Adds a function to be called whenever there are no higher priority
events pending to the default main loop. The function is given the
default idle priority,
The function will only be called once and then the source will be automatically removed from the main context.
This function otherwise behaves like g_idle_add().
Available since: 2.74
This function is not directly available to language bindings.
Function to call.
Data to pass to
The argument can be
The data is owned by the caller of the function.