Re: Possible bug with multiple copies of a window in multiple threads.

[muppet <scott asofyet org>]

On Saturday, January 10, 2004, at 10:27 AM, Ross McFarland wrote:

> On Fri, 2004-01-09 at 06:44, Student wrote:
> > Can someone enlighten me on what is going wrong.
>
> basically you're running into several issues. some of with are the 
> app's
> fault and others which aren't (from what i can tell) as a rule (at this
> point) if you use threads you have to spawn them before ANY Gtk2-Perl
> variables have been created. the reasons for this are rather complex 
> and
> the solutions even more so.

another rule of thumb for X11 apps --- access the gui *only* from one 
thread.  creating a window in one thread and calling gtk_main in 
another is a recipe for disaster.

we have a faq entry about this...

   http://gtk2-perl.sourceforge.net/faq/#38


as for *why* not to use the gui from more than one thread:  X11 is 
thread-safe, but not threadable.  the client library uses a single 
socket connection to the window server; multiple threads and even 
forked child processes have a copy of that file descriptor, and can 
confuse the client library if they use it.  for example, common problem 
include shutting down the parent's X connection in the child, and 
confusing the state machines in a parent thread by triggering events 
from a child thread.

you can indeed succeed at getting multiple threads to work with the 
gui, but it makes me shudder to think about the race conditions, and 
personally i avoid it at all costs.

--
muppet <scott at asofyet dot org>