1 files changed, 27 insertions, 0 deletions
diff --git a/browser/actors/SwitchDocumentDirectionChild.sys.mjs b/browser/actors/SwitchDocumentDirectionChild.sys.mjs
new file mode 100644
index 0000000000..302662f07b
--- /dev/null
+++ b/browser/actors/SwitchDocumentDirectionChild.sys.mjs
@@ -0,0 +1,27 @@
+/* vim: set ts=2 sw=2 sts=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+export class SwitchDocumentDirectionChild extends JSWindowActorChild {
+  receiveMessage(message) {
+    if (message.name == "SwitchDocumentDirection") {
+      let docShell = this.manager.browsingContext.docShell;
+      let document = docShell.QueryInterface(Ci.nsIWebNavigation).document;
+      this.switchDocumentDirection(document);
+    }
+  }
+
+  switchDocumentDirection(document) {
+    // document.dir can also be "auto", in which case it won't change
+    if (document.dir == "ltr" || document.dir == "") {
+      document.dir = "rtl";
+    } else if (document.dir == "rtl") {
+      document.dir = "ltr";
+    }
+
+    for (let frame of document.defaultView.frames) {
+      this.switchDocumentDirection(frame.document);
+    }
+  }
+}