We have g_idle_add() and g_timeout_add(). But these return
those odd guint source ids. That is totally pointless. The
only potential benefit is that a guint is only 4 bytes while
a pointer is 8 bytes (on 64 bit systems). Otherwise, it seems
always preferable to have an actual GSource instance instead
of an integer. It also saves the overhead in g_source_remove()
which first needs to do a hash lookup to find the GSource.
A GSource instance would theoretically work with multiple
GMainContext instances, while g_source_remove() only works
wit g_main_context_default().
On the other hand we have helper API like nm_g_idle_source_new()
and nm_g_timeout_source_new(), which is fully flexible and sensible
because it returns a reference to the GSource instance. However, it
is a bit verbose to use in the common case.
Add helper functions that simplify the use and are conceptionally
similar to g_{idle,timeout}_add() (hence the name).