Re: Gtk::Widget::on_hide

[Kjell Ahlstedt <kjell ahlstedt bredband net>]

> Okay... I just finished applying the patches.  I've by no means 
> carried out any exhaustive testing but initial signs are that it's 
> fixed the crashing issue.  I'll do some more comprehensive testing 
> tomorrow but my first impression is that this stuff is still some way 
> from working elegantly.  For example, Gtk::Widget::on_unrealize() is a 
> virtual function.  However, if I override it in my derived class 
> (MyDialog, which is derived from Gtk::Dialog), 
> Gtk::Widget::on_unrealize() continues to get called, instead of 
> MyDialog::on_unrealize().  Unfortunately, I can't tell whether that 
> problem already existed or whether the patches are somehow 
> responsible.  To be fair though, that's the only issue I've noticed so 
> I think we can definitely regard this as progress!
A backtrace from gdb when unrealize_callback() is called, looks like so:

#0  Gtk::Widget_Class::unrealize_callback (self=0x6c60d0) at widget.cc:4038
#1  0x00007ffff5291007 in _g_closure_invoke_va (closure=0x6af8f0, 
return_value=0x0,
    instance=0x6c60d0, args=0x7fffffffd728, n_params=0, 
param_types=0x0) at gclosure.c:840
#2  0x00007ffff52aae5c in g_signal_emit_valist (instance=0x6c60d0, 
signal_id=<optimized out>,
    detail=<optimized out>, var_args=var_args entry=0x7fffffffd728) at 
gsignal.c:3238
#3  0x00007ffff52ab732 in g_signal_emit (instance=instance entry=0x6c60d0,
    signal_id=<optimized out>, detail=detail entry=0) at gsignal.c:3386
#4  0x00007ffff59c3592 in IA__gtk_widget_unrealize (widget=0x6c60d0) at 
gtkwidget.c:3605
#5  0x00007ffff59c4a20 in gtk_widget_dispose (object=0x6c60d0) at 
gtkwidget.c:8791
#6  0x00007ffff5297730 in g_object_run_dispose (object=0x6c60d0) at 
gobject.c:1077
#7  0x00007ffff7a1817f in Gtk::Dialog::~Dialog (this=0x6ac020,
    __vtt_parm=0x405688 <VTT for MyDialog+8>, __in_chrg=<optimized 
out>) at dialog.cc:226
#8  0x000000000040509a in MyDialog::~MyDialog (this=0x6ac020, 
__in_chrg=<optimized out>,
    __vtt_parm=<optimized out>) at main2.cc:9
#9  0x0000000000405188 in MyDialog::~MyDialog (this=0x6ac020, 
__in_chrg=<optimized out>,
    __vtt_parm=<optimized out>) at main2.cc:11
#10 0x0000000000404f82 in main (argc=1, argv=0x7fffffffd9c8) at main2.cc:34

It's called (indirectly) from Gtk::Dialog::~Dialog(). At that time the 
object is not a MyDialog any more. Calling virtual functions from 
constructors and destructors is best avoided. It's not always easy to 
guess which override will be called.

Kjell