Move project status string management to new attached object class

src/ProjectStatus.cpp

@@ -0,0 +1,48 @@
+/**********************************************************************
+
+Audacity: A Digital Audio Editor
+
+ProjectStatus.h
+
+Paul Licameli
+
+**********************************************************************/
+
+#include "ProjectStatus.h"
+
+#include "Project.h"
+
+wxDEFINE_EVENT(EVT_PROJECT_STATUS_UPDATE, wxCommandEvent);
+
+static const AudacityProject::AttachedObjects::RegisteredFactory key{
+  []( AudacityProject &parent ){
+     return std::make_shared< ProjectStatus >( parent );
+   }
+};
+
+ProjectStatus &ProjectStatus::Get( AudacityProject &project )
+{
+   return project.AttachedObjects::Get< ProjectStatus >( key );
+}
+
+const ProjectStatus &ProjectStatus::Get( const AudacityProject &project )
+{
+   return Get( const_cast< AudacityProject & >( project ) );
+}
+
+ProjectStatus::ProjectStatus( AudacityProject &project )
+   : mProject{ project }
+{
+}
+
+ProjectStatus::~ProjectStatus() = default;
+
+void ProjectStatus::Set(const wxString &msg)
+{
+   auto &project = mProject;
+   if ( msg != mLastMainStatusMessage ) {
+      mLastMainStatusMessage = msg;
+      wxCommandEvent evt{ EVT_PROJECT_STATUS_UPDATE };
+      project.ProcessEvent( evt );
+   }
+}