diff -r 000000000000 -r 6474c204b198 widget/xpwidgets/GfxInfoCollector.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/widget/xpwidgets/GfxInfoCollector.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,94 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * 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/. */
+
+#ifndef __mozilla_widget_GfxInfoCollector_h__
+#define __mozilla_widget_GfxInfoCollector_h__
+
+#include "mozilla/Attributes.h"
+#include "nsStringFwd.h"
+#include "js/RootingAPI.h"
+
+namespace mozilla {
+namespace widget {
+
+
+/* this is handy wrapper around JSAPI to make it more pleasant to use.
+ * We collect the JSAPI errors and so that callers don't need to */
+class MOZ_STACK_CLASS InfoObject
+{
+  friend class GfxInfoBase;
+
+  public:
+  void DefineProperty(const char *name, int value);
+  void DefineProperty(const char *name, nsAString &value);
+  void DefineProperty(const char *name, const char *value);
+
+  private:
+  // We need to ensure that this object lives on the stack so that GC sees it properly
+  InfoObject(JSContext *aCx);
+  InfoObject(InfoObject&);
+
+  JSContext *mCx;
+  JS::Rooted<JSObject*> mObj;
+  bool mOk;
+};
+
+/*
+
+   Here's an example usage:
+
+   class Foo {
+   Foo::Foo() : mInfoCollector(this, &Foo::GetAweseomeness) {}
+
+   void GetAwesomeness(InfoObject &obj) {
+     obj.DefineProperty("awesome", mAwesome);
+   }
+
+   int mAwesome;
+
+   GfxInfoCollector<Foo> mInfoCollector;
+   }
+
+   This will define a property on the object
+   returned from calling getInfo() on a
+   GfxInfo object. e.g.
+
+       gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
+       info = gfxInfo.getInfo();
+       if (info.awesome)
+          alert(info.awesome);
+
+*/
+
+class GfxInfoCollectorBase
+{
+  public:
+  GfxInfoCollectorBase();
+  virtual void GetInfo(InfoObject &obj) = 0;
+  virtual ~GfxInfoCollectorBase();
+};
+
+template<class T>
+class GfxInfoCollector : public GfxInfoCollectorBase
+{
+  public:
+  GfxInfoCollector(T* aPointer, void (T::*aFunc)(InfoObject &obj)) : mPointer(aPointer), mFunc(aFunc) {
+  }
+  virtual void GetInfo(InfoObject &obj) {
+    (mPointer->*mFunc)(obj);
+  }
+
+  protected:
+  T* mPointer;
+  void (T::*mFunc)(InfoObject &obj);
+
+};
+
+}
+}
+
+#endif