Re: Graphics properties as objects

[John W. Eaton]

On  4-Jan-2008, Michael Goffioul wrote:

| On 1/4/08, John W. Eaton <address@hidden> wrote:
| > I would really prefer to have the properties be objects instead of
| > pointers to objects.
| >
| > What do you really need the map for?
| 
| I think it significantly simplify any code that access properties
| by name, because it provides a unified access.
| 
| > Even if they are not stored in a map, all property types can still be
| > derived from a base class that stores things like the hidden flag.
| 
| Indeed, that's what I have for the moment. Actually, I just thought
| about something else. Keep the property field as typed classes
| in the nested "properties" classes (as it is now); keep the interface
| "property" class (as I proposed) as unified access and for reference
| count; store all properties in a std::map<caseless_str,property>,
| but for fixed properties, artificially increment the internal count by
| one to take into account the field use for direct access. That is
| something like this:
| 
|     string_property string;
| 
|     const string_property& get_string (void) const { return string; }
| 
|     void set_string (const octave_value& v) { string = v; }
| 
| and to store the property in the global map, do something like
| (conceptually):
| 
|     property p (&string);
|     p.increment_count_by_one ();
|     xproperties.add (p);
| 
| Would this be better?

Is it even necessary to have the base class do reference counting
here?

Since the properties are tied to the graphics objects that contain
them, shouldn't we only expect them to exist as long as the graphics
object exists?

If individual properties do need to exist longer than the graphics
objects that contain them, then wouldn't it be sufficient to simply
have a copy of the property?  Aren't most (all) of the property
classes composed of objects that are already reference counted?  So
copying them should be relatively cheap and since they are passed
around by value, they should not be deleted unnecessarily?

Why should get_string return a reference instead of a value?

jwe