Re: Threads and main-loops

["Brian J. Tarricone" <bjt23 cornell edu>]

Russell Shaw wrote:

> Hi,
>
> If i make multiple loops with:
>
>   GMainLoop *loop1=g_main_loop_new(context1,TRUE);
>   GMainLoop *loop2=g_main_loop_new(context2,TRUE);
>   GMainLoop *loop3=g_main_loop_new(context3,TRUE);
>   g_main_loop_run(loop1);
>   g_main_loop_run(loop2);
>   g_main_loop_run(loop3);
>
> Are all these running in a single gtk thread? If so, can their
> callbacks call GUI widgets without thread-locking problems? 

i think you're misunderstanding something here.  the first 
g_main_loop_run() call will block until loop1 is exited (usually by 
calling g_main_loop_quit(loop1) in some callback or timeout function). 
then loop2 will run, and after it exits, loop3 will run.

i'm not sure exactly what you're trying to do here, but i suspect this 
isn't what you're looking for.  gtk itself is not multithreaded.  put 
simply, it uses an event-loop mechanism.  callbacks run in the main 
thread.  everything runs in a single thread, unless you explicitly 
create other threads (either via the GThread interface, or using raw 
pthread calls; GThread is just a wrapper around pthreads on linux).  if 
you need separate threads, you either can only do gtk operations in the 
main thread, or you need to initialise gdk's threads support and use 
gdk_threads_enter() and gdk_threads_leave() to protect gtk calls in the 
other threads.  there is plenty of information in tutorials and whatnot 
on how to do this, so i won't repeat it here.

   -brian