On Wed, 11 Oct 2017 18:42:26 -0300
Antonio Scuri <[email protected]> wrote:
> Actually I take back what I said, we can use your fix:
>
> + g_signal_handlers_disconnect_by_data(G_OBJECT(ih->handle), ih);
> + parent = iupDialogGetNativeParent(ih);
> + if (parent)
> + g_signal_handlers_disconnect_by_func(G_OBJECT(parent),
> gtkDialogChildDestroyEvent, ih);
>
>
> But I think there is another serious problem in what we are doing.
> Suppose we have several dialogs that set their parentdialog to the
> same main dialog. Those "child" dialogs will all call:
>
> g_signal_connect(G_OBJECT(parent), "destroy",
> G_CALLBACK(gtkDialogChildDestroyEvent), ih);
>
> So for the same parent, they will al set destroy, but each time one
> will replace another and only the last one set will actually be
> called. Am I right? Or I misunderstood g_signal_connect? Does every
> call to g_signal_connect with a different data will ensure a
> different callback association? I can't remember and I couldn't find
> this info explicit in GLIB docs.
>
> Thanks,
> Scuri
>
> PS: already committed your contribution.
>
Thanks for committing the fix.
As for the GLib signals handlers, I think you are safe and no problems
should occur in that regard.
Each call of g_signal_connect() creates a unique signal handler that is
identified by an ID (returned by g_signal_connect()).
Even if the GLib docs may not be explicit, the behaviour can be
inferred from various description in Glib docs.
This sentence from
https://developer.gnome.org/gobject/stable/signal.html
"When a signal is emitted on a given type instance, all the closures
connected to this signal on this type instance will be invoked. All the
closures connected to such a signal represent callbacks whose signature
looks like..."
seems to support that best.
The signal handlers are also called in a deterministic way.
https://developer.gnome.org/gobject/stable/gobject-Signals.html says:
"The user-provided signal handlers are called in the order they were
connected in."
And if you look at the source code, you would find that the handlers
are all stored in a hash table and don't replace itself.
I've written a quick test confirming that all signal handlers are
called (even if the g_signal_connect() is completely the same,
including the data parameter). Find the code in the attachment.
Best regards,
blueowl
PS: GLib documentation is traditionally cumbersome. Not only in regards
to signals. But the very basic concept of GObject creation is very hard
to understand from the official documentation [1]. It is described much
much better here [2].
[1] https://developer.gnome.org/gobject/stable/chapter-gobject.html
[2]
https://blogs.gnome.org/desrt/2012/02/26/a-gentle-introduction-to-gobject-construction/
/*
* Test for calling signals that only differ in 'data'
*
* The original base code was copied from
* https://developer.gnome.org/gtk3/stable/gtk-getting-started.html
*
* gcc `pkg-config --cflags gtk+-3.0` -o signals signals.c `pkg-config --libs gtk+-3.0`
*/
#include <gtk/gtk.h>
static void activate (GtkApplication* app, gpointer user_data)
{
GtkWidget *window;
if (user_data) {
g_print ("Activate handler, data: %s\n", (char *)user_data);
return;
}
window = gtk_application_window_new (app);
gtk_window_set_title (GTK_WINDOW (window), "Window");
gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);
gtk_widget_show_all (window);
}
int main (int argc, char **argv)
{
GtkApplication *app;
int status;
gulong sig1, sig2, sig3, sig4;
char *mydata = "World";
app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
sig1 = g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
sig2 = g_signal_connect (app, "activate", G_CALLBACK (activate), "Hello");
sig3 = g_signal_connect (app, "activate", G_CALLBACK (activate), mydata);
sig4 = g_signal_connect (app, "activate", G_CALLBACK (activate), mydata);
g_print ("Signal handlers connected: sig1=%ld (%s), sig2=%ld (%s), sig3=%ld (%s), sig4=%ld (%s)\n",
sig1, g_signal_handler_is_connected (app, sig1) ? "yes" : "no",
sig2, g_signal_handler_is_connected (app, sig2) ? "yes" : "no",
sig3, g_signal_handler_is_connected (app, sig3) ? "yes" : "no",
sig4, g_signal_handler_is_connected (app, sig4) ? "yes" : "no");
status = g_application_run (G_APPLICATION (app), argc, argv);
g_object_unref (app);
return status;
}
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