gimp/app/undo.c

/* The GIMP -- an image manipulation program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include "config.h"

#include <stdlib.h>
#include <string.h>
#include "appenv.h"
#include "by_color_select.h"
#include "channel.h"
#include "drawable.h"
#include "errors.h"
#include "floating_sel.h"
#include "gdisplay.h"
#include "gdisplay_ops.h"
#include "gimage_mask.h"
#include "gimprc.h"
#include "layer.h"
#include "paint_core.h"
#include "paint_funcs.h"
#include "parasitelist.h"
#include "tools.h"
#include "transform_core.h"
#include "undo.h"

#include "drawable_pvt.h"
#include "layer_pvt.h"
#include "channel_pvt.h"
#include "tile_manager_pvt.h"
#include "tile.h"			/* ick. */

#include "libgimp/parasite.h"
#include "libgimp/gimpintl.h"
#include "gimpparasite.h"

typedef enum {
    UNDO = 0,
    REDO = 1
} undo_state;


typedef int   (* UndoPopFunc)  (GImage *, undo_state, undo_type, void *);
typedef void  (* UndoFreeFunc) (undo_state, void *);

typedef struct _undo Undo;

struct _undo
{
  undo_type     type;          /* undo type                           */
  void *        data;          /* data to implement the undo, NULL for group */
  long          bytes;         /* size of undo item                   */
  gboolean      dirties_image; /* TRUE if undo mutates image */

  UndoPopFunc   pop_func;      /* function pointer to undo pop proc   */
  UndoFreeFunc  free_func;     /* function with specifics for freeing */
};

/*  Pop functions  */

static int undo_pop_image            (GImage *, undo_state, undo_type, void *);
static int undo_pop_mask             (GImage *, undo_state, undo_type, void *);
static int undo_pop_layer_displace   (GImage *, undo_state, undo_type, void *);
static int undo_pop_transform        (GImage *, undo_state, undo_type, void *);
static int undo_pop_paint            (GImage *, undo_state, undo_type, void *);
static int undo_pop_layer            (GImage *, undo_state, undo_type, void *);
static int undo_pop_layer_mod        (GImage *, undo_state, undo_type, void *);
static int undo_pop_layer_mask       (GImage *, undo_state, undo_type, void *);
static int undo_pop_channel          (GImage *, undo_state, undo_type, void *);
static int undo_pop_channel_mod      (GImage *, undo_state, undo_type, void *);
static int undo_pop_fs_to_layer      (GImage *, undo_state, undo_type, void *);
static int undo_pop_fs_rigor         (GImage *, undo_state, undo_type, void *);
static int undo_pop_fs_relax         (GImage *, undo_state, undo_type, void *);
static int undo_pop_gimage_mod       (GImage *, undo_state, undo_type, void *);
static int undo_pop_guide            (GImage *, undo_state, undo_type, void *);
static int undo_pop_parasite         (GImage *, undo_state, undo_type, void *);
static int undo_pop_qmask            (GImage *, undo_state, undo_type, void *);
static int undo_pop_layer_rename     (GImage *, undo_state, undo_type, void *);
static int undo_pop_cantundo         (GImage *, undo_state, undo_type, void *);


/*  Free functions  */

static void     undo_free_image           (undo_state, void *);
static void     undo_free_mask            (undo_state, void *);
static void     undo_free_layer_displace  (undo_state, void *);
static void     undo_free_transform       (undo_state, void *);
static void     undo_free_paint           (undo_state, void *);
static void     undo_free_layer           (undo_state, void *);
static void     undo_free_layer_mod       (undo_state, void *);
static void     undo_free_layer_mask      (undo_state, void *);
static void     undo_free_channel         (undo_state, void *);
static void     undo_free_channel_mod     (undo_state, void *);
static void     undo_free_fs_to_layer     (undo_state, void *);
static void     undo_free_fs_rigor        (undo_state, void *);
static void     undo_free_fs_relax        (undo_state, void *);
static void     undo_free_gimage_mod      (undo_state, void *);
static void     undo_free_guide           (undo_state, void *);
static void     undo_free_parasite        (undo_state, void *);
static void     undo_free_qmask           (undo_state, void *);
static void     undo_free_layer_rename    (undo_state, void *);
static void     undo_free_cantundo        (undo_state, void *);


/*  Sizing functions  */
static int   layer_size            (Layer *);
static int   channel_size          (Channel *);

static const char *undo_type_to_name (undo_type);

static int   shrink_wrap = FALSE;


static int
layer_size (Layer *layer)
{
  int size;

  size = sizeof (Layer) + 
    GIMP_DRAWABLE(layer)->width * GIMP_DRAWABLE(layer)->height * GIMP_DRAWABLE(layer)->bytes + 
    strlen (GIMP_DRAWABLE(layer)->name);

  if (layer_get_mask (layer))
    size += channel_size (GIMP_CHANNEL (layer_get_mask (layer)));

  return size;
}


static int
channel_size (Channel *channel)
{
  int size;

  size = sizeof (Channel) + GIMP_DRAWABLE(channel)->width * GIMP_DRAWABLE(channel)->height +
    strlen (GIMP_DRAWABLE(channel)->name);

  return size;
}


static void
undo_free_list (GImage     *gimage,
		undo_state  state,
		GSList     *list)
{
  GSList * orig;
  Undo * undo;

  orig = list;

  while (list)
    {
      undo = (Undo *) list->data;
      if (undo)
	{
	  (* undo->free_func) (state, undo->data);
	  gimage->undo_bytes -= undo->bytes;
	  g_free (undo);
	}
      list = g_slist_next (list);
    }

  g_slist_free (orig);
}


static GSList *
remove_stack_bottom (GImage *gimage)
{
  GSList *list;
  GSList *last;
  int in_group = 0;

  list = gimage->undo_stack;

  last = NULL;
  while (list)
    {
      if (list->next == NULL)
	{
	  if (last)
	    undo_free_list (gimage, UNDO, last->next);
	  else
	    undo_free_list (gimage, UNDO, list);

	  gimage->undo_levels --;
	  if (last)
	    last->next = NULL;
	  list = NULL;

	  gimp_image_undo_event (gimage, UNDO_EXPIRED);
	}
      else
	{
	  if (list->data == NULL)
	    in_group = (in_group) ? 0 : 1;

	  /*  Make sure last points to only a single item, or the
	   *  tail of an aggregate undo item
	   */
	  if ((list->data && !in_group) ||
	      (!list->data && !in_group))
	      last = list;

	  list = g_slist_next (list);
	}
    }

  if (last)
    return gimage->undo_stack;
  else
    return NULL;

}


static int
undo_free_up_space (GImage *gimage)
{
  /*  If there are 0 levels of undo return FALSE.
   */
  if (levels_of_undo == 0)
    return FALSE;

  /*  Delete the item on the bottom of the stack if we have the maximum
   *  levels of undo already
   */
  while (gimage->undo_levels >= levels_of_undo)
    gimage->undo_stack = remove_stack_bottom (gimage);

  return TRUE;
}



static Undo *
undo_push (GImage   *gimage,
	   long      size,
	   undo_type type,
	   gboolean  dirties_image)
{
  Undo * new;

  /* Does this undo dirty the image?  If so, we always want to mark
   * image dirty, even if we can't actually push the undo. */
  if (dirties_image)
      gimp_image_dirty (gimage);

  if (! gimage->undo_on)
    return NULL;

  size += sizeof (Undo);

  if (gimage->redo_stack)
    {
      undo_free_list (gimage, REDO, gimage->redo_stack);
      gimage->redo_stack = NULL;

      /* If the image was dirty, but could become clean by redo-ing
       * some actions, then it should now become 'infinitely' dirty.
       * This is because we've just nuked the actions that would allow
       * the image to become clean again.  The only hope for salvation
       * is to save the image now!  -- austin */
      if (gimage->dirty < 0)
	  gimage->dirty = 10000;
    }

  if (!gimage->pushing_undo_group)
    if (! undo_free_up_space (gimage))
      return NULL;

  new = (Undo *) g_malloc (sizeof (Undo));

  new->bytes = size;
  gimage->undo_bytes += size;
  new->dirties_image = dirties_image;
  if (!gimage->pushing_undo_group)  /*  only increment levels if not in a group  */
    {
      new->type = type;
      gimage->undo_levels ++;
    }
  else
    new->type = gimage->pushing_undo_group;

  gimage->undo_stack = g_slist_prepend (gimage->undo_stack, (void *) new);

  /* lastly, tell people about the newly pushed undo (must come after
   * modification of undo_stack).  */
  if (!gimage->pushing_undo_group)
      gimp_image_undo_event (gimage, UNDO_PUSHED);

  return new;
}


static int
pop_stack (GImage      *gimage,
	   GSList     **stack_ptr,
	   GSList     **unstack_ptr,
	   undo_state   state)
{
  Undo * object;
  GSList *stack;
  GSList *tmp;
  int status = 0;
  int in_group = 0;
  int x, y;
  GDisplay *gdisp;

  /*  Keep popping until we pop a valid object
   *  or get to the end of a group if we're in one
   */
  while (*stack_ptr)
    {
      stack = *stack_ptr;

      object = (Undo *) stack->data;
      if (object == NULL)
	{
	  in_group = (in_group) ? 0 : 1;
	  if (in_group)
	    gimage->undo_levels += (state == UNDO) ? -1 : 1;

	  if (status && !in_group)
	    status = 1;
	  else
	    status = 0;
	}
      else
	{
	  status = (* object->pop_func) (gimage, state, object->type,
					 object->data);

	  if (object->dirties_image)
	  {
	      switch (state) {
	      case UNDO:
		  gimp_image_clean (gimage);
		  break;
	      case REDO:
		  gimp_image_dirty (gimage);
		  break;
	      }
	  }

	  if (!in_group)
	    gimage->undo_levels += (state == UNDO) ? -1 : 1;
	}

      *unstack_ptr = g_slist_prepend (*unstack_ptr, (void *) object);

      tmp = stack;
      *stack_ptr = g_slist_next (*stack_ptr);
      tmp->next = NULL;
      g_slist_free (tmp);

      if (status && !in_group)
	{
	  /*  Flush any image updates and displays  */
	  gdisp = gdisplay_active();
	  if (gdisp != NULL) {
	    if (gdisp->disp_xoffset || gdisp->disp_yoffset)
	      {
		gdk_window_get_size (gdisp->canvas->window, &x, &y);
		if (gdisp->disp_yoffset)
		  {
		    gdisplay_expose_area (gdisp, 0, 0, gdisp->disp_width,
					  gdisp->disp_yoffset);
		    gdisplay_expose_area (gdisp, 0, gdisp->disp_yoffset + y,
					  gdisp->disp_width, gdisp->disp_height);
		  }
		if (gdisp->disp_xoffset)
		  {
		    gdisplay_expose_area (gdisp, 0, 0, gdisp->disp_xoffset,
					  gdisp->disp_height);
		    gdisplay_expose_area (gdisp, gdisp->disp_xoffset + x, 0,
					  gdisp->disp_width, gdisp->disp_height);
		  }
	      }
	  }
	  gdisplays_flush ();

	  /*  If the shrink_wrap flag was set  */
	  if (shrink_wrap)
	    {
	      gdisplays_shrink_wrap (gimage);
	      shrink_wrap = FALSE;
	    }

	  /* let others know that we just popped an action */
	  gimp_image_undo_event (gimage,
				 (state == UNDO)? UNDO_POPPED : UNDO_REDO);

	  return TRUE;
	}
    }

  return FALSE;
}



int
undo_pop (GImage *gimage)
{
  /* Very bad idea to pop an action off the undo stack if we're in the
   * middle of a group, since the whole group won't be popped.  Might
   * leave unbalanced group start marker earlier in the stack too,
   * causing much confusion when it's later reached and
   * mis-interpreted as a group start.  */
  g_return_val_if_fail (gimage->pushing_undo_group == 0, FALSE);

  return pop_stack (gimage, &gimage->undo_stack, &gimage->redo_stack, UNDO);
}


int
undo_redo (GImage *gimage)
{
  /* ditto for redo stack */
  g_return_val_if_fail (gimage->pushing_undo_group == 0, FALSE);

  return pop_stack (gimage, &gimage->redo_stack, &gimage->undo_stack, REDO);
}



/* Return the name of the action that would be used if undo_pop or
 * undo_redo is called, or NULL if there are no actions pushed on the
 * stack.  */
static const char *
undo_get_topitem_name (GSList *stack)
{
    Undo *undo;

    if (!stack)
	return NULL;

    undo = stack->data;

    /* is this the start of an undo group? */
    if (!undo)
    {
	/* Peek at the next action's type. All actions in an undo
	 * group have the same type, that of the group. */
	stack = g_slist_next (stack);
	g_return_val_if_fail (stack != NULL, NULL);

	undo = stack->data;
	g_return_val_if_fail (undo != NULL, NULL); /* empty group? */
    }
    
    return undo_type_to_name (undo->type);
}

const char *
undo_get_undo_name (GImage *gimage)
{
    g_return_val_if_fail (gimage != NULL, NULL);

    /* don't want to encourage undo while a group is open */
    if (gimage->pushing_undo_group != 0)
	return NULL;

    return undo_get_topitem_name (gimage->undo_stack);
}


const char *
undo_get_redo_name (GImage *gimage)
{
    g_return_val_if_fail (gimage != NULL, NULL);

    /* don't want to encourage redo while a group is open */
    if (gimage->pushing_undo_group != 0)
	return NULL;

    return undo_get_topitem_name (gimage->redo_stack);
}




static void
undo_map_over_stack (GSList *stack, undo_map_fn fn, void *data)
{
    int in_group = 0;
    int count = 0;
    Undo *undo;

    while (stack)
    {
	if (stack->data == NULL)
	    in_group = !in_group;

	/* keep track of group length.  0 means not in group, 1 is
         * group start, >= 2 are group members */
	if (in_group)
	    count++;
	else
	    count = 0;

	/* non-groups + initial group member */
	if (stack->data && (count <= 2))
	{
	    undo = stack->data;
	    if (fn (undo_type_to_name (undo->type), data))
		return; /* early termination option exercised */
	}

	stack = g_slist_next (stack);
    }
}

void
undo_map_over_undo_stack (GImage *gimage, undo_map_fn fn, void *data)
{
    undo_map_over_stack (gimage->undo_stack, fn, data);
}

void
undo_map_over_redo_stack (GImage *gimage, undo_map_fn fn, void *data)
{
    undo_map_over_stack (gimage->redo_stack, fn, data);
}




void
undo_free (GImage *gimage)
{
  undo_free_list (gimage, UNDO, gimage->undo_stack);
  undo_free_list (gimage, REDO, gimage->redo_stack);
  gimage->undo_stack = NULL;
  gimage->redo_stack = NULL;
  gimage->undo_bytes = 0;
  gimage->undo_levels = 0;

  /* If the image was dirty, but could become clean by redo-ing
   * some actions, then it should now become 'infinitely' dirty.
   * This is because we've just nuked the actions that would allow
   * the image to become clean again.  The only hope for salvation
   * is to save the image now!  -- austin */
  if (gimage->dirty < 0)
      gimage->dirty = 10000;

  /* The same applies to the case where the image would become clean
   * due to undo actions, but since user can't undo without an undo
   * stack, that's not so much a problem. */

  gimp_image_undo_event (gimage, UNDO_FREE);
}


/**********************/
/*  group Undo funcs  */

int
undo_push_group_start (GImage    *gimage,
		       undo_type  type)
{
  if (! gimage->undo_on)
    return FALSE;

  /* Bad idea to push 0 as the group type, since that won't
   * be recognized as the start of the group later. */
  g_return_val_if_fail (type != 0, FALSE);

  gimage->group_count ++;

  /*  If we're already in a group...ignore  */
  if (gimage->group_count > 1)
    return TRUE;

  if (gimage->redo_stack)
    {
      undo_free_list (gimage, REDO, gimage->redo_stack);
      gimage->redo_stack = NULL;
      /* If the image was dirty, but could become clean by redo-ing
       * some actions, then it should now become 'infinitely' dirty.
       * This is because we've just nuked the actions that would allow
       * the image to become clean again.  The only hope for salvation
       * is to save the image now!  -- austin  */
      if (gimage->dirty < 0)
	  gimage->dirty = 10000;
    }

  if (! undo_free_up_space (gimage))
    return FALSE;

  gimage->pushing_undo_group = type;
  gimage->undo_stack = g_slist_prepend (gimage->undo_stack, NULL);
  gimage->undo_levels++;

  return TRUE;
}


int
undo_push_group_end (GImage *gimage)
{
  if (! gimage->undo_on)
    return FALSE;

  gimage->group_count --;

  if (gimage->group_count == 0)
    {
      gimage->pushing_undo_group = 0;
      gimage->undo_stack = g_slist_prepend (gimage->undo_stack, NULL);

      /* Do it here, since undo_push doesn't emit this event while in the
       * middle of a group */
      gimp_image_undo_event (gimage, UNDO_PUSHED);
    }

  return TRUE;
}


/*********************************/
/*  Image Undo functions         */

typedef struct _image_undo ImageUndo;

struct _image_undo
{
  TileManager *tiles;
  GimpDrawable *drawable;
  int x1, y1, x2, y2;
  int sparse;
};


int
undo_push_image (GImage       *gimage,
		 GimpDrawable *drawable,
		 int           x1,
		 int           y1,
		 int           x2,
		 int           y2)
{
  long size;
  Undo *new;
  ImageUndo *image_undo;
  TileManager *tiles;
  PixelRegion srcPR, destPR;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (drawable);

  x1 = BOUNDS (x1, 0, drawable_width (drawable));
  y1 = BOUNDS (y1, 0, drawable_height (drawable));
  x2 = BOUNDS (x2, 0, drawable_width (drawable));
  y2 = BOUNDS (y2, 0, drawable_height (drawable));

  size = (x2 - x1) * (y2 - y1) * drawable_bytes (drawable) + sizeof (void *) * 2;

  if ((new = undo_push (gimage, size, IMAGE_UNDO, TRUE)))
    {
      image_undo = (ImageUndo *) g_malloc (sizeof (ImageUndo));

      /*  If we cannot create a new temp buf--either because our parameters are
       *  degenerate or something else failed, simply return an unsuccessful push.
       */
      tiles = tile_manager_new ((x2 - x1), (y2 - y1), drawable_bytes (drawable));
      pixel_region_init (&srcPR, drawable_data (drawable), x1, y1, (x2 - x1), (y2 - y1), FALSE);
      pixel_region_init (&destPR, tiles, 0, 0, (x2 - x1), (y2 - y1), TRUE);
      copy_region (&srcPR, &destPR);

      /*  set the image undo structure  */
      image_undo->tiles = tiles;
      image_undo->drawable = drawable;
      image_undo->x1 = x1;
      image_undo->y1 = y1;
      image_undo->x2 = x2;
      image_undo->y2 = y2;
      image_undo->sparse = FALSE;

      new->data      = image_undo;
      new->pop_func  = undo_pop_image;
      new->free_func = undo_free_image;

      return TRUE;
    }
  else
    return FALSE;
}


int
undo_push_image_mod (GImage       *gimage,
		     GimpDrawable *drawable,
		     int           x1,
		     int           y1,
		     int           x2,
		     int           y2,
		     void         *tiles_ptr,
		     int           sparse)
{
  long size;
  int dwidth, dheight;
  Undo * new;
  ImageUndo *image_undo;
  TileManager *tiles;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (drawable);

  if (! tiles_ptr)
    return FALSE;

  dwidth = drawable_width (drawable);
  dheight = drawable_height (drawable);

  x1 = BOUNDS (x1, 0, dwidth);
  y1 = BOUNDS (y1, 0, dheight);
  x2 = BOUNDS (x2, 0, dwidth);
  y2 = BOUNDS (y2, 0, dheight);

  tiles = (TileManager *) tiles_ptr;
  size = tiles->width * tiles->height *
    tiles->bpp + sizeof (void *) * 2;

  if ((new = undo_push (gimage, size, IMAGE_MOD_UNDO, TRUE)))
    {
      image_undo = (ImageUndo *) g_malloc (sizeof (ImageUndo));
      image_undo->tiles = tiles;
      image_undo->drawable = drawable;
      image_undo->x1 = x1;
      image_undo->y1 = y1;
      image_undo->x2 = x2;
      image_undo->y2 = y2;
      image_undo->sparse = sparse;

      new->data      = image_undo;
      new->pop_func  = undo_pop_image;
      new->free_func = undo_free_image;

      return TRUE;
    }
  else
    {
      tile_manager_destroy (tiles);
      return FALSE;
    }
}


static int
undo_pop_image (GImage    *gimage,
		undo_state state,
		undo_type  type,
		void      *image_undo_ptr)
{
  ImageUndo *image_undo;
  TileManager *tiles;
  PixelRegion PR1, PR2;
  int x, y;
  int w, h;

  image_undo = (ImageUndo *) image_undo_ptr;
  tiles = image_undo->tiles;

  switch (state)
    {
    case UNDO:
      drawable_clean (image_undo->drawable);
      break;
    case REDO:
      drawable_dirty (image_undo->drawable);
      break;
    }

  /*  some useful values  */
  x = image_undo->x1;
  y = image_undo->y1;

  if (image_undo->sparse == FALSE)
    {
      w = tiles->width;
      h = tiles->height;

      pixel_region_init (&PR1, tiles, 0, 0, w, h, TRUE);
      pixel_region_init (&PR2, drawable_data (image_undo->drawable), x, y, w, h, TRUE);

      /*  swap the regions  */
      swap_region (&PR1, &PR2);
    }
  else
    {
      int i, j;
      Tile *src_tile;
      Tile *dest_tile;

      w = image_undo->x2 - image_undo->x1;
      h = image_undo->y2 - image_undo->y1;

      for (i = y; i < image_undo->y2; i += (TILE_HEIGHT - (i % TILE_HEIGHT)))
	{
	  for (j = x; j < image_undo->x2; j += (TILE_WIDTH - (j % TILE_WIDTH)))
	    {
	      src_tile = tile_manager_get_tile (tiles, j, i, FALSE, FALSE);
	      if (tile_is_valid (src_tile) == TRUE)
		{
		  /* swap tiles, not pixels! */

		  src_tile = tile_manager_get_tile (tiles, j, i, TRUE, FALSE /* TRUE */);
		  dest_tile = tile_manager_get_tile (drawable_data (image_undo->drawable), j, i, TRUE, FALSE /* TRUE */);

		  tile_manager_map_tile (tiles, j, i, dest_tile);
		  tile_manager_map_tile (drawable_data (image_undo->drawable), j, i, src_tile);
#if 0
		  swap_pixels (tile_data_pointer (src_tile, 0, 0),
			       tile_data_pointer (dest_tile, 0, 0),
			       tile_size (src_tile));
#endif
		  
		  tile_release (dest_tile, FALSE /* TRUE */);
		  tile_release (src_tile, FALSE /* TRUE */);
		}
	    }
	}
    }

  drawable_update (image_undo->drawable, x, y, w, h);

  return TRUE;
}


static void
undo_free_image (undo_state  state,
		 void       *image_undo_ptr)
{
  ImageUndo *image_undo;

  image_undo = (ImageUndo *) image_undo_ptr;

  tile_manager_destroy (image_undo->tiles);
  g_free (image_undo);
}


/******************************/
/*  Mask Undo functions  */

int
undo_push_mask (GImage *gimage,
		void   *mask_ptr)
{
  Undo *new;
  MaskUndo *mask_undo;
  int size;

  mask_undo = (MaskUndo *) mask_ptr;
  if (mask_undo->tiles)
    size = mask_undo->tiles->width * mask_undo->tiles->height;
  else
    size = 0;

  if ((new = undo_push (gimage, size, MASK_UNDO, FALSE)))
    {
      new->data          = mask_undo;
      new->pop_func      = undo_pop_mask;
      new->free_func     = undo_free_mask;

      return TRUE;
    }
  else
    {
      if (mask_undo->tiles)
	tile_manager_destroy (mask_undo->tiles);
      g_free (mask_undo);
      return FALSE;
    }
}


static int
undo_pop_mask (GImage     *gimage,
	       undo_state  state,
	       undo_type   type,
	       void       *mask_ptr)
{
  MaskUndo *mask_undo;
  TileManager *new_tiles;
  Channel *sel_mask;
  PixelRegion srcPR, destPR;
  int selection;
  int x1, y1, x2, y2;
  int width, height;
  unsigned char empty = 0;

  width = height = 0;

  mask_undo = (MaskUndo *) mask_ptr;

  /*  save current selection mask  */
  sel_mask = gimage_get_mask (gimage);
  selection = channel_bounds (sel_mask, &x1, &y1, &x2, &y2);
  pixel_region_init (&srcPR, GIMP_DRAWABLE(sel_mask)->tiles, x1, y1, (x2 - x1), (y2 - y1), FALSE);

  if (selection)
    {
      new_tiles = tile_manager_new (srcPR.w, srcPR.h, 1);
      pixel_region_init (&destPR, new_tiles, 0, 0, srcPR.w, srcPR.h, TRUE);

      copy_region (&srcPR, &destPR);

      pixel_region_init (&srcPR, GIMP_DRAWABLE(sel_mask)->tiles, x1, y1, (x2 - x1), (y2 - y1), TRUE);
      color_region (&srcPR, &empty);
    }
  else
    new_tiles = NULL;

  if (mask_undo->tiles)
    {
      width = mask_undo->tiles->width;
      height = mask_undo->tiles->height;
      pixel_region_init (&srcPR, mask_undo->tiles, 0, 0, width, height, FALSE);
      pixel_region_init (&destPR, GIMP_DRAWABLE(sel_mask)->tiles, mask_undo->x, mask_undo->y, width, height, TRUE);
      copy_region (&srcPR, &destPR);

      tile_manager_destroy (mask_undo->tiles);
    }

  /* invalidate the current bounds and boundary of the mask */
  gimage_mask_invalidate (gimage);

  if (mask_undo->tiles)
    {
      sel_mask->empty = FALSE;
      sel_mask->x1 = mask_undo->x;
      sel_mask->y1 = mask_undo->y;
      sel_mask->x2 = mask_undo->x + width;
      sel_mask->y2 = mask_undo->y + height;
    }
  else
    {
      sel_mask->empty = TRUE;
      sel_mask->x1 = 0;
      sel_mask->y1 = 0;
      sel_mask->x2 = GIMP_DRAWABLE(sel_mask)->width;
      sel_mask->y2 = GIMP_DRAWABLE(sel_mask)->height;
    }

  /*  set the new mask undo parameters  */
  mask_undo->tiles = new_tiles;
  mask_undo->x = x1;
  mask_undo->y = y1;

  /* we know the bounds */
  sel_mask->bounds_known = TRUE;

  /*  if there is a "by color" selection dialog active
   *  for this gimage's mask, send it an update notice
   */
  if (gimage->by_color_select)
    by_color_select_initialize_by_image (gimage);

  return TRUE;
}


static void
undo_free_mask (undo_state state,
		void      *mask_ptr)
{
  MaskUndo *mask_undo;

  mask_undo = (MaskUndo *) mask_ptr;
  if (mask_undo->tiles)
    tile_manager_destroy (mask_undo->tiles);
  g_free (mask_undo);
}


/***************************************/
/*  Layer displacement Undo functions  */

int
undo_push_layer_displace (GImage    *gimage,
			  GimpLayer *layer)
{
  Undo * new;
  int * info;

  if ((new = undo_push (gimage, 12, LAYER_DISPLACE_UNDO, TRUE)))
    {
      new->data          = (void *) g_malloc (sizeof (int) * 3);
      new->pop_func      = undo_pop_layer_displace;
      new->free_func     = undo_free_layer_displace;

      info = (int *) new->data;
      info[0] = drawable_ID(GIMP_DRAWABLE(layer));
      info[1] = GIMP_DRAWABLE(layer)->offset_x;
      info[2] = GIMP_DRAWABLE(layer)->offset_y;

      return TRUE;
    }
  else
    return FALSE;
}


static int
undo_pop_layer_displace (GImage     *gimage,
			 undo_state  state,
			 undo_type   type,
			 void       *info_ptr)
{
  Layer * layer;
  int old_offsets[2];
  int *info;

  info = (int *) info_ptr;
  layer = layer_get_ID (info[0]);
  if (layer)
    {
      old_offsets[0] = GIMP_DRAWABLE(layer)->offset_x;
      old_offsets[1] = GIMP_DRAWABLE(layer)->offset_y;
      drawable_update (GIMP_DRAWABLE(layer), 0, 0,
		       GIMP_DRAWABLE(layer)->width,
		       GIMP_DRAWABLE(layer)->height);

      GIMP_DRAWABLE(layer)->offset_x = info[1];
      GIMP_DRAWABLE(layer)->offset_y = info[2];
      drawable_update (GIMP_DRAWABLE(layer), 0, 0,
		       GIMP_DRAWABLE(layer)->width,
		       GIMP_DRAWABLE(layer)->height);
      
      if (layer->mask) 
	{
	  GIMP_DRAWABLE(layer->mask)->offset_x = info[1];
	  GIMP_DRAWABLE(layer->mask)->offset_y = info[2];
	  drawable_update (GIMP_DRAWABLE(layer->mask), 0, 0,
			   GIMP_DRAWABLE(layer->mask)->width,
			   GIMP_DRAWABLE(layer->mask)->height);
	}


      /*  invalidate the selection boundary because of a layer modification  */
      layer_invalidate_boundary (layer);

      info[1] = old_offsets[0];
      info[2] = old_offsets[1];

      return TRUE;
    }
  else
    return FALSE;
}


static void
undo_free_layer_displace (undo_state state,
			  void      *info_ptr)
{
  g_free (info_ptr);
}


/*********************************/
/*  Transform Undo               */

int
undo_push_transform (GImage *gimage,
		     void   *tu_ptr)
{
  Undo * new;
  int size;

  size = sizeof (TransformUndo);

  if ((new = undo_push (gimage, size, TRANSFORM_UNDO, FALSE)))
    {
      new->data          = tu_ptr;
      new->pop_func      = undo_pop_transform;
      new->free_func     = undo_free_transform;

      return TRUE;
    }
  else
    {
      g_free (tu_ptr);
      return FALSE;
    }
}


static int
undo_pop_transform (GImage    *gimage,
		    undo_state state,
		    undo_type  type,
		    void      *tu_ptr)
{
  TransformCore * tc;
  TransformUndo * tu;
  TileManager * temp;
  double d;
  int i;

  /* Can't have ANY tool selected - maybe a plugin running */
  if (active_tool == NULL)
    return TRUE;

  tc = (TransformCore *) active_tool->private;
  tu = (TransformUndo *) tu_ptr;

  paths_transform_do_undo(gimage,tu->path_undo);

  /*  only pop if the active tool is the tool that pushed this undo  */
  if (tu->tool_ID != active_tool->ID)
    return TRUE;

  /*  swap the transformation information arrays  */
  for (i = 0; i < TRAN_INFO_SIZE; i++)
    {
      d = tu->trans_info[i];
      tu->trans_info[i] = tc->trans_info[i];
      tc->trans_info[i] = d;
    }

  /*  swap the original buffer--the source buffer for repeated transforms
   */
  temp = tu->original;
  tu->original = tc->original;
  tc->original = temp;

  /*  If we're re-implementing the first transform, reactivate tool  */
  if (state == REDO && tc->original)
    {
      active_tool->state = ACTIVE;
      draw_core_resume (tc->core, active_tool);
    }

  return TRUE;
}


static void
undo_free_transform (undo_state  state,
		     void       *tu_ptr)
{
  TransformUndo * tu;

  tu = (TransformUndo *) tu_ptr;
  if (tu->original)
    tile_manager_destroy (tu->original);
  paths_transform_free_undo(tu->path_undo);
  g_free (tu);
}


/*********************************/
/*  Paint Undo                   */

int
undo_push_paint (GImage *gimage,
		 void   *pu_ptr)
{
  Undo * new;
  int size;

  size = sizeof (PaintUndo);

  if ((new = undo_push (gimage, size, PAINT_UNDO, FALSE)))
    {
      new->data          = pu_ptr;
      new->pop_func      = undo_pop_paint;
      new->free_func     = undo_free_paint;

      return TRUE;
    }
  else
    {
      g_free (pu_ptr);
      return FALSE;
    }
}


static int
undo_pop_paint (GImage    *gimage,
		undo_state state,
		undo_type  type,
		void      *pu_ptr)
{
  PaintCore * pc;
  PaintUndo * pu;
  double tmp;

  /* Can't have ANY tool selected - maybe a plugin running */
  if (active_tool == NULL)
    return TRUE;

  pc = (PaintCore *) active_tool->private;
  pu = (PaintUndo *) pu_ptr;

  /*  only pop if the active tool is the tool that pushed this undo  */
  if (pu->tool_ID != active_tool->ID)
    return TRUE;

  /*  swap the paint core information  */
  tmp = pc->lastx;
  pc->lastx = pu->lastx;
  pu->lastx = tmp;

  tmp = pc->lasty;
  pc->lasty = pu->lasty;
  pu->lasty = tmp;

  tmp = pc->lastpressure;
  pc->lastpressure = pu->lastpressure;
  pu->lastpressure = tmp;

  tmp = pc->lastxtilt;
  pc->lastxtilt = pu->lastxtilt;
  pu->lastxtilt = tmp;

  tmp = pc->lastytilt;
  pc->lastytilt = pu->lastytilt;
  pu->lastytilt = tmp;

  return TRUE;
}


static void
undo_free_paint (undo_state state,
		 void      *pu_ptr)
{
  PaintUndo * pu;

  pu = (PaintUndo *) pu_ptr;
  g_free (pu);
}


/*********************************/
/*  New Layer Undo               */

int
undo_push_layer (GImage *gimage,
		 void   *lu_ptr)
{
  LayerUndo *lu;
  Undo *new;
  int size;

  lu = (LayerUndo *) lu_ptr;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (GIMP_DRAWABLE(lu->layer));

  size = layer_size (lu->layer) + sizeof (LayerUndo);

  if ((new = undo_push (gimage, size, LAYER_UNDO, TRUE)))
    {
      new->data          = lu_ptr;
      new->pop_func      = undo_pop_layer;
      new->free_func     = undo_free_layer;

      return TRUE;
    }
  else
    {
      /*  if this is a remove layer, delete the layer  */
      if (lu->undo_type == LAYER_REMOVE_UNDO)
	layer_unref (lu->layer);
      g_free (lu);
      return FALSE;
    }
}


static int
undo_pop_layer (GImage    *gimage,
		undo_state state,
		undo_type  type,
		void      *lu_ptr)
{
  LayerUndo *lu;

  lu = (LayerUndo *) lu_ptr;

  switch (state)
    {
    case UNDO:
      drawable_clean (GIMP_DRAWABLE(lu->layer));
      break;
    case REDO:
      drawable_dirty (GIMP_DRAWABLE(lu->layer));
      break;
    }

  /*  remove layer  */
  if ((state == UNDO && lu->undo_type == LAYER_ADD_UNDO) ||
      (state == REDO && lu->undo_type == LAYER_REMOVE_UNDO))
    {
      /*  record the current position  */
      lu->prev_position = gimage_get_layer_index (gimage, lu->layer);
      /*  set the previous layer  */
      gimage_set_active_layer (gimage, lu->prev_layer);

      /*  remove the layer  */
      gimage->layers = g_slist_remove (gimage->layers, lu->layer);
      gimage->layer_stack = g_slist_remove (gimage->layer_stack, lu->layer);

      /*  reset the gimage values  */
      if (layer_is_floating_sel (lu->layer))
	{
	  gimage->floating_sel = NULL;
	  /*  reset the old drawable  */
	  floating_sel_reset (lu->layer);
	}

      drawable_update (GIMP_DRAWABLE(lu->layer), 0, 0,
		       GIMP_DRAWABLE(lu->layer)->width,
		       GIMP_DRAWABLE(lu->layer)->height);
    }
  /*  restore layer  */
  else
    {
      /*  record the active layer  */
      lu->prev_layer = gimage->active_layer;

      /*  hide the current selection--for all views  */
      if (gimage->active_layer != NULL)
	layer_invalidate_boundary ((gimage->active_layer));

      /*  if this is a floating selection, set the fs pointer  */
      if (layer_is_floating_sel (lu->layer))
	gimage->floating_sel = lu->layer;

      /*  add the new layer  */
      gimage->layers = g_slist_insert (gimage->layers, lu->layer,
				       lu->prev_position);
      gimage->layer_stack = g_slist_prepend (gimage->layer_stack, lu->layer);
      gimage->active_layer = lu->layer;

      drawable_update (GIMP_DRAWABLE(lu->layer), 0, 0,
		       GIMP_DRAWABLE(lu->layer)->width,
		       GIMP_DRAWABLE(lu->layer)->height);
    }

  return TRUE;
}


static void
undo_free_layer (undo_state state,
		 void      *lu_ptr)
{
  LayerUndo *lu;

  lu = (LayerUndo *) lu_ptr;

  /*  Only free the layer if we're freeing from the redo
   *  stack and it's a layer add, or if we're freeing from
   *  the undo stack and it's a layer remove
   */
  if ((state == REDO && lu->undo_type == LAYER_ADD_UNDO) ||
      (state == UNDO && lu->undo_type == LAYER_REMOVE_UNDO))
    layer_unref (lu->layer);

  g_free (lu);
}



/*********************************/
/*  Layer Mod Undo               */

int
undo_push_layer_mod (GImage *gimage,
		     void   *layer_ptr)
{
  Layer *layer;
  Undo *new;
  TileManager *tiles;
  void **data;
  int size;

  layer = (Layer *) layer_ptr;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (GIMP_DRAWABLE(layer));

  tiles = GIMP_DRAWABLE(layer)->tiles;
  tiles->x = GIMP_DRAWABLE(layer)->offset_x;
  tiles->y = GIMP_DRAWABLE(layer)->offset_y;
  size = GIMP_DRAWABLE(layer)->width * GIMP_DRAWABLE(layer)->height * 
    GIMP_DRAWABLE(layer)->bytes + sizeof (void *) * 3;

  if ((new = undo_push (gimage, size, LAYER_MOD, TRUE)))
    {
      data               = (void **) g_malloc (sizeof (void *) * 3);
      new->data          = data;
      new->pop_func      = undo_pop_layer_mod;
      new->free_func     = undo_free_layer_mod;

      data[0] = layer_ptr;
      data[1] = (void *) tiles;
      data[2] = (void *) ((long) GIMP_DRAWABLE(layer)->type);

      return TRUE;
    }
  else
    {
      tile_manager_destroy (tiles);
      return FALSE;
    }
}


static int
undo_pop_layer_mod (GImage    *gimage,
		    undo_state state,
		    undo_type  type,
		    void      *data_ptr)
{
  void **data;
  int layer_type;
  TileManager *tiles;
  TileManager *temp;
  Layer *layer;

  data = (void **) data_ptr;
  layer = (Layer *) data[0];

  switch (state)
    {
    case UNDO:
      drawable_clean (GIMP_DRAWABLE(layer));
      break;
    case REDO:
      drawable_dirty (GIMP_DRAWABLE(layer));
      break;
    }

  tiles = (TileManager *) data[1];

  /*  Issue the first update  */
  gdisplays_update_area (gimage,
			 GIMP_DRAWABLE(layer)->offset_x, GIMP_DRAWABLE(layer)->offset_y,
			 GIMP_DRAWABLE(layer)->width, GIMP_DRAWABLE(layer)->height);

  /*  Create a tile manager to store the current layer contents  */
  temp = GIMP_DRAWABLE(layer)->tiles;
  temp->x = GIMP_DRAWABLE(layer)->offset_x;
  temp->y = GIMP_DRAWABLE(layer)->offset_y;
  layer_type = (long) data[2];
  data[2] = (void *) ((long) GIMP_DRAWABLE(layer)->type);

  /*  restore the layer's data  */
  GIMP_DRAWABLE(layer)->tiles = tiles;
  GIMP_DRAWABLE(layer)->offset_x = tiles->x;
  GIMP_DRAWABLE(layer)->offset_y = tiles->y;
  GIMP_DRAWABLE(layer)->width = tiles->width;
  GIMP_DRAWABLE(layer)->height = tiles->height;
  GIMP_DRAWABLE(layer)->bytes = tiles->bpp;
  GIMP_DRAWABLE(layer)->type = layer_type;
  GIMP_DRAWABLE(layer)->has_alpha = TYPE_HAS_ALPHA (layer_type);

  if (layer->mask) 
    {
      GIMP_DRAWABLE(layer->mask)->offset_x = tiles->x;
      GIMP_DRAWABLE(layer->mask)->offset_y = tiles->y;
    }

  /*  If the layer type changed, update the gdisplay titles  */
  if (GIMP_DRAWABLE(layer)->type != (long) data[2])
    gdisplays_update_title (GIMP_DRAWABLE(layer)->gimage);

  /*  Set the new tile manager  */
  data[1] = temp;

  /*  Issue the second update  */
  drawable_update (GIMP_DRAWABLE(layer), 0, 0, 
		   GIMP_DRAWABLE(layer)->width, GIMP_DRAWABLE(layer)->height);

  return TRUE;
}


static void
undo_free_layer_mod (undo_state state,
		     void      *data_ptr)
{
  void ** data;

  data = (void **) data_ptr;
  tile_manager_destroy ((TileManager *) data[1]);
  g_free (data);
}


/*********************************/
/*  Layer Mask Undo               */

int
undo_push_layer_mask (GImage *gimage,
		      void   *lmu_ptr)
{
  LayerMaskUndo *lmu;
  Undo *new;
  int size;

  lmu = (LayerMaskUndo *) lmu_ptr;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (GIMP_DRAWABLE(lmu->layer));

  size = channel_size (GIMP_CHANNEL (lmu->mask)) + sizeof (LayerMaskUndo);

  if ((new = undo_push (gimage, size, LAYER_MASK_UNDO, TRUE)))
    {
      new->data          = lmu_ptr;
      new->pop_func      = undo_pop_layer_mask;
      new->free_func     = undo_free_layer_mask;

      return TRUE;
    }
  else
    {
      if (lmu->undo_type == LAYER_REMOVE_UNDO)
	layer_mask_delete (lmu->mask);
      g_free (lmu);
      return FALSE;
    }
}


static int
undo_pop_layer_mask (GImage    *gimage,
		     undo_state state,
		     undo_type  type,
		     void      *lmu_ptr)
{
  LayerMaskUndo *lmu;

  lmu = (LayerMaskUndo *) lmu_ptr;

  switch (state)
    {
    case UNDO:
      drawable_clean (GIMP_DRAWABLE(lmu->layer));
      break;
    case REDO:
      drawable_dirty (GIMP_DRAWABLE(lmu->layer));
      break;
    }

  /*  remove layer mask  */
  if ((state == UNDO && lmu->undo_type == LAYER_ADD_UNDO) ||
      (state == REDO && lmu->undo_type == LAYER_REMOVE_UNDO))
    {
      /*  remove the layer mask  */
      lmu->layer->mask       = NULL;
      lmu->layer->apply_mask = FALSE;
      lmu->layer->edit_mask  = FALSE;
      lmu->layer->show_mask  = FALSE;

      /*  if this is redoing a remove operation &
       *  the mode of application was DISCARD or
       *  this is undoing an add...
       */
      if ((state == REDO && lmu->mode == DISCARD) || state == UNDO)
	drawable_update (GIMP_DRAWABLE(lmu->layer), 0, 0, 
			 GIMP_DRAWABLE(lmu->layer)->width, GIMP_DRAWABLE(lmu->layer)->height);
    }
  /*  restore layer  */
  else
    {
      lmu->layer->mask       = lmu->mask;
      lmu->layer->apply_mask = lmu->apply_mask;
      lmu->layer->edit_mask  = lmu->edit_mask;
      lmu->layer->show_mask  = lmu->show_mask;

      gimage_set_layer_mask_edit (gimage, lmu->layer, lmu->edit_mask);

      /*  if this is undoing a remove operation &
       *  the mode of application was DISCARD or
       *  this is redoing an add
       */
      if ((state == UNDO && lmu->mode == DISCARD) || state == REDO)
	drawable_update (GIMP_DRAWABLE(lmu->layer), 0, 0, 
			 GIMP_DRAWABLE(lmu->layer)->width, GIMP_DRAWABLE(lmu->layer)->height);
    }

  return TRUE;
}


static void
undo_free_layer_mask (undo_state state,
		      void      *lmu_ptr)
{
  LayerMaskUndo *lmu;

  lmu = (LayerMaskUndo *) lmu_ptr;

  /*  Only free the layer mask if we're freeing from the redo
   *  stack and it's a layer add, or if we're freeing from
   *  the undo stack and it's a layer remove
   */
  if ((state == REDO && lmu->undo_type == LAYER_ADD_UNDO) ||
      (state == UNDO && lmu->undo_type == LAYER_REMOVE_UNDO))
    layer_mask_delete (lmu->mask);

  g_free (lmu);
}


/*********************************/
/*  New Channel Undo               */

int
undo_push_channel (GImage *gimage,
		   void   *cu_ptr)
{
  ChannelUndo *cu;
  Undo *new;
  int size;

  cu = (ChannelUndo *) cu_ptr;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (GIMP_DRAWABLE(cu->channel));

  size = channel_size (cu->channel) + sizeof (ChannelUndo);

  if ((new = undo_push (gimage, size, CHANNEL_UNDO, TRUE)))
    {
      new->data          = cu_ptr;
      new->pop_func      = undo_pop_channel;
      new->free_func     = undo_free_channel;

      return TRUE;
    }
  else
    {
      if (cu->undo_type == CHANNEL_REMOVE_UNDO)
	channel_delete (cu->channel);
      g_free (cu);
      return FALSE;
    }
}


static int
undo_pop_channel (GImage    *gimage,
		  undo_state state,
		  undo_type  type,
		  void      *cu_ptr)
{
  ChannelUndo *cu;

  cu = (ChannelUndo *) cu_ptr;

  switch (state)
    {
    case UNDO:
      drawable_clean (GIMP_DRAWABLE(cu->channel));
      break;
    case REDO:
      drawable_dirty (GIMP_DRAWABLE(cu->channel));
      break;
    }

  /*  remove channel  */
  if ((state == UNDO && cu->undo_type == CHANNEL_ADD_UNDO) ||
      (state == REDO && cu->undo_type == CHANNEL_REMOVE_UNDO))
    {
      /*  record the current position  */
      cu->prev_position = gimage_get_channel_index (gimage, cu->channel);

      /*  remove the channel  */
      gimage->channels = g_slist_remove (gimage->channels, cu->channel);

      /*  set the previous channel  */
      gimage_set_active_channel (gimage, cu->prev_channel);

      /*  update the area  */
      drawable_update (GIMP_DRAWABLE(cu->channel), 0, 0, 
		       GIMP_DRAWABLE(cu->channel)->width, GIMP_DRAWABLE(cu->channel)->height);
    }
  /*  restore channel  */
  else
    {
      /*  record the active channel  */
      cu->prev_channel = gimage->active_channel;

      /*  add the new channel  */
      gimage->channels = g_slist_insert (gimage->channels, cu->channel, cu->prev_position);

      /*  set the new channel  */
      gimage_set_active_channel (gimage, cu->channel);

      /*  update the area  */
      drawable_update (GIMP_DRAWABLE(cu->channel), 0, 0, 
		       GIMP_DRAWABLE(cu->channel)->width, GIMP_DRAWABLE(cu->channel)->height);
    }

  return TRUE;
}


static void
undo_free_channel (undo_state state,
		   void      *cu_ptr)
{
  ChannelUndo *cu;

  cu = (ChannelUndo *) cu_ptr;

  /*  Only free the channel if we're freeing from the redo
   *  stack and it's a channel add, or if we're freeing from
   *  the undo stack and it's a channel remove
   */
  if ((state == REDO && cu->undo_type == CHANNEL_ADD_UNDO) ||
      (state == UNDO && cu->undo_type == CHANNEL_REMOVE_UNDO))
    channel_delete (cu->channel);

  g_free (cu);
}



/*********************************/
/*  Channel Mod Undo               */

int
undo_push_channel_mod (GImage *gimage,
		       void   *channel_ptr)
{
  Channel *channel;
  TileManager *tiles;
  Undo *new;
  void **data;
  int size;

  channel = (Channel *) channel_ptr;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (GIMP_DRAWABLE(channel));

  tiles = GIMP_DRAWABLE(channel)->tiles;
  size = GIMP_DRAWABLE(channel)->width * GIMP_DRAWABLE(channel)->height + sizeof (void *) * 2;

  if ((new = undo_push (gimage, size, CHANNEL_MOD, TRUE)))
    {
      data               = (void **) g_malloc (sizeof (void *) * 2);
      new->data          = data;
      new->pop_func      = undo_pop_channel_mod;
      new->free_func     = undo_free_channel_mod;

      data[0] = channel_ptr;
      data[1] = (void *) tiles;

      return TRUE;
    }
  else
    {
      tile_manager_destroy (tiles);
      return FALSE;
    }
}


static int
undo_pop_channel_mod (GImage    *gimage,
		      undo_state state,
		      undo_type  type,
		      void      *data_ptr)
{
  void **data;
  TileManager *tiles;
  TileManager *temp;
  Channel *channel;

  data = (void **) data_ptr;
  channel = (Channel *) data[0];

  switch (state)
    {
    case UNDO:
      drawable_clean (GIMP_DRAWABLE(channel));
      break;
    case REDO:
      drawable_dirty (GIMP_DRAWABLE(channel));
      break;
    }

  tiles = (TileManager *) data[1];

  /*  Issue the first update  */
  drawable_update (GIMP_DRAWABLE(channel), 0, 0, 
		   GIMP_DRAWABLE(channel)->width, GIMP_DRAWABLE(channel)->height);

  temp = GIMP_DRAWABLE(channel)->tiles;
  GIMP_DRAWABLE(channel)->tiles = tiles;
  GIMP_DRAWABLE(channel)->width = tiles->width;
  GIMP_DRAWABLE(channel)->height = tiles->height;

  /*  Set the new buffer  */
  data[1] = temp;

  /*  Issue the second update  */
  drawable_update (GIMP_DRAWABLE(channel), 0, 0, 
		   GIMP_DRAWABLE(channel)->width, GIMP_DRAWABLE(channel)->height);

  return TRUE;
}


static void
undo_free_channel_mod (undo_state state,
		       void      *data_ptr)
{
  void ** data;

  data = (void **) data_ptr;
  tile_manager_destroy ((TileManager *) data[1]);
  g_free (data);
}


/**************************************/
/*  Floating Selection to Layer Undo  */

int
undo_push_fs_to_layer (GImage *gimage,
		       void   *fsu_ptr)
{
  FStoLayerUndo *fsu;
  Undo *new;
  int size;

  fsu = (FStoLayerUndo *) fsu_ptr;

  /*  increment the dirty flag for this drawable  */
  drawable_dirty (GIMP_DRAWABLE(fsu->layer));

  size = sizeof (FStoLayerUndo);

  if ((new = undo_push (gimage, size, CHANNEL_MOD, TRUE)))
    {
      new->data          = fsu_ptr;
      new->pop_func      = undo_pop_fs_to_layer;
      new->free_func     = undo_free_fs_to_layer;

      return TRUE;
    }
  else
    {
      tile_manager_destroy (fsu->layer->fs.backing_store);
      g_free (fsu);
      return FALSE;
    }
}


static int
undo_pop_fs_to_layer (GImage    *gimage,
		      undo_state state,
		      undo_type  type,
		      void      *fsu_ptr)
{
  FStoLayerUndo *fsu;

  fsu = (FStoLayerUndo *) fsu_ptr;

  switch (state)
    {
    case UNDO:
      drawable_clean (GIMP_DRAWABLE(fsu->layer));
      break;
    case REDO:
      drawable_dirty (GIMP_DRAWABLE(fsu->layer));
      break;
    }

  switch (state)
    {
    case UNDO:
      /*  Update the preview for the floating sel  */
      drawable_invalidate_preview (GIMP_DRAWABLE(fsu->layer));

      fsu->layer->fs.drawable = fsu->drawable;
      gimage->active_layer = fsu->layer;
      gimage->floating_sel = fsu->layer;

      /*  restore the contents of the drawable  */
      floating_sel_store (fsu->layer, 
			  GIMP_DRAWABLE(fsu->layer)->offset_x, 
			  GIMP_DRAWABLE(fsu->layer)->offset_y,
			  GIMP_DRAWABLE(fsu->layer)->width, 
			  GIMP_DRAWABLE(fsu->layer)->height);
      fsu->layer->fs.initial = TRUE;

      /*  clear the selection  */
      layer_invalidate_boundary (fsu->layer);

      /*  Update the preview for the gimage and underlying drawable  */
      drawable_invalidate_preview (GIMP_DRAWABLE(fsu->layer));
      break;

    case REDO:
      /*  restore the contents of the drawable  */
      floating_sel_restore (fsu->layer, 
			    GIMP_DRAWABLE(fsu->layer)->offset_x, 
			    GIMP_DRAWABLE(fsu->layer)->offset_y,
			    GIMP_DRAWABLE(fsu->layer)->width, 
			    GIMP_DRAWABLE(fsu->layer)->height);

      /*  Update the preview for the gimage and underlying drawable  */
      drawable_invalidate_preview (GIMP_DRAWABLE(fsu->layer));

      /*  clear the selection  */
      layer_invalidate_boundary (fsu->layer);

      /*  update the pointers  */
      fsu->layer->fs.drawable = NULL;
      gimage->floating_sel = NULL;

      /*  Update the fs drawable  */
      drawable_invalidate_preview (GIMP_DRAWABLE(fsu->layer));
      break;
    }

  return TRUE;
}


static void
undo_free_fs_to_layer (undo_state state,
		       void      *fsu_ptr)
{
  FStoLayerUndo *fsu;

  fsu = (FStoLayerUndo *) fsu_ptr;

  if (state == UNDO)
    tile_manager_destroy (fsu->layer->fs.backing_store);
  g_free (fsu);
}


/***********************************/
/*  Floating Selection Rigor Undo  */

int
undo_push_fs_rigor (GImage *gimage,
		    int     layer_id)
{
  Undo *new;
  int size;

  size = sizeof (int);

  if ((new = undo_push (gimage, size, FS_RIGOR, FALSE)))
    {
      new->data          = g_new (int, 1);
      new->pop_func      = undo_pop_fs_rigor;
      new->free_func     = undo_free_fs_rigor;

      *((int *) new->data) = layer_id;

      return TRUE;
    }
  else
    return FALSE;
}


static int
undo_pop_fs_rigor (GImage    *gimage,
		   undo_state state,
		   undo_type  type,
		   void      *layer_ptr)
{
  int layer_id;
  Layer *floating_layer;

  layer_id = *((int *) layer_ptr);
  if ((floating_layer = layer_get_ID (layer_id)) == NULL)
    return FALSE;
  if (! layer_is_floating_sel (floating_layer))
    return FALSE;

  switch (state)
    {
    case UNDO:
      /*  restore the contents of drawable the floating layer is attached to  */
      if (floating_layer->fs.initial == FALSE)
	floating_sel_restore (floating_layer,
			      GIMP_DRAWABLE(floating_layer)->offset_x, 
			      GIMP_DRAWABLE(floating_layer)->offset_y,
			      GIMP_DRAWABLE(floating_layer)->width, 
			      GIMP_DRAWABLE(floating_layer)->height);
      floating_layer->fs.initial = TRUE;
      break;

    case REDO:
      /*  store the affected area from the drawable in the backing store  */
      floating_sel_store (floating_layer,
			  GIMP_DRAWABLE(floating_layer)->offset_x, 
			  GIMP_DRAWABLE(floating_layer)->offset_y,
			  GIMP_DRAWABLE(floating_layer)->width, 
			  GIMP_DRAWABLE(floating_layer)->height);
      floating_layer->fs.initial = TRUE;
      break;
    }

  return TRUE;
}


static void
undo_free_fs_rigor (undo_state state,
		    void      *layer_ptr)
{
  g_free (layer_ptr);
}


/***********************************/
/*  Floating Selection Relax Undo  */

int
undo_push_fs_relax (GImage *gimage,
		    int     layer_id)
{
  Undo *new;
  int size;

  size = sizeof (int);

  if ((new = undo_push (gimage, size, FS_RELAX, FALSE)))
    {
      new->data          = g_new (int, 1);
      new->pop_func      = undo_pop_fs_relax;
      new->free_func     = undo_free_fs_relax;

      *((int *) new->data) = layer_id;

      return TRUE;
    }
  else
    return FALSE;
}


static int
undo_pop_fs_relax (GImage    *gimage,
		   undo_state state,
		   undo_type  type,
		   void      *layer_ptr)
{
  int layer_id;
  Layer *floating_layer;

  layer_id = *((int *) layer_ptr);
  if ((floating_layer = layer_get_ID (layer_id)) == NULL)
    return FALSE;
  if (! layer_is_floating_sel (floating_layer))
    return FALSE;

  switch (state)
    {
    case UNDO:
      /*  store the affected area from the drawable in the backing store  */
      floating_sel_store (floating_layer,
			  GIMP_DRAWABLE(floating_layer)->offset_x, 
			  GIMP_DRAWABLE(floating_layer)->offset_y,
			  GIMP_DRAWABLE(floating_layer)->width, 
			  GIMP_DRAWABLE(floating_layer)->height);
      floating_layer->fs.initial = TRUE;
      break;

    case REDO:
      /*  restore the contents of drawable the floating layer is attached to  */
      if (floating_layer->fs.initial == FALSE)
	floating_sel_restore (floating_layer,
			      GIMP_DRAWABLE(floating_layer)->offset_x, 
			      GIMP_DRAWABLE(floating_layer)->offset_y,
			      GIMP_DRAWABLE(floating_layer)->width, 
			      GIMP_DRAWABLE(floating_layer)->height);
      floating_layer->fs.initial = TRUE;
      break;
    }

  return TRUE;
}


static void
undo_free_fs_relax (undo_state state,
		    void       *layer_ptr)
{
  g_free (layer_ptr);
}


/*********************/
/*  GImage Mod Undo  */

int
undo_push_gimage_mod (GImage *gimage)
{
  Undo *new;
  int *data;
  int size;

  size = sizeof (int) * 3;

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      data               = (int *) g_malloc (sizeof (int) * 3);
      new->data          = data;
      new->pop_func      = undo_pop_gimage_mod;
      new->free_func     = undo_free_gimage_mod;

      data[0] = gimage->width;
      data[1] = gimage->height;
      data[2] = gimage->base_type;

      return TRUE;
    }

  return FALSE;
}


static int
undo_pop_gimage_mod (GImage    *gimage,
		     undo_state state,
		     undo_type  type,
		     void       *data_ptr)
{
  int *data;
  int tmp;

  data = (int *) data_ptr;
  tmp = data[0];
  data[0] = gimage->width;
  gimage->width = tmp;
  tmp = data[1];
  data[1] = gimage->height;
  gimage->height = tmp;
  tmp = data[2];
  data[2] = gimage->base_type;
  gimage->base_type = tmp;

  gimage_projection_realloc (gimage);

  gimage_mask_invalidate (gimage);
  channel_invalidate_previews (gimage);
  layer_invalidate_previews (gimage);
  gimage_invalidate_preview (gimage);
  gdisplays_update_full (gimage);
  gdisplays_update_title (gimage);

  gimp_image_colormap_changed (gimage, -1);

  if (gimage->width != (int) data[0] || gimage->height != (int) data[1])
    shrink_wrap = TRUE;

  return TRUE;
}


static void
undo_free_gimage_mod (undo_state state,
		      void       *data_ptr)
{
  g_free (data_ptr);
}

/***********/
/*  Qmask  */

typedef struct _QmaskUndo QmaskUndo;

struct _QmaskUndo
{
  GImage *gimage;
  int qmask;
  int orig;
};


int 
undo_push_qmask (GImage *gimage, 
                 int qmask)
{
  Undo *new;
  QmaskUndo *data;
  long size;

  size = sizeof (QmaskUndo);

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      data               = g_new (QmaskUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_qmask;
      new->free_func     = undo_free_qmask;

      data->gimage = gimage;
      data->qmask = qmask;
      data->orig = data->qmask;

      return TRUE;
    }

  return FALSE;
}

static int
undo_pop_qmask (GImage    *gimage,
		undo_state state,
		undo_type  type,
		void      *data_ptr)
{
  QmaskUndo *data;
  int tmp;

  data = data_ptr;
  
  tmp = data->qmask;
  data->qmask = data->orig;
  data->orig = tmp;

  gimage->qmask_state = data->qmask;

  return TRUE;
}


static void
undo_free_qmask (undo_state state,
		 void       *data_ptr)
{
  g_free (data_ptr);
}

/***********/
/*  Guide  */

typedef struct _GuideUndo GuideUndo;

struct _GuideUndo
{
  GImage *gimage;
  Guide *guide;
  Guide orig;
};

int
undo_push_guide (GImage *gimage,
		 void   *guide)
{
  Undo *new;
  GuideUndo *data;
  long size;

  size = sizeof (GuideUndo);

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      ((Guide *)(guide))->ref_count++;
      data               = g_new (GuideUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_guide;
      new->free_func     = undo_free_guide;

      data->gimage = gimage;
      data->guide = guide;
      data->orig = *(data->guide);

      return TRUE;
    }

  return FALSE;
}


static int
undo_pop_guide (GImage    *gimage,
		undo_state state,
		undo_type  type,
		void      *data_ptr)
{
  GuideUndo *data;
  Guide tmp;
  int tmp_ref;

  data = data_ptr;

  gdisplays_expose_guide (gimage, data->guide);
  gdisplays_expose_guide (gimage, &data->orig);

  tmp_ref = data->guide->ref_count;
  tmp = *(data->guide);
  *(data->guide) = data->orig;
  data->guide->ref_count = tmp_ref;
  data->orig = tmp;

  return TRUE;
}


static void
undo_free_guide (undo_state state,
		 void      *data_ptr)
{
  GuideUndo *data;

  data = data_ptr;

  data->guide->ref_count--;
  if (data->guide->position < 0 && data->guide->ref_count <= 0)
      gimage_delete_guide (data->gimage, data->guide);

  g_free (data_ptr);
}


/************/
/* Parasite */

typedef struct _ParasiteUndo ParasiteUndo;

struct _ParasiteUndo
{
  GImage       *gimage;
  GimpDrawable *drawable;
  Parasite     *parasite;
  char         *name;
};

int
undo_push_image_parasite (GImage   *gimage,
			  void     *parasite)
{
  Undo *new;
  ParasiteUndo *data;
  long size;

  size = sizeof (ParasiteUndo);

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      data               = g_new (ParasiteUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_parasite;
      new->free_func     = undo_free_parasite;

      data->gimage   = gimage;
      data->drawable = NULL;
      data->name     = g_strdup (parasite_name (parasite));
      data->parasite = parasite_copy (gimp_image_find_parasite (gimage, data->name));

      return TRUE;
    }

  return FALSE;
}

int
undo_push_image_parasite_remove (GImage      *gimage,
				 const char  *name)
{
  Undo *new;
  ParasiteUndo *data;
  long size;

  size = sizeof (ParasiteUndo);

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      data               = g_new (ParasiteUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_parasite;
      new->free_func     = undo_free_parasite;

      data->gimage = gimage;
      data->drawable = NULL;
      data->name     = g_strdup (name);
      data->parasite = parasite_copy (gimp_image_find_parasite (gimage, data->name));

      return TRUE;
    }

  return FALSE;
}

int
undo_push_drawable_parasite (GImage       *gimage,
			     GimpDrawable *drawable,
			     void         *parasite)
{
  Undo *new;
  ParasiteUndo *data;
  long size;

  size = sizeof (ParasiteUndo);

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      data               = g_new (ParasiteUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_parasite;
      new->free_func     = undo_free_parasite;

      data->gimage   = NULL;
      data->drawable = drawable;
      data->name     = g_strdup (parasite_name (parasite));
      data->parasite = parasite_copy (gimp_drawable_find_parasite (drawable, data->name));
      return TRUE;
    }

  return FALSE;
}

int
undo_push_drawable_parasite_remove (GImage       *gimage,
				    GimpDrawable *drawable,
				    const char   *name)
{
  Undo *new;
  ParasiteUndo *data;
  long size;

  size = sizeof (ParasiteUndo);

  if ((new = undo_push (gimage, size, GIMAGE_MOD, TRUE)))
    {
      data               = g_new (ParasiteUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_parasite;
      new->free_func     = undo_free_parasite;

      data->gimage   = NULL;
      data->drawable = drawable;
      data->name     = g_strdup (name);
      data->parasite = parasite_copy (gimp_drawable_find_parasite (drawable, data->name));
      return TRUE;
    }

  return FALSE;
}


static int
undo_pop_parasite (GImage    *gimage,
		   undo_state state,
		   undo_type  type,
		   void      *data_ptr)
{
  ParasiteUndo *data;
  Parasite *tmp;

  data = data_ptr;

  tmp = data->parasite;
  
  if (data->gimage)
  {
    data->parasite = parasite_copy (gimp_image_find_parasite (gimage,
							      data->name));
    if (tmp)
      parasite_list_add (data->gimage->parasites, tmp);
    else
      parasite_list_remove (data->gimage->parasites, data->name);
  }
  else if (data->drawable)
  {
    data->parasite = parasite_copy (gimp_drawable_find_parasite (data->drawable,
								 data->name));
    if (tmp)
      parasite_list_add (data->drawable->parasites, tmp);
    else
      parasite_list_remove (data->drawable->parasites, data->name);
  }
  else
  {
    data->parasite = parasite_copy (gimp_find_parasite (data->name));
    if (tmp)
      gimp_attach_parasite (tmp);
    else
      gimp_detach_parasite (data->name);
  }
    
  if (tmp)
    parasite_free (tmp);

  return TRUE;
}


static void
undo_free_parasite (undo_state state,
		    void      *data_ptr)
{
  ParasiteUndo *data;

  data = data_ptr;

  if (data->parasite)
    parasite_free (data->parasite);
  if (data->name)
    g_free (data->name);

  g_free (data_ptr);
}




/*************/
/* Layer name change */

typedef struct {
    Layer *layer;
    gchar *old_name;
} LayerRenameUndo;

int
undo_push_layer_rename (GImage *gimage, Layer *layer)
{
  Undo *new;
  LayerRenameUndo *data;
  long size;

  /*  increment the dirty flag for this gimage  */
  gimage_dirty (gimage);

  size = sizeof (LayerRenameUndo);

  if ((new = undo_push (gimage, size, LAYER_CHANGE, TRUE)))
  {
      data               = g_new (LayerRenameUndo, 1);
      new->data          = data;
      new->pop_func      = undo_pop_layer_rename;
      new->free_func     = undo_free_layer_rename;

      data->layer    = layer;
      data->old_name = g_strdup (layer_get_name (layer));

      return TRUE;
    }

  return FALSE;
}

static int
undo_pop_layer_rename (GImage    *gimage,
		       undo_state state,
		       undo_type  type,
		       void      *data_ptr)
{
    LayerRenameUndo *data = data_ptr;
    gchar *tmp;

    tmp = g_strdup (layer_get_name (data->layer));
    layer_set_name (data->layer, data->old_name);
    g_free (data->old_name);
    data->old_name = tmp;

    switch (state) {
    case UNDO:
	gimp_image_clean (gimage);
	break;

    case REDO:
	gimp_image_dirty (gimage);
	break;
    }

    return TRUE;
}

static void
undo_free_layer_rename (undo_state state,
			void      *data_ptr)
{
    LayerRenameUndo *data = data_ptr;

    g_free (data->old_name);
    g_free (data);
}



/*************/
/* Something for which programmer is too lazy to write an undo 
 * function for.
 */

int
undo_push_cantundo (GImage     *gimage,
		    const char *action)
{
    Undo *new;

    /* This is the sole purpose of this type of undo: the ability to
     * mark an image as having been mutated, without really providing
     * any adequate undo facility. */
    gimp_image_dirty (gimage);

    new = undo_push (gimage, 0, GIMAGE_MOD, TRUE);
    if (!new)
	return FALSE;

    new->data      = (void*)action;
    new->pop_func  = undo_pop_cantundo;
    new->free_func = undo_free_cantundo;

    return TRUE;
}

static int
undo_pop_cantundo (GImage    *gimage,
		   undo_state state,
		   undo_type  type,
		   void      *data_ptr)
{
    char *action = data_ptr;

    switch (state) {
    case UNDO:
	g_message (_("Can't undo %s"), action);
	gimp_image_clean (gimage);
	break;

    case REDO:
	gimp_image_dirty (gimage);
	break;
    }

    return TRUE;
}

static void
undo_free_cantundo (undo_state state, void *data_ptr)
{
}


static struct undo_name_t {
    undo_type type;
    const char *name;
} undo_name[] = {
    {0,			N_("<<invalid>>")},
    {IMAGE_UNDO,	N_("image")},
    {IMAGE_MOD_UNDO,	N_("image mod")},
    {MASK_UNDO,		N_("mask")},
    {LAYER_DISPLACE_UNDO, N_("layer move")},
    {TRANSFORM_UNDO,	N_("transform")},
    {PAINT_UNDO,	N_("paint")},
    {LAYER_UNDO,	N_("layer")},
    {LAYER_MOD,		N_("layer mod")},
    {LAYER_MASK_UNDO,	N_("layer mask")},
    {LAYER_CHANGE,	N_("layer change")},
    {LAYER_POSITION,	N_("layer position")},
    {CHANNEL_UNDO,	N_("channel")},
    {CHANNEL_MOD,	N_("channel mod")},
    {FS_TO_LAYER_UNDO,	N_("FS to layer")},
    {GIMAGE_MOD,	N_("gimage")},
    {FS_RIGOR,		N_("FS rigor")},
    {FS_RELAX,		N_("FS relax")},
    {GUIDE_UNDO,	N_("guide")},
    {FLOAT_MASK_UNDO,	N_("float selection")},
    {EDIT_PASTE_UNDO,	N_("paste")},
    {EDIT_CUT_UNDO,	N_("cut")},
    {TRANSFORM_CORE_UNDO, N_("transform core")},
    {PAINT_CORE_UNDO,	N_("paint core")},
    {FLOATING_LAYER_UNDO, N_("floating layer")}, /* unused! */
    {LINKED_LAYER_UNDO,	N_("linked layer")},
    {LAYER_APPLY_MASK_UNDO, N_("apply layer mask")},
    {LAYER_MERGE_UNDO,	N_("layer merge")},
    {FS_ANCHOR_UNDO,	N_("FS anchor")},
    {GIMAGE_MOD_UNDO,	N_("gimage mod")},
    {CROP_UNDO,		N_("crop")},
    {LAYER_SCALE_UNDO,	N_("layer scale")},
    {LAYER_RESIZE_UNDO,	N_("layer resize")},
    {QMASK_UNDO,	N_("quickmask")},
    {MISC_UNDO,		N_("misc")}
};
#define NUM_NAMES (sizeof (undo_name) / sizeof (struct undo_name_t))


static const char *
undo_type_to_name (undo_type type)
{
    int i;

    for (i=0; i < NUM_NAMES; i++)
	if (undo_name[i].type == type)
	    return gettext (undo_name[i].name);

    /* no name found */
    return "";
}