2 files changed, 27 insertions, 4 deletions
diff --git a/lib/Graph/GEXF/Role/Viz/Color.pm b/lib/Graph/GEXF/Role/Viz/Color.pm
index 166186f..e168ad1 100644
--- a/lib/Graph/GEXF/Role/Viz/Color.pm
+++ b/lib/Graph/GEXF/Role/Viz/Color.pm
@@ -3,14 +3,28 @@ package Graph::GEXF::Role::Viz::Color;
 use Moose::Role;
 use Moose::Util::TypeConstraints;
 
-subtype RGBColor => as 'Int' => where { $_ >= 0 && $_ <= 255 };
+subtype RGBColor => as 'Num' => where { $_ >= 0 && $_ <= 255 };
+subtype Alpha => as 'Num' => where { $_ > 0 and $_ <= 1 };
+
+my $_has_colors  = 0;
 
 has [qw/r g b/] => (
-    is  => 'rw',
-    isa => 'RGBColor',
+    is      => 'rw',
+    isa     => 'RGBColor',
+    default => 0,
+    trigger => sub {$_has_colors++},
+);
+
+has a => (
+    is      => 'rw',
+    isa     => 'Alpha',
+    default => 1,
 );
 
+sub has_colors { $_has_colors }
+
 no Moose::Util::TypeConstraints;
 no Moose::Role;
 
+
 1;
diff --git a/lib/Graph/GEXF/Role/Viz/Shape.pm b/lib/Graph/GEXF/Role/Viz/Shape.pm
index f522786..f8e57de 100644
--- a/lib/Graph/GEXF/Role/Viz/Shape.pm
+++ b/lib/Graph/GEXF/Role/Viz/Shape.pm
@@ -14,7 +14,16 @@ parameter for => (
 role {
     my $p = shift;
 
-    my $type = lcfirst( $p->for ) . 'Shape';
+    my ( $type, $default );
+
+    $type = lcfirst( $p->for ) . 'Shape';
+
+    if ( $p->for eq 'node' ) {
+        $default = 'disc';
+    }
+    else {
+        $default = 'solid';
+    }
 
     has shape => (
         is  => 'rw',