Re: Objects & Layers relationships

[Lars Clausen <lrclause cs uiuc edu>]

On 12 Aug 2003, Matthew J. Smith wrote:
> Hello all-
> As a Dia user, I just wanted to throw out one of my own observations. 
> Currently, an object seems to reside in a single layer, and can have no
> interaction (for example, connecting lines) with objects in another
> layer.
> I use layers all the time to show/hide the different components of my
> drawing.  For example, an IT Environment diagram may have a physical
> network layer, a logical routing layer, a server layer, an application
> layer, etc.
> It would be very useful to me to have an object that can belong in
> multiple layers.  In the above example, it would be great to have the
> firewall in all my layers, so that all objects can be connected.  As
> well, I'd like to hide all layers except for the one I am interested in,
> and still have the firewall show up.
> I think the easiest solution would be to make layer membership a
> multi-value attribute of an object.  A layer view would then abstractly
> be a query to find all the objects with the selected layer(s) listed as
> an attribute.  This would also allow all objects to connect with all
> others, regardless of layer, since all objects could belong to some
> common "primary" layer.
> Would this type of functionality be useful to anyone else?  Or, should
> I just re-evaluate my use of layers in diagrams?

Your suggestion seems rather slow -- remember that when moving line-ends,
we have to search for nearby objects to connect with, and that would make
us search through a list of layers on each object in the whole diagram,
rather than just the current layer.

What I've considered is to allow connections between layers.  Just like
Gimp allows several layers to be marked as moveable together, we could allow
layers to be marked for connectivity as well as visibility.  In your case,
you'd make one layer that has the firewall, always have that visible and
connectable, but turn visibility and connectibility on and of on the other
layers (by switching current, i.e. selectable, layer).  I think that'd be
fairly easy to do.

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| HĂ„rdgrim 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?