libgimp: add gimp_image_list_selected_drawables().

Similar to other functions, we want a variant which returns a GList.

libgimp/gimp.def

@@ -451,6 +451,7 @@ EXPORTS
 	gimp_image_list_channels
 	gimp_image_list_layers
 	gimp_image_list_selected_channels
+	gimp_image_list_selected_drawables
 	gimp_image_list_selected_layers
 	gimp_image_list_selected_vectors
 	gimp_image_list_vectors

libgimp/gimpimage.c

@@ -524,6 +524,44 @@ gimp_image_list_vectors (GimpImage *image)
   return g_list_reverse (list);
 }
 
+/**
+ * gimp_image_list_selected_drawables:
+ * @image: The image.
+ *
+ * Returns the list of drawables selected in the specified image.
+ *
+ * This procedure returns the list of drawables selected in the specified
+ * image.
+ * These can be either a list of layers or a list of channels (a list mixing
+ * layers and channels is not possible), or it can be a layer mask (a list
+ * containing only a layer mask as single item), if a layer mask is in edit
+ * mode.
+ *
+ * Returns: (element-type GimpItem) (transfer container):
+ *          The list of selected drawables in the image.
+ *          The returned list must be freed with g_list_free(). Layer
+ *          elements belong to libgimp and must not be freed.
+ *
+ * Since: 3.0
+ **/
+GList *
+gimp_image_list_selected_drawables (GimpImage *image)
+{
+  GimpItem **drawables;
+  gint       num_drawables;
+  GList     *list = NULL;
+  gint       i;
+
+  drawables = gimp_image_get_selected_drawables (image, &num_drawables);
+
+  for (i = 0; i < num_drawables; i++)
+    list = g_list_prepend (list, drawables[i]);
+
+  g_free (drawables);
+
+  return g_list_reverse (list);
+}
+
 /**
  * gimp_image_get_colormap:
  * @image:      The image.

libgimp/gimpimage.h

@@ -56,6 +56,8 @@ GList    * gimp_image_list_selected_vectors  (GimpImage    *image);
 gboolean   gimp_image_take_selected_vectors  (GimpImage    *image,
                                               GList        *vectors);
 
+GList    * gimp_image_list_selected_drawables(GimpImage    *image);
+
 guchar       * gimp_image_get_colormap       (GimpImage    *image,
                                               gint         *num_colors);
 gboolean       gimp_image_set_colormap       (GimpImage    *image,