[gimp/gimp-2-10] Issue #4366 - Color-to-alpha unnecessarily grayed out for grayscale images

[Ell <ell src gnome org>]

commit b55afe87033849c67c5225b721ac5a5037a6b1f3
Author: Ell <ell_se yahoo com>
Date:   Fri Jan 17 12:03:07 2020 +0200

    Issue #4366 - Color-to-alpha unnecessarily grayed out for grayscale images
    
    Don't disable color-to-alpha for grayscale drawable, since the
    operation is applicable to grayscale images (in particular, it
    doesn't add color where there was none), and since we no longer
    distinguish between layers and channels according to the drawable
    format when updating the filters actions.

 app/actions/filters-actions.c | 2 +-
 app/pdb/plug-in-compat-cmds.c | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)
---
diff --git a/app/actions/filters-actions.c b/app/actions/filters-actions.c
index f5fb1cb856..1f66c0efce 100644
--- a/app/actions/filters-actions.c
+++ b/app/actions/filters-actions.c
@@ -895,7 +895,7 @@ filters_actions_update (GimpActionGroup *group,
   SET_SENSITIVE ("filters-dither",                  writable);
   SET_SENSITIVE ("filters-color-rotate",            writable);
   SET_SENSITIVE ("filters-color-temperature",       writable && !gray);
-  SET_SENSITIVE ("filters-color-to-alpha",          writable && !gray && supports_alpha);
+  SET_SENSITIVE ("filters-color-to-alpha",          writable && supports_alpha);
   SET_SENSITIVE ("filters-component-extract",       writable);
   SET_SENSITIVE ("filters-convolution-matrix",      writable);
   SET_SENSITIVE ("filters-cubism",                  writable);
diff --git a/app/pdb/plug-in-compat-cmds.c b/app/pdb/plug-in-compat-cmds.c
index 3b68d028d9..d6e07beac8 100644
--- a/app/pdb/plug-in-compat-cmds.c
+++ b/app/pdb/plug-in-compat-cmds.c
@@ -1040,8 +1040,6 @@ plug_in_colortoalpha_invoker (GimpProcedure         *procedure,
                                      GIMP_PDB_ITEM_CONTENT, error) &&
           gimp_pdb_item_is_not_group (GIMP_ITEM (drawable), error))
         {
-          /* XXX: fixme disable for gray */
-
           GeglColor *gegl_color = gimp_gegl_color_new (&color);
           GeglNode  *node =
             gegl_node_new_child (NULL,