gutter support

GutterLayer.js

@@ -0,0 +1,22 @@
+function GutterLayer(parentEl)
+{
+  this.element = document.createElement("div");
+  this.element.className = "layer gutter-layer";
+  parentEl.appendChild(this.element);
+}
+
+GutterLayer.prototype.update = function(config)
+{
+  var html = [];
+  for (var i=config.firstRow; i<config.lastRow; i++)
+  {
+    html.push(
+      "<div class='gutter-cell' style='height:" + config.lineHeight + "px;'>",
+      i,
+      "</div>"
+    );
+    html.push("</div>");
+  }
+  
+  this.element.innerHTML = html.join("");  
+};