[DRE-maint] [Bug 514899] Re: Multithreaded Gtk applications using Ruby bindings freeze

[Launchpad Bug Tracker]

This bug was fixed in the package ruby-gnome2 - 0.19.0-2ubuntu4.1

---------------
ruby-gnome2 (0.19.0-2ubuntu4.1) karmic-proposed; urgency=low

  * debian/patches/gtk-threads.patch: apply two patches from ruby-gnome2 0.19.2
    to fix a problem with threads freezing the GTK+ main loop (LP: #514899).
 -- Mike Massonnet <mmassonnet at gmail.com>   Fri, 19 Feb 2010 02:04:05 +0100

** Changed in: ruby-gnome2 (Ubuntu Karmic)
       Status: Fix Committed => Fix Released

-- 
Multithreaded Gtk applications using Ruby bindings freeze
https://bugs.launchpad.net/bugs/514899
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Status in “ruby-gnome2” package in Ubuntu: Fix Released
Status in “ruby-gnome2” source package in Karmic: Fix Released

Bug description:
Binary package hint: libgtk2-ruby

In Ubuntu 9.10 with the version of libgtk2-ruby from the repositories (0.19.0), new threads cause the Gtk main loop to freeze. As an example, the following code will never produce any output:

===== Impact =====
I don't know which program available directly within Ubuntu is written in Ruby-GTK+, but those which do and which are using the Ruby Thread class are broken, and of course developing such a program is broken too.

The fix is available in ruby-gnome2 since version 0.19.2 and was introduced through SVN revisions 3692[1] and 3694[2]. Both are within the attachment "ruby-gnome2-gtk-thread-patch.debdiff" in comment #1.

[1] http://ruby-gnome2.svn.sourceforge.net/viewvc/ruby-gnome2?view=rev&revision=3692
[2] http://ruby-gnome2.svn.sourceforge.net/viewvc/ruby-gnome2?view=rev&revision=3694

TEST CASE:
 require 'gtk2'

 Thread.new do
   sleep 1 # Look busy
   exit    # Finished, exit
 end

 # Main loop
 loop do
   # Process all currently pending events
   Gtk.main_iteration while Gtk.events_pending?
   print '.'
 end

However, when the latest version of the bindings is installed (0.19.3) the program works as expected, filling the screen with dots.

TEST CASE 2:
Here is another example for reproducing this bug:

require "gtk2"
include Gtk, GLib
# Create widgets
window = Window.new
vbox = VBox.new(false, 2)
button = Button.new("Run Thread")
progress = ProgressBar.new
# Pack widgets
window.add(vbox)
vbox.add(button)
vbox.add(progress)
# Set default window size
window.default_width = 120
window.default_height = 50
window.show_all
# Connect signals
button.signal_connect("clicked") do
        Thread.new do
                puts "Thread started!"
		loop do
			progress.pulse
			sleep 1 
		end
        end
end
window.signal_connect("destroy") { main_quit }
# Show all and run
main # start the GTK+ main loop

The test program shows a window with a button and a progress bar. Clicking the button will execute a Ruby Thread object, and the GUI visual elements/the GTK+ main loop will remain freezed.

REGRESSION:
The following applications use libgtk2-ruby and threads:  fantasdic-1.0beta7 geekast-0.1.3 kazehakase-0.5.8 mhc-0.25.1+20090120 rbbr-0.6.0 xnetcardconfig-0.2.1

The example in the bug description is supposed to print dots, and instead it doesn't.

This problem is also reported at:
http://sourceforge.net/mailarchive/forum.php?thread_name=dc3bf8581001120746kb5da118udd0a74439cc4dcd9%40mail.gmail.com&forum_name=ruby-gnome2-devel-en