This function works like set_qdata, but in addition, a `void (*destroy) (
gpointer)` function may be specified which is called with data
as argument when the this is
finalized, or the data is being overwritten by a call to set_qdata with the
same quark
.
this |
the ParamSpec to set store a user data pointer |
quark |
a Quark, naming the user data pointer |
data |
an opaque user data pointer |
destroy |
function to invoke with |