Re: [boost] Reading DOT files with Boost.Graph

From: Marshall Clow (marshall_at_[hidden])
Date: 2007-06-21 12:20:33

At 11:36 AM -0400 6/21/07, Ronald Garcia wrote:
>On Jun 20, 2007, at 4:44 PM, Marshall Clow wrote:
>>
>>How do I keep "global settings" when reading and writing a graphviz file?
>>
>>For example, consider the following file:
>>
>>digraph G {
>>     node [ color=blue ];
>>     rankDir=LR
>>
>>     a0 [ label = "//depot/path/to/file_1#4" ];
>>     a1 [ label = "//depot/path/to/file_2#9" ];
>>
>>     a0 -> a1 [ color=gray ];
>>}
>>
>>when read and written (with no changes) becomes:
>>
>>digraph G {
>>     a0 [ color="blue" , label = "//depot/path/to/file_1#4" ];
>>     a1 [ color="blue" , label = "//depot/path/to/file_2#9" ];
>>     a0 -> a1 [ color="gray" ];
>>}
>>
>>As you can see, the global property "node [ color=blue ];" has been 
>>set in each individual node,
>>and the "rankdir=LR" has been completely lost. The first one 
>>doesn't change how the graph gets rendered, but the second one 
>>certainly does.
>>
>>Any way to preserve either of these?
>
>Because of the way the graphviz language works, the node and edge 
>settings are associated directly with the nodes and edges of the 
>graph.  Node and edge settings are only global until another setting 
>is put in place.  It's legal to write:
>
>digraph G {
>   node [color=blue];
>   a0
>   a1
>   node [color=gray];
>   a2
>}
>
>and that is semantically equivalent to
>
>digraph G {
>   a0 [color=blue]
>   a1 [color=blue]
>   a2 [color=gray];
>}

Ok. That's what I figured - it is unfortunate, but I can live with that.

>As for the graph properties, the reader in CVS supports graph 
>properties.  For an example use, look at 
>libs/boost/graph/test/graphviz_test.cpp.

Do you mean boost/libs/graph/test/graphviz_test.cpp?

I looked in the file, and the only graph properties that I can see 
are the types of the node and edge properties. Am I missing something?

I have two goals here, one short term, and one long term.
The short term goal is to read and write a Graphviz file successfully 
(which I am mostly doing, thanks in large part to your answers and 
bug fixes!), and the long term one is to understand what the graph 
library is doing so that I can use it better.

The short term problem that I am trying to solve is that when I read 
and then write a Graphviz file,
I don't get all the information back. In particular, I get results like this:

Input:
digraph G {
     rankDir=LR

     a0 [ label = "//depot/path/to/file_1#4" ];
     a1 [ label = "//depot/path/to/file_2#9" ];

     a0 -> a1 [ color=gray ];
}

Output:
digraph G {
     a0 [ label = "//depot/path/to/file_1#4" ];
     a1 [ label = "//depot/path/to/file_2#9" ];
     a0 -> a1 [ color="gray" ];
}

The line:	    rankDir=LR
has been lost, and Graphviz renders the file quite differently in the 
absence of this line. I called this a "graph property" in my earlier 
email, which may not have been the right term. Is there an easy way 
to convince the Graphviz reader and writer to preserve that command?

-- 
-- Marshall
Marshall Clow     Idio Software   <mailto:marshall_at_[hidden]>
It is by caffeine alone I set my mind in motion.
It is by the beans of Java that thoughts acquire speed,
the hands acquire shaking, the shaking becomes a warning.
It is by caffeine alone I set my mind in motion.