The type of bus to watch a name on.
The name (well-known or unique) to watch.
Flags from the #GBusNameWatcherFlags enumeration.
Handler to invoke when @name is known to exist or %NULL.
Handler to invoke when @name is known to not exist or %NULL.
User data to pass to handlers.
Function for freeing @user_data or %NULL.
Return: An identifier (never 0) that an be used with g_bus_unwatch_name() to stop watching the name.
2.26
Starts watching @name on the bus specified by @bus_type and calls @name_appeared_handler and @name_vanished_handler when the name is known to have a owner respectively known to lose its owner. Callbacks will be invoked in the [thread-default main context][g-main-context-push-thread-default] of the thread you are calling this function from.
You are guaranteed that one of the handlers will be invoked after calling this function. When you are done watching the name, just call g_bus_unwatch_name() with the watcher id this function returns.
If the name vanishes or appears (for example the application owning the name could restart), the handlers are also invoked. If the #GDBusConnection that is used for watching the name disconnects, then @name_vanished_handler is invoked since it is no longer possible to access the name.
Another guarantee is that invocations of @name_appeared_handler and @name_vanished_handler are guaranteed to alternate; that is, if @name_appeared_handler is invoked then you are guaranteed that the next time one of the handlers is invoked, it will be @name_vanished_handler. The reverse is also true.
This behavior makes it very simple to write applications that want to take action when a certain [name exists][gdbus-watching-names]. Basically, the application should create object proxies in @name_appeared_handler and destroy them again (if any) in @name_vanished_handler.