mark_busy

Increases the busy count of this.

Use this function to indicate that the application is busy, for instance while a long running operation is pending.

The busy state will be exposed to other processes, so a session shell will use that information to indicate the state to the user (e.g. with a spinner).

To cancel the busy indication, use unmark_busy.

The application must be registered before calling this function.

Parameters:

this	a Application