Use the helper to create a View class

    script/myapp_create.pl view GraphViz GraphViz

This creates the MyApp::View::GraphViz class.

Build the GraphViz object

    #In some method (some View method, since
    #that's where the View code should go. See below.)
    use GraphViz;
    $graph = GraphViz->new();
    $graph->add_node("Hello", shape => 'box');
    $graph->add_node("world", shape => 'box');
    $graph->add_edge("Hello", "world");
    
    $c->stash->{graphviz}->{graph} = $graph;
    $c->stash->{graphviz}->{format} = "cmapx"; #HTML image map (default: png)

Forward to the View

    #Meanwhile, maybe in a private end action
    if(!$c->res->body) {
        if($c->stash->{template}) {
            $c->forward('MyApp::View::TT');
        } elsif($c->stash->{graphviz}->{graph}) {
            $c->forward('MyApp::View::GraphViz');
        } else {
            die("No output method!\n");
        }
    }

MyApp::View::OddEvenGraph

Our model object is set like this somewhere (for a quick demo, just put it in the MyApp::default sub):

    $c->stash->{graphview}->{object} = {
        3 => 2,
        4 => 3,
        1 => 3,
        2 => 1,
    };

This can of course be anything that you can interpret as a graph and would like to visualize using GraphViz, not necessarily a single deep data structure like this. It could equally well be an array ref with model objects which together form a graph.

After setting up the model object, we assign the correct View class to render it.

    $c->stash->{graphview}->{view} = "MyApp::View::OddEvenGraph";
    $c->stash->{graphviz}->{format} = "cmapx";  #Optionally override the format

And, maybe in a private "end" action, we forward to the view if it's set, like this:

    sub end : Private {
        my ( $self, $c ) = @_;

        if(!$c->res->body) {
            if($c->stash->{template}) {
                $c->forward('MyApp::View::TT');
            } elsif(my $view = $c->stash->{graphview}->{view}) {
                $c->forward($view);
            } else {
                die("No output method!\n");
            }
        }
    }

That's what your application looks like. Now we need to create the actual View class MyApp::View::OddEvenGraph. Use the helper GraphView:

  script/myapp_create.pl view OddEvenGraph GraphView

In the class MyApp::View::OddEvenGraph you can modify the process sub to suit your needs.

    sub process {
        my ($self, $c) = @_;

        my $graph = $c->stash->{graphview}->{object} or
                die('No object specified in $c->stash->{graphview}->{object} for rendering');

        my $graphviz = GraphViz->new(node => {
            name => "oddeven",
        });

        $graphviz->add_node($_, shape => ($_ % 2) ? "box" : "ellipse") for(keys %$graph);
        while(my ($from, $to) = each %$graph) {
            $graphviz->add_edge($from, $to);
        }


        $c->stash->{graphviz}->{graph} = $graphviz;
        $c->forward('MyApp::View::GraphViz');

        return 1;
    }

As you can see, the purpose of this method is to transform the model graph object into a GraphViz object, which is then forwarded to the GraphViz View.

Render as an Imagemap

    sub png : Local {
        my ( $self, $c ) = @_;
        $c->stash->{graphview}->{view} = "MyApp::View::OddEvenGraph";
        $c->stash->{graphview}->{object} = ...;
    }

then your imap action should look like this:

    sub imap : Local {
        my ( $self, $c ) = @_;
        $c->stash->{graphview}->{view} = "MyApp::View::OddEvenGraph";
        $c->stash->{graphview}->{object} = ...;
        $c->stash->{graphviz}->{format} = "cmapx";
    }

Call the Imagemap Action

    use Catalyst qw/SubRequest/;

This is how to perform the SubRequest. Let's assume these actions are in the Controller "Graph":

    $c->stash->{html_imagemap} = $c->subreq("/graph/imap");

    #Reset after subreq (until this bug is fixed: http://rt.cpan.org/NoAuth/Bug.html?id=15790 )
    $c->response->content_type("text/html");

Now you can simply output the imagemap text in the template

    [% html_imagemap %]
    <img name="graph" src="/graph/png" USEMAP="#oddeven" border=0>

Note 1: The name "oddeven" is the same as the one set in the

    GraphViz->new(name => "oddeven");

Note 1a: Unfortunately this isn't quite true. The name of the GraphViz image is always hardcoded to "test". Bug that needs to be fixed: http://rt.cpan.org/NoAuth/Bug.html?id=14882

Note 2: The nodes will not be clickable unless they have a URL property, so you need to specify that for each

    $graphviz->add_node(URL => "/graph/node/select?name=$name");

in the View class. Actually, there is a clever shortcut in GraphViz for this, so instead of specifying it for each node, you can set a default when calling

    my $graphviz = GraphViz->new(node => { URL => '/graph/node/select?name=\N' });

The \N is a placeholder for the name of each node.

new($c)

process($c)

Output is stored in "$c->response->output".

0.05

0.01 - 0.04