/******************************************************************************

  fractaltrace.c  -- This is a plug-in for GIMP 1.0

  Copyright (C) 1997  Hirotsuna Mizuno
                      s1041150@u-aizu.ac.jp

  This program is free software: you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the Free
  Software Foundation; either version 3 of the License, or (at your option)
  any later version.

  This program is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  more details.

  You should have received a copy of the GNU General Public License along with
  this program.  If not, see <https://www.gnu.org/licenses/>.

******************************************************************************/

#define PLUG_IN_PROC     "plug-in-fractal-trace"
#define PLUG_IN_BINARY   "fractal-trace"
#define PLUG_IN_ROLE     "gimp-fractal-trace"
#define PLUG_IN_VERSION  "v0.4 test version (Dec. 25 1997)"

/*****************************************************************************/

#include "config.h"

#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>

#include "libgimp/stdplugins-intl.h"

/******************************************************************************/

static void query  (void);
static void run    (const gchar      *name,
                    gint              nparams,
                    const GimpParam  *param,
                    gint             *nreturn_vals,
                    GimpParam       **return_vals);

static void filter      (GimpDrawable *drawable);

static void pixels_init (GimpDrawable *drawable);
static void pixels_free (void);

static int  dialog_show         (void);
static void dialog_preview_draw (void);

/******************************************************************************/

const GimpPlugInInfo PLUG_IN_INFO =
{
  NULL,  /* init_proc  */
  NULL,  /* quit_proc  */
  query, /* query_proc */
  run    /* run_proc   */
};

MAIN ()

/******************************************************************************/

enum
{
  OUTSIDE_TYPE_WRAP,
  OUTSIDE_TYPE_TRANSPARENT,
  OUTSIDE_TYPE_BLACK,
  OUTSIDE_TYPE_WHITE
};

typedef struct
{
  gdouble x1;
  gdouble x2;
  gdouble y1;
  gdouble y2;
  gint32  depth;
  gint32  outside_type;
} parameter_t;

static parameter_t parameters =
{
  -1.0,
  +0.5,
  -1.0,
  +1.0,
  3,
  OUTSIDE_TYPE_WRAP
};

/******************************************************************************/

static void
query (void)
{
  static const GimpParamDef args[] =
  {
    { GIMP_PDB_INT32,    "run-mode",     "The run mode { RUN-INTERACTIVE (0), RUN-NONINTERACTIVE (1) }" },
    { GIMP_PDB_IMAGE,    "image",        "Input image (unused)"             },
    { GIMP_PDB_DRAWABLE, "drawable",     "Input drawable"                   },
    { GIMP_PDB_FLOAT,    "xmin",         "xmin fractal image delimiter"     },
    { GIMP_PDB_FLOAT,    "xmax",         "xmax fractal image delimiter"     },
    { GIMP_PDB_FLOAT,    "ymin",         "ymin fractal image delimiter"     },
    { GIMP_PDB_FLOAT,    "ymax",         "ymax fractal image delimiter"     },
    { GIMP_PDB_INT32,    "depth",        "Trace depth"                      },
    { GIMP_PDB_INT32,    "outside-type", "Outside type "
                                         "{ WRAP (0), TRANS (1), BLACK (2), WHITE (3) }" }
  };

  gimp_install_procedure (PLUG_IN_PROC,
                          N_("Transform image with the Mandelbrot Fractal"),
                          "transform image with the Mandelbrot Fractal",
                          "Hirotsuna Mizuno <s1041150@u-aizu.ac.jp>",
                          "Copyright (C) 1997 Hirotsuna Mizuno",
                          PLUG_IN_VERSION,
                          N_("_Fractal Trace (legacy)..."),
                          "RGB*, GRAY*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (args), 0,
                          args, NULL);

  gimp_plugin_menu_register (PLUG_IN_PROC, "<Image>/Filters/Map");
}

/******************************************************************************/

typedef struct
{
  gint     x1;
  gint     x2;
  gint     y1;
  gint     y2;
  gint     width;
  gint     height;
  gdouble  center_x;
  gdouble  center_y;
} selection_t;

typedef struct
{
  gint         width;
  gint         height;
  gint         bpp;
  gint         alpha;
} image_t;

static selection_t selection;
static image_t     image;

/******************************************************************************/

static void
run (const gchar      *name,
     gint              argc,
     const GimpParam  *args,
     gint             *retc,
     GimpParam       **rets)
{
  GimpDrawable      *drawable;
  GimpRunMode        run_mode;
  GimpPDBStatusType  status;
  static GimpParam   returns[1];

  run_mode = args[0].data.d_int32;
  status   = GIMP_PDB_SUCCESS;

  INIT_I18N ();

  drawable     = gimp_drawable_get (args[2].data.d_drawable);
  image.width  = gimp_drawable_width( drawable->drawable_id);
  image.height = gimp_drawable_height (drawable->drawable_id);
  image.bpp    = gimp_drawable_bpp (drawable->drawable_id);
  image.alpha  = gimp_drawable_has_alpha (drawable->drawable_id);

  if (! gimp_drawable_mask_intersect (drawable->drawable_id,
                                      &selection.x1, &selection.y1,
                                      &selection.width, &selection.height))
    {
      returns[0].type          = GIMP_PDB_STATUS;
      returns[0].data.d_status = status;
      *retc = 1;
      *rets = returns;

      return;
    }

  selection.x2       = selection.x1 + selection.width;
  selection.y2       = selection.y1 + selection.height;
  selection.center_x = selection.x1 + (gdouble) selection.width / 2.0;
  selection.center_y = selection.y1 + (gdouble) selection.height / 2.0;

  pixels_init (drawable);

  if (!gimp_drawable_is_rgb(drawable->drawable_id) &&
      !gimp_drawable_is_gray(drawable->drawable_id))
    {
      status = GIMP_PDB_EXECUTION_ERROR;
    }

  switch (run_mode)
    {
    case GIMP_RUN_WITH_LAST_VALS:
      gimp_get_data (PLUG_IN_PROC, &parameters);
      break;

    case GIMP_RUN_INTERACTIVE:
      gimp_get_data (PLUG_IN_PROC, &parameters);
      if (!dialog_show ())
        {
          status = GIMP_PDB_EXECUTION_ERROR;
          break;
        }
      gimp_set_data (PLUG_IN_PROC, &parameters, sizeof (parameter_t));
      break;

    case GIMP_RUN_NONINTERACTIVE:
      if (argc != 9)
        {
          status = GIMP_PDB_CALLING_ERROR;
        }
      else
        {
          parameters.x1           = args[3].data.d_float;
          parameters.x2           = args[4].data.d_float;
          parameters.y1           = args[5].data.d_float;
          parameters.y2           = args[6].data.d_float;
          parameters.depth        = args[7].data.d_int32;
          parameters.outside_type = args[8].data.d_int32;
        }
      break;
    }

  if (status == GIMP_PDB_SUCCESS)
    {
      gimp_tile_cache_ntiles(2 * (drawable->width / gimp_tile_width() + 1));
      filter (drawable);
      if (run_mode != GIMP_RUN_NONINTERACTIVE)
        gimp_displays_flush();
    }

  gimp_drawable_detach (drawable);

  pixels_free ();

  returns[0].type          = GIMP_PDB_STATUS;
  returns[0].data.d_status = status;
  *retc = 1;
  *rets = returns;
}

/******************************************************************************/

static guchar    **spixels;
static guchar    **dpixels;
static GimpPixelRgn   sPR;
static GimpPixelRgn   dPR;

typedef struct
{
  guchar r;
  guchar g;
  guchar b;
  guchar a;
} pixel_t;

static void
pixels_init (GimpDrawable *drawable)
{
  gint y;

  gimp_pixel_rgn_init (&sPR, drawable,
                       0, 0, image.width, image.height, FALSE, FALSE);
  gimp_pixel_rgn_init (&dPR, drawable,
                       0, 0, image.width, image.height, TRUE, TRUE);

  spixels = g_new (guchar *, image.height);
  dpixels = g_new (guchar *, image.height);

  for (y = 0; y < image.height; y++)
    {
      spixels[y] = g_new (guchar, image.width * image.bpp);
      dpixels[y] = g_new (guchar, image.width * image.bpp);
      gimp_pixel_rgn_get_row (&sPR, spixels[y], 0, y, image.width);
    }
}

static void
pixels_free (void)
{
  gint y;

  for (y = 0; y < image.height; y++)
    {
      g_free (spixels[y]);
      g_free (dpixels[y]);
    }
  g_free (spixels);
  g_free (dpixels);
}

static void
pixels_get (gint     x,
            gint     y,
            pixel_t *pixel)
{
  if(x < 0) x = 0; else if (image.width  <= x) x = image.width  - 1;
  if(y < 0) y = 0; else if (image.height <= y) y = image.height - 1;

  switch (image.bpp)
    {
    case 1: /* GRAY */
      pixel->r = spixels[y][x*image.bpp];
      pixel->g = spixels[y][x*image.bpp];
      pixel->b = spixels[y][x*image.bpp];
      pixel->a = 255;
      break;
    case 2: /* GRAY+A */
      pixel->r = spixels[y][x*image.bpp];
      pixel->g = spixels[y][x*image.bpp];
      pixel->b = spixels[y][x*image.bpp];
      pixel->a = spixels[y][x*image.bpp+1];
      break;
    case 3: /* RGB */
      pixel->r = spixels[y][x*image.bpp];
      pixel->g = spixels[y][x*image.bpp+1];
      pixel->b = spixels[y][x*image.bpp+2];
      pixel->a = 255;
      break;
    case 4: /* RGB+A */
      pixel->r = spixels[y][x*image.bpp];
      pixel->g = spixels[y][x*image.bpp+1];
      pixel->b = spixels[y][x*image.bpp+2];
      pixel->a = spixels[y][x*image.bpp+3];
      break;
    }
}

static void
pixels_get_biliner (gdouble  x,
                    gdouble  y,
                    pixel_t *pixel)
{
  pixel_t A, B, C, D;
  gdouble a, b, c, d;
  gint    x1, y1, x2, y2;
  gdouble dx, dy;
  gdouble alpha;

  x1 = (gint) floor (x);
  x2 = x1 + 1;
  y1 = (gint) floor (y);
  y2 = y1 + 1;

  dx = x - (gdouble) x1;
  dy = y - (gdouble) y1;
  a  = (1.0 - dx) * (1.0 - dy);
  b  = dx * (1.0 - dy);
  c  = (1.0 - dx) * dy;
  d  = dx * dy;

  pixels_get (x1, y1, &A);
  pixels_get (x2, y1, &B);
  pixels_get (x1, y2, &C);
  pixels_get (x2, y2, &D);

  alpha = 1.0001*(a * (gdouble) A.a + b * (gdouble) B.a
                 + c * (gdouble) C.a + d * (gdouble) D.a);
  pixel->a = (guchar) alpha;

  if (pixel->a)
    {
      pixel->r = (guchar) ((a * (gdouble) A.r * A.a
                            + b * (gdouble) B.r * B.a
                            + c * (gdouble) C.r * C.a
                            + d * (gdouble) D.r * D.a) / alpha);
      pixel->g = (guchar) ((a * (gdouble) A.g * A.a
                            + b * (gdouble) B.g * B.a
                            + c * (gdouble) C.g * C.a
                            + d * (gdouble) D.g * D.a) / alpha);
      pixel->b = (guchar) ((a * (gdouble) A.b * A.a
                            + b * (gdouble) B.b * B.a
                            + c * (gdouble) C.b * C.a
                            + d * (gdouble) D.b * D.a) / alpha);
    }
}

static void
pixels_set (gint     x,
            gint     y,
            pixel_t *pixel)
{
  switch (image.bpp)
    {
    case 1: /* GRAY */
      dpixels[y][x*image.bpp]   = pixel->r;
      break;
    case 2: /* GRAY+A */
      dpixels[y][x*image.bpp]   = pixel->r;
      dpixels[y][x*image.bpp+1] = pixel->a;
      break;
    case 3: /* RGB */
      dpixels[y][x*image.bpp]   = pixel->r;
      dpixels[y][x*image.bpp+1] = pixel->g;
      dpixels[y][x*image.bpp+2] = pixel->b;
      break;
    case 4: /* RGB+A */
      dpixels[y][x*image.bpp]   = pixel->r;
      dpixels[y][x*image.bpp+1] = pixel->g;
      dpixels[y][x*image.bpp+2] = pixel->b;
      dpixels[y][x*image.bpp+3] = pixel->a;
      break;
    }
}

static void
pixels_store (void)
{
  gint y;

  for (y = selection.y1; y < selection.y2; y++)
    {
      gimp_pixel_rgn_set_row (&dPR, dpixels[y], 0, y, image.width);
    }
}

/******************************************************************************/

static void
mandelbrot (gdouble  x,
            gdouble  y,
            gdouble *u,
            gdouble *v)
{
  gint    iter = 0;
  gdouble xx   = x;
  gdouble yy   = y;
  gdouble x2   = xx * xx;
  gdouble y2   = yy * yy;
  gdouble tmp;

  while (iter < parameters.depth)
    {
      tmp = x2 - y2 + x;
      yy  = 2 * xx * yy + y;
      xx  = tmp;
      x2  = xx * xx;
      y2  = yy * yy;
      iter++;
    }
  *u = xx;
  *v = yy;
}

/******************************************************************************/

static void
filter (GimpDrawable *drawable)
{
  gint    x, y;
  pixel_t pixel;
  gdouble scale_x, scale_y;
  gdouble cx, cy;
  gdouble px, py;
  gint h_percent;

  gimp_progress_init (_("Fractal Trace"));

  if (selection.width == 0 || selection.height == 0)
    return;

  h_percent = selection.height / 100;

  scale_x = (parameters.x2 - parameters.x1) / selection.width;
  scale_y = (parameters.y2 - parameters.y1) / selection.height;

  for (y = selection.y1; y < selection.y2; y++)
    {
      cy = parameters.y1 + (y - selection.y1) * scale_y;
      for (x = selection.x1; x < selection.x2; x++)
        {
          cx = parameters.x1 + (x - selection.x1) * scale_x;
          mandelbrot (cx, cy, &px, &py);
          px = (px - parameters.x1) / scale_x + selection.x1;
          py = (py - parameters.y1) / scale_y + selection.y1;
          if (0 <= px && px < image.width && 0 <= py && py < image.height)
            {
              pixels_get_biliner (px, py, &pixel);
            }
          else
            {
              switch (parameters.outside_type)
                {
                case OUTSIDE_TYPE_WRAP:
                  px = fmod (px, image.width);
                  py = fmod (py, image.height);
                  if( px < 0.0) px += image.width;
                  if (py < 0.0) py += image.height;
                  pixels_get_biliner (px, py, &pixel);
                  break;
                case OUTSIDE_TYPE_TRANSPARENT:
                  pixel.r = pixel.g = pixel.b = 0;
                  pixel.a = 0;
                  break;
                case OUTSIDE_TYPE_BLACK:
                  pixel.r = pixel.g = pixel.b = 0;
                  pixel.a = 255;
                  break;
                case OUTSIDE_TYPE_WHITE:
                  pixel.r = pixel.g = pixel.b = 255;
                  pixel.a = 255;
                  break;
                }
            }
          pixels_set (x, y, &pixel);
        }

      if (h_percent == 0 || ((y - selection.y1) % h_percent) == 0)
        gimp_progress_update ((gdouble) (y-selection.y1) / selection.height);
    }

  gimp_progress_update (1.0);

  pixels_store ();

  gimp_drawable_flush (drawable);
  gimp_drawable_merge_shadow (drawable->drawable_id, TRUE);
  gimp_drawable_update (drawable->drawable_id,
                        selection.x1, selection.y1,
                        selection.width, selection.height);
}

/******************************************************************************/

#define PREVIEW_SIZE 200

typedef struct
{
  GtkWidget  *preview;
  guchar     *pixels;
  gdouble     scale;
  gint        width;
  gint        height;
  gint        bpp;
} preview_t;

static preview_t preview;

static void
dialog_preview_setpixel (gint     x,
                         gint     y,
                         pixel_t *pixel)
{
  preview.pixels[(y * preview.width + x) * 4 + 0] = pixel->r;
  preview.pixels[(y * preview.width + x) * 4 + 1] = pixel->g;
  preview.pixels[(y * preview.width + x) * 4 + 2] = pixel->b;
  preview.pixels[(y * preview.width + x) * 4 + 3] = pixel->a;
}

static void
dialog_preview_init (void)
{
  pixel_t  pixel;
  gint     x, y;
  gdouble  cx, cy;

  if (image.width < image.height)
    preview.scale = (gdouble)selection.height / (gdouble)PREVIEW_SIZE;
  else
    preview.scale = (gdouble)selection.width / (gdouble)PREVIEW_SIZE;
  preview.width  = (gdouble)selection.width / preview.scale;
  preview.height = (gdouble)selection.height / preview.scale;

  preview.preview = gimp_preview_area_new ();
  gtk_widget_set_size_request (preview.preview,
                               preview.width, preview.height);

  preview.pixels = g_new (guchar, preview.height * preview.width * 4);

  for (y = 0; y < preview.height; y++)
    {
      cy = selection.y1 + (gdouble)y * preview.scale;
      for (x = 0; x < preview.width; x++)
        {
          cx = selection.x1 + (gdouble)x * preview.scale;
          pixels_get_biliner (cx, cy, &pixel);
          dialog_preview_setpixel (x, y, &pixel);
        }
    }
  gimp_preview_area_draw (GIMP_PREVIEW_AREA (preview.preview),
                          0, 0, preview.width, preview.height,
                          GIMP_RGBA_IMAGE,
                          preview.pixels,
                          preview.width *4);
}

static void
dialog_preview_draw (void)
{
  gint    x, y;
  pixel_t pixel;
  gdouble scale_x, scale_y;
  gdouble cx, cy;
  gdouble px, py;

  scale_x = (parameters.x2 - parameters.x1) / preview.width;
  scale_y = (parameters.y2 - parameters.y1) / preview.height;

  for (y = 0; y < preview.height; y++)
    {
      cy = parameters.y1 + y * scale_y;
      for (x = 0; x < preview.width; x++)
        {
          cx = parameters.x1 + x * scale_x;
          mandelbrot(cx, cy, &px, &py);
          px = (px - parameters.x1) / scale_x * preview.scale + selection.x1;
          py = (py - parameters.y1) / scale_y * preview.scale + selection.y1;
          if (0 <= px && px < image.width && 0 <= py && py < image.height)
            {
              pixels_get_biliner (px, py, &pixel);
            }
          else
            {
              switch (parameters.outside_type)
                {
                case OUTSIDE_TYPE_WRAP:
                  px = fmod (px, image.width);
                  py = fmod (py, image.height);
                  if (px < 0.0) px += image.width;
                  if (py < 0.0) py += image.height;
                  pixels_get_biliner (px, py, &pixel);
                  break;
                case OUTSIDE_TYPE_TRANSPARENT:
                  pixel.r = pixel.g = pixel.b = 0;
                  pixel.a = 0;
                  break;
                case OUTSIDE_TYPE_BLACK:
                  pixel.r = pixel.g = pixel.b = 0;
                  pixel.a = 255;
                  break;
                case OUTSIDE_TYPE_WHITE:
                  pixel.r = pixel.g = pixel.b = 255;
                  pixel.a = 255;
                  break;
                }
            }
          dialog_preview_setpixel (x, y, &pixel);
        }
    }
  gimp_preview_area_draw (GIMP_PREVIEW_AREA (preview.preview),
                          0, 0, preview.width, preview.height,
                          GIMP_RGBA_IMAGE,
                          preview.pixels,
                          preview.width *4);
}

/******************************************************************************/

static void
dialog_int_adjustment_update (GtkAdjustment *adjustment,
                              gpointer       data)
{
  gimp_int_adjustment_update (adjustment, data);

  dialog_preview_draw ();
}

static void
dialog_double_adjustment_update (GtkAdjustment *adjustment,
                                 gpointer       data)
{
  gimp_double_adjustment_update (adjustment, data);

  dialog_preview_draw ();
}

static void
dialog_outside_type_callback (GtkWidget *widget,
                              gpointer  *data)
{
  gimp_radio_button_update (widget, data);

  if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (widget)))
    dialog_preview_draw ();
}

/******************************************************************************/

static gboolean
dialog_show (void)
{
  GtkWidget *dialog;
  GtkWidget *mainbox;
  GtkWidget *hbox;
  GtkWidget *table;
  GtkWidget *frame;
  GtkWidget *abox;
  GtkObject *adj;
  gboolean   run;

  gimp_ui_init (PLUG_IN_BINARY, TRUE);

  dialog = gimp_dialog_new (_("Fractal Trace"), PLUG_IN_ROLE,
                            NULL, 0,
                            gimp_standard_help_func, PLUG_IN_PROC,

                            _("_Cancel"), GTK_RESPONSE_CANCEL,
                            _("_OK"),     GTK_RESPONSE_OK,

                            NULL);

  gtk_dialog_set_alternative_button_order (GTK_DIALOG (dialog),
                                           GTK_RESPONSE_OK,
                                           GTK_RESPONSE_CANCEL,
                                           -1);

  gimp_window_set_transient (GTK_WINDOW (dialog));

  mainbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 12);
  gtk_container_set_border_width (GTK_CONTAINER (mainbox), 12);
  gtk_box_pack_start (GTK_BOX (gtk_dialog_get_content_area (GTK_DIALOG (dialog))),
                      mainbox, TRUE, TRUE, 0);
  gtk_widget_show (mainbox);

  hbox = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 12);
  gtk_box_pack_start (GTK_BOX (mainbox), hbox, FALSE, FALSE, 0);
  gtk_widget_show (hbox);

  /*  Preview  */
  abox = gtk_alignment_new (0.0, 0.0, 0.0, 0.0);
  gtk_box_pack_start (GTK_BOX (hbox), abox, FALSE, FALSE, 0);
  gtk_widget_show (abox);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_container_add (GTK_CONTAINER (abox), frame);
  gtk_widget_show (frame);

  dialog_preview_init ();
  gtk_container_add (GTK_CONTAINER (frame), preview.preview);
  gtk_widget_show (preview.preview);

  /*  Settings  */
  frame = gimp_int_radio_group_new (TRUE, _("Outside Type"),
                                    G_CALLBACK (dialog_outside_type_callback),
                                    &parameters.outside_type,
                                    parameters.outside_type,

                                    _("_Wrap"),
                                    OUTSIDE_TYPE_WRAP, NULL,
                                    _("_Transparent"),
                                    OUTSIDE_TYPE_TRANSPARENT, NULL,
                                    _("_Black"),
                                    OUTSIDE_TYPE_BLACK, NULL,
                                    _("_White"),
                                    OUTSIDE_TYPE_WHITE, NULL,

                                 NULL);
  gtk_box_pack_start (GTK_BOX (hbox), frame, FALSE, FALSE, 0);
  gtk_widget_show (frame);

  frame = gimp_frame_new (_("Mandelbrot Parameters"));
  gtk_box_pack_start (GTK_BOX (mainbox), frame, FALSE, FALSE, 0);
  gtk_widget_show (frame);

  table = gtk_table_new (5, 3, FALSE);
  gtk_table_set_row_spacings (GTK_TABLE (table), 6);
  gtk_table_set_col_spacings (GTK_TABLE (table), 6);
  gtk_container_add (GTK_CONTAINER (frame), table);
  gtk_widget_show (table);

  adj = gimp_scale_entry_new (GTK_TABLE (table), 0, 0,
                              _("X_1:"), 0, 6,
                              parameters.x1, -50, 50, 0.1, 0.5, 2,
                              TRUE, 0, 0,
                              NULL, NULL);
  g_signal_connect (adj, "value-changed",
                    G_CALLBACK (dialog_double_adjustment_update),
                    &parameters.x1);

  adj = gimp_scale_entry_new (GTK_TABLE (table), 0, 1,
                              _("X_2:"), 0, 6,
                              parameters.x2, -50, 50, 0.1, 0.5, 2,
                              TRUE, 0, 0,
                              NULL, NULL);
  g_signal_connect (adj, "value-changed",
                    G_CALLBACK (dialog_double_adjustment_update),
                    &parameters.x2);

  adj = gimp_scale_entry_new (GTK_TABLE (table), 0, 2,
                              _("Y_1:"), 0, 6,
                              parameters.y1, -50, 50, 0.1, 0.5, 2,
                              TRUE, 0, 0,
                              NULL, NULL);
  g_signal_connect (adj, "value-changed",
                    G_CALLBACK (dialog_double_adjustment_update),
                    &parameters.y1);

  adj = gimp_scale_entry_new (GTK_TABLE (table), 0, 3,
                              _("Y_2:"), 0, 6,
                              parameters.y2, -50, 50, 0.1, 0.5, 2,
                              TRUE, 0, 0,
                              NULL, NULL);
  g_signal_connect (adj, "value-changed",
                    G_CALLBACK (dialog_double_adjustment_update),
                    &parameters.y2);

  adj = gimp_scale_entry_new (GTK_TABLE (table), 0, 4,
                              _("_Depth:"), 0, 6,
                              parameters.depth, 1, 50, 1, 5, 0,
                              TRUE, 0, 0,
                              NULL, NULL);
  g_signal_connect (adj, "value-changed",
                    G_CALLBACK (dialog_int_adjustment_update),
                    &parameters.depth);

  gtk_widget_show (dialog);
  dialog_preview_draw ();

  run = (gimp_dialog_run (GIMP_DIALOG (dialog)) == GTK_RESPONSE_OK);

  gtk_widget_destroy (dialog);

  return run;
}