Memoize event handlers

Stop virtualdom from swapping out every event handler on every update

renderer/lib/dispatcher.js

@@ -0,0 +1,36 @@
+module.exports = {
+  setDispatch,
+  dispatch,
+  dispatcher
+}
+
+// _memoize most of our event handlers, which are functions in the form
+// () => dispatch(<args>)
+// ... this prevents virtual-dom from updating tons of listeners on every update()
+var _dispatchers = {}
+var _dispatch = () => {}
+
+function setDispatch (dispatch) {
+  _dispatch = dispatch
+}
+
+// Get a _memoized event handler that calls dispatch()
+// All args must be JSON-able
+function dispatcher (...args) {
+  var json = JSON.stringify(args)
+  var handler = _dispatchers[json]
+  if (!handler) {
+    _dispatchers[json] = (e) => {
+      // Don't click on whatever is below the button
+      e.stopPropagation()
+      // Don't regisiter clicks on disabled buttons
+      if (e.target.classList.contains('disabled')) return
+      _dispatch.apply(null, args)
+    }
+  }
+  return handler
+}
+
+function dispatch (...args) {
+  _dispatch.apply(null, args)
+}