Re: Graphics properties implementation

[Shai Ayal]

On Jan 17, 2008 6:00 PM, Michael Goffioul <address@hidden> wrote:
> On 1/14/08, Kai Habel <address@hidden> wrote:
> > Hello Michael,
> >
> > yes I will look into the additional method needed, but it will take some
> > time. After a first look into the respective jhandles file [1] it seems
> > straightforward to translate the methods for face/vertex <-->  X/Y/Z
> > conversion and normals computation into C++.
> >
> > I assume these functions should be called (if needed) from a not yet
> > existing validate method as well.
>
> Indeed, that's a possible solution. Actually, IMO there's a need for a
> built-in self-listener mechanism in the properties classes (the one
> derived from base_properties); this mechanism would be responsible
> for calling the appropriate update function. In practice, I mean something
> like the following (I just included the relevant code):
>
> class base_properties
> {
> public:
>   virtual void validate (const std::string& pname) { }
> };
>
> class patch
> {
> public:
>   class properties : public base_properties
>   {
>   public:
>     void update_xyz_data (void);
>     void validate (const std::string& pname)
>     {
>       if (pname == "faces" || pname == "vertices")
>         update_xyz ();
>     }
>
>     BEGIN_PROPERTIES(patch)
>       array_property faces v , Matrix ()
>     END_PROPERTIES
>   };
> };
>
> The 'v' modifier would expand set_faces as
>
> void set_faces (const octave_value& v)
> {
>   if (! error_state)
>   {
>     faces = v;
>     validate ("faces");
>     mark_modified ();
>   }
> }
>
> This should fit pretty easy in the code generation. Shai, John: comments?

This is similar to the postset checks I suggested. Maybe we should
make it more generic and add a preset & postset functions which would
be called from set (with the "v" modifier):

void set_faces (const octave_value& v)
{
  if (! error_state)
  {
     preset ("faces", v);
     if (! error_state)
     {
        faces = v;
        postset ("faces");
        mark_modified ();
     }
  }
}

this allows for further checks of the input before setting the value
-- I'm sure it will come in handy sometime ...

Shai