/* GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * GimpGroupLayer
 * Copyright (C) 2009  Michael Natterer <mitch@gimp.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <string.h>

#include <gegl.h>

#include "libgimpbase/gimpbase.h"
#include "libgimpmath/gimpmath.h"

#include "core-types.h"

#include "base/tile-manager.h"

#include "gimpgrouplayer.h"
#include "gimpimage.h"
#include "gimpimage-undo-push.h"
#include "gimpdrawablestack.h"
#include "gimppickable.h"
#include "gimpprojectable.h"
#include "gimpprojection.h"

#include "gimp-intl.h"


static void            gimp_projectable_iface_init   (GimpProjectableInterface  *iface);

static void            gimp_group_layer_set_property (GObject         *object,
                                                      guint            property_id,
                                                      const GValue    *value,
                                                      GParamSpec      *pspec);
static void            gimp_group_layer_get_property (GObject         *object,
                                                      guint            property_id,
                                                      GValue          *value,
                                                      GParamSpec      *pspec);
static void            gimp_group_layer_finalize     (GObject         *object);

static gint64          gimp_group_layer_get_memsize  (GimpObject      *object,
                                                      gint64          *gui_size);

static GimpContainer * gimp_group_layer_get_children (GimpViewable    *viewable);

static GimpItem      * gimp_group_layer_duplicate    (GimpItem        *item,
                                                      GType            new_type);
static void            gimp_group_layer_convert      (GimpItem        *item,
                                                      GimpImage       *dest_image);
static void            gimp_group_layer_translate    (GimpItem        *item,
                                                      gint             offset_x,
                                                      gint             offset_y,
                                                      gboolean         push_undo);
static void            gimp_group_layer_scale        (GimpItem        *item,
                                                      gint             new_width,
                                                      gint             new_height,
                                                      gint             new_offset_x,
                                                      gint             new_offset_y,
                                                      GimpInterpolationType  interp_type,
                                                      GimpProgress    *progress);
static void            gimp_group_layer_resize       (GimpItem        *item,
                                                      GimpContext     *context,
                                                      gint             new_width,
                                                      gint             new_height,
                                                      gint             offset_x,
                                                      gint             offset_y);
static void            gimp_group_layer_flip         (GimpItem        *item,
                                                      GimpContext     *context,
                                                      GimpOrientationType flip_type,
                                                      gdouble          axis,
                                                      gboolean         clip_result);
static void            gimp_group_layer_rotate       (GimpItem        *item,
                                                      GimpContext     *context,
                                                      GimpRotationType rotate_type,
                                                      gdouble          center_x,
                                                      gdouble          center_y,
                                                      gboolean         clip_result);
static void            gimp_group_layer_transform    (GimpItem        *item,
                                                      GimpContext     *context,
                                                      const GimpMatrix3 *matrix,
                                                      GimpTransformDirection direction,
                                                      GimpInterpolationType  interpolation_type,
                                                      gint             recursion_level,
                                                      GimpTransformResize clip_result,
                                                      GimpProgress    *progress);

static gint64      gimp_group_layer_estimate_memsize (const GimpDrawable *drawable,
                                                      gint             width,
                                                      gint             height);
static void            gimp_group_layer_convert_type (GimpDrawable      *drawable,
                                                      GimpImage         *dest_image,
                                                      GimpImageBaseType  new_base_type,
                                                      gboolean           push_undo);

static GeglNode      * gimp_group_layer_get_graph    (GimpProjectable *projectable);
static GList         * gimp_group_layer_get_layers   (GimpProjectable *projectable);

static void            gimp_group_layer_child_add    (GimpContainer   *container,
                                                      GimpLayer       *child,
                                                      GimpGroupLayer  *group);
static void            gimp_group_layer_child_remove (GimpContainer   *container,
                                                      GimpLayer       *child,
                                                      GimpGroupLayer  *group);
static void            gimp_group_layer_child_move   (GimpLayer       *child,
                                                      GParamSpec      *pspec,
                                                      GimpGroupLayer  *group);
static void            gimp_group_layer_child_resize (GimpLayer       *child,
                                                      GimpGroupLayer  *group);

static void            gimp_group_layer_update       (GimpGroupLayer  *group);
static void            gimp_group_layer_update_size  (GimpGroupLayer  *group);

static void            gimp_group_layer_stack_update (GimpDrawableStack *stack,
                                                      gint               x,
                                                      gint               y,
                                                      gint               width,
                                                      gint               height,
                                                      GimpGroupLayer    *group);
static void            gimp_group_layer_proj_update  (GimpProjection    *proj,
                                                      gboolean           now,
                                                      gint               x,
                                                      gint               y,
                                                      gint               width,
                                                      gint               height,
                                                      GimpGroupLayer    *group);


G_DEFINE_TYPE_WITH_CODE (GimpGroupLayer, gimp_group_layer, GIMP_TYPE_LAYER,
                         G_IMPLEMENT_INTERFACE (GIMP_TYPE_PROJECTABLE,
                                                gimp_projectable_iface_init))

#define parent_class gimp_group_layer_parent_class


static void
gimp_group_layer_class_init (GimpGroupLayerClass *klass)
{
  GObjectClass      *object_class      = G_OBJECT_CLASS (klass);
  GimpObjectClass   *gimp_object_class = GIMP_OBJECT_CLASS (klass);
  GimpViewableClass *viewable_class    = GIMP_VIEWABLE_CLASS (klass);
  GimpItemClass     *item_class        = GIMP_ITEM_CLASS (klass);
  GimpDrawableClass *drawable_class    = GIMP_DRAWABLE_CLASS (klass);

  object_class->set_property       = gimp_group_layer_set_property;
  object_class->get_property       = gimp_group_layer_get_property;
  object_class->finalize           = gimp_group_layer_finalize;

  gimp_object_class->get_memsize   = gimp_group_layer_get_memsize;

  viewable_class->default_stock_id = "gtk-directory";
  viewable_class->get_children     = gimp_group_layer_get_children;

  item_class->duplicate            = gimp_group_layer_duplicate;
  item_class->convert              = gimp_group_layer_convert;
  item_class->translate            = gimp_group_layer_translate;
  item_class->scale                = gimp_group_layer_scale;
  item_class->resize               = gimp_group_layer_resize;
  item_class->flip                 = gimp_group_layer_flip;
  item_class->rotate               = gimp_group_layer_rotate;
  item_class->transform            = gimp_group_layer_transform;

  item_class->default_name         = _("Layer Group");
  item_class->rename_desc          = C_("undo-type", "Rename Layer Group");
  item_class->translate_desc       = C_("undo-type", "Move Layer Group");
  item_class->scale_desc           = C_("undo-type", "Scale Layer Group");
  item_class->resize_desc          = C_("undo-type", "Resize Layer Group");
  item_class->flip_desc            = C_("undo-type", "Flip Layer Group");
  item_class->rotate_desc          = C_("undo-type", "Rotate Layer Group");
  item_class->transform_desc       = C_("undo-type", "Transform Layer Group");

  drawable_class->estimate_memsize = gimp_group_layer_estimate_memsize;
  drawable_class->convert_type     = gimp_group_layer_convert_type;
}

static void
gimp_projectable_iface_init (GimpProjectableInterface *iface)
{
  iface->get_image          = (GimpImage * (*) (GimpProjectable *)) gimp_item_get_image;
  iface->get_image_type     = (GimpImageType (*) (GimpProjectable *)) gimp_drawable_type;
  iface->get_offset         = (void (*) (GimpProjectable*, gint*, gint*)) gimp_item_get_offset;
  iface->get_size           = (void (*) (GimpProjectable*, gint*, gint*)) gimp_viewable_get_size;
  iface->get_graph          = gimp_group_layer_get_graph;
  iface->invalidate_preview = (void (*) (GimpProjectable*)) gimp_viewable_invalidate_preview;
  iface->get_layers         = gimp_group_layer_get_layers;
  iface->get_channels       = NULL;
}

static void
gimp_group_layer_init (GimpGroupLayer *group)
{
  group->children = gimp_drawable_stack_new (GIMP_TYPE_LAYER);

  g_signal_connect (group->children, "add",
                    G_CALLBACK (gimp_group_layer_child_add),
                    group);
  g_signal_connect (group->children, "remove",
                    G_CALLBACK (gimp_group_layer_child_remove),
                    group);

  gimp_container_add_handler (group->children, "notify::offset-x",
                              G_CALLBACK (gimp_group_layer_child_move),
                              group);
  gimp_container_add_handler (group->children, "notify::offset-y",
                              G_CALLBACK (gimp_group_layer_child_move),
                              group);
  gimp_container_add_handler (group->children, "size-changed",
                              G_CALLBACK (gimp_group_layer_child_resize),
                              group);

  g_signal_connect (group->children, "update",
                    G_CALLBACK (gimp_group_layer_stack_update),
                    group);

  group->projection = gimp_projection_new (GIMP_PROJECTABLE (group));

  g_signal_connect (group->projection, "update",
                    G_CALLBACK (gimp_group_layer_proj_update),
                    group);
}

static void
gimp_group_layer_set_property (GObject      *object,
                               guint         property_id,
                               const GValue *value,
                               GParamSpec   *pspec)
{
  switch (property_id)
    {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
      break;
    }
}

static void
gimp_group_layer_get_property (GObject    *object,
                               guint       property_id,
                               GValue     *value,
                               GParamSpec *pspec)
{
  switch (property_id)
    {
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
      break;
    }
}

static void
gimp_group_layer_finalize (GObject *object)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (object);

  if (group->children)
    {
      g_signal_handlers_disconnect_by_func (group->children,
                                            gimp_group_layer_child_add,
                                            group);
      g_signal_handlers_disconnect_by_func (group->children,
                                            gimp_group_layer_child_remove,
                                            group);
      g_signal_handlers_disconnect_by_func (group->children,
                                            gimp_group_layer_stack_update,
                                            group);

      g_object_unref (group->children);
      group->children = NULL;
    }

  if (group->projection)
    {
      g_object_unref (group->projection);
      group->projection = NULL;
    }

  if (group->graph)
    {
      g_object_unref (group->graph);
      group->graph = NULL;
    }

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static gint64
gimp_group_layer_get_memsize (GimpObject *object,
                              gint64     *gui_size)
{
  GimpGroupLayer *group   = GIMP_GROUP_LAYER (object);
  gint64          memsize = 0;

  memsize += gimp_object_get_memsize (GIMP_OBJECT (group->children), gui_size);
  memsize += gimp_object_get_memsize (GIMP_OBJECT (group->projection), gui_size);

  return memsize + GIMP_OBJECT_CLASS (parent_class)->get_memsize (object,
                                                                  gui_size);
}

static GimpContainer *
gimp_group_layer_get_children (GimpViewable *viewable)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (viewable);

  return group->children;
}

static GimpItem *
gimp_group_layer_duplicate (GimpItem *item,
                            GType     new_type)
{
  GimpItem *new_item;

  g_return_val_if_fail (g_type_is_a (new_type, GIMP_TYPE_DRAWABLE), NULL);

  new_item = GIMP_ITEM_CLASS (parent_class)->duplicate (item, new_type);

  if (GIMP_IS_GROUP_LAYER (new_item))
    {
      GimpGroupLayer *group     = GIMP_GROUP_LAYER (item);
      GimpGroupLayer *new_group = GIMP_GROUP_LAYER (new_item);
      gint            position  = 0;
      GList          *list;

      gimp_group_layer_suspend_resize (new_group, FALSE);

      for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
           list;
           list = g_list_next (list))
        {
          GimpItem      *child = list->data;
          GimpItem      *new_child;
          GimpLayerMask *mask;

          new_child = gimp_item_duplicate (child, G_TYPE_FROM_INSTANCE (child));

          gimp_object_set_name (GIMP_OBJECT (new_child),
                                gimp_object_get_name (child));

          mask = gimp_layer_get_mask (GIMP_LAYER (child));

          if (mask)
            {
              GimpLayerMask *new_mask;

              new_mask = gimp_layer_get_mask (GIMP_LAYER (new_child));

              gimp_object_set_name (GIMP_OBJECT (new_mask),
                                    gimp_object_get_name (mask));
            }

          gimp_viewable_set_parent (GIMP_VIEWABLE (new_child),
                                    GIMP_VIEWABLE (new_group));

          gimp_container_insert (new_group->children,
                                 GIMP_OBJECT (new_child),
                                 position++);
        }

      /* FIXME: need to change the item's extents to resume_resize()
       * will actually reallocate the projection's pyramid
       */
      GIMP_ITEM (new_group)->width++;

      gimp_group_layer_resume_resize (new_group, FALSE);
    }

  return new_item;
}

static void
gimp_group_layer_convert (GimpItem  *item,
                          GimpImage *dest_image)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GList          *list;

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpItem *child = list->data;

      GIMP_ITEM_GET_CLASS (child)->convert (child, dest_image);
    }

  GIMP_ITEM_CLASS (parent_class)->convert (item, dest_image);
}

static void
gimp_group_layer_translate (GimpItem *item,
                            gint      offset_x,
                            gint      offset_y,
                            gboolean  push_undo)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GimpLayerMask  *mask;
  GList          *list;

  /*  don't push an undo here because undo will call us again  */
  gimp_group_layer_suspend_resize (group, FALSE);

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpItem *child = list->data;

      gimp_item_translate (child, offset_x, offset_y, push_undo);
    }

  mask = gimp_layer_get_mask (GIMP_LAYER (group));

  if (mask)
    {
      gint off_x, off_y;

      gimp_item_get_offset (item, &off_x, &off_y);
      gimp_item_set_offset (GIMP_ITEM (mask), off_x, off_y);

      gimp_viewable_invalidate_preview (GIMP_VIEWABLE (mask));
    }

  /*  don't push an undo here because undo will call us again  */
  gimp_group_layer_resume_resize (group, FALSE);
}

static void
gimp_group_layer_scale (GimpItem              *item,
                        gint                   new_width,
                        gint                   new_height,
                        gint                   new_offset_x,
                        gint                   new_offset_y,
                        GimpInterpolationType  interpolation_type,
                        GimpProgress          *progress)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GimpLayerMask  *mask;
  GList          *list;
  gdouble         width_factor;
  gdouble         height_factor;
  gint            old_offset_x;
  gint            old_offset_y;

  width_factor  = (gdouble) new_width  / (gdouble) gimp_item_get_width  (item);
  height_factor = (gdouble) new_height / (gdouble) gimp_item_get_height (item);

  old_offset_x = gimp_item_get_offset_x (item);
  old_offset_y = gimp_item_get_offset_y (item);

  gimp_group_layer_suspend_resize (group, TRUE);

  list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));

  while (list)
    {
      GimpItem *child = list->data;
      gint      child_width;
      gint      child_height;
      gint      child_offset_x;
      gint      child_offset_y;

      list = g_list_next (list);

      child_width    = ROUND (width_factor  * gimp_item_get_width  (child));
      child_height   = ROUND (height_factor * gimp_item_get_height (child));
      child_offset_x = ROUND (width_factor  * (gimp_item_get_offset_x (child) -
                                               old_offset_x));
      child_offset_y = ROUND (height_factor * (gimp_item_get_offset_y (child) -
                                               old_offset_y));

      child_offset_x += new_offset_x;
      child_offset_y += new_offset_y;

      if (child_width > 0 && child_height > 0)
        {
          gimp_item_scale (child,
                           child_width, child_height,
                           child_offset_x, child_offset_y,
                           interpolation_type, progress);
        }
      else if (gimp_item_is_attached (item))
        {
          gimp_image_remove_layer (gimp_item_get_image (item),
                                   GIMP_LAYER (child),
                                   TRUE, NULL);
        }
      else
        {
          gimp_container_remove (group->children, GIMP_OBJECT (child));
        }
    }

  mask = gimp_layer_get_mask (GIMP_LAYER (group));

  if (mask)
    gimp_item_scale (GIMP_ITEM (mask),
                     new_width, new_height,
                     new_offset_x, new_offset_y,
                     interpolation_type, progress);

  gimp_group_layer_resume_resize (group, TRUE);
}

static void
gimp_group_layer_resize (GimpItem    *item,
                         GimpContext *context,
                         gint         new_width,
                         gint         new_height,
                         gint         offset_x,
                         gint         offset_y)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GimpLayerMask  *mask;
  GList          *list;
  gint            x, y;

  x = gimp_item_get_offset_x (item) - offset_x;
  y = gimp_item_get_offset_y (item) - offset_y;

  gimp_group_layer_suspend_resize (group, TRUE);

  list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));

  while (list)
    {
      GimpItem *child = list->data;
      gint      child_width;
      gint      child_height;
      gint      child_x;
      gint      child_y;

      list = g_list_next (list);

      if (gimp_rectangle_intersect (x,
                                    y,
                                    new_width,
                                    new_height,
                                    gimp_item_get_offset_x (child),
                                    gimp_item_get_offset_y (child),
                                    gimp_item_get_width  (child),
                                    gimp_item_get_height (child),
                                    &child_x,
                                    &child_y,
                                    &child_width,
                                    &child_height))
        {
          gint child_offset_x = gimp_item_get_offset_x (child) - child_x;
          gint child_offset_y = gimp_item_get_offset_y (child) - child_y;

          gimp_item_resize (child, context,
                            child_width, child_height,
                            child_offset_x, child_offset_y);
        }
      else if (gimp_item_is_attached (item))
        {
          gimp_image_remove_layer (gimp_item_get_image (item),
                                   GIMP_LAYER (child),
                                   TRUE, NULL);
        }
      else
        {
          gimp_container_remove (group->children, GIMP_OBJECT (child));
        }
    }

  mask = gimp_layer_get_mask (GIMP_LAYER (group));

  if (mask)
    gimp_item_resize (GIMP_ITEM (mask), context,
                      new_width, new_height, offset_x, offset_y);

  gimp_group_layer_resume_resize (group, TRUE);
}

static void
gimp_group_layer_flip (GimpItem            *item,
                       GimpContext         *context,
                       GimpOrientationType  flip_type,
                       gdouble              axis,
                       gboolean             clip_result)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GimpLayerMask  *mask;
  GList          *list;

  gimp_group_layer_suspend_resize (group, TRUE);

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpItem *child = list->data;

      gimp_item_flip (child, context,
                      flip_type, axis, clip_result);
    }

  mask = gimp_layer_get_mask (GIMP_LAYER (group));

  if (mask)
    gimp_item_flip (GIMP_ITEM (mask), context,
                    flip_type, axis, clip_result);

  gimp_group_layer_resume_resize (group, TRUE);
}

static void
gimp_group_layer_rotate (GimpItem         *item,
                         GimpContext      *context,
                         GimpRotationType  rotate_type,
                         gdouble           center_x,
                         gdouble           center_y,
                         gboolean          clip_result)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GimpLayerMask  *mask;
  GList          *list;

  gimp_group_layer_suspend_resize (group, TRUE);

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpItem *child = list->data;

      gimp_item_rotate (child, context,
                        rotate_type, center_x, center_y, clip_result);
    }

  mask = gimp_layer_get_mask (GIMP_LAYER (group));

  if (mask)
    gimp_item_rotate (GIMP_ITEM (mask), context,
                      rotate_type, center_x, center_y, clip_result);

  gimp_group_layer_resume_resize (group, TRUE);
}

static void
gimp_group_layer_transform (GimpItem               *item,
                            GimpContext            *context,
                            const GimpMatrix3      *matrix,
                            GimpTransformDirection  direction,
                            GimpInterpolationType   interpolation_type,
                            gint                    recursion_level,
                            GimpTransformResize     clip_result,
                            GimpProgress           *progress)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (item);
  GimpLayerMask  *mask;
  GList          *list;

  gimp_group_layer_suspend_resize (group, TRUE);

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpItem *child = list->data;

      gimp_item_transform (child, context,
                           matrix, direction,
                           interpolation_type, recursion_level,
                           clip_result, progress);
    }

  mask = gimp_layer_get_mask (GIMP_LAYER (group));

  if (mask)
    gimp_item_transform (GIMP_ITEM (mask), context,
                         matrix, direction,
                         interpolation_type, recursion_level,
                         clip_result, progress);

  gimp_group_layer_resume_resize (group, TRUE);
}

static gint64
gimp_group_layer_estimate_memsize (const GimpDrawable *drawable,
                                   gint                width,
                                   gint                height)
{
  GimpGroupLayer    *group   = GIMP_GROUP_LAYER (drawable);
  GList             *list;
  GimpImageBaseType  base_type;
  gint64             memsize = 0;

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpDrawable *child = list->data;
      gint          child_width;
      gint          child_height;

      child_width  = (gimp_item_get_width (GIMP_ITEM (child)) *
                      width /
                      gimp_item_get_width (GIMP_ITEM (drawable)));
      child_height = (gimp_item_get_height (GIMP_ITEM (child)) *
                      height /
                      gimp_item_get_height (GIMP_ITEM (drawable)));

      memsize += gimp_drawable_estimate_memsize (child,
                                                 child_width,
                                                 child_height);
    }

  base_type = GIMP_IMAGE_TYPE_BASE_TYPE (gimp_drawable_type (drawable));

  memsize += gimp_projection_estimate_memsize (base_type, width, height);

  return memsize + GIMP_DRAWABLE_CLASS (parent_class)->estimate_memsize (drawable,
                                                                         width,
                                                                         height);
}

static void
gimp_group_layer_convert_type (GimpDrawable      *drawable,
                               GimpImage         *dest_image,
                               GimpImageBaseType  new_base_type,
                               gboolean           push_undo)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (drawable);
  TileManager    *tiles;
  GimpImageType   new_type;

  if (push_undo)
    {
      GimpImage *image = gimp_item_get_image (GIMP_ITEM (group));

      gimp_image_undo_push_group_layer_convert (image, NULL, group);
    }

  new_type = GIMP_IMAGE_TYPE_FROM_BASE_TYPE (new_base_type);

  if (gimp_drawable_has_alpha (drawable))
    new_type = GIMP_IMAGE_TYPE_WITH_ALPHA (new_type);

  /*  FIXME: find a better way to do this: need to set the drawable's
   *  type to the new values so the projection will create its tiles
   *  with the right depth
   */
  drawable->type  = new_type;
  drawable->bytes = GIMP_IMAGE_TYPE_BYTES (new_type);

  gimp_projectable_structure_changed (GIMP_PROJECTABLE (drawable));

  tiles = gimp_projection_get_tiles_at_level (group->projection,
                                              0, NULL);

  gimp_drawable_set_tiles_full (drawable,
                                FALSE, NULL,
                                tiles, new_type,
                                gimp_item_get_offset_x (GIMP_ITEM (drawable)),
                                gimp_item_get_offset_y (GIMP_ITEM (drawable)));
}

static GeglNode *
gimp_group_layer_get_graph (GimpProjectable *projectable)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (projectable);
  GeglNode       *layers_node;
  GeglNode       *output;
  gint            off_x;
  gint            off_y;

  if (group->graph)
    return group->graph;

  group->graph = gegl_node_new ();

  layers_node =
    gimp_drawable_stack_get_graph (GIMP_DRAWABLE_STACK (group->children));

  gegl_node_add_child (group->graph, layers_node);

  gimp_item_get_offset (GIMP_ITEM (group), &off_x, &off_y);

  group->offset_node = gegl_node_new_child (group->graph,
                                            "operation", "gegl:translate",
                                            "x",         (gdouble) -off_x,
                                            "y",         (gdouble) -off_y,
                                            NULL);

  gegl_node_connect_to (layers_node,        "output",
                        group->offset_node, "input");

  output = gegl_node_get_output_proxy (group->graph, "output");

  gegl_node_connect_to (group->offset_node, "output",
                        output,             "input");

  return group->graph;
}

static GList *
gimp_group_layer_get_layers (GimpProjectable *projectable)
{
  GimpGroupLayer *group = GIMP_GROUP_LAYER (projectable);

  return gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
}


/*  public functions  */

GimpLayer *
gimp_group_layer_new (GimpImage *image)
{
  GimpGroupLayer *group;

  g_return_val_if_fail (GIMP_IS_IMAGE (image), NULL);

  group = g_object_new (GIMP_TYPE_GROUP_LAYER, NULL);

  gimp_drawable_configure (GIMP_DRAWABLE (group),
                           image,
                           0, 0, 1, 1,
                           gimp_image_base_type_with_alpha (image),
                           NULL);

  if (gimp_image_get_projection (image)->use_gegl)
    group->projection->use_gegl = TRUE;

  return GIMP_LAYER (group);
}

void
gimp_group_layer_suspend_resize (GimpGroupLayer *group,
                                 gboolean        push_undo)
{
  GimpItem *item;

  g_return_if_fail (GIMP_IS_GROUP_LAYER (group));

  item = GIMP_ITEM (group);

  if (! gimp_item_is_attached (item))
    push_undo = FALSE;

  if (push_undo)
    gimp_image_undo_push_group_layer_suspend (gimp_item_get_image (item),
                                              NULL, group);

  group->suspend_resize++;
}

void
gimp_group_layer_resume_resize (GimpGroupLayer *group,
                                gboolean        push_undo)
{
  GimpItem *item;

  g_return_if_fail (GIMP_IS_GROUP_LAYER (group));
  g_return_if_fail (group->suspend_resize > 0);

  item = GIMP_ITEM (group);

  if (! gimp_item_is_attached (item))
    push_undo = FALSE;

  if (push_undo)
    gimp_image_undo_push_group_layer_resume (gimp_item_get_image (item),
                                             NULL, group);

  group->suspend_resize--;

  if (group->suspend_resize == 0)
    {
      gimp_group_layer_update_size (group);
    }
}


/*  private functions  */

static void
gimp_group_layer_child_add (GimpContainer  *container,
                            GimpLayer      *child,
                            GimpGroupLayer *group)
{
  gimp_group_layer_update (group);
}

static void
gimp_group_layer_child_remove (GimpContainer  *container,
                               GimpLayer      *child,
                               GimpGroupLayer *group)
{
  gimp_group_layer_update (group);
}

static void
gimp_group_layer_child_move (GimpLayer      *child,
                             GParamSpec     *pspec,
                             GimpGroupLayer *group)
{
  gimp_group_layer_update (group);
}

static void
gimp_group_layer_child_resize (GimpLayer      *child,
                               GimpGroupLayer *group)
{
  gimp_group_layer_update (group);
}

static void
gimp_group_layer_update (GimpGroupLayer *group)
{
  if (group->suspend_resize == 0)
    {
      gimp_group_layer_update_size (group);
    }
}

static void
gimp_group_layer_update_size (GimpGroupLayer *group)
{
  GimpItem *item       = GIMP_ITEM (group);
  gint      old_x      = gimp_item_get_offset_x (item);
  gint      old_y      = gimp_item_get_offset_y (item);
  gint      old_width  = gimp_item_get_width  (item);
  gint      old_height = gimp_item_get_height (item);
  gint      x          = 0;
  gint      y          = 0;
  gint      width      = 1;
  gint      height     = 1;
  gboolean  first      = TRUE;
  GList    *list;

  for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (group->children));
       list;
       list = g_list_next (list))
    {
      GimpItem *child = list->data;

      if (first)
        {
          x      = gimp_item_get_offset_x (child);
          y      = gimp_item_get_offset_y (child);
          width  = gimp_item_get_width    (child);
          height = gimp_item_get_height   (child);

          first = FALSE;
        }
      else
        {
          gimp_rectangle_union (x, y, width, height,
                                gimp_item_get_offset_x (child),
                                gimp_item_get_offset_y (child),
                                gimp_item_get_width    (child),
                                gimp_item_get_height   (child),
                                &x, &y, &width, &height);
        }
    }

  if (x      != old_x     ||
      y      != old_y     ||
      width  != old_width ||
      height != old_height)
    {
      if (width  != old_width ||
          height != old_height)
        {
          TileManager *tiles;

          /*  FIXME: find a better way to do this: need to set the item's
           *  extents to the new values so the projection will create
           *  its tiles with the right size
           */
          item->width  = width;
          item->height = height;

          gimp_projectable_structure_changed (GIMP_PROJECTABLE (group));

          tiles = gimp_projection_get_tiles_at_level (group->projection,
                                                      0, NULL);

          /*  FIXME: need to set the item's extents back to the old
           *  values so gimp_drawable_set_tiles_full() will emit all
           *  signals needed by the layer tree to update itself
           */
          item->width  = old_width;
          item->height = old_height;

          gimp_drawable_set_tiles_full (GIMP_DRAWABLE (group),
                                        FALSE, NULL,
                                        tiles,
                                        gimp_drawable_type (GIMP_DRAWABLE (group)),
                                        x, y);
        }
      else
        {
          gimp_item_set_offset (item, x, y);

          /*  invalidate the entire projection since the position of
           *  the children relative to each other might have changed
           *  in a way that happens to leave the group's width and
           *  height the same
           */
          gimp_projectable_invalidate (GIMP_PROJECTABLE (group),
                                       x, y, width, height);
        }

      if (group->offset_node)
        gegl_node_set (group->offset_node,
                       "x", (gdouble) -x,
                       "y", (gdouble) -y,
                       NULL);
    }
}

static void
gimp_group_layer_stack_update (GimpDrawableStack *stack,
                               gint               x,
                               gint               y,
                               gint               width,
                               gint               height,
                               GimpGroupLayer    *group)
{
#if 0
  g_printerr ("%s (%s) %d, %d (%d, %d)\n",
              G_STRFUNC, gimp_object_get_name (group),
              x, y, width, height);
#endif

  /*  the layer stack's update signal speaks in image coordinates,
   *  pass to the projection as-is.
   */
  gimp_projectable_invalidate (GIMP_PROJECTABLE (group),
                               x, y, width, height);

  /*  flush the pickable not the projectable because flushing the
   *  pickable will finish all invalidation on the projection so it
   *  can be used as source (note that it will still be constructed
   *  when the actual read happens, so this it not a performance
   *  problem)
   */
  gimp_pickable_flush (GIMP_PICKABLE (group->projection));
}

static void
gimp_group_layer_proj_update (GimpProjection *proj,
                              gboolean        now,
                              gint            x,
                              gint            y,
                              gint            width,
                              gint            height,
                              GimpGroupLayer *group)
{
#if 0
  g_printerr ("%s (%s) %d, %d (%d, %d)\n",
              G_STRFUNC, gimp_object_get_name (group),
              x, y, width, height);
#endif

  /*  the projection speaks in image coordinates, transform to layer
   *  coordinates when emitting our own update signal.
   */
  gimp_drawable_update (GIMP_DRAWABLE (group),
                        x - gimp_item_get_offset_x (GIMP_ITEM (group)),
                        y - gimp_item_get_offset_y (GIMP_ITEM (group)),
                        width, height);
}
