Issue 5090 - Use user stylesheets for element hiding if possible

lib/elemHideHelper.js

Index: lib/elemHideHelper.js
diff --git a/background.js b/lib/elemHideHelper.js
similarity index 56%
copy from background.js
copy to lib/elemHideHelper.js
index cb7a861be117f6a390b74ffa1370bb9de50ba33f..83de8426f36c396ac69b747d586e935bf979732d 100644
--- a/background.js
+++ b/lib/elemHideHelper.js
@@ -15,6 +15,8 @@
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/** @module elemHideHelper */
+
 "use strict";
 
 const {RegExpFilter} = require("filterClasses");
@@ -23,6 +25,28 @@ const {checkWhitelisted} = require("whitelisting");
 const {extractHostFromFrame} = require("url");
 const {port} = require("messaging");
 const devtools = require("devtools");
+const info = require("info");
+
+let userStylesheetsSupported = info.platform == "gecko" &&
+                               info.platformVersion.split(".")[0] >= 53;
+
+function hideElements(tabId, frameId, selectors, callback)
+{
+  let code = selectors.join(", ") + "{display: none !important;}";
+
+  chrome.tabs.insertCSS(tabId,
+    {
+      code,
+      cssOrigin: "user",
+      frameId,
+      matchAboutBlank: true
+    },
+    () =>
+    {
+      callback(chrome.runtime.lastError);
+    }
+  );
+}
 
 port.on("get-selectors", (msg, sender) =>
 {
@@ -45,22 +69,41 @@ port.on("get-selectors", (msg, sender) =>
     selectors = [];
   }
 
-  return {selectors, trace};
+  if (!userStylesheetsSupported)
+    return {selectors, trace, inject: true};
+
+  if (selectors.length == 0)
+  {
+    if (trace)
+      return {selectors, trace, inject: false};
+
+    return {trace, inject: false};
+  }
+
+  return new Promise(resolve =>
+  {
+    hideElements(sender.page.id, sender.frame.id, selectors, error =>
+    {
+      let response = {trace, inject: !!error};
+
+      if (trace || error)
+        response.selectors = selectors;
+
+      resolve(response);
+    });
+  });
 });
 
-port.on("forward", (msg, sender) =>
+port.on("hide-elements", (msg, sender) =>
 {
-  let targetPage;
-  if (msg.targetPageId)
-    targetPage = ext.getPage(msg.targetPageId);
-  else
-    targetPage = sender.page;
+  if (!msg.selectors || msg.selectors.length == 0)
+    return {success: true};
 
-  if (targetPage)
+  return new Promise(resolve =>
   {
-    msg.payload.sender = sender.page.id;
-    if (msg.expectsResponse)
-      return new Promise(targetPage.sendMessage.bind(targetPage, msg.payload));
-    targetPage.sendMessage(msg.payload);
-  }
+    hideElements(sender.page.id, sender.frame.id, msg.selectors, error =>
+    {
+      resolve({success: !error});
+    });
+  });
 });