Issue 5090 - Use user stylesheets for element hiding if possible

lib/cssInjection.js

Index: lib/cssInjection.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/cssInjection.js
@@ -0,0 +1,93 @@
+/*
+ * 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/>.
+ */
+
+/** @module cssInjection */
+
+"use strict";
+
+const {RegExpFilter} = require("filterClasses");
+const {ElemHide} = require("elemHide");
+const {checkWhitelisted} = require("whitelisting");
+const {extractHostFromFrame} = require("url");
+const {port} = require("messaging");
+const devtools = require("devtools");
+
+let userStylesheetsSupported = true;
+
+function hideElements(tabId, frameId, selectors)
+{
+  let code = selectors.join(", ") + "{display: none !important;}";
+
+  try
+  {
+    chrome.tabs.insertCSS(tabId,
+      {
+        code,
+        cssOrigin: "user",
+        frameId,
+        matchAboutBlank: true
+      }
+    );
+    return true;
+  }
+  catch (error)
+  {
+    if (/\bError processing cssOrigin\b/.test(error.message) == -1)
+      throw error;
+
+    userStylesheetsSupported = false;
+    return false;
+  }
+}
+
+port.on("elemhide.getSelectors", (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 = [];
+  }
+
+  if (selectors.length == 0 || userStylesheetsSupported &&
+      hideElements(sender.page.id, sender.frame.id, selectors))
+  {
+    if (trace)
+      return {selectors, trace: true, inject: false};
+
+    return {trace: false, inject: false};
+  }
+
+  return {selectors, trace, inject: true};
+});
+
+port.on("elemhide.injectSelectors", (msg, sender) =>
+{
+  return hideElements(sender.page.id, sender.frame.id, msg.selectors);
+});