From: James Gray <james@...>
Date: 2008-01-04T07:45:37+09:00
Subject: Re: Way of handling CLI interface for chat program.

On Jan 3, 2008, at 3:53 PM, Michael wrote:
> Consider the following example:
> ---------------------------------------------------
>    th = Thread.new { loop do puts "Hello, Ruby!"; sleep(10) end }
>    while (line = Readline.readline("prompt> ", true))
>      puts "#{line}: processed"
>    end
> ---------------------------------------------------
>
> This code will produce such results:
> ---------------------------------------------------
> $ ./cli.rb
> Hello, Ruby!
> prompt> I WAS TYPING HERE FOR 10 SECONDSHello, Ruby!
> ---------------------------------------------------
> And what I want, it's ALL lines be put above my input prompt, and not
> interrupting me while I'm typing.

This doesn't clear the lines as you were asking for, but hopefully it  
will give you new ideas:

#!/usr/bin/env ruby -wKU

require "thread"
require "timeout"

require "rubygems"
require "highline/system_extensions"

incoming_messages = Queue.new
output_buffer     = String.new

# simulate incoming server messages
Thread.new do
   loop do
     incoming_messages << "AnnoyingUser:  Hi, I'm still here!"
     sleep 5
   end
end

# main event loop
prompt = true
loop do
   # handle output
   unless incoming_messages.empty?
     puts unless prompt
     puts incoming_messages.shift until incoming_messages.empty?
     prompt = true
   end
   puts incoming_messages.shift until incoming_messages.empty?

   # prompt
   if prompt
     print ">> #{output_buffer}"
     $stdout.flush
     prompt = false
   end

   # fetch input
   begin
     Timeout.timeout(0.1) do
       if char = HighLine::SystemExtensions.get_character.chr
         output_buffer << char
         print char
         $stdout.flush
       end
     end
   rescue Timeout::Error
     # do nothing -- we'll try again later
   end

   # handle full lines of input
   if output_buffer[-1, 1] == "\n"
     incoming_messages << "Sending '#{output_buffer.chomp}' to  
server..."
     output_buffer = String.new
     prompt = true
   end
end

__END__

James Edward Gray II