Change all action callbacks so they can be invoked by a GAction:
- add GimpActionCallback typedef:
void (* cb) (GimpAction*, GVariant*, gpointer)
- change all action callbacks to the GimpActionCallback signature
- add "gimp-activate" and "gimp-change-state" signals to GimpAction,
with the same signature as the resp. GAction signals
- remove all other custom action signals and only use the new
GimpAction signals
- pass around appropriate GVariants containing booleans, int32,
strings
- badly hack around to force a GimpProcedure pointer into a
uint64 variant
- remove all G_CALLBACK() casts from all action callbacks,
they all have the same signature now
(cherry picked from commit 3b6b3fc189)
Try to sort all GIMP_ICON_* defines into FDO categories like in
https://specifications.freedesktop.org/icon-naming-spec/latest/ar01s04.html
Add defines for all icons we override, rename some icons to their FDO
standard names, and mark the ones we duplicate with a comment so we
don't forget to rename those to standard names in 3.0.
Have "Save" and "Restore" buttons in both the tool preset list/grid
and the tool preset editor. The save button stores the active tool's
options in the preset, if possible.
