[gimp] app: layers-merge-group multi-layer aware.

[Jehan <jehanp src gnome org>]

commit ae4abbabfdcebe90ddef65e2892d37fad502a593
Author: Jehan <jehan girinstud io>
Date:   Thu May 21 15:06:48 2020 +0200

    app: layers-merge-group multi-layer aware.
    
    Also layers-flatten-image does not care about the layer selection and
    layers-anchor works anyway only when there is a floating selection,
    which means only one layer selected.

 app/actions/layers-actions.c  | 12 +++++-----
 app/actions/layers-commands.c | 54 +++++++++++++++++++++++++++++++++++++------
 2 files changed, 53 insertions(+), 13 deletions(-)
---
diff --git a/app/actions/layers-actions.c b/app/actions/layers-actions.c
index f6681719dd..275803ea9e 100644
--- a/app/actions/layers-actions.c
+++ b/app/actions/layers-actions.c
@@ -187,8 +187,8 @@ static const GimpActionEntry layers_actions[] =
     GIMP_HELP_LAYER_MERGE_DOWN },
 
   { "layers-merge-group", NULL,
-    NC_("layers-action", "Merge Layer Group"), NULL,
-    NC_("layers-action", "Merge the layer group's layers into one normal layer"),
+    NC_("layers-action", "Merge Layer Groups"), NULL,
+    NC_("layers-action", "Merge the layer groups' layers into one normal layer"),
     layers_merge_group_cmd_callback,
     GIMP_HELP_LAYER_MERGE_GROUP },
 
@@ -1035,15 +1035,15 @@ layers_actions_update (GimpActionGroup *group,
   SET_SENSITIVE ("layers-lower",            n_layers > 0 && !fs && !ac && have_next);
   SET_SENSITIVE ("layers-lower-to-bottom",  n_layers > 0 && !fs && !ac && have_next);
 
-  SET_VISIBLE   ("layers-anchor",            layer &&  fs && !ac);
+  SET_VISIBLE   ("layers-anchor",            fs && !ac);
   SET_VISIBLE   ("layers-merge-down",        !fs);
   SET_SENSITIVE ("layers-merge-down",        layer && !fs && !ac && visible && next_visible);
   SET_VISIBLE   ("layers-merge-down-button", !fs);
   SET_SENSITIVE ("layers-merge-down-button", layer && !fs && !ac);
-  SET_VISIBLE   ("layers-merge-group",       children);
-  SET_SENSITIVE ("layers-merge-group",       layer && !fs && !ac && children);
+  SET_VISIBLE   ("layers-merge-group",       have_groups);
+  SET_SENSITIVE ("layers-merge-group",       n_layers && !fs && !ac && have_groups);
   SET_SENSITIVE ("layers-merge-layers",      n_layers > 0 && !fs && !ac);
-  SET_SENSITIVE ("layers-flatten-image",     layer && !fs && !ac);
+  SET_SENSITIVE ("layers-flatten-image",     !fs && !ac);
 
   SET_VISIBLE   ("layers-text-discard",       text_layer && !ac);
   SET_VISIBLE   ("layers-text-to-vectors",    text_layer && !ac);
diff --git a/app/actions/layers-commands.c b/app/actions/layers-commands.c
index aa886278b5..4b5b69af95 100644
--- a/app/actions/layers-commands.c
+++ b/app/actions/layers-commands.c
@@ -805,12 +805,13 @@ layers_anchor_cmd_callback (GimpAction *action,
                             gpointer    data)
 {
   GimpImage *image;
-  GimpLayer *layer;
-  return_if_no_layer (image, layer, data);
+  GList     *layers;
+  return_if_no_layers (image, layers, data);
 
-  if (gimp_layer_is_floating_sel (layer))
+  if (g_list_length (layers) == 1 &&
+      gimp_layer_is_floating_sel (layers->data))
     {
-      floating_sel_anchor (layer);
+      floating_sel_anchor (layers->data);
       gimp_image_flush (image);
     }
 }
@@ -838,10 +839,49 @@ layers_merge_group_cmd_callback (GimpAction *action,
                                  gpointer    data)
 {
   GimpImage *image;
-  GimpLayer *layer;
-  return_if_no_layer (image, layer, data);
+  GList     *layers;
+  GList     *merge_layers = NULL;
+  GList     *iter;
+  return_if_no_layers (image, layers, data);
+
+  for (iter = layers; iter; iter = iter->next)
+    {
+      if (gimp_viewable_get_children (GIMP_VIEWABLE (iter->data)))
+        {
+          GList *iter2;
+
+          for (iter2 = layers; iter2; iter2 = iter2->next)
+            {
+              /* Do not merge a layer when we already merge one of its
+               * ancestors.
+               */
+              if (gimp_item_is_ancestor (iter->data, iter2->data))
+                break;
+            }
+
+          if (iter2 == NULL)
+            merge_layers = g_list_prepend (merge_layers, iter->data);
+        }
+    }
+
+  if (g_list_length (merge_layers) > 1)
+    {
+      gchar *undo_name;
+
+      undo_name = g_strdup_printf (C_("undo-type", "Merge %d Layer Groups"),
+                                   g_list_length (merge_layers));
+      gimp_image_undo_group_start (image, GIMP_UNDO_GROUP_IMAGE_LAYERS_MERGE,
+                                   undo_name);
+      g_free (undo_name);
+    }
+
+  for (iter = merge_layers; iter; iter = iter->next)
+    gimp_image_merge_group_layer (image, GIMP_GROUP_LAYER (iter->data));
+
+  if (g_list_length (merge_layers) > 1)
+    gimp_image_undo_group_end (image);
 
-  gimp_image_merge_group_layer (image, GIMP_GROUP_LAYER (layer));
+  g_list_free (merge_layers);
   gimp_image_flush (image);
 }