[gimp] app: don't highlight layers dialog "new" button when pasting to channel

[N/A <ell src gnome org>]

commit 378c5d3b87f1dc81e1e7c9588d500b460d8665ac
Author: Ell <ell_se yahoo com>
Date:   Wed Mar 7 09:31:02 2018 -0500

    app: don't highlight layers dialog "new" button when pasting to channel
    
    We disallow creating a new layer from a floating selection when its
    associated drawable is a channel, so there's no point in
    highlighting the "new layer" button in this case.  Note that the
    "layers-new" action remains sensitive, showing an error message if
    activated.  Not sure if it's a good thing or not, but whatever.

 app/widgets/gimplayertreeview.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/app/widgets/gimplayertreeview.c b/app/widgets/gimplayertreeview.c
index 15d7b89..519f00b 100644
--- a/app/widgets/gimplayertreeview.c
+++ b/app/widgets/gimplayertreeview.c
@@ -32,11 +32,13 @@
 #include "widgets-types.h"
 
 #include "core/gimp.h"
+#include "core/gimpchannel.h"
 #include "core/gimpcontainer.h"
 #include "core/gimpimage-undo.h"
 #include "core/gimpimage.h"
 #include "core/gimpitemundo.h"
 #include "core/gimplayer.h"
+#include "core/gimplayer-floating-selection.h"
 #include "core/gimplayer-new.h"
 #include "core/gimplayermask.h"
 #include "core/gimptreehandler.h"
@@ -930,7 +932,8 @@ gimp_layer_tree_view_floating_selection_changed (GimpImage         *image,
 
   gimp_highlightable_button_set_highlight (
     GIMP_HIGHLIGHTABLE_BUTTON (gimp_item_tree_view_get_new_button (item_view)),
-    floating_sel != NULL);
+    floating_sel != NULL &&
+    ! GIMP_IS_CHANNEL (gimp_layer_get_floating_sel_drawable (floating_sel)));
   gimp_highlightable_button_set_highlight (
     GIMP_HIGHLIGHTABLE_BUTTON (gimp_item_tree_view_get_delete_button (item_view)),
     floating_sel != NULL);