1 files changed, 78 insertions, 0 deletions
diff --git a/toolkit/jetpack/sdk/event/dom.js b/toolkit/jetpack/sdk/event/dom.js
new file mode 100644
index 000000000..da99dec7a
--- /dev/null
+++ b/toolkit/jetpack/sdk/event/dom.js
@@ -0,0 +1,78 @@
+/* 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";
+
+module.metadata = {
+  "stability": "unstable"
+};
+
+const { Ci } = require("chrome");
+
+var { emit } = require("./core");
+var { when: unload } = require("../system/unload");
+var listeners = new WeakMap();
+
+const { Cu } = require("chrome");
+const { ShimWaiver } = Cu.import("resource://gre/modules/ShimWaiver.jsm");
+const { ThreadSafeChromeUtils } = Cu.import("resource://gre/modules/Services.jsm", {});
+
+var getWindowFrom = x =>
+                    x instanceof Ci.nsIDOMWindow ? x :
+                    x instanceof Ci.nsIDOMDocument ? x.defaultView :
+                    x instanceof Ci.nsIDOMNode ? x.ownerDocument.defaultView :
+                    null;
+
+function removeFromListeners() {
+  ShimWaiver.getProperty(this, "removeEventListener")("DOMWindowClose", removeFromListeners);
+  for (let cleaner of listeners.get(this))
+    cleaner();
+
+  listeners.delete(this);
+}
+
+// Simple utility function takes event target, event type and optional
+// `options.capture` and returns node style event stream that emits "data"
+// events every time event of that type occurs on the given `target`.
+function open(target, type, options) {
+  let output = {};
+  let capture = options && options.capture ? true : false;
+  let listener = (event) => emit(output, "data", event);
+
+  // `open` is currently used only on DOM Window objects, however it was made
+  // to be used to any kind of `target` that supports `addEventListener`,
+  // therefore is safer get the `window` from the `target` instead assuming
+  // that `target` is the `window`.
+  let window = getWindowFrom(target);
+
+  // If we're not able to get a `window` from `target`, there is something
+  // wrong. We cannot add listeners that can leak later, or results in
+  // "dead object" exception.
+  // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1001833
+  if (!window)
+    throw new Error("Unable to obtain the owner window from the target given.");
+
+  let cleaners = listeners.get(window);
+  if (!cleaners) {
+    cleaners = [];
+    listeners.set(window, cleaners);
+
+    // We need to remove from our map the `window` once is closed, to prevent
+    // memory leak
+    ShimWaiver.getProperty(window, "addEventListener")("DOMWindowClose", removeFromListeners);
+  }
+
+  cleaners.push(() => ShimWaiver.getProperty(target, "removeEventListener")(type, listener, capture));
+  ShimWaiver.getProperty(target, "addEventListener")(type, listener, capture);
+
+  return output;
+}
+
+unload(() => {
+  let keys = ThreadSafeChromeUtils.nondeterministicGetWeakMapKeys(listeners)
+  for (let window of keys)
+    removeFromListeners.call(window);
+});
+
+exports.open = open;