add Draw Helpers changed notification + physx draw helpers listens to it (#1456)

Code/Framework/AzToolsFramework/AzToolsFramework/Viewport/ViewportMessages.h

@@ -210,6 +210,19 @@ namespace AzToolsFramework
         //! Type to inherit to implement ViewportInteractionRequests.
         using ViewportInteractionRequestBus = AZ::EBus<ViewportInteractionRequests, ViewportEBusTraits>;
 
+        //! An interface to notify when changes to viewport settings have happened.
+        class ViewportSettingNotifications
+        {
+        public:
+            virtual void OnGridSnappingChanged([[maybe_unused]] bool enabled) {}
+            virtual void OnDrawHelpersChanged([[maybe_unused]] bool enabled) {}
+
+        protected:
+            ViewportSettingNotifications() = default;
+        };
+
+        using ViewportSettingsNotificationBus = AZ::EBus<ViewportSettingNotifications, ViewportEBusTraits>;
+
         //! Requests to freeze the Viewport Input
         //! Added to prevent a bug with the legacy CryEngine Viewport code that would
         //! keep doing raycast tests even when no level is loaded, causing a crash.

Code/Sandbox/Editor/ViewportTitleDlg.cpp

@@ -45,6 +45,7 @@
 
 #include <AzCore/std/algorithm.h>
 #include <AzCore/Casting/numeric_cast.h>
+#include <AzToolsFramework/Viewport/ViewportMessages.h>
 
 AZ_PUSH_DISABLE_DLL_EXPORT_MEMBER_WARNING
 #include "ui_ViewportTitleDlg.h"
@@ -57,13 +58,16 @@ inline namespace Helpers
 {
     void ToggleHelpers()
     {
-        GetIEditor()->GetDisplaySettings()->DisplayHelpers(!GetIEditor()->GetDisplaySettings()->IsDisplayHelpers());
+        const bool newValue = !GetIEditor()->GetDisplaySettings()->IsDisplayHelpers();
+        GetIEditor()->GetDisplaySettings()->DisplayHelpers(newValue);
         GetIEditor()->Notify(eNotify_OnDisplayRenderUpdate);
 
-        if (GetIEditor()->GetDisplaySettings()->IsDisplayHelpers() == false)
+        if (newValue == false)
         {
             GetIEditor()->GetObjectManager()->SendEvent(EVENT_HIDE_HELPER);
         }
+        AzToolsFramework::ViewportInteraction::ViewportSettingsNotificationBus::Broadcast(
+            &AzToolsFramework::ViewportInteraction::ViewportSettingNotifications::OnDrawHelpersChanged, newValue);
     }
 
     bool IsHelpersShown()