Re: Delay time to spawn new threads?

[Osmo Antero <osmoma gmail com>]

My audio-recorder that was based on GTK2 had some threads that also
modified the GUI-elements. I had to call
GDK_THREADS_ENTER<https://developer.gnome.org/gdk3/3.10/gdk3-Threads.html#GDK-THREADS-ENTER:CAPS>
 / GDK_THREADS_LEAVE<https://developer.gnome.org/gdk3/3.10/gdk3-Threads.html#GDK-THREADS-ENTER:CAPS>
 before modifying the GTK-elements, otherwise the GUI froze.

Now in GTK3, I've replaced the threads with
g_timeout_add_full<https://developer.gnome.org/glib/2.30/glib-The-Main-Event-Loop.html#g-timeout-add-full>
() and GAsyncQueue<https://developer.gnome.org/glib/2.26/glib-Asynchronous-Queues.html#GAsyncQueue>
.
g_timeout_full_id() runs within the MainLoop so GUI-locking is handled
automatically.

The code is here:
http://bazaar.launchpad.net/~osmoma/audio-recorder/trunk/view/head:/src/rec-manager.c
The recorder receives commands (like: start/stop/pause/etc.) from various
modules and sources. All commands go through the GAsyncQueue.

 Bom dia
   Osmo (Moma) Antero


On Thu, Nov 28, 2013 at 3:32 AM, David Buchan <pdbuchan yahoo com> wrote:

> David Buchan <pdbuchan yahoo com> wrote:
> > Hi Michael,
> >
> > My 32-bit, GTK+2 version does
> >
> >   // Secure glib
> >   if (!g_thread_supported ()) {
> >     g_thread_init (NULL);
> >   }
> >
> > at the beginning, and then the thread is spawned via:
>  on_button1_clicked (GtkButton *button1, MyData *data)
> > {
> >   GThread *thread;
> >   GError *error = NULL;
> >
> >   thread = g_thread_create ((GThreadFunc) my_function, data, FALSE,
> > &error); if (! thread) {
> >       g_print ("Error: Unable to create new thread for my_function()
> > in on_button1_clicked().%s\n", error->message); exit (EXIT_FAILURE);
> >     }
> >
> > My 64-bit, GTK+3 versions does not do the g_thread_init() call.
> >
> > It spawns a new thread via:
> >
> > int
> > on_button1_clicked (GtkButton *button1, MyData *data)
> > {
> >   GThread *thread;
> >
> >   thread = g_thread_new ("my_function", (GThreadFunc) my_function,
> > data); if (! thread) {
> >       fprintf (stderr, "Error: Unable to create new thread for
> > my_function() in on_button1_clicked().\n"); exit (EXIT_FAILURE);
> >     }
>
> Show us your my_function(): you are almost certainly doing something
> wrong. Best of all, provide a complete compilable example which
> demonstrates the problem. And why are you casting the function pointer
> to GThreadFunc?  You do not need to call g_thread_init() with glib >=
> 2.32, and you do with earlier versions. Prior to version 2.24
> g_thread_init() had to be the first glib call. Between 2.24 and 2.30 it
> had to be the first
>  call relevant to threads.
>
> Also, please don't top post.
>
> Chris
> ==========================================
> Hi Chris,
>
>
> I removed the call to g_thread_init() and it still works fine! Great catch
> there.
>
> I had put the cast to GThreadFunc there because otherwise I get the
> following error:
>
> callbacks.c: In function ‘on_button1_clicked’:
> callbacks.c:3829: warning: passing argument 1 of ‘g_thread_create_full’
> from incompatible pointer type
> /usr/include/glib-2.0/glib/gthread.h:225: note: expected ‘GThreadFunc’ but
> argument is of type ‘int (*)(struct MyData *)’
>
> I saw other people on the web do the cast as well to remove that error. Is
> there a mistake in how I use g_thread_create()? I'd like to drop the cast
> if I can. It seemed strange at the time I put it in.
>
> Top-posting is due to the way Yahoo mail handles replies.
> Maybe this
>  is better, but it didn't put the >'s in, thus the "====..." line. I
> dunno. Sorry about that.
>
> I'm still investigating the delay. The my_function() code is hundreds of
> lines, so I'd need to create a small example to post.
> Let me continue to investigate.
>
> Dave
>
> ==========================
> ... and now I see what's going on.
>
> My newly spawned thread calls a function which starts a messaging
> idle-function.
>
> [my main program] ---> [my new thread] ----> [post_message function] ===>
> [update GUI idle function]
>
> In my new thread, I call:
>
> post_message (text, data);
>
> and that looks like:
>
> // Start an instance of activity_message() idle function.
> int
> post_message (char *message, MyData *data)
> {
>   // Allocate memory for string; Idle function will free it.
>   data->activity_message = allocate_strmem (TEXTLEN);
>   // Copy message.
>   strncpy (data->activity_message, message, TEXTLEN - 1);  // Minus 1 for
> string termination.
>
>   g_idle_add ((GSourceFunc) activity_message, data);
>   sleep (1);
>   return (EXIT_SUCCESS);
> }
>
> // Idle function to add a message to the activity textview
> // This idle function returns 0 in order to stop.
> int
> activity_message (MyData *data)
> {
>   ...
>   Update a textview with our message ...
>
>   return (0)
> }
>
> I set it up this way so the GUI can be updated.
>
> The call to sleep() protects me against the situation in which my thread
> makes a second call to post_message() when activity_message() hasn't
> finished updating the GUI from the first call.
>
> Is there a way to have my thread call post_message() whenever it needs to,
> and have the messages queue-up?
>
> Dave
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// moma
   http://www.futuredesktop.org