Re: [gtk-list] Re: ItemFactory anyone?

[Tim Janik <timj gtk org>]

On Thu, 14 Jan 1999, Jan Kratochvil wrote:

> > On Wed, Jan 13, 1999 at 05:04:43PM -0800, Brandon Long wrote:
> > 
> > > For instance, what is a callback action?  We no longer have a space in
> > > the entry for the callback data..
> > 
> > Looking at the header file, it's just an integer that can be used as an
> > index.
> > 
> > struct _GtkItemFactoryEntry
> > {
> >   gchar *path;
> >   gchar *accelerator;
> > 
> >   GtkItemFactoryCallback callback;
> >   guint			 callback_action;
> >   gchar		 *item_type;
> > };
> > 
> > void	gtk_item_factory_create_items	(GtkItemFactory		*ifactory,
> > 					 guint			 n_entries,
> > 					 GtkItemFactoryEntry	*entries,
> > 					 gpointer		 callback_data);
> > 					 
> > 
> > So I suppose if you have some data you want to associate with a menu item
> > you can pass in an array or gslist as the callback_data.  Then in your
> > callback function retrieve the data item you want by indexing into the array
> > or gslist using the passed in callback_action integer.
> > 
> > If you already know what the menu items are going to be and they won't
> > change at runtime you can just use a case statement in your callback.
> 
>   Oh my god, why just don't cast the needed pointer (it WILL be probably pointer),
> to "guint"? Like in the following example:
> 
> typedef struct {
> 	...
>         GtkWidget *highscorebox,*highscorelist;
> 	...
> } UI;
> UI ui;
> 
> static void widgetshowfn (gpointer callback_data,guint callback_action,GtkWidget *widget)
> { gtk_widget_show(GTK_WIDGET(*(GtkWidget **)callback_action)); }
> 
> static GtkItemFactoryEntry menu[]=
> {
> 	...
>         {"/Game/View _high scores","<control>H",(GtkItemFactoryCallback)widgetshowfn ,(guint)&ui.highscorebox,NULL         },
> 	...
> };

you can't rely on sizeof (guint) to always be >= sizeof (gpointer), e.g. alphas
have sizeof (guint)==4 and sizeof(gpointer)==8, so you'll most probably screw your
pointers on some machines with the above code.

> 
> P.S.: This example is from my port of xBill under GTK. The prerelease can be found on:
> 
> http://atrey.karlin.mff.cuni.cz/~short/sw/#xbill
> 
>   Unfortunately I have exams now, I'll be able to finish it (like Gnomization, currently
> done parts should be stable, at least I hope so :-) ) sometimes in march if all wents well.
> If someone can do it instead, I'll be pleased to hear about it.
> 
> 
> 
> 							Lace
> 

---
ciaoTJ