Calls the given function for each data element of the datalist. The
function is called with each data element’s
GQuark id and data,
together with the given
user_data parameter. Note that this
function is NOT thread-safe. So unless
datalist can be protected
from any modifications during invocation of this function, it should
not be called.
func can make changes to
datalist, but the iteration will not
reflect changes made during the
g_datalist_foreach() call, other
than skipping over elements that are removed.