gimp/app/paint/gimppaintcore.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 <string.h>

#include <glib-object.h>

#include "paint-types.h"

#include "base/pixel-region.h"
#include "base/temp-buf.h"
#include "base/tile-manager.h"
#include "base/tile.h"

#include "paint-funcs/paint-funcs.h"

#include "core/gimp.h"
#include "core/gimpcontainer.h"
#include "core/gimpdrawable.h"
#include "core/gimpimage.h"
#include "core/gimpimage-undo.h"
#include "core/gimppaintinfo.h"

#include "gimppaintcore.h"
#include "gimppaintcore-undo.h"
#include "gimppaintoptions.h"

#include "gimp-intl.h"


/*  local function prototypes  */

static void      gimp_paint_core_class_init        (GimpPaintCoreClass *klass);
static void      gimp_paint_core_init              (GimpPaintCore      *core);

static void      gimp_paint_core_finalize            (GObject          *object);

static gboolean  gimp_paint_core_real_start          (GimpPaintCore    *core,
                                                      GimpDrawable     *drawable,
                                                      GimpPaintOptions *paint_options,
                                                      GimpCoords       *coords);
static gboolean  gimp_paint_core_real_pre_paint      (GimpPaintCore    *core,
                                                      GimpDrawable     *drawable,
                                                      GimpPaintOptions *options,
                                                      GimpPaintCoreState paint_state,
                                                      guint32           time);
static void      gimp_paint_core_real_paint          (GimpPaintCore    *core,
                                                      GimpDrawable     *drawable,
                                                      GimpPaintOptions *options,
                                                      GimpPaintCoreState paint_state,
                                                      guint32           time);
static void      gimp_paint_core_real_interpolate    (GimpPaintCore    *core,
                                                      GimpDrawable     *drawable,
                                                      GimpPaintOptions *options,
                                                      guint32           time);
static TempBuf * gimp_paint_core_real_get_paint_area (GimpPaintCore    *core,
                                                      GimpDrawable     *drawable,
                                                      GimpPaintOptions *options);

static void      paint_mask_to_canvas_tiles          (GimpPaintCore    *core,
                                                      PixelRegion      *paint_maskPR,
                                                      gdouble           paint_opacity);
static void      paint_mask_to_canvas_buf            (GimpPaintCore    *core,
                                                      PixelRegion      *paint_maskPR,
                                                      gdouble           paint_opacity);
static void      canvas_tiles_to_canvas_buf          (GimpPaintCore    *core);


static GimpObjectClass *parent_class = NULL;

static gint global_core_ID = 1;


GType
gimp_paint_core_get_type (void)
{
  static GType core_type = 0;

  if (! core_type)
    {
      static const GTypeInfo core_info =
      {
        sizeof (GimpPaintCoreClass),
        (GBaseInitFunc) NULL,
        (GBaseFinalizeFunc) NULL,
        (GClassInitFunc) gimp_paint_core_class_init,
        NULL,           /* class_finalize */
        NULL,           /* class_data     */
        sizeof (GimpPaintCore),
        0,              /* n_preallocs    */
        (GInstanceInitFunc) gimp_paint_core_init,
      };

      core_type = g_type_register_static (GIMP_TYPE_OBJECT,
                                          "GimpPaintCore",
                                          &core_info, 0);
    }

  return core_type;
}

static void
gimp_paint_core_class_init (GimpPaintCoreClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  object_class->finalize  = gimp_paint_core_finalize;

  klass->traces_on_window = FALSE;
  klass->start            = gimp_paint_core_real_start;
  klass->pre_paint        = gimp_paint_core_real_pre_paint;
  klass->paint            = gimp_paint_core_real_paint;
  klass->interpolate      = gimp_paint_core_real_interpolate;
  klass->get_paint_area   = gimp_paint_core_real_get_paint_area;
}

static void
gimp_paint_core_init (GimpPaintCore *core)
{
  core->ID           = global_core_ID++;

  core->distance     = 0.0;
  core->pixel_dist   = 0.0;
  core->x1           = 0;
  core->y1           = 0;
  core->x2           = 0;
  core->y2           = 0;

  core->use_pressure = FALSE;

  core->undo_tiles   = NULL;
  core->canvas_tiles = NULL;

  core->orig_buf     = NULL;
  core->canvas_buf   = NULL;
}

static void
gimp_paint_core_finalize (GObject *object)
{
  GimpPaintCore *core = GIMP_PAINT_CORE (object);

  gimp_paint_core_cleanup (core);

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

static gboolean
gimp_paint_core_real_start (GimpPaintCore    *core,
                            GimpDrawable     *drawable,
                            GimpPaintOptions *paint_options,
                            GimpCoords       *coords)
{
  return TRUE;
}

static gboolean
gimp_paint_core_real_pre_paint (GimpPaintCore      *core,
                                GimpDrawable       *drawable,
                                GimpPaintOptions   *paint_options,
                                GimpPaintCoreState  paint_state,
                                guint32             time)
{
  return TRUE;
}

static void
gimp_paint_core_real_paint (GimpPaintCore      *core,
                            GimpDrawable       *drawable,
                            GimpPaintOptions   *paint_options,
                            GimpPaintCoreState  paint_state,
                            guint32             time)
{
}

static void
gimp_paint_core_real_interpolate (GimpPaintCore    *core,
                                  GimpDrawable     *drawable,
                                  GimpPaintOptions *paint_options,
                                  guint32           time)
{
  gimp_paint_core_paint (core, drawable, paint_options,
                         MOTION_PAINT, time);

  core->last_coords = core->cur_coords;
}

static TempBuf *
gimp_paint_core_real_get_paint_area (GimpPaintCore    *core,
                                     GimpDrawable     *drawable,
                                     GimpPaintOptions *paint_options)
{
  return NULL;
}

void
gimp_paint_core_paint (GimpPaintCore      *core,
                       GimpDrawable       *drawable,
                       GimpPaintOptions   *paint_options,
                       GimpPaintCoreState  paint_state,
                       guint32             time)
{
  g_return_if_fail (GIMP_IS_PAINT_CORE (core));
  g_return_if_fail (GIMP_IS_DRAWABLE (drawable));
  g_return_if_fail (gimp_item_is_attached (GIMP_ITEM (drawable)));
  g_return_if_fail (GIMP_IS_PAINT_OPTIONS (paint_options));

  if (GIMP_PAINT_CORE_GET_CLASS (core)->pre_paint (core, drawable,
                                                   paint_options,
                                                   paint_state, time))
    {
      if (paint_state == MOTION_PAINT)
        {
          /* Save coordinates for gimp_paint_core_interpolate() */
          core->last_paint.x = core->cur_coords.x;
          core->last_paint.y = core->cur_coords.y;
        }

      GIMP_PAINT_CORE_GET_CLASS (core)->paint (core, drawable,
                                               paint_options,
                                               paint_state, time);
    }
}

gboolean
gimp_paint_core_start (GimpPaintCore    *core,
                       GimpDrawable     *drawable,
                       GimpPaintOptions *paint_options,
                       GimpCoords       *coords)
{
  GimpItem *item;

  g_return_val_if_fail (GIMP_IS_PAINT_CORE (core), FALSE);
  g_return_val_if_fail (GIMP_IS_DRAWABLE (drawable), FALSE);
  g_return_val_if_fail (gimp_item_is_attached (GIMP_ITEM (drawable)), FALSE);
  g_return_val_if_fail (GIMP_IS_PAINT_OPTIONS (paint_options), FALSE);
  g_return_val_if_fail (coords != NULL, FALSE);

  item = GIMP_ITEM (drawable);

  core->cur_coords = *coords;

  if (! GIMP_PAINT_CORE_GET_CLASS (core)->start (core, drawable,
                                                 paint_options,
                                                 coords))
    {
      return FALSE;
    }

  /*  Allocate the undo structure  */
  if (core->undo_tiles)
    tile_manager_unref (core->undo_tiles);

  core->undo_tiles = tile_manager_new (gimp_item_width (item),
                                       gimp_item_height (item),
                                       gimp_drawable_bytes (drawable));

  /*  Allocate the canvas blocks structure  */
  if (core->canvas_tiles)
    tile_manager_unref (core->canvas_tiles);

  core->canvas_tiles = tile_manager_new (gimp_item_width (item),
                                         gimp_item_height (item),
                                         1);

  /*  Get the initial undo extents  */

  core->x1           = core->x2 = core->cur_coords.x;
  core->y1           = core->y2 = core->cur_coords.y;

  core->last_paint.x = -1e6;
  core->last_paint.y = -1e6;

  return TRUE;
}

void
gimp_paint_core_finish (GimpPaintCore *core,
                        GimpDrawable  *drawable)
{
  GimpPaintInfo *paint_info;
  GimpImage     *gimage;

  g_return_if_fail (GIMP_IS_PAINT_CORE (core));
  g_return_if_fail (GIMP_IS_DRAWABLE (drawable));
  g_return_if_fail (gimp_item_is_attached (GIMP_ITEM (drawable)));

  gimage = gimp_item_get_image (GIMP_ITEM (drawable));

  /*  Determine if any part of the image has been altered--
   *  if nothing has, then just return...
   */
  if ((core->x2 == core->x1) || (core->y2 == core->y1))
    return;

  paint_info = (GimpPaintInfo *)
    gimp_container_get_child_by_name (gimage->gimp->paint_info_list,
                                      g_type_name (G_TYPE_FROM_INSTANCE (core)));

  gimp_image_undo_group_start (gimage, GIMP_UNDO_GROUP_PAINT,
                               paint_info ? paint_info->blurb : _("Paint"));

  gimp_paint_core_push_undo (gimage, NULL, core);

  gimp_drawable_push_undo (drawable, NULL,
                           core->x1, core->y1,
                           core->x2, core->y2,
                           core->undo_tiles,
                           TRUE);

  tile_manager_unref (core->undo_tiles);
  core->undo_tiles = NULL;

  gimp_image_undo_group_end (gimage);

  /*  invalidate the previews -- have to do it here, because
   *  it is not done during the actual painting.
   */
  gimp_viewable_invalidate_preview (GIMP_VIEWABLE (drawable));
  gimp_viewable_invalidate_preview (GIMP_VIEWABLE (gimage));
}

static void
gimp_paint_core_copy_valid_tiles (TileManager *src_tiles,
                                  TileManager *dest_tiles,
                                  gint         x,
                                  gint         y,
                                  gint         w,
                                  gint         h)
{
  Tile *src_tile;
  gint  i, j;

  for (i = y; i < (y + h); i += (TILE_HEIGHT - (i % TILE_HEIGHT)))
    {
      for (j = x; j < (x + w); j += (TILE_WIDTH - (j % TILE_WIDTH)))
        {
          src_tile = tile_manager_get_tile (src_tiles,
                                            j, i, FALSE, FALSE);

          if (tile_is_valid (src_tile))
            {
              src_tile = tile_manager_get_tile (src_tiles,
                                                j, i, TRUE, FALSE);

              tile_manager_map_tile (dest_tiles, j, i, src_tile);

              tile_release (src_tile, FALSE);
            }
        }
    }
}

void
gimp_paint_core_cancel (GimpPaintCore *core,
			GimpDrawable  *drawable)
{
  g_return_if_fail (GIMP_IS_PAINT_CORE (core));
  g_return_if_fail (GIMP_IS_DRAWABLE (drawable));
  g_return_if_fail (gimp_item_is_attached (GIMP_ITEM (drawable)));

  /*  Determine if any part of the image has been altered--
   *  if nothing has, then just return...
   */
  if ((core->x2 == core->x1) || (core->y2 == core->y1))
    return;

  gimp_paint_core_copy_valid_tiles (core->undo_tiles,
                                    gimp_drawable_data (drawable),
                                    core->x1, core->y1,
                                    core->x2 - core->x1,
                                    core->y2 - core->y1);

  tile_manager_unref (core->undo_tiles);
  core->undo_tiles = NULL;

  gimp_drawable_update (drawable,
                        core->x1, core->y1,
                        core->x2 - core->x1, core->y2 - core->y1);
}

void
gimp_paint_core_cleanup (GimpPaintCore *core)
{
  g_return_if_fail (GIMP_IS_PAINT_CORE (core));

  if (core->undo_tiles)
    {
      tile_manager_unref (core->undo_tiles);
      core->undo_tiles = NULL;
    }

  if (core->canvas_tiles)
    {
      tile_manager_unref (core->canvas_tiles);
      core->canvas_tiles = NULL;
    }

  if (core->orig_buf)
    {
      temp_buf_free (core->orig_buf);
      core->orig_buf = NULL;
    }

  if (core->canvas_buf)
    {
      temp_buf_free (core->canvas_buf);
      core->canvas_buf = NULL;
    }
}

/**
 * gimp_paint_core_constrain_helper:
 * @dx: the (fixed) delta-x
 * @dy: a suggested delta-y
 *
 * Returns an adjusted dy' near dy such that the slope (dx,dy') is a
 * multiple of 15 degrees.
 **/
static gdouble
gimp_paint_core_constrain_helper (gdouble dx,
                                  gdouble dy)
{
  static gdouble slope[4]   = { 0, 0.26795, 0.57735, 1 };
  static gdouble divider[3] = { 0.13165, 0.41421, 0.76732 };
  gint           i;

  if (dy < 0)
    return - gimp_paint_core_constrain_helper (dx,-dy);
  dx = fabs (dx);
  for (i = 0; i < 3; i ++)
    if (dy < dx * divider[i])
      break;
  dy = dx * slope[i];
  return dy;
}

/**
 * gimp_paint_core_constrain:
 * @core: the #GimpPaintCore.
 *
 * Restricts the (core->last_coords, core->cur_coords) vector to 15
 * degree steps, possibly changing core->cur_coords.
 **/
void
gimp_paint_core_constrain (GimpPaintCore *core)
{
  gdouble dx, dy;

  g_return_if_fail (GIMP_IS_PAINT_CORE (core));

  dx = core->cur_coords.x - core->last_coords.x;
  dy = core->cur_coords.y - core->last_coords.y;

  /*  This algorithm changes only one of dx and dy, and does not try
   *  to constrain the resulting dx and dy to integers. This gives
   *  at least two benefits:
   *    1. gimp_paint_core_constrain is idempotent, even if followed by
   *       a rounding operation.
   *    2. For any two lines with the same starting-point and ideal
   *       15-degree direction, the points plotted by
   *       gimp_paint_core_interpolate for the shorter line will always
   *       be a superset of those plotted for the longer line.
   */
  if (fabs (dx) > fabs (dy))
    core->cur_coords.y = (core->last_coords.y +
                          gimp_paint_core_constrain_helper (dx,dy));
  else
    core->cur_coords.x = (core->last_coords.x +
                          gimp_paint_core_constrain_helper (dy,dx));
}

void
gimp_paint_core_interpolate (GimpPaintCore    *core,
                             GimpDrawable     *drawable,
                             GimpPaintOptions *paint_options,
                             guint32           time)
{
  g_return_if_fail (GIMP_IS_PAINT_CORE (core));
  g_return_if_fail (GIMP_IS_DRAWABLE (drawable));
  g_return_if_fail (gimp_item_is_attached (GIMP_ITEM (drawable)));
  g_return_if_fail (GIMP_IS_PAINT_OPTIONS (paint_options));

  GIMP_PAINT_CORE_GET_CLASS (core)->interpolate (core, drawable,
                                                 paint_options, time);
}


/*  protected functions  */

TempBuf *
gimp_paint_core_get_paint_area (GimpPaintCore    *core,
                                GimpDrawable     *drawable,
                                GimpPaintOptions *paint_options)
{
  g_return_val_if_fail (GIMP_IS_PAINT_CORE (core), NULL);
  g_return_val_if_fail (GIMP_IS_DRAWABLE (drawable), NULL);
  g_return_val_if_fail (gimp_item_is_attached (GIMP_ITEM (drawable)), NULL);
  g_return_val_if_fail (GIMP_IS_PAINT_OPTIONS (paint_options), NULL);

  return GIMP_PAINT_CORE_GET_CLASS (core)->get_paint_area (core, drawable,
                                                           paint_options);
}

TempBuf *
gimp_paint_core_get_orig_image (GimpPaintCore *core,
                                GimpDrawable  *drawable,
                                gint           x1,
                                gint           y1,
                                gint           x2,
                                gint           y2)
{
  PixelRegion  srcPR;
  PixelRegion  destPR;
  Tile        *undo_tile;
  gboolean     release_tile;
  gint         h;
  gint         pixelwidth;
  gint         drawable_width;
  gint         drawable_height;
  guchar      *s;
  guchar      *d;
  gpointer     pr;

  core->orig_buf = temp_buf_resize (core->orig_buf,
                                    gimp_drawable_bytes (drawable),
                                    x1, y1,
                                    (x2 - x1), (y2 - y1));

  drawable_width  = gimp_item_width  (GIMP_ITEM (drawable));
  drawable_height = gimp_item_height (GIMP_ITEM (drawable));

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

  /*  configure the pixel regions  */
  pixel_region_init (&srcPR, gimp_drawable_data (drawable),
                     x1, y1,
                     (x2 - x1), (y2 - y1),
                     FALSE);

  destPR.bytes     = core->orig_buf->bytes;
  destPR.x         = 0;
  destPR.y         = 0;
  destPR.w         = (x2 - x1);
  destPR.h         = (y2 - y1);
  destPR.rowstride = core->orig_buf->bytes * core->orig_buf->width;
  destPR.data      = (temp_buf_data (core->orig_buf) +
                      (y1 - core->orig_buf->y) * destPR.rowstride +
                      (x1 - core->orig_buf->x) * destPR.bytes);

  for (pr = pixel_regions_register (2, &srcPR, &destPR);
       pr != NULL;
       pr = pixel_regions_process (pr))
    {
      /*  If the undo tile corresponding to this location is valid, use it  */
      undo_tile = tile_manager_get_tile (core->undo_tiles,
                                         srcPR.x, srcPR.y,
                                         FALSE, FALSE);

      if (tile_is_valid (undo_tile))
        {
          release_tile = TRUE;

          undo_tile = tile_manager_get_tile (core->undo_tiles,
                                             srcPR.x, srcPR.y,
                                             TRUE, FALSE);
	  s = ((guchar *) tile_data_pointer (undo_tile, 0, 0) +
               srcPR.rowstride * (srcPR.y % TILE_HEIGHT) +
               srcPR.bytes * (srcPR.x % TILE_WIDTH)); /* dubious... */
        }
      else
        {
          release_tile = FALSE;

          s = srcPR.data;
        }

      d = destPR.data;
      pixelwidth = srcPR.w * srcPR.bytes;
      h = srcPR.h;
      while (h --)
        {
          memcpy (d, s, pixelwidth);
          s += srcPR.rowstride;
          d += destPR.rowstride;
        }

      if (release_tile)
        tile_release (undo_tile, FALSE);
    }

  return core->orig_buf;
}

void
gimp_paint_core_paste (GimpPaintCore            *core,
		       PixelRegion              *paint_maskPR,
		       GimpDrawable             *drawable,
		       gdouble                   paint_opacity,
		       gdouble                   image_opacity,
		       GimpLayerModeEffects      paint_mode,
		       GimpPaintApplicationMode  mode)
{
  GimpImage   *gimage;
  PixelRegion  srcPR;
  TileManager *alt = NULL;
  gint         offx;
  gint         offy;

  gimage = gimp_item_get_image (GIMP_ITEM (drawable));

  /*  set undo blocks  */
  gimp_paint_core_validate_undo_tiles (core, drawable,
                                       core->canvas_buf->x,
                                       core->canvas_buf->y,
                                       core->canvas_buf->width,
                                       core->canvas_buf->height);

  /*  If the mode is CONSTANT:
   *   combine the canvas buf, the paint mask to the canvas tiles
   */
  if (mode == GIMP_PAINT_CONSTANT)
    {
      /* Some tools (ink) paint the mask to paint_core->canvas_tiles
       * directly. Don't need to copy it in this case.
       */
      if (paint_maskPR->tiles != core->canvas_tiles)
        {
          /*  initialize any invalid canvas tiles  */
          gimp_paint_core_validate_canvas_tiles (core,
                                                 core->canvas_buf->x,
                                                 core->canvas_buf->y,
                                                 core->canvas_buf->width,
                                                 core->canvas_buf->height);

          paint_mask_to_canvas_tiles (core, paint_maskPR, paint_opacity);
        }

      canvas_tiles_to_canvas_buf (core);
      alt = core->undo_tiles;
    }
  /*  Otherwise:
   *   combine the canvas buf and the paint mask to the canvas buf
   */
  else
    {
      paint_mask_to_canvas_buf (core, paint_maskPR, paint_opacity);
    }

  /*  intialize canvas buf source pixel regions  */
  srcPR.bytes     = core->canvas_buf->bytes;
  srcPR.x         = 0;
  srcPR.y         = 0;
  srcPR.w         = core->canvas_buf->width;
  srcPR.h         = core->canvas_buf->height;
  srcPR.rowstride = core->canvas_buf->width * core->canvas_buf->bytes;
  srcPR.data      = temp_buf_data (core->canvas_buf);

  /*  apply the paint area to the gimage  */
  gimp_drawable_apply_region (drawable, &srcPR,
                              FALSE, NULL,
                              image_opacity, paint_mode,
                              alt,  /*  specify an alternative src1  */
                              core->canvas_buf->x,
                              core->canvas_buf->y);

  /*  Update the undo extents  */
  core->x1 = MIN (core->x1, core->canvas_buf->x);
  core->y1 = MIN (core->y1, core->canvas_buf->y);
  core->x2 = MAX (core->x2, core->canvas_buf->x + core->canvas_buf->width);
  core->y2 = MAX (core->y2, core->canvas_buf->y + core->canvas_buf->height);

  /*  Update the gimage -- It is important to call gimp_image_update()
   *  instead of gimp_drawable_update() because we don't want the
   *  drawable and image previews to be constantly invalidated
   */
  gimp_item_offsets (GIMP_ITEM (drawable), &offx, &offy);
  gimp_image_update (gimage,
                     core->canvas_buf->x + offx,
                     core->canvas_buf->y + offy,
                     core->canvas_buf->width,
                     core->canvas_buf->height);
}

/* This works similarly to gimp_paint_core_paste. However, instead of
 * combining the canvas to the paint core drawable using one of the
 * combination modes, it uses a "replace" mode (i.e. transparent
 * pixels in the canvas erase the paint core drawable).

 * When not drawing on alpha-enabled images, it just paints using
 * NORMAL mode.
 */
void
gimp_paint_core_replace (GimpPaintCore            *core,
                         PixelRegion              *paint_maskPR,
                         GimpDrawable             *drawable,
                         gdouble                   paint_opacity,
                         gdouble                   image_opacity,
                         GimpPaintApplicationMode  mode)
{
  GimpImage   *gimage;
  PixelRegion  srcPR;
  gint         offx;
  gint         offy;

  if (! gimp_drawable_has_alpha (drawable))
    {
      gimp_paint_core_paste (core, paint_maskPR, drawable,
                             paint_opacity,
                             image_opacity, GIMP_NORMAL_MODE,
                             mode);
      return;
    }

  gimage = gimp_item_get_image (GIMP_ITEM (drawable));

  /*  set undo blocks  */
  gimp_paint_core_validate_undo_tiles (core, drawable,
                                       core->canvas_buf->x,
                                       core->canvas_buf->y,
                                       core->canvas_buf->width,
                                       core->canvas_buf->height);

  if (mode == GIMP_PAINT_CONSTANT)
    {
      /* Some tools (ink) paint the mask to paint_core->canvas_tiles
       * directly. Don't need to copy it in this case.
       */
      if (paint_maskPR->tiles != core->canvas_tiles)
        {
          /*  initialize any invalid canvas tiles  */
          gimp_paint_core_validate_canvas_tiles (core,
                                                 core->canvas_buf->x,
                                                 core->canvas_buf->y,
                                                 core->canvas_buf->width,
                                                 core->canvas_buf->height);

          /* combine the paint mask and the canvas tiles */
          paint_mask_to_canvas_tiles (core, paint_maskPR, paint_opacity);

          /* initialize the maskPR from the canvas tiles */
          pixel_region_init (paint_maskPR, core->canvas_tiles,
                             core->canvas_buf->x,
                             core->canvas_buf->y,
                             core->canvas_buf->width,
                             core->canvas_buf->height,
                             FALSE);
        }
    }
  else
    {
      /* The mask is just the paint_maskPR */
    }

  /*  intialize canvas buf source pixel regions  */
  srcPR.bytes     = core->canvas_buf->bytes;
  srcPR.x         = 0;
  srcPR.y         = 0;
  srcPR.w         = core->canvas_buf->width;
  srcPR.h         = core->canvas_buf->height;
  srcPR.rowstride = core->canvas_buf->width * core->canvas_buf->bytes;
  srcPR.data      = temp_buf_data (core->canvas_buf);

  /*  apply the paint area to the gimage  */
  gimp_drawable_replace_region (drawable, &srcPR,
                                FALSE, NULL,
                                image_opacity,
                                paint_maskPR,
                                core->canvas_buf->x,
                                core->canvas_buf->y);

  /*  Update the undo extents  */
  core->x1 = MIN (core->x1, core->canvas_buf->x);
  core->y1 = MIN (core->y1, core->canvas_buf->y);
  core->x2 = MAX (core->x2, core->canvas_buf->x + core->canvas_buf->width) ;
  core->y2 = MAX (core->y2, core->canvas_buf->y + core->canvas_buf->height) ;

  /*  Update the gimage -- It is important to call gimp_image_update()
   *  instead of gimp_drawable_update() because we don't want the
   *  drawable and image previews to be constantly invalidated
   */
  gimp_item_offsets (GIMP_ITEM (drawable), &offx, &offy);
  gimp_image_update (gimage,
                     core->canvas_buf->x + offx,
                     core->canvas_buf->y + offy,
                     core->canvas_buf->width,
                     core->canvas_buf->height);
}

static void
canvas_tiles_to_canvas_buf (GimpPaintCore *core)
{
  PixelRegion srcPR;
  PixelRegion maskPR;

  /*  combine the canvas tiles and the canvas buf  */
  srcPR.bytes     = core->canvas_buf->bytes;
  srcPR.x         = 0;
  srcPR.y         = 0;
  srcPR.w         = core->canvas_buf->width;
  srcPR.h         = core->canvas_buf->height;
  srcPR.rowstride = core->canvas_buf->width * core->canvas_buf->bytes;
  srcPR.data      = temp_buf_data (core->canvas_buf);

  pixel_region_init (&maskPR, core->canvas_tiles,
                     core->canvas_buf->x,
                     core->canvas_buf->y,
                     core->canvas_buf->width,
                     core->canvas_buf->height,
                     FALSE);

  /*  apply the canvas tiles to the canvas buf  */
  apply_mask_to_region (&srcPR, &maskPR, OPAQUE_OPACITY);
}

static void
paint_mask_to_canvas_tiles (GimpPaintCore *core,
                            PixelRegion   *paint_maskPR,
                            gdouble        paint_opacity)
{
  PixelRegion srcPR;

  /*   combine the paint mask and the canvas tiles  */
  pixel_region_init (&srcPR, core->canvas_tiles,
                     core->canvas_buf->x,
                     core->canvas_buf->y,
                     core->canvas_buf->width,
                     core->canvas_buf->height,
                     TRUE);

  /*  combine the mask to the canvas tiles  */
  combine_mask_and_region (&srcPR, paint_maskPR, paint_opacity * 255.999);
}

static void
paint_mask_to_canvas_buf (GimpPaintCore *core,
                          PixelRegion   *paint_maskPR,
                          gdouble        paint_opacity)
{
  PixelRegion srcPR;

  /*  combine the canvas buf and the paint mask to the canvas buf  */
  srcPR.bytes     = core->canvas_buf->bytes;
  srcPR.x         = 0;
  srcPR.y         = 0;
  srcPR.w         = core->canvas_buf->width;
  srcPR.h         = core->canvas_buf->height;
  srcPR.rowstride = core->canvas_buf->width * core->canvas_buf->bytes;
  srcPR.data      = temp_buf_data (core->canvas_buf);

  /*  apply the mask  */
  apply_mask_to_region (&srcPR, paint_maskPR, paint_opacity * 255.999);
}

void
gimp_paint_core_validate_undo_tiles (GimpPaintCore *core,
                                     GimpDrawable  *drawable,
                                     gint           x,
                                     gint           y,
                                     gint           w,
                                     gint           h)
{
  gint  i;
  gint  j;
  Tile *src_tile;
  Tile *dest_tile;

  if (! core->undo_tiles)
    {
      g_warning ("set_undo_tiles: undo_tiles is null");
      return;
    }

  for (i = y; i < (y + h); i += (TILE_HEIGHT - (i % TILE_HEIGHT)))
    {
      for (j = x; j < (x + w); j += (TILE_WIDTH - (j % TILE_WIDTH)))
        {
          dest_tile = tile_manager_get_tile (core->undo_tiles, j, i,
                                             FALSE, FALSE);

          if (! tile_is_valid (dest_tile))
            {
              src_tile = tile_manager_get_tile (gimp_drawable_data (drawable),
                                                j, i, TRUE, FALSE);
              tile_manager_map_tile (core->undo_tiles, j, i, src_tile);
              tile_release (src_tile, FALSE);
            }
        }
    }
}

void
gimp_paint_core_validate_canvas_tiles (GimpPaintCore *core,
                                       gint           x,
                                       gint           y,
                                       gint           w,
                                       gint           h)
{
  gint  i;
  gint  j;
  Tile *tile;

  for (i = y; i < (y + h); i += (TILE_HEIGHT - (i % TILE_HEIGHT)))
    {
      for (j = x; j < (x + w); j += (TILE_WIDTH - (j % TILE_WIDTH)))
        {
          tile = tile_manager_get_tile (core->canvas_tiles, j, i,
                                        FALSE, FALSE);

          if (! tile_is_valid (tile))
            {
              tile = tile_manager_get_tile (core->canvas_tiles, j, i,
                                            TRUE, TRUE);
              memset (tile_data_pointer (tile, 0, 0), 0, tile_size (tile));
              tile_release (tile, TRUE);
            }
        }
    }
}