Graphics properties as objects

[Michael Goffioul]

On 1/6/08, John W. Eaton <jwe at bevo.che.wisc.edu> wrote:
> OK, I think my understanding of the problem is better now.
>
> Can we hide some of the details so that we can write
>
>  all_props.insert ("my_property", string_property (...));
>
> ?  I don't mind that the property class might need a series of
> constructors like
>
>  property (const color_property& p) : rep (new color_property (p)) { ... }
>  property (const radio_property& p) : rep (new radio_property (p)) { ... }
>  property (const string_property& p) : rep (new string_property (p)) { ... }
>  ...
>
> Also, I'd like to hide the following details in some way:
>
>  property p (&string);
>  p.increment_count_by_one ();
>  xproperties.add (p);
>
> So maybe we could write
>
>  axes::properties::properties (const graphics_handle& mh,
>                                const graphics_handle& p)
>    : base_properties (go_name, mh, p),
>      position (Matrix ()),
>      ...
>  {
>    ...
>
>    all_props.insert_static_property ("position", position);
>    ...
>  }
>
> and have all the reference counting and address-of details hidden?

I agree with the concept og hiding things, but from the code above,
I have the impression that the typed property object (contained in
the "property" interface object) stored in the property map would be
a copy of the typed property field contained in the graphic object.
Is this what you want? Or do you mean that "insert_static_property"
should get an implementation like the following to make sure the
typed property object is really shared:

void insert_static_property (const std::string& name, position_property& p)
{
    all_props[name] = property (&p);
}

I have the impression that using a copy of "position" in the property map
will get you into trouble: if you change the position from octave, the
obvious implementation will probably be to access the map and change
the property. But the C++ backend will use get_position() to access
the property. If you use copies, the values won't match?
Or did I miss something?

Michael.