In the context of screens, windows and like media, arrangements for automatically detecting when a recipient has entered or left a public setting so that privacy configuration changes can be automatically invoked. Also broadly contemplated herein is an arrangement for selectively displaying messages on the recipient's screen but deferring the messages from being visible on a remote hardware device or software display which is publicly visible. Furthermore, there is broadly contemplated herein a secure arrangement for revealing and responding to deferred messages. More generally, there is broadly contemplated herein a new approach to the provision of application notifications and to alarm control during a desktop screen sharing mode, based on the automatic detection of a screen sharing state and on notifying registered applications of the screen sharing in a unified, consistent manner.