Move some screen utilities to the global util directory so that they can be used for other things too.

lib/util/statequeue.js

@@ -0,0 +1,30 @@
+function StateQueue() {
+  this.queue = []
+}
+
+StateQueue.prototype.next = function() {
+  return this.queue.shift()
+}
+
+StateQueue.prototype.empty = function() {
+  return this.queue.length === 0
+}
+
+StateQueue.prototype.push = function(state) {
+  var found = false
+
+  // Not super efficient, but this shouldn't be running all the time anyway.
+  for (var i = 0, l = this.queue.length; i < l; ++i) {
+    if (this.queue[i] === state) {
+      this.queue.splice(i + 1)
+      found = true
+      break
+    }
+  }
+
+  if (!found) {
+    this.queue.push(state)
+  }
+}
+
+module.exports = StateQueue