Re: ID Recalculation

[Hans Breuer <hans breuer org>]

At 04.12.2009 14:08, Luis Villa wrote:
> Hello all,
>
> First of all, I want to tell you I think your work is pretty good! :)
Thanks.

> I'm using Dia to create diagrams I'll use as an input to a program. For
> accomplishing this, I parse the resultant xml and mix it with an internal
> structure. I use 'id' attribute in 'dia:object' tags to match the xml object
> with the saved internal object.
The dia:object id is not maintained during Dia's runtime. It is just 
generated during save to restore connections on load. But after loading the 
diagram again all ids are intentionally forgotten.

> The problem I found is that, when I delete a
> object, it seems the id is recalculated, so all internal objects are now
> invalid.Does it works that way?
>
As I said the object id is already lost before the deletion. And it will 
also change when you change the layer or the z-order of the objects.

> Is it possible to change Dia not to do this  recalculation?
Not without an extra layer of complexity I'd like to avoid. The main issue 
would be to ensure the uniqueness of such an id during copy, maybe even 
across different diagrams. Also there arise questions when to change the 
object id (if stored in a different diagram, on change of all object 
properties or only if it's name would change, etc. pp.)

Without knowing your exact use case it might be possible for you to 
generate your own object id and store it as

      <dia:attribute name="meta">
        <dia:composite type="dict">
          <dia:attribute name="some-id">
            <dia:string>#123#</dia:string>
          </dia:attribute>
        </dia:composite>
      </dia:attribute>

Of course that would also not solve the issues I mentioned above regarding 
uniqueness. The content of the 'dict' is not changed by Dia, there even is 
no user interface to do so at the moment.

-------- Hans "at" Breuer "dot" Org -----------
Tell me what you need, and I'll tell you how to
get along without it.                -- Dilbert