I found the crashing point and here's a fix for it. I think this is more GDK problem because it was gdk_region_polygon() function that caused the crash.
** Attachment added: "fix" http://librarian.launchpad.net/4945647/crashfix.patch -- segfault when moving slider https://launchpad.net/bugs/69344 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs