Added ability to choose which attributes get passed to the dot graph node/edge.

[ducky427]

I've added the ability to filter out or add additional keys to the attributes of a dot node or a dot edge.

This is useful as some data is not really part of the loom node/edge but it is meta-data like shape, colour etc. This gives the user a way to add that information if needed.

I've also added a way to add some metadata for the global dot nodes and edges.

[aysylu]

Could you please provide some examples? What kind of metadata might one want to add for the global dot nodes and edges?

[ducky427]

I've needed to add metadata like fontname, fontsize for the edges and nodes. For nodes, I've also had to add shape.

Usage would be something like:

(def g (graph [1 2] [2 3] {3 [4] 5 [6 7]} 7 8 9))

(dot g "graph.dot" {:node {:shape "Mrecord"
                           :fontname "Bitstream Vera Sans"
                           :fontsize "8"}
                    :edge {:fontsize 8
                           :fontname "Bitstream Vera Sans"
                           :arrowhead "vee"}})

[ducky427]

Another example:

(def g (-> (digraph 0 1)
           (add-attr 0 :name "Alice" :type "Sender")
           (add-attr 1 :name "Bob" :type "Receiver")
           (add-edges [0 1])))

(defn get-node-props
  [x]
  {:label (format "{%s|%s}" (:type x) (:name x))})

(dot g "graph.dot" {:node-attrs get-node-props
                    :node {:shape "Mrecord"
                           :fontname "Bitstream Vera Sans"
                           :fontsize "8"}
                    :edge {:fontsize "8"
                           :fontname "Bitstream Vera Sans"
                           :arrowhead "vee"}})

[ducky427]

For my last example, I could have easily used the node-label variable as well. But using the node-attrs variable, I have the ability to set other properties of the dot graph node itself like colour, etc. The same thing goes for edge-attrs.

I feel that these 2 are generalizations of node-label and edge-label.

[aysylu]

Thanks for the clarifications! I see your point. You're right that node-attrs and edge-attrs is more general and powerful, but I think we can eliminate the need for both by creating a transform-edge-attrs (similarly, for nodes) that will take all loom attrs and create a new graph with the added dot attrs (see below). What do you think?

(def transform-edge-attrs [g f]
  (reduce
      (fn [g e]
           ; this is an approximation, needs to actually work (see return values of attrs and add-attr)
           (add-attr g e (f (attrs g n1 n2)))
       g
      (edges g))

[ducky427]

I agree. transform-edge-attrs and transform-node-attrs would be even more general.

I'll work up another pull request with those two functions along with remove-attrs function. This function would work the same as remove-attr except it would take a sequence of keys to remove.

[aysylu]

Sounds good, @ducky427. Let me know when the PR is ready.