[DRE-maint] Bug#502262: libgtk2-ruby1.8: Gtk UI rendering hangs when another thread is working

[Johan Walles]

Package: libgtk2-ruby1.8
Version: 0.17.0~rc1-6
Severity: normal


I have a GTK program with a UI that is repeatedly updated from another thread using the technique 
described here:
http://ruby-gnome2.sourceforge.jp/hiki.cgi?tips_threads

If the updating thread doesn't sleep for *more* than 0.001s every iteration, the UI never gets 
updated.

I tried adding Thread.pass to the working thread, but it didn't help.

I expect the UI to be rendered even when another thread is working.

Expected behavior of the sample code below is to display a window with a button saying "Flash 
Gordon".  Current behavior is to display an empty gray window.

I'm on ruby1.8 1.8.7.72-1.

  Regards //Johan

=== Begin sample code
#!/usr/bin/ruby

=begin
This program has a GTK UI that is updated by a separate thread.  The
program doesn't work (the UI isn't even rendered) unless the updating
thread sleeps for *over* 1ms sometimes.

Search for FIXME to see what helps and what doesn't.

The failing trials were run on Debian i686 with Ruby 1.8.7.72-1 and
libgtk2-ruby1.8 0.17.0~rc1-6.

johan.walles at gmail.com
=end

require 'gtk2'
require 'monitor'

# From http://ruby-gnome2.sourceforge.jp/hiki.cgi?tips_threads
module Gtk
  GTK_PENDING_BLOCKS = []
  GTK_PENDING_BLOCKS_LOCK = Monitor.new

  def Gtk.queue &block
    if Thread.current == Thread.main
      block.call
    else
      GTK_PENDING_BLOCKS_LOCK.synchronize do
        GTK_PENDING_BLOCKS << block
      end
    end
  end

  def Gtk.main_with_queue(timeout_ms = 100)
    Gtk.timeout_add timeout_ms do
      GTK_PENDING_BLOCKS_LOCK.synchronize do
        for block in GTK_PENDING_BLOCKS
          block.call
        end
        GTK_PENDING_BLOCKS.clear
      end
      true
    end
    Gtk.main
  end
end

# Create UI
button = Gtk::Button.new("Hello World")
window = Gtk::Window.new

window.signal_connect("destroy") {
  Gtk.main_quit
}

# Lay out UI
window.border_width = 10
window.add(button)
window.show_all

Thread.new {
  while true
    Gtk.queue do
      button.label = "Flash Gordon"
    end

    # FIXME: Sleeping 0.001s does not help:
    # sleep 0.001

    # FIXME: Sleeping 0.0011s *does* help:
    # sleep 0.0011

    # FIXME: Thread.pass does not help:
    # Thread.pass
  end
}

Gtk.main_with_queue
=== End sample code

-- System Information:
Debian Release: lenny/sid
  APT prefers testing
  APT policy: (990, 'testing')
Architecture: i386 (i686)

Kernel: Linux 2.6.26-1-686 (SMP w/2 CPU cores)
Locale: LANG=sv_SE.UTF-8, LC_CTYPE=sv_SE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages libgtk2-ruby1.8 depends on:
ii  libatk1-ruby1.8             0.17.0~rc1-6 ATK bindings for the Ruby language
ii  libatk1.0-0                 1.22.0-1     The ATK accessibility toolkit
ii  libc6                       2.7-14       GNU C Library: Shared libraries
ii  libcairo2                   1.6.4-6      The Cairo 2D vector graphics libra
ii  libgdk-pixbuf2-ruby1.8      0.17.0~rc1-6 Gdk-Pixbuf 2 bindings for the Ruby
ii  libglib2.0-0                2.16.6-1     The GLib library of C routines
ii  libgtk2.0-0                 2.12.11-3    The GTK+ graphical user interface 
ii  libpango1-ruby1.8           0.17.0~rc1-6 Pango bindings for the Ruby langua
ii  libpango1.0-0               1.20.5-2     Layout and rendering of internatio
ii  libruby1.8                  1.8.7.72-1   Libraries necessary to run Ruby 1.

libgtk2-ruby1.8 recommends no packages.

libgtk2-ruby1.8 suggests no packages.

-- no debconf information