diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/input/window.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/input/window.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,80 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { windows, isInteractive, isDocumentLoaded,
+        getOuterId, isTopLevel } = require("../window/utils");
+const { InputPort } = require("./system");
+const { lift, merges, foldp, keepIf, start, Input } = require("../event/utils");
+const { patch } = require("diffpatcher/index");
+const { on } = require("../event/core");
+const { Sequence,  seq, filter, object, pairs } = require("../util/sequence");
+
+
+// Create lazy iterators from the regular arrays, although
+// once https://github.com/mozilla/addon-sdk/pull/1314 lands
+// `windows` will be transforme to lazy iterators.
+// When iterated over belowe sequences items will represent
+// state of windows at the time of iteration.
+const opened = seq(function*() {
+  const items = windows(null, {includePrivates: true});
+  for (let item of items)
+    yield [getOuterId(item), item];
+});
+const interactive = filter(([_, window]) => isInteractive(window), opened);
+const loaded = filter(([_, window]) => isDocumentLoaded(window), opened);
+
+// Helper function that converts given argument to a delta.
+const Update = window => window && object([getOuterId(window), window]);
+const Delete = window => window && object([getOuterId(window), null]);
+
+// Signal represents delta for last opened top level window.
+const LastOpened = lift(Update, new InputPort({topic: "domwindowopened"}));
+exports.LastOpened = LastOpened;
+
+// Signal represents delta for last top level window close.
+const LastClosed = lift(Delete, new InputPort({topic: "domwindowclosed"}));
+exports.LastClosed = LastClosed;
+
+const windowFor = document => document && document.defaultView;
+
+// Signal represent delta for last top level window document becoming interactive.
+const InteractiveDoc = new InputPort({topic: "chrome-document-interactive"});
+const InteractiveWin = lift(windowFor, InteractiveDoc);
+const LastInteractive = lift(Update, keepIf(isTopLevel, null, InteractiveWin));
+exports.LastInteractive = LastInteractive;
+
+// Signal represent delta for last top level window loaded.
+const LoadedDoc = new InputPort({topic: "chrome-document-loaded"});
+const LoadedWin = lift(windowFor, LoadedDoc);
+const LastLoaded = lift(Update, keepIf(isTopLevel, null, LoadedWin));
+exports.LastLoaded = LastLoaded;
+
+
+const initialize = input => {
+  if (!input.initialized) {
+    input.value = object(...input.value);
+    Input.start(input);
+    input.initialized = true;
+  }
+};
+
+// Signal represents set of currently opened top level windows, updated
+// to new set any time window is opened or closed.
+const Opened = foldp(patch, opened, merges([LastOpened, LastClosed]));
+Opened[start] = initialize;
+exports.Opened = Opened;
+
+// Signal represents set of top level interactive windows, updated any
+// time new window becomes interactive or one get's closed.
+const Interactive = foldp(patch, interactive, merges([LastInteractive,
+                                                      LastClosed]));
+Interactive[start] = initialize;
+exports.Interactive = Interactive;
+
+// Signal represents set of top level loaded window, updated any time
+// new window becomes interactive or one get's closed.
+const Loaded = foldp(patch, loaded, merges([LastLoaded, LastClosed]));
+Loaded[start] = initialize;
+exports.Loaded = Loaded;