1 files changed, 94 insertions, 0 deletions
diff --git a/dom/base/UIDirectionManager.cpp b/dom/base/UIDirectionManager.cpp
new file mode 100644
index 0000000000..4a55555a4a
--- /dev/null
+++ b/dom/base/UIDirectionManager.cpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 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/. */
+
+#include "mozilla/dom/UIDirectionManager.h"
+#include "mozilla/Preferences.h"
+#include "nsIObserverService.h"
+#include "nsIWindowMediator.h"
+#include "nsDocShell.h"
+#include "nsServiceManagerUtils.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/Services.h"
+#include "mozilla/SimpleEnumerator.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_ISUPPORTS(UIDirectionManager, nsIObserver)
+
+/* static */
+NS_IMETHODIMP
+UIDirectionManager::Observe(nsISupports* aSubject, const char* aTopic,
+                            const char16_t* aData) {
+  NS_ENSURE_FALSE(strcmp(aTopic, "intl:app-locales-changed"), NS_ERROR_FAILURE);
+
+  // Iterate over all of the windows and notify them of the direction change.
+  nsCOMPtr<nsIWindowMediator> windowMediator =
+      do_GetService(NS_WINDOWMEDIATOR_CONTRACTID);
+  NS_ENSURE_TRUE(windowMediator, NS_ERROR_FAILURE);
+
+  nsCOMPtr<nsISimpleEnumerator> windowEnumerator;
+  windowMediator->GetEnumerator(nullptr, getter_AddRefs(windowEnumerator));
+  NS_ENSURE_TRUE(windowEnumerator, NS_ERROR_FAILURE);
+
+  for (auto& elements : SimpleEnumerator<nsISupports>(windowEnumerator)) {
+    nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryInterface(elements);
+    if (window->Closed()) {
+      continue;
+    }
+
+    RefPtr<BrowsingContext> context = window->GetBrowsingContext();
+    MOZ_DIAGNOSTIC_ASSERT(context);
+
+    if (context->IsDiscarded()) {
+      continue;
+    }
+
+    context->PreOrderWalk([](BrowsingContext* aContext) {
+      if (dom::Document* doc = aContext->GetDocument()) {
+        doc->ResetDocumentDirection();
+      }
+    });
+  }
+  return NS_OK;
+}
+
+/* static */
+void UIDirectionManager::Initialize() {
+  MOZ_ASSERT(!gUIDirectionManager);
+  MOZ_ASSERT(NS_IsMainThread());
+
+  RefPtr<UIDirectionManager> observer = new UIDirectionManager();
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (NS_WARN_IF(!obs)) {
+    return;
+  }
+  obs->AddObserver(observer, "intl:app-locales-changed", false);
+
+  gUIDirectionManager = observer;
+}
+
+/* static */
+void UIDirectionManager::Shutdown() {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!gUIDirectionManager) {
+    return;
+  }
+  RefPtr<UIDirectionManager> observer = gUIDirectionManager;
+  gUIDirectionManager = nullptr;
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (!obs) {
+    return;
+  }
+
+  obs->RemoveObserver(observer, "intl:app-locales-changed");
+}
+
+mozilla::StaticRefPtr<UIDirectionManager>
+    UIDirectionManager::gUIDirectionManager;
+
+}  // namespace mozilla::dom