Re: Xlib-error in threaded GTK+

[Tomas Berndtsson <tomas nocrew org>]

Owen Taylor <otaylor@redhat.com> writes:

> > So, how do I avoid the error? Do I put another pair of
> > gdk_threads_enter/gdk_threads_leave around the GTK+ calls in the
> > second thread?
> 
> Well - the whole point of gdk_threads_enter() / gdk_threads_leave ()
> is to allow multiple threads to coordinate access to GTK+. (They
> are unnecessary if you are only making GTK+ calls from a single thread
> thread.)
> 
> So, yes, making full use of these calls would be one way of approaching
> the problem. (You'll want to read the threading section of the GTK+ 
> FAQ and look at the example there.)
> 
> Another approach would be to figure out a way of communicating from
> the second thread to the first thread and letting the first thread
> do the work. You could use pipes, or you could take advantage 
> of the fact that the GLib main loop is fully thread safe, do:
> 
>  g_idle_add (function_to_run_in_main_thread, data_for_function);
> 
> The first approach is preferable if the GUI work is heavily split
> up between the threads, the second may be easier if you are mostly
> doing GUI work in the main thread, but have one or two things you
> want to trigger from the second thread.

Ok, thanks a lot!

I'll try one of these, or perhaps try both, and see what's best. They
both seems fairly easy to put in. If I want my function to return a
value, when using the g_idle_add() method, I suppose I have to put it
all in a struct which is passed in the data_for_function, right? 

Are there more overhead in any of them? The small extra thing I have
in the second thread, is called quite a lot of times, so if one of
them is better for small, frequent routines, I guess that would be
best to use.


Tomas