This reverts commit 06cd254954.
GObject Introspection tools somehow fail to introspect some macros in a
very bizarre way. See issue #14668.
I thought #pragma once was somewhat standard, but it turns out it's not.
And Wikipedia even stays about this:
> While #pragma once is available in most modern compilers, its
> implementation is tricky and might not always be reliable.
Anyway clearly it's not reliable at least regarding GIR tools. I believe
we should hold up on using #pragma once at the very least within our
libgimp* libraries. It is probably fine for app/ or plug-ins/ where we
don't need to introspect anything (and so far we haven't had any
compilation mishap because of this preprocessing directive).
New libgimpbase functions:
- gimp_param_spec_choice_get_choice
- gimp_param_spec_choice_get_default
Now the only GParamSpec in libgimpbase whose struct is visible is
GimpParamSpecObject. This can't change since it is derived into param
specs defined in libgimp and therefore needs to be visible.
This is used in the generated GUIs for GimpChoice arguments, but also for
validation of property setting.
New functions:
* gimp_choice_set_sensitive()
* gimp_string_combo_box_set_sensitivity()
This will be used for creating limited lists of strings as argument types for
procedures.
Ideally enums are the best type for this, but it can only be used for generic
libgimp* enum types, not custom enums created only for a given plug-in. For
this, we currently just demote the args to ints which lose any semantic. A
limited list of string will give back some semantic and some better validation,
even though it's a tiny bit more annoying to work with strings than int types
(at least in C).
