Re: Threads...

[Richard Boaz <riboaz xs4all nl>]

from inside your init routine, whenever you require your message box:

g_idle_add() a function to make the message box.  this function  
should be gtk+ library aware and your message box will be made  
without problems.

and that's it.

richard

On Jul 25, 2006, at 6:00 PM, Christian Schaubschlaeger wrote:

> Hello!
>
> I have kind of a conceptual problem concerning a multithreaded app.
> Let me describe the following small scenario:
>
> Below you can see a very simple gtk+ program (or at least the  
> important
> parts of it). In the main function the threads environment is  
> initialized,
> then a "dialog_init" is created and shown:
>
> int main(int argc, char **argv)
> {
> 	if (!g_thread_supported ())
> 	{
> 		g_thread_init (NULL);
> 		gdk_threads_init();
> 		printf("Threads initialized\n");
> 	}
> 	else
> 	{
> 		printf("Threads not supported!\n");
> 		exit(1);
> 	}
> 	gtk_init(&argc, &argv);
>
> 	dialog_init = create_dialog_init();
> 	gtk_widget_show(dialog_init);
>
> 	gdk_threads_enter();
> 	gtk_main();
> 	gdk_threads_leave();
> }
>
> The purpose of this "dialog_init" is to
>
> 	1) call the function "init_app()", which does the actual  
> initialization stuff
> 	   (which takes a long time), and
>
> 	2) display and update a progress bar until init_app() is finished.
>
> I have implemented this in the following way, which actually works  
> fine:
>
> void on_dialog_init_show()
> {
> 	...
> 	g_timeout_add(10,on_dialog_init_login_update_pb,NULL);
> 	g_init = g_thread_create(t_init,NULL,FALSE,&error);
> }
>
> gboolean on_dialog_init_login_update_pb(gpointer data)
> {
> 	... update the progress bar...
> 	if (init_finished) return FALSE;
> 	else return TRUE;
> }
>
> void *t_init(void *p)
> {
> 	init_app();
> 	init_finished = 1;  // global var, indicates that init_app() has  
> finished
> 	return NULL;
> }
>
> on_dialog_init_login_update_pb is called periodically and updates  
> the pb,
> until init_app is finished.
>
> Now during initialization it is necessary to occasionally popup  
> messageboxes,
> ie. it might be the case, that from somewhere within init_app() a  
> messagebox
> is shown.
>
> init_app() is a function which doesn't know anything about gtk+  
> (since I want
> it to be independent from a GUI), therefore I provide a callback  
> function
> (cb_messagebox) to init_app, which - when called - shows a messagebox.
>
> Since init_app() runs in a separate thread, it is necessary to use
> gdk_threads_enter and gdk_threads_leave, therefore I have changed the
> thread function to:
>
> void *t_init(void *p)
> {
> 	gdk_threads_enter();
> 	init_app(cb_messagebox);
> 	gdk_threads_leave();
>
> 	init_finished = 1;  // global var, indicates that init_app() has  
> finished
> 	return NULL;
> }
>
> void cb_messagebox(char *msg_text)
> {
> 	// popup a gtk+ messagebox displaying
> 	// msg_text
> 	...
> 	gtk_dialog_run(...);
> 	...
> }
>
> Unfortunately now the progress bar is no longer updated, which is  
> quite clear,
> since the call to gdk_threads_enter in t_init blocks all 'drawing  
> requests'
> from outside this thread, especially those from the progress bar,  
> until
> gdk_threads_leave is called.
>
> My question now is: how can I solve or avoid this problem?
> I _need_ to popup messageboxes from within init_app (which forces  
> me to use
> gdk_threads_enter), but I still want the progress bar to be updated.
>
> What I could do is not to use gdk_threads_enter in t_init, but in
> cb_messagebox (before the call to gtk_dialog_run), but this is not  
> a good
> soluion, since cb_messagebox is sometimes called from within a  
> separate
> thread, and sometimes from within the main process (which inhibits  
> the use of
> gdk_threads_enter).
>
> Tricky...
>
> Looking forward for suggestions!
> Thanks!
> Christian
>
> _______________________________________________
> gtk-list mailing list
> gtk-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtk-list