Re: Graphics properties as objects

[Michael Goffioul]

On 1/8/08, John W. Eaton <address@hidden> wrote:
> | class property
> | {
> | public:
> |     property (base_property *p, bool persist = false);
> |     ...
> | };
>
> What is the rest of this class?  Does it include reference counting?
> How is it expected to be used?

See the attached file for a full patch corresponding to my current
status (note: this is unfinished work-in-progress, it does not compile).
The class "property" is a wrapper around base_property with reference
counting. It provides a value-typed generic interface for accessing
properties, suitable for storing in a map.

> | class base_properties
> | {
> | public:
> |     ...
> |
> |     // this method is to add dynamic properties into the map
> |     void insert_property (const std::string& name, property p)
> |       {
> |         p.set_name (name);
> |         p.set_parent (__myhandle__);
> |         all_props[name] = p;
> |       }
>
> I'm surprised to see the property argument above not be a reference or
> pointer.  Doesn't this cause a copy to be made when insert_property is
> called?

It just increases the reference counting of the underlying base_property
object.

> |     Matrix get_position (void) const { return position.matrix_value (); }
>
> Would the backend never need access to the additional information
> stored in the matrix_property object?  If not then I think this is
> OK.  Otherwise, why not just return the matrix_property object
> directly?

That's why I also added a "get_property" method to the base_properties
class (see attached patch), to keep the possibility to access the
property object. I'm not sure about that part of my proposal: initially, this
was intended to make life easier in the C++ backend, because it would
typically access position with something like "get_position().matrix_value()"
(provided get_position returns matrix_property). For radio properties,
the equivalent accessor would be something like
"bool xlimmode_is (const std::string& val) const;". So in the end, while
maybe making the C++ code easier to write, it would make genprops.awk
more complex, because the accessors will be different for every kind of
property.

Michael.

graphics.diff.bz2
Description: BZip2 compressed data