Question

I am developing an extension on Firefox’s Addon SDK (v1.9). My extension blocks or allows resources by implementing nsIContentPolicy and testing their URIs against a database of URIs to block.

Problem

I need to have access to the tab object (if available) from the shouldLoad function of nsIContentPolicy.

I assume the part to use for this is the “context” parameter on the shouldLoad function which is nsISupports. I have tried using getTabForWindow(win) with no luck since context is not nsIDOMWindow (Identify tab that made request in Firefox Addon SDK)

Answer 1

The context parameter is either a document or an element. Getting from there to a window isn’t hard:

var {Ci} = require("chrome");
if (!(context instanceof Ci.nsIDOMWindow))
{
  // If this is an element, get the corresponding document
  if (context instanceof Ci.nsIDOMNode && context.ownerDocument)
    context = context.ownerDocument;

  // Now we should have a document, get its window
  if (context instanceof Ci.nsIDOMDocument)
    context = context.defaultView;
  else
    context = null;
}

// If we have a window now - get the tab
if (context)
{
  var tabsLib = require("tabs/tab.js");
  return tabsLib.getTabForWindow(context.top);
}
else
  return null;

For reference: Node, Document,window.