ulfalizer / readline-and-ncurses

Example demonstrating combining of readline and ncurses

Example demonstrating combining of readline and ncurses

Features

Supports seamless and efficient terminal resizing and multibyte/combining/wide characters. (Wide characters are those that use more than one terminal column.)

One of the trickier aspects is that readline only exports the cursor position as a byte offset (rl_point), which won't correspond to the correct terminal cursor column for many strings with special characters. We therefore have to calculate the terminal cursor column ourselves. readline itself does it as part of the default rl_redisplay() function.

Limitations

• Some invalid strings and meta characters could still cause the cursor position to be off (though it's only a visual annoyance).

• Entering multibyte characters during search (e.g., Ctrl-R) does not work, due to a readline issue. The only workaround I've found is to let readline directly from stdin instead (e.g., via a select(2) loop: The readline manual has an example program). Buffering bytes until they form a complete multibyte character (e.g., via get_wch() + wcrtomb(3)) doesn't help either.

  A neat setup on Linux is to use signalfd(2) (libevent might be a portable option) to catch the SIGWINCH generated by the terminal resize in the select(2) (or epoll(7)) loop and then calling resizeterm() and updating the windows (the manual resizeterm() is needed since we override ncurses' default SIGWINCH handler). I have a WIP that uses that approach in a branch for another project. I could push it on request.

• To keep things simple, the readline (bottom) window does not scroll horizontally. It would require some care to get special characters right.

Screenshot

The contents of the top window is set to whatever is entered. To exit, press Ctrl-D on an empty line.

License

See LICENSE.txt. SPDX license identifiers are used in the source code.

readline-and-ncurses's Issues

Disable RL completion

readline-and-ncurses/rlncurses.c

Line 284 in dcf6fb0

// Disable completion. TODO: Is there a more robust way to do this?

You should be able to do this:

char buf[64] = "set disable-completion on";
rl_parse_and_bind(buf);

Just keep in mind that the rl_parse_and_bind() parameter could not be const, or it will segfault.
So rl_parse_and_bind("set disable-completion on"); is not possible.

Use keypad keycodes in ncurses

Hello !
Your code has greatly helped me to intergrate readline in ncurses for a student project.
I would like to replicate an irssi interface for an IRC-like protocol.
I want to catch keypresses events (like F(n) keys, or shift-arrow combinaisons) in the ncurses part and not forward them to readline. The catching is done with keypad, but as you wrote:

Do not enable keypad() since we want to pass unadulterated input to readline

How can I handle special keys events in the ncurses scope, while passing unadulterated input to readline ? Is is possible ? Maybe with a inverse transformation ?
What if I do keypad, then test if its a special char, if so disable keypad and somehow ungetch the character ?

Or is the only solution to wait and watch for the sequence of unadulterated input ? ncurses.faq.html#modified_keys

Thank you for your time.

PS: can I use your code ? Is is MIT licensed ?

Multiline input example

Would you mind adding a multiline input example?