Bug 1554761 - Notify with a 'mac_app_activate' topic when the App has been activated, capturing Command-Tabbing behavior. OSX only. r=spohl

Differential Revision: https://phabricator.services.mozilla.com/D39936

widget/cocoa/nsAppShell.mm

@@ -46,6 +46,9 @@
 #include "nsIDOMWakeLockListener.h"
 #include "nsIPowerManagerService.h"
 
+#include "nsIObserverService.h"
+#include "mozilla/Services.h"
+
 using namespace mozilla;
 using namespace mozilla::widget;
 
@@ -881,6 +884,11 @@ nsAppShell::AfterProcessNextEvent(nsIThreadInternal* aThread, bool aEventWasProc
         [currentEvent modifierFlags] & NSDeviceIndependentModifierFlagsMask;
   }
 
+  nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
+  if (observerService) {
+    observerService->NotifyObservers(nullptr, NS_WIDGET_MAC_APP_ACTIVATE_OBSERVER_TOPIC, nullptr);
+  }
+
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 

widget/nsIWidget.h

@@ -261,6 +261,12 @@ enum nsTopLevelWidgetZPlacement {  // for PlaceBehind()
  */
 #define NS_WIDGET_RESUME_PROCESS_OBSERVER_TOPIC "resume_process_notification"
 
+/**
+ * When an app(-shell) is activated by the OS, this topic is notified.
+ * Currently, this only happens on Mac OSX.
+ */
+#define NS_WIDGET_MAC_APP_ACTIVATE_OBSERVER_TOPIC "mac_app_activate"
+
 namespace mozilla {
 namespace widget {