Feature #13604: Exposing alternative interface of readline

• Status: Closed
• Assignee: aycabta (aycabta .)
• Target version: -

[graywolf (Gray Wolf)]

GNU Readline has multiple modes of operation. At the moment, the readline extension only supports typical, Readline.readline mode. However, there is also alternative callback-based interface which is also useful.

require_relative 'readline'

PROMPT = "rltest$ "

$running = true
$sigwinch_received = false

Readline.handler_install(PROMPT, add_hist: true) do |line|
	# Can use ^D (stty eof) or `exit' to exit.
	if !line || line == "exit"
		puts unless line
		puts "exit"
		Readline.handler_remove
		$running = false
	else
		puts "input line: #{line}"
	end
end

Signal.trap('SIGWINCH') { $sigwinch_received = true }

while $running do
	rs = IO.select([$stdin])
	if $sigwinch_received
		Readline.resize_terminal
		$sigwinch_received = false
	end
	Readline.read_char if r = rs[0]
end

puts "rltest: Event loop has exited"

Patch adding support for this is attached. This is my first try at contributing to ruby, so please tell me what I did wrong (I'm sure something, C is not my strong language).

[shevegen (Robert A. Heiler)]

All improvements to Readline are great - I can't have commandline user interfaces in ruby (on linux) without Readline these days. :)

The only thing that I think isn't too great is the use of global variables. Is it possible to get rid of them?

[graywolf (Gray Wolf)]

It should be possible. The bool is easy (I just set it on Readline module just like I do the handler block and I try to find a way to pass char * inside VALUE. I'll find a way and post updated patch.

I don't really see a benefit though, it's not like you can use Readline multiple times at once anyway, underlying C library doesn't support it (afaict).

[graywolf (Gray Wolf)]

• File readline_alternative_interface_update1.diff readline_alternative_interface_update1.diff added

I think I managed to simplify it quite a bit, if you would take a look :)

Also I'm thinking about exposing the add_hist setting, since it's saved on mReadline anyway, it would allow user to dynamicly enable/disable auto-adding of history between each invocation of read_char. What do you think?

[hsbt (Hiroshi SHIBATA)]

• Status changed from Open to Assigned
• Assignee set to kouji (Kouji Takao)

@kouji (Kouji Takao) or @nobu (Nobuyoshi Nakada)

Can you review this patch?

[graywolf (Gray Wolf)]

any update on this?

[nobu (Nobuyoshi Nakada)]

• Assignee changed from kouji (Kouji Takao) to aycabta (aycabta .)

[hsbt (Hiroshi SHIBATA)]

• Status changed from Assigned to Closed

The C wrapper library of libreadline is extracted https://github.com/ruby/readline-ext from Ruby 3.3. If you still interest this, can you submit your proposal to upstream?