Added class definitions to nodes

Removed the inline styling of nodes with classes, replaced with class
attributes and a common CSS Style section at the start of the SVG.

src/utils.js

@@ -25,3 +25,31 @@ module.exports.detectType = function(text,a){
 
     return "graph";
 };
+
+/**
+ * Copies all relevant CSS content into the graph SVG.
+ * This allows the SVG to be copied as is while keeping class based styling
+ * @param {element} svg The root element of the SVG
+ * @param {string} defaultStyle Default style definitions (for elements without classes)
+ */
+module.exports.cloneCssStyles = function(svg, defaultStyle){
+    var used = "";
+    var sheets = document.styleSheets;
+    for (var i = 0; i < sheets.length; i++) {
+        var rules = sheets[i].cssRules;
+        for (var j = 0; j < rules.length; j++) {
+            var rule = rules[j];
+            if (typeof(rule.style) != "undefined") {
+                var elems = svg.querySelectorAll(rule.selectorText);
+                if (elems.length > 0) {
+                    used += rule.selectorText + " { " + rule.style.cssText + " }\n";
+                }
+            }
+        }
+    }
+
+    var s = document.createElement('style');
+    s.setAttribute('type', 'text/css');
+    s.innerHTML = "/* <![CDATA[ */\n" + defaultStyle + "\n" + used + "\n/* ]]> */";
+    svg.insertBefore(s, svg.firstChild);
+};