Re: Restricting possible connections

[Lars Clausen <lrclause cs uiuc edu>]

On Thu, 24 Oct 2002, ml@knorke.in-berlin.de wrote:
> On Thu, Oct 24, 2002 at 09:23:48AM -0500, Lars Clausen wrote:
>> The right place to add a checking call would be in
>> layer_find_closest_connectionpoint() in app/diagramdata.c.  Problem is,
>> that loop goes over all objects in a layer, so we can't afford to spend
>> a lot of time there.  Well, we can keep it within the if, that'll cut
>> out most of it.  And instead of adding code to DrawFunc, a new object
>> func should be defined for it.
> 
> OK, I try to resume:
> 
> 1. A restriction on possible connections seems to be a good
>    idea.  Think of network diagrams, not to speak of
>    UML/Database/SDL/... code generation.
> 
> 2. Of course, this must be an option to the user.  Maybe a
>    diagram specific or a global option?

Hmmm... good question.  Global options are easier to make and do away
with.  I really don't know which is better.

> 3. The method to check has to be a new object function.
>    Something like:
> 
>    typedef gboolean (*AllowConnectFunc) (Object* obj_me,
>                                          Object* obj_other,
>                                          ... /* ? */ );

You may want to give the handle and connection point to the function.
Could be some objects will allow objects to connect in certain ways and not
in others.

> 4. This function will be called twice (once for the
>    connecting object, once for the connected one) from
>    layer_find_closest_connectionpoint().  I don't see
>    performance hits, if functions will be called after
>    the "if (dist<mindist)" and only if the option is set.

Sounds about right.

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| Hårdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?