paramValuesCmp
Compares @value1 with @value2 according to @pspec, and return -1, 0 or +1, if @value1 is found to be less than, equal to or greater than @value2, respectively.
Return
-1, 0 or +1, for a less than, equal to or greater than result
Parameters
pspec
a valid #GParamSpec
value1
a #GValue of correct type for @pspec
value2
a #GValue of correct type for @pspec