Re: [gtk-list] Re: Argument handling

[Tim Janik <timj gtk org>]

On Wed, 3 Feb 1999, J.A.M. Molenaar wrote:

> Federico Mena Quintero wrote:
> > 
> > >  I've been coding for a while an ran up to a (minor) question. I'm
> > >  creating some GnomeCanvas things that use the GTK Argument System. It
> > >  allows me to set attributes on creation and set them after I have
> > >  created them. The problem is that I can't figure out what function is
> > >  used to retrieve information. gtk_object_get ()? I dunno...
> > 
> > You can use the gtk_object_getv() function.  Here is a small example
> > from the Gnomecal sources:
> > 
> >         GtkArg args[3];
> >         double text_height;
> >         double clip_height;
> >         double y_offset;
> > 
> >         args[0].name = "text_height";
> >         args[1].name = "clip_height";
> >         args[2].name = "y_offset";
> >         gtk_object_getv (GTK_OBJECT (mv->text[day_index]), 3, args);
> > 
> >         text_height = GTK_VALUE_DOUBLE (args[0]);
> >         clip_height = GTK_VALUE_DOUBLE (args[1]);
> >         y_offset = GTK_VALUE_DOUBLE (args[2]);
> > 
> > In this case, mv->text[day_index] is a GnomeCanvasText item.
> > 
> >   Federico
> > 
> 
> Thanx!!! This will simplify my program a lot!

it should be noted, that string-like values that are retrived this way need
an explicit call to g_free to not leak memory:

for (i = 0; i < 3; i++)
{
  if (GTK_FUNDAMENTAL_TYPE (args[i].type) == GTK_TYPE_STRING)
    g_free (GTK_VALUE_STRING (args[i]));
}

i also wonder whether people would be interested in an elipsis type
interface to query such values, so you could write the above as:

gdouble text_height;
gdouble clip_height;
gdouble y_offset;

gtk_object_get (GTK_OBJECT (mv->text[day_index]),
                "text_height", &text_height,
                "clip_height", &clip_height,
                "y_offset", &y_offset,
                NULL);

of course, this lacks type safety as much as the current _set() interface
does, and certain constrains have to be taken care about, e.g.

fundamental type		 var arg collected
GTK_TYPE_DOUBLE		expects: gdouble*
GTK_TYPE_FLOAT		expects: gdouble*
GTK_TYPE_INT		expects: gint*
GTK_TYPE_CHAR		expects: gint*
GTK_TYPE_UCHAR		expects: guint*
GTK_TYPE_LONG		expects: glong*

etc...
(the actuall mappings of fundamental types to var arg types can be
found in the guts of gtkargcollector.c).


> 
> _A_
> 

---
ciaoTJ