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

lib/child/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 15 matching lines @@
   let property = Object.getOwnPropertyDescriptor(proto, "Components");
   if (property && property.get)
     delete proto.Components;
 }
 catch (e)
 {
   Cu.reportError(e);
 }
 
 let {XPCOMUtils} = Cu.import("resource://gre/modules/XPCOMUtils.jsm", {});
+let {Services} = Cu.import("resource://gre/modules/Services.jsm", {});
 
 let {shouldAllowAsync} = require("child/contentPolicy");
+let {getFrames, isPrivate} = require("child/utils");
+let {RequestNotifier} = require("child/requestNotifier");
 let {port} = require("messaging");
 let {Utils} = require("utils");
 
 // The allowXBL binding below won't have any effect on the element. For elements
 // that should be hidden however we don't return any binding at all, this makes
 // Gecko stop constructing the node - it cannot be shown.
 const allowXBL = "<bindings xmlns='http://www.mozilla.org/xbl'><binding id='dummy' bindToUntrustedContent='true'/></bindings>";
 const hideXBL = "<bindings xmlns='http://www.mozilla.org/xbl'/>";
 
 const notImplemented = () => Cr.NS_ERROR_NOT_IMPLEMENTED;
@@ skipping 238 matching lines @@
     return new Promise((resolve, reject) =>
     {
       let window = Utils.getRequestWindow(this);
       shouldAllowAsync(window, window.document, "ELEMHIDE", this.key, allow =>
       {
         resolve(allow ? allowXBL : hideXBL);
       });
     });
   }
 };
+
+let observer = {
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsIObserver, Ci.nsISupportsWeakReference
+  ]),
+
+  topic: "content-document-global-created",
+  styleURL: Utils.makeURI("about:abp-elemhide?css"),
+  sheet: null,
+
+  init: function()
+  {
+    Services.obs.addObserver(this, this.topic, true);
+    onShutdown.add(() =>
+    {
+      Services.obs.removeObserver(this, this.topic);
+    });
+
+    port.on("elemhideupdate", () =>
+    {
+      this.sheet = null;

[Thomas Greiner, 2016/06/23 14:12:42]

If I understand this correctly, we no longer apply changes in element hiding
rules right away but only after the page reloads. That'd be a regression to the
current behavior in Firefox (and probably also Element Hiding Helper) even
though that's how the extension currently behaves on other platforms.

If so, was this change intentional to make it more consistent with our other
versions or is this a performance optimization?

[Wladimir Palant, 2016/06/29 16:18:21]

Yes, this is very much desirable and indeed listed under "issues solved" in the
description of https://issues.adblockplus.org/ticket/521.

Element Hiding Helper will have to be adjusted slightly, I guess that ideally it
should make sure the styles for the current webpage get reapplied.

+    });
+  },
+
+  observe: function(subject, topic, data)
+  {
+    if (topic != this.topic)
+      return;
+
+    port.emitWithResponse("elemhideEnabled", {
+      frames: getFrames(subject),
+      isPrivate: isPrivate(subject)
+    }).then(({
+      enabled, contentType, docDomain, thirdParty, location, filter,
+      filterType
+    }) =>
+    {
+      if (enabled)
+      {
+        if (!this.sheet)
+        {
+          this.sheet = Utils.styleService.preloadSheet(this.styleURL,
+              Ci.nsIStyleSheetService.USER_SHEET);
+        }
+
+        let utils = subject.QueryInterface(Ci.nsIInterfaceRequestor)
+                           .getInterface(Ci.nsIDOMWindowUtils);
+        utils.addSheet(this.sheet, Ci.nsIStyleSheetService.USER_SHEET);
+      }
+      else if (filter)
+      {
+        RequestNotifier.addNodeData(subject.document, subject.top, {
+          contentType, docDomain, thirdParty, location, filter, filterType
+        });
+      }
+    });
+  }
+};
+observer.init();