Re: bug in gtk_signal_emit_by_name

[Owen Taylor <otaylor redhat com>]

briot@gnat.com writes:

> Hi,
> 
> One of the users of GtkAda as reported a bug in gtk_signal_emit_by_name.
> Here is a small test case that reproduces the problem.
> Note that apparently the bug is specific to "expose_event", since it does not
> appear with other events like "leave".
> Let me know if I should report this bug to another mailing list.

I'm sure that the maintainers of GtkAda are aware that
all GTK+ signals handlers do not have the same signature. ;-)

The prototype for expose_event (and any other event)
is:

gint
expose_event_handler (GtkWidget *widget, GdkEventExpose *event, gpointer data);

So, you need to correspondingly call:

 gint return_val;
 gtk_signal_emit_by_name (GTK_OBJECT (widget), "expose_event",
                          event, &return_val);

Of course, one almost certainly should be using
gtk_widget_event() instead. Or probably calling
gtk_widget_draw() or gtk_widget_queue_draw()...

Regards,
                                        Owen

> Emmanuel
> 
> /* Compile with :
>    gcc `gtk-config --cflags` project2.c `gtk-config --libs`
> 
>    This program core dumps when the button is pressed...
>    This seems to be because of "expose_event". It works with for instance
>    "leave".
> */
> 
> #include <gtk/gtk.h>
> #include <stdio.h>
> 
> void
> on_clicked (GtkObject* obj, GtkDrawingArea draw)
> {
>   printf ("on_clicked\n");
>   gtk_signal_emit_by_name ((GtkObject*)obj, "expose_event");
>   printf ("leave\n");
> }
> 
> int
> main (int argc, char *argv[])
> {
>   GtkWindow* win;
>   GtkButton* button1;
> 
>   gtk_set_locale();
>   gtk_init (&argc, &argv);
> 
>   win = (GtkWindow*) gtk_window_new (GTK_WINDOW_TOPLEVEL);
>   button1 = (GtkButton*) gtk_button_new_with_label ("button1");
>   gtk_container_add ((GtkContainer*)win, (GtkWidget*) button1);
> 
>   (void) gtk_signal_connect ((GtkObject*)button1,
>                              "clicked",
>                              (GtkSignalFunc)&on_clicked,
>                              (gpointer)button1);
> 
>   gtk_widget_show_all ((GtkWidget*)win);
>   gtk_main ();
>   return 1;
> }