Issue 521- Inject our stylesheet on per-site basis rather than globally

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -66,59 +66,90 @@ let styleURL = null;
 let ElemHide = exports.ElemHide =
 {
   /**
    * Indicates whether filters have been added or removed since the last apply() call.
    * @type Boolean
    */
   isDirty: false,
 
-  /**
-   * Inidicates whether the element hiding stylesheet is currently applied.
-   * @type Boolean
-   */
-  applied: false,
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
 
   /**
    * Called on module startup.
    */
   init: function()
   {
     TimeLine.enter("Entered ElemHide.init()");
     Prefs.addListener(function(name)
     {
       if (name == "enabled")
         ElemHide.apply();
     });

[Wladimir Palant, 2014/05/20 19:36:12]

This code is no longer necessary.

     onShutdown.add(function()
     {
-      ElemHide.unapply();
-    });
+      Services.obs.removeObserver(this, "content-document-global-created");
+    }.bind(this));
 
     TimeLine.log("done adding prefs listener");
 
     let styleFile = IO.resolveFilePath(Prefs.data_directory);
     styleFile.append("elemhide.css");
     styleURL = Services.io.newFileURI(styleFile).QueryInterface(Ci.nsIFileURL);
     TimeLine.log("done determining stylesheet URL");
 
+    Services.obs.addObserver(this, "content-document-global-created", true);
+
     TimeLine.leave("ElemHide.init() done");
   },
 
   /**
    * Removes all known filters
    */
   clear: function()
   {
     filterByKey = {__proto__: null};
     keyByFilter = {__proto__: null};
     knownExceptions = {__proto__: null};
     exceptions = {__proto__: null};
     ElemHide.isDirty = false;
-    ElemHide.unapply();
+  },
+
+  observe: function (subject, topic, data, additional)
+  {
+    if (topic != "content-document-global-created")
+      return;
+
+    if (!Prefs.enabled)
+      return;
+
+    let uri = subject.document.documentURIObject;
+    if (!uri)
+      return;
+
+    switch(uri.scheme)
+    {
+      case "http":
+      case "https":
+      case "mailbox":
+      case "imap":
+      case "news":
+      case "snews":
+        break;
+      default:
+        // Avoid injecting in chrome documents
+        return;
+    }

[Wladimir Palant, 2014/05/20 19:36:12]

Please use Policy.isBlockableScheme() here (from contentPolicy.js).

+
+    // XXX is there some better way to test if it's disabled on that domain that we should do before?
+    if (!ElemHide.anySelectorForDomain(uri.host))
+      return;

[Wladimir Palant, 2014/05/20 19:36:12]

Wow, performance will go down the drain here. We can simply assume that there
are always *some* filters applying - as long as element hiding isn't generally
disabled.

Currently this check is being performed in Policy.processNode() (called from
elemHideHitRegistration.js). We need to move this logic into a separate
function, it will now be called both from Policy.processNode() and from here.
For the window and each of its parents, check whether the scheme is blockable at
all, whether any exception rule for type DOCUMENT or type ELEMHIDE exists for
that URL, plus sitekey-based exceptions.

The logic in elemHideHitRegistration.js should be simplified then. Rather than
going through the full Policy.processNode() processing, it should merely check
whether any element hiding exceptions apply and register a hit.

+
+    var windowUtils = subject.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
+    windowUtils.loadSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
   },
 
   /**
    * Add a new element hiding filter
    * @param {ElemHideFilter} filter
    */
   add: function(filter)
   {
@@ -205,54 +236,29 @@ let ElemHide = exports.ElemHide =
   /**
    * Will be set to true if an apply() call arrives while apply() is already
    * running (delayed execution).
    * @type Boolean
    */
   _needsApply: false,
 
   /**
-   * Generates stylesheet URL and applies it globally
+   * Generates stylesheet URL.
    */
+  // XXX Rename
   apply: function()

[Wladimir Palant, 2014/05/20 19:36:12]

saveStylesheet()?

   {
     if (this._applying)
     {
       this._needsApply = true;
       return;
     }
 
     TimeLine.enter("Entered ElemHide.apply()");
 
-    if (!ElemHide.isDirty || !Prefs.enabled)
-    {
-      // Nothing changed, looks like we merely got enabled/disabled
-      if (Prefs.enabled && !ElemHide.applied)
-      {
-        try
-        {
-          Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
-          ElemHide.applied = true;
-        }
-        catch (e)
-        {
-          Cu.reportError(e);
-        }
-        TimeLine.log("Applying existing stylesheet finished");
-      }
-      else if (!Prefs.enabled && ElemHide.applied)
-      {
-        ElemHide.unapply();
-        TimeLine.log("ElemHide.unapply() finished");
-      }
-
-      TimeLine.leave("ElemHide.apply() done (no file changes)");
-      return;
-    }
-
     IO.writeToFile(styleURL.file, this._generateCSSContent(), function(e)
     {
       TimeLine.enter("ElemHide.apply() write callback");
       this._applying = false;
 
       // _generateCSSContent is throwing NS_ERROR_NOT_AVAILABLE to indicate that
       // there are no filters. If that exception is passed through XPCOM we will
       // see a proper exception here, otherwise a number.
@@ -269,33 +275,16 @@ let ElemHide = exports.ElemHide =
       {
         this._needsApply = false;
         this.apply();
       }
       else if (!e)
       {
         ElemHide.isDirty = false;
 
-        ElemHide.unapply();
-        TimeLine.log("ElemHide.unapply() finished");
-
-        if (!noFilters)
-        {
-          try
-          {
-            Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
-            ElemHide.applied = true;
-          }
-          catch (e)
-          {
-            Cu.reportError(e);
-          }
-          TimeLine.log("Applying stylesheet finished");
-        }
-
         FilterNotifier.triggerListeners("elemhideupdate");

[Wladimir Palant, 2014/05/20 19:36:12]

Apparently, this is dead code. This notification has been introduced in
https://hg.adblockplus.org/adblockplus/rev/1c10d9bd251d and is no longer used
anywhere - the e10s support is no more. Feel free to remove it while at it.

       }
       TimeLine.leave("ElemHide.apply() write callback done");
     }.bind(this), "ElemHideWrite");
 
     this._applying = true;
 
     TimeLine.leave("ElemHide.apply() done", "ElemHideWrite");
@@ -356,35 +345,23 @@ let ElemHide = exports.ElemHide =
     }
   },
 
   /**
    * Unapplies current stylesheet URL
    */
   unapply: function()
   {
-    if (ElemHide.applied)
-    {
-      try
-      {
-        Utils.styleService.unregisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
-      }
-      catch (e)
-      {
-        Cu.reportError(e);
-      }
-      ElemHide.applied = false;
-    }
   },

[Wladimir Palant, 2014/05/20 19:36:12]

This function should be removed.

 
   /**
    * Retrieves the currently applied stylesheet URL
    * @type String
    */
-  get styleURL() ElemHide.applied ? styleURL.spec : null,
+  get styleURL() styleURL.spec,

[Wladimir Palant, 2014/05/20 19:36:12]

This getter was also introduced in
https://hg.adblockplus.org/adblockplus/rev/1c10d9bd251d and is no longer being
used either, feel free to remove it.

 
   /**
    * Retrieves an element hiding filter by the corresponding protocol key
    */
   getFilterByKey: function(/**String*/ key) /**Filter*/
   {
     return (key in filterByKey ? filterByKey[key] : null);
   },
@@ -407,10 +384,23 @@ let ElemHide = exports.ElemHide =
 
       if (specificOnly && (!domains || domains[""]))
         continue;
 
       if (filter.isActiveOnDomain(domain) && !this.getException(filter, domain))
         result.push(filter.selector);
     }
     return result;
+  },
+
+  anySelectorForDomain: function(/**String*/ domain)
+  {
+    for (let key in filterByKey)
+    {
+      let filter = filterByKey[key];
+
+      if (filter.isActiveOnDomain(domain) && !this.getException(filter, domain))
+        return true;
+    }
+
+    return false;
   }
 };