Re: [graphviz-interest] Moving nodes and edges between [sub]graphs using the gv library

On 02/27/2014 05:33 PM, Emden R. Gansner wrote:
> I think a couple of corrections are necessary.
>
>>
>> A node can't be a direct member of more than one subgraph. Subgraphs 
>> can be added to other subgraphs, forming a tree,
>> so indirectly a node is a member of all its parent subgraphs, and the 
>> parent graph. 
> This isn't true. Otherwise, you could do things like:
>    {rank=same a b}
>    subgraph cluster {a b }
> Nodes and edges can be put into any subgraphs anywhere. The two 
> restrictions are, with cgraph, subgraphs must now
> form a tree (in libgraph, they could form a dag), and nodes should 
> have a unique immediate cluster.
>
>> So, to move a node from one subgraph to another I would need to create
>> a new node, copy all the attributes, create copies of all the existing
>> edges to/from the old node, copy all of their attributes, then delete
>> the old node (and the old edges?)?
> No, you just remove it and stick it anywhere else in the graph you want.
> The restriction is that nodes and edges do live in a unique root 
> graph. You can't remove a node from
> a root graph and stick it into another root graph. In this case, you 
> would have to make a clone of the
> node in the new graph. The library provides functions for cloning
>
>> Yes, except that presumably the reason for moving it to a subgraph is 
>> so that you inherit a number of the attributes from the subgraph 
>> tree, so you wouldn't need to rewrite those. 
> No, when a node is created, it inherits its attributes active 
> currently defined in the chain of subgraphs containing it. After
> that, if you change the containing graph's node attributes, or move 
> the node to a new subgraph, it keeps the attributes
> it had when created. After creation, the only way to alter the node's 
> attributes is to reset them explicitly.
>
>     Emden
>
> _______________________________________________
> [email protected]
> http://lists.research.att.com/mailman/listinfo/graphviz-interest


I defer to Emden's expertise,   but none of the existing language 
bindings provide functions for moving nodes, so
I assume this is from C ?

Perhaps some example C code and I could extend the language bindings....

So if the attribute inheritance doesn't change, this only makes sense 
for cluster to cluster moves, and moves from top-level into and out of a 
cluster?

_______________________________________________
[email protected]
http://lists.research.att.com/mailman/listinfo/graphviz-interest