bit of cleanup

lib/site/handlers.js

@@ -3443,14 +3443,42 @@ return {
  }())
   },
   "comments": {
-    handler: (function() { return {
+    handler: (function() { /**
+ * We REALLY don't want disqus to load unless the user
+ * is actually looking at the comments section, because it
+ * tacks on 2.5+ MB in network transfers...
+ */
+return {
   componentDidMount() {
-    if (typeof document !== "undefined") {
-      var script = document.createElement("script");
-      script.src = "lib/site/disqus.js";
-      script.async = true;
-      document.head.appendChild(script);
+    if (typeof document === "undefined") {
+      return this.silence();
     }
+    this.heading = document.getElementById(this.props.page);
+    document.addEventListener("scroll", this.scrollHandler, {passive:true});
+  },
+
+  scrollHandler(evt) {
+    var bbox = this.heading.getBoundingClientRect();
+    var top = bbox.top;
+    var limit = window.innerHeight;
+    if (top<limit) { this.loadDisqus(); }
+  },
+
+  loadDisqus() {
+    var script = document.createElement("script");
+    script.src = "lib/site/disqus.js";
+    script.async = true;
+    document.head.appendChild(script);
+    this.silence();
+    this.unlisten();
+  },
+
+  silence() {
+    this.loadDisqus = () => {};
+  },
+
+  unlisten() {
+    document.removeEventListener("scroll", this.scrollHandler);
   }
 };
  }())