connection, because not only the client shell but also the terminal emulator may be capturing or pre-processing keystrokes.

    the safe thing is to not use those key combinations, and stick to ASCII and function keys. some of readline's more advanced editing features may not work but basic things should be pretty robust.

readline is actually highly configurable. its bindings and escape sequences are determined by ~/.inputrc and /etc/inputrc, and can be overridden by environment variables. excrutiating detail available with man readline.

  1. getting window-resize signals. with telnet/SSH, the client should pass SIGWINCH to the server, which we are handling. for a serial line that might not happen. a good terminal emulator should get SIGWINCH from the client shell, and also trap resize signals from the TTY device, and negotiate between them approppriately. this is an annoyingly involved topic. here is one discussion about it.

so in the worst case maybe we won't get resize events. i should make sure the default sizes are usable (80x24 characters or something,) but this is not a big deal.