[gimp] app: "drawable-linked" multi-drawable aware.

[Jehan <jehanp src gnome org>]

commit e50f522d5bff841c9dcce32bffe3d52f62694dcd
Author: Jehan <jehan girinstud io>
Date:   Mon Aug 17 18:28:26 2020 +0200

    app: "drawable-linked" multi-drawable aware.

 app/actions/drawable-actions.c  | 12 ++++----
 app/actions/drawable-commands.c | 66 +++++++++++++++++++++++++++++++++--------
 2 files changed, 61 insertions(+), 17 deletions(-)
---
diff --git a/app/actions/drawable-actions.c b/app/actions/drawable-actions.c
index 23faac0722..99e1d222cc 100644
--- a/app/actions/drawable-actions.c
+++ b/app/actions/drawable-actions.c
@@ -161,8 +161,8 @@ drawable_actions_update (GimpActionGroup *group,
   GimpDrawable *drawable     = NULL;
   GList        *drawables    = NULL;
   gboolean      has_visible  = FALSE;
+  gboolean      has_linked   = FALSE;
   gboolean      is_rgb       = FALSE;
-  gboolean      linked       = FALSE;
   gboolean      locked       = FALSE;
   gboolean      can_lock     = FALSE;
   gboolean      locked_pos   = FALSE;
@@ -184,7 +184,10 @@ drawable_actions_update (GimpActionGroup *group,
           if (gimp_item_get_visible (iter->data))
             has_visible = TRUE;
 
-          if (has_visible)
+          if (gimp_item_get_linked (iter->data))
+            has_linked = TRUE;
+
+          if (has_visible && has_linked)
             break;
         }
 
@@ -199,7 +202,6 @@ drawable_actions_update (GimpActionGroup *group,
           else
             item = GIMP_ITEM (drawable);
 
-          linked        = gimp_item_get_linked (item);
           locked        = gimp_item_get_lock_content (item);
           can_lock      = gimp_item_can_lock_content (item);
           writable      = ! gimp_item_is_content_locked (item);
@@ -221,12 +223,12 @@ drawable_actions_update (GimpActionGroup *group,
   SET_SENSITIVE ("drawable-levels-stretch", writable && !children && is_rgb);
 
   SET_SENSITIVE ("drawable-visible",       drawables);
-  SET_SENSITIVE ("drawable-linked",        drawable);
+  SET_SENSITIVE ("drawable-linked",        drawables);
   SET_SENSITIVE ("drawable-lock-content",  can_lock);
   SET_SENSITIVE ("drawable-lock-position", can_lock_pos);
 
   SET_ACTIVE ("drawable-visible",       has_visible);
-  SET_ACTIVE ("drawable-linked",        linked);
+  SET_ACTIVE ("drawable-linked",        has_linked);
   SET_ACTIVE ("drawable-lock-content",  locked);
   SET_ACTIVE ("drawable-lock-position", locked_pos);
 
diff --git a/app/actions/drawable-commands.c b/app/actions/drawable-commands.c
index 4e920562f7..720c40fb58 100644
--- a/app/actions/drawable-commands.c
+++ b/app/actions/drawable-commands.c
@@ -90,30 +90,72 @@ drawable_linked_cmd_callback (GimpAction *action,
                               gpointer    data)
 {
   GimpImage    *image;
-  GimpDrawable *drawable;
+  GList        *drawables;
+  GList        *iter;
+  GimpUndo     *undo      = NULL;
+  gboolean      push_undo = TRUE;
   gboolean      linked;
-  return_if_no_drawable (image, drawable, data);
+
+  return_if_no_drawables (image, drawables, data);
 
   linked = g_variant_get_boolean (value);
 
-  if (GIMP_IS_LAYER_MASK (drawable))
-    drawable =
-      GIMP_DRAWABLE (gimp_layer_mask_get_layer (GIMP_LAYER_MASK (drawable)));
+  if (GIMP_IS_LAYER_MASK (drawables->data))
+    {
+      GimpLayerMask *mask = GIMP_LAYER_MASK (drawables->data);
 
-  if (linked != gimp_item_get_linked (GIMP_ITEM (drawable)))
+      g_list_free (drawables);
+      drawables = g_list_prepend (NULL, gimp_layer_mask_get_layer (mask));
+    }
+
+  for (iter = drawables; iter; iter = iter->next)
     {
-      GimpUndo *undo;
-      gboolean  push_undo = TRUE;
+      if (linked && gimp_item_get_linked (iter->data))
+        {
+          /* If any of the drawables are already linked, we don't
+           * toggle the link. This prevents the SET_ACTIVE() in
+           * drawables-actions.c to toggle links unexpectedly.
+           */
+          g_list_free (drawables);
+          return;
+        }
+    }
+
+  for (iter = drawables; iter; iter = iter->next)
+    if (linked != gimp_item_get_linked (iter->data))
+      break;
+
+  if (! iter)
+    {
+      g_list_free (drawables);
+      return;
+    }
 
+  if (g_list_length (drawables) == 1)
+    {
       undo = gimp_image_undo_can_compress (image, GIMP_TYPE_ITEM_UNDO,
                                            GIMP_UNDO_ITEM_LINKED);
 
-      if (undo && GIMP_ITEM_UNDO (undo)->item == GIMP_ITEM (drawable))
-        push_undo = FALSE;
 
-      gimp_item_set_linked (GIMP_ITEM (drawable), linked, push_undo);
-      gimp_image_flush (image);
+      if (undo && GIMP_ITEM_UNDO (undo)->item == GIMP_ITEM (drawables->data))
+        push_undo = FALSE;
     }
+  else
+    {
+      /* TODO: undo groups cannot be compressed so far. */
+      gimp_image_undo_group_start (image,
+                                   GIMP_UNDO_GROUP_ITEM_LINKED,
+                                   "Link/Unlink items");
+    }
+
+  for (; iter; iter = iter->next)
+    if (linked != gimp_item_get_linked (iter->data))
+      gimp_item_set_linked (iter->data, linked, push_undo);
+
+  if (g_list_length (drawables) != 1)
+    gimp_image_undo_group_end (image);
+
+  gimp_image_flush (image);
 }
 
 void