I updated GimpScaleEntry and GimpColorScaleEntry header to use
respectively the macros G_DECLARE_DERIVABLE_TYPE and
G_DECLARE_FINAL_TYPE.
Though having the `priv` structure directly in the object data is
extremely comfortable for developing (hence we don't want to use this
macro on core code as it makes coding a bit more bothersome), it is true
that it does not make for a very pretty public interface (showing a
`priv` member which nobody can actually use, and a private type which
has no associated functions). So it might be a good idea to use these
macros at least on libgimp side.
I am still not sure though if it is a good idea so we could say it's an
experiment. At least the docs says that using G_DECLARE_FINAL_TYPE does
not affect ABI stability as it can later be changed into a
G_DECLARE_DERIVABLE_TYPE because the class structure stays private. So
at least that's one good point.
P.S.: also reordering gimpwidgets.def.
Similarly to GimpScaleEntry, this is meant to replace usage of
gimp_color_scale_entry_new() by having a proper widget. This is a child
class of GimpScaleEntry which simply replaces the GtkScale by a
GimpColorScale by adding a GimpScaleEntry class method to create the
scale widget (only restriction: it must be a GtkRange subtype).
This also triggers me to rename gimp_scale_entry_get_scale() into
gimp_scale_entry_get_range() (as well as the 2 plug-ins already using
this function).
Jehan