curses, ncurses, threads and non-blocking getch

[William Morgan]

Hello all.

It looks like non-blocking getch (i.e. when nodelay = 1) with Ruby's
standard curses library blocks when there are other Threads running.
Once the other Thread dies, it resumes non-blocking operation once a key
is pressed. With the ncurses library, this problem doesn't happen.

I'm not a curses/ncurses expert, so maybe I'm doing something wrong.
Here's the code:

require "curses"

begin
Curses.init_screen
Curses.noecho
Curses.stdscr.nodelay = 1

start = Time.now
Thread.new { sleep 5; }

while true
Curses.stdscr.setpos(5, 5)
Curses.stdscr.addstr("#{(Time.now - start).round} waiting for input...")
Curses.refresh

x = Curses.stdscr.getch

Curses.stdscr.setpos(5, 5)
Curses.stdscr.addstr("#{(Time.now - start).round} got: #{x} ")
Curses.refresh

sleep 0.5
end
ensure
Curses.echo
Curses.close_screen
end

You'll see that getch blocks ("waiting for input" is displayed) until
after the first five seconds, when the thread dies. Then as soon as you
press a key, getch is back in non-blocking mode. If you remove the
Thread.new call, everything works as it should.

This is on ruby 1.8.2 (2005-01-10) [i386-linux].

For reference, here's the equivalent Ncurses code, which works fine:

require "ncurses"

begin
Ncurses.initscr
Ncurses.noecho
Ncurses.stdscr.nodelay true

start = Time.now
Thread.new { sleep 5; }

while true
Ncurses.stdscr.move(5, 5)
Ncurses.stdscr.addstr("#{(Time.now - start).round} waiting for input...")
Ncurses.refresh

x = Ncurses.stdscr.getch

Ncurses.stdscr.move(5, 5)
Ncurses.stdscr.addstr("#{(Time.now - start).round} got: #{x} ")
Ncurses.refresh

sleep 0.5
end
ensure
Ncurses.endwin
end