Re: Dialog destruction signals.

[Count Zero <countzero cyberdeck org>]

Farooq Mela was overheared mumbling something about this on Wed, 14 Jun 2000
00:19:59 -0700 (PDT)

>	/* gtk_signal_connect(GTK_OBJECT(dialog),
>  "delete_event",
>		GTK_SIGNAL_FUNC(on_dialog_delete), dialog); */

on_dialog_delete will get "dialog" as "widget" so no need to pass it as data...

>	gtk_signal_connect(GTK_OBJECT(dialog), "destroy",
>		GTK_SIGNAL_FUNC(on_dialog_delete), dialog);

Same here...

>  static gint
>  on_dialog_delete(GtkWidget *widget, gpointer data)
>  {
>	GtkWidget *dialog;
>	struct file_info *fi;
>	int answer;

Again, widget == dialog... so no need to do GtkWidget *dialog or:
  
>	dialog = data;

This line either...

>	fi = gtk_object_get_data(GTK_OBJECT(dialog),
>  "file_info");

fi = gtk_object_get_data(GTK_OBJECT(widget), "file_info");

>	if(!fi->changed) {
>		gtk_widget_destroy(dialog);

Problem here... you are doing this in the "delete_event" signal...

If you return FALSE, gtk is going to do gtk_widget_destroy() for you anyway, so
that will now FAIL if you destroy it... so, don't destroy here, just return
FALSE (Meaning, "Gtk, I did some stuff, but I didn't completely deal with the
"delete_event" signal, you go ahead and do your stuff too")

>		return FALSE;
>	}
>  
>	fi->changed = 0;
>  
>	answer = yesnocancel_dialog("This file has
>  changed.\nDo you wish to save changes?",
>		fi->filename, TRUE);

I assume yesnocancel_dialog() is modal? 

>	if(answer == 0) {
>		gtk_widget_destroy(dialog);

bad, just return FALSE

>	} else if(answer == 1) {
>		on_file_save(widget, data);
>		gtk_widget_destroy(dialog);

Again, just return FALSE

>	} else {
>		return TRUE;

Good, now your widget won't get destroyed...

>	}
>	return FALSE;

Good, now your widget WILL get destroyed....

>  }
>  
>  /* -- END CODE -- */
>  
>  The problem is that the "delete_event" and "destroy"
>  signals do not seem to be doing what they are supposed
>  to. The delete_event signal, according to
>  documentation, should be emitted before the destroy
>  signal, and the emission of the destroy signal should
>  be dependant upon the return value of the signal
>  handler associated with the delete_event signal.

It does... problem is, you have already destroyed the widget and then you
return FALSE telling Gtk to try to destroy the widget too....

>  In my
>  program, connecting to the delete_event signal causes
>  an assertation failure (caused by the call to
>  `gtk_object_get_data' above) and then a segfault:
>  
>  Gtk-WARNING **: invalid unclassed pointer in cast to
>  `GtkObject'
>  
>  Gtk-CRITICAL **: file gtkobject.c: line 1080
>  (gtk_object_get_data): assertion `GTK_IS_OBJECT
>  (object)' failed.
>  Segmentation fault (core dumped)
>  
>  This obviously leads me to believe that the object was
>  deconstructed and destroyed _before_ the signal
>  handler for delete_event was called.

No, you destroyed the widget _before_ Gtk's signal handler for "delete_event"
was called.

>  However,
>  connecting to the "destroy" signal causes no such
>  assertation failure. However, when connecting to the
>  `destroy' signal, the dialog appears to be destroyed,
>  before the dialog box from the `yesnocancel_dialog'
>  function appears. But in reality it is only hidden,
>  because the contents of the GtkText in that dialog can
>  be saved from the signal handler!

"Destroy" is an informative signal.  Gtk is saying "I am destroying this
widget, heres a last chance for you do do some stuff"  But no matter what you
do, the widget will still be destroyed.

>  This behaviour is really confusing me; it seems to be
>  inconsistent with the way the `destroy' and
>  `delete_event' signals work. Could this perhaps be
>  caused by that fact that the dialog created is a
>  GTK_WINDOW_DIALOG and not a GTK_WINDOW_TOPLEVEL?

No... windows are windows... the GTK_WINDOW_DIALOG and GTK_WINDOW_TOPLEVEL just
set some Window Manager hints so that they MAY look different (different border
styles, etc) but other than that, there is no difference...

>  My second question is, how can I set the icon for my
>  application? I.E., if the application is minimized,
>  the icon I have set for the application appears rather
>  than the default icon as set by the window manager?

GtkWidget *window;
GdkPixmap *pixmap;
GdkBitmap *mask;
GdkColormap *colormap;

window = gtk_window_new();
colormap = gtk_widget_get_colormap(window);
pixmap = gdk_pixmap_colormap_create_from_xpm(NULL, colormap, &mask, NULL,
"filename.xpm");
gdk_window_set_icon(window->window, NULL, pixmap, mask);
gdk_pixmap_unref(pixmap);
gdk_bitmap_unref(mask);


Of course, what icon gets displayed when a program is minimized is 100% up to
the Window Manager... We can only ASK that our icon gets displayed... What
actually happens will be WM and user preference dependant...

>  Regards,
>  
>  Farooq
>  

Your welcome,

-Count Zero
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