Issue 5090 - Use user stylesheets for element hiding if possible

background.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 const {RegExpFilter} = require("filterClasses");
 const {ElemHide} = require("elemHide");
 const {checkWhitelisted} = require("whitelisting");
 const {extractHostFromFrame} = require("url");
+const {hideElements} = require("css");
 const {port} = require("messaging");
 const devtools = require("devtools");
 
+let tryInsertCSS = true;
+
 port.on("get-selectors", (msg, sender) =>
 {
   let selectors;
   let trace = devtools && devtools.hasPanel(sender.page);
 
   if (!checkWhitelisted(sender.page, sender.frame,
                         RegExpFilter.typeMap.DOCUMENT |
                         RegExpFilter.typeMap.ELEMHIDE))
   {
     let specificOnly = checkWhitelisted(sender.page, sender.frame,
                                         RegExpFilter.typeMap.GENERICHIDE);
     selectors = ElemHide.getSelectorsForDomain(
       extractHostFromFrame(sender.frame),
       specificOnly ? ElemHide.SPECIFIC_ONLY : ElemHide.ALL_MATCHING
     );
   }
   else
   {
     selectors = [];
   }
 
-  return {selectors, trace};
+  if (!tryInsertCSS)
+    return {selectors, trace, inject: true};
+
+  return new Promise(resolve =>
+  {
+    hideElements(sender.page.id, sender.frame.id, selectors, error =>
+    {
+      if (error && /\bError processing cssOrigin\b/.test(error.message) != -1)

[kzar, 2017/04/20 06:17:15]

From the discussion in the Chromium issue it seems like they expect us to just
check the user agent string to figure out if user stylesheets can be injected,
and the cssOrigin option won't be supported anyway.

So I wonder if we're better off just using the info module to check platform +
version in order to see if the feature is supported, rather than seeing if an
exception is thrown that matches this regexp?

We're just going to have to change the logic in the future otherwise. For
example we're going to have to check the platform and version here anyway and
we're going to have to at least check the platform in lib/css.js before passing
the cssOrigin option which Chrome doesn't like.

[Manish Jethani, 2017/04/20 12:50:32]

Yeah, this makes sense. I've added a userStylesheetsSupported property to the
css module now. The background page checks the value before trying to use the
hideElements function.

[kzar, 2017/04/21 11:20:22]

Nice, looks good. Could you update the issue description to match?

+        tryInsertCSS = false;
+
+      let response = {trace, inject: !!error};
+
+      if (trace || error)
+        response.selectors = selectors;
+
+      resolve(response);
+    });
+  });
+});
+
+port.on("hide-elements", (msg, sender) =>
+{
+  return new Promise(resolve =>
+  {
+    hideElements(sender.page.id, sender.frame.id, msg.selectors, error =>
+    {
+      resolve({success: !error});
+    });
+  });
 });
 
 port.on("forward", (msg, sender) =>
 {
   let targetPage;
   if (msg.targetPageId)
     targetPage = ext.getPage(msg.targetPageId);
   else
     targetPage = sender.page;
 
   if (targetPage)
   {
     msg.payload.sender = sender.page.id;
     if (msg.expectsResponse)
       return new Promise(targetPage.sendMessage.bind(targetPage, msg.payload));
     targetPage.sendMessage(msg.payload);
   }
 });