--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/extension/modules/content-injector.js	Thu Aug 06 14:53:41 2009 -0700
@@ -0,0 +1,72 @@
+var EXPORTED_SYMBOLS = ["init"];
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+
+function buildRequestor(window) {
+  return function request(caps, callback) {
+    if (!(typeof(caps) == "object" ||
+          typeof(caps) == "string"))
+      throw new Error("Must provide capabilities as first parameter.");
+
+    if (typeof(callback) != "function")
+      throw new Error("Must provide callback as second parameter");
+
+    if (typeof(caps) == "object")
+      caps = new XPCSafeJSObjectWrapper(caps);
+    callback = new XPCSafeJSObjectWrapper(callback);
+
+    // TODO: Present UI to user and inject requested capabilities.
+  };
+}
+
+var listener = {
+  QueryInterface : XPCOMUtils.generateQI([Ci.nsIWebProgressListener,
+                                          Ci.nsISupportsWeakReference]),
+
+  onStateChange : function (aWebProgress, aRequest,
+                            aStateFlags,  aStatus) {
+    // STATE_START is too early, doc is still the old page.
+    // STATE_STOP is inconviently late (it's onload)
+    if (!(aStateFlags & Ci.nsIWebProgressListener.STATE_TRANSFERRING))
+      return;
+
+    var window = aWebProgress.DOMWindow;
+
+    if (window.wrappedJSObject) {
+      var sandbox = Cu.Sandbox(window);
+      sandbox.importFunction(buildRequestor(window));
+      sandbox.window = window.wrappedJSObject;
+
+      function setupPowerbox() {
+        window.powerbox = {request: request};
+      }
+
+      Cu.evalInSandbox("(" + setupPowerbox.toString() + ")();", sandbox);
+    }
+  },
+
+  // stubs for the nsIWebProgressListener interfaces which we don't use.
+  onProgressChange : function() { },
+  onLocationChange : function() { },
+  onStatusChange   : function() { },
+  onSecurityChange : function() { }
+};
+
+function init() {
+  // WebProgressListener for getting notification of new doc loads.
+  // XXX Ugh. Since we're a chrome overlay, it would be nice to just
+  // use gBrowser.addProgressListener(). But that isn't sending
+  // STATE_TRANSFERRING, and the earliest we can get at the page is
+  // STATE_STOP (which is onload, and is inconviently late).
+  // We'll use the docloader service instead, but that means we need to
+  // filter out loads for other windows.
+  var docsvc = Cc["@mozilla.org/docloaderservice;1"].
+               getService(Ci.nsIWebProgress);
+
+  docsvc.addProgressListener(listener,
+                             Ci.nsIWebProgress.NOTIFY_STATE_DOCUMENT);
+}