reworked event handling again; added scrollapp example

examples/scrollapp/scrollapp.nim

@@ -0,0 +1,24 @@
+## Example that shows how to accomplish an "infinitely scrolling" app.
+
+include karaxprelude
+import jstrutils, dom
+
+var entries: seq[cstring] = @[]
+for i in 1..500:
+  entries.add(cstring("Entry ") & &i)
+
+proc scrollEvent(ev: Event; n: VNode) =
+  let d = n.dom
+  if d != nil and inViewport(d.lastChild):
+    # "load" more data:
+    for i in 1..50:
+      entries.add(cstring("Loaded Entry ") & &i)
+
+proc createDom(): VNode =
+  result = buildHtml():
+    tdiv(onscroll=scrollEvent, style="height: 400px; overflow: scroll"):
+      for x in entries:
+        tdiv:
+          text x
+
+setRenderer createDom