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

[Ell <ell src gnome org>]

commit 85a19da868b7a4af476978973a4b3eab4bf4422e
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 539d43fbb4..7a5155bb87 100644
--- a/app/pdb/plug-in-compat-cmds.c
+++ b/app/pdb/plug-in-compat-cmds.c
@@ -1083,8 +1083,6 @@ 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, NULL);
           GeglNode  *node =
             gegl_node_new_child (NULL,