Question

I am trying to make a firefox extension which looks at all the new pages that a user views and look at the URL. I was looking at the nsINavHistoryObserver interface and was interested in the onVisit function. Is there a way to create an event listener that can listen to whenever the onVisit function is called?

Thanks

Answer 1

you can find some information about Places (the bookmarks and history system) in Mozilla Developer Center: https://developer.mozilla.org/en/Places

you can find examples in our tests unit (notice some of them could not be optimized for performance)
h t t p://mxr.mozilla.org/mozilla-central/search?string=nsINavHistoryobserver&find=tests

What you need is to get history service, and attach an history observer to it

Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");

var hs = Cc["@mozilla.org/browser/nav-history-service;1"].
         getService(Ci.nsINavHistoryService);

var historyObserver = {
  onBeginUpdateBatch: function() {},
  onEndUpdateBatch: function() {},
  onVisit: function(aURI, aVisitID, aTime, aSessionID, aReferringID, aTransitionType) {},
  onTitleChanged: function(aURI, aPageTitle) {},
  onBeforeDeleteURI: function(aURI) {},
  onDeleteURI: function(aURI) {},
  onClearHistory: function() {},
  onPageChanged: function(aURI, aWhat, aValue) {},
  onDeleteVisits: function() {},
  QueryInterface: XPCOMUtils.generateQI([Ci.nsINavHistoryObserver])
};

hs.addObserver(historyObserver, false);

You should try to reduce most as possible the work you do in the addVisit notification, you should really handle it asynchronously to avoid slowing down the basic browser functionality.