Problem running the GTK main loop in a separate thread (different from the main one).

[Cristi Cobzarenco <cristi cobzarenco gmail com>]

Hi, I've been using GTK for a pretty long time but I've never used threads with it and I'm not able to properly run the GTK main loop in a separate thread.

More to the point if I create a window, for example, in a thread other than the GTK one, it becomes unresponsive. Other GTK calls (that don't create widgets) seem to work fine, however.

I've attached a sample program to show what I mean, the flag "create_in_gt" sets whether to create the widgets in the GTK thread or in the main one.

Is this normal behaviour, am I not supposed to do this, or is it a bug?

(NOTE: The first time I've sent this message it was detected as spam so I'll include the file instead of attaching it)

threadtest1.cpp:

#include <gtk/gtk.h>

const int create_in_gt = FALSE; // Whether to create the widgets in the GTK thread.

GtkWidget *win, *but;

// Creates a window with a button in it.

// This function will be called in the GTK thread if "create_in_gt" is TRUE

// or in the main thread otherwise.

int create_widgets(void*) {

    win = gtk_window_new(GTK_WINDOW_TOPLEVEL);

    but = gtk_button_new_with_label("My Button");

    gtk_container_add(GTK_CONTAINER(win),but);

    gtk_widget_show_all(win);

    return FALSE;

}

// The GTK thread function

void* gtkthread(void *) {

    gdk_threads_enter(); // GTK calls to follow - locking.

    // Inits gtk in this thread (I have tried initing it in both threads, the

    // result is the same.)

    gtk_init(NULL,NULL);

    // Creates the widgets if neccesary and then enters the main loop.

    if( create_in_gt ) create_widgets(NULL);

    gtk_main();

    gdk_threads_leave(); // GTK calls end here - unlocking

}

int main(int argc, char *argv[]) {

    g_thread_init(NULL); // Init threads in main thread.

    gdk_threads_init();

    // Creates the GTK thread.

    GThread *gt = g_thread_create(gtkthread, NULL, TRUE,NULL);

    // Waits 1 second, creates widgets if neccesary then, waits 2 more seconds.

    g_usleep( 1000000 );

    if( !create_in_gt )

        g_idle_add(create_widgets,NULL);

    g_usleep( 2000000 );

    gdk_threads_enter(); // Quits GTK safely.

    gtk_main_quit();

    gdk_threads_leave();

    g_thread_join(gt); // Waits for GTK to quit.

    return 0;

}

-- 
Cristi Cobzarenco