+ * window status is kind of anemic on win32 as there are no window messages
+ * to notify us that the window is covered by other windows or not.
+ * Should one want to query this, see
+ * http://stackoverflow.com/questions/5445889/get-which-process-window-is-actually-visible-in-c-sharp
+ * for an implementation outline (but it would be polling based, not push based).