gimp/libgimpwidgets/gimppreviewarea.c

/* LIBGIMP - The GIMP Library
 * Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; 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 <gtk/gtk.h>

#include "libgimpbase/gimpbase.h"

#include "gimpwidgetstypes.h"

#include "gimppreviewarea.h"

#include "libgimp/libgimp-intl.h"


enum
{
  PROP_0,
  PROP_CHECK_SIZE,
  PROP_CHECK_TYPE
};


#define DEFAULT_CHECK_SIZE  GIMP_CHECK_SIZE_MEDIUM_CHECKS
#define DEFAULT_CHECK_TYPE  GIMP_CHECK_TYPE_GRAY_CHECKS


static void      gimp_preview_area_class_init    (GimpPreviewAreaClass *klass);
static void      gimp_preview_area_init          (GimpPreviewArea *area);

static void      gimp_preview_area_finalize      (GObject         *object);
static void      gimp_preview_area_set_property  (GObject         *object,
                                                  guint            property_id,
                                                  const GValue    *value,
                                                  GParamSpec      *pspec);
static void      gimp_preview_area_get_property  (GObject         *object,
                                                  guint            property_id,
                                                  GValue          *value,
                                                  GParamSpec      *pspec);

static void      gimp_preview_area_size_allocate (GtkWidget       *widget,
                                                  GtkAllocation   *allocation);
static gboolean  gimp_preview_area_expose        (GtkWidget       *widget,
                                                  GdkEventExpose  *event);


static GtkDrawingAreaClass *parent_class = NULL;


#define CHECK_COLOR(area, row, col)        \
  (((((area)->offset_y + (row)) & size) ^  \
    (((area)->offset_x + (col)) & size)) ? dark : light)


GType
gimp_preview_area_get_type (void)
{
  static GType view_type = 0;

  if (! view_type)
    {
      static const GTypeInfo view_info =
      {
        sizeof (GimpPreviewAreaClass),
        NULL,           /* base_init */
        NULL,           /* base_finalize */
        (GClassInitFunc) gimp_preview_area_class_init,
        NULL,           /* class_finalize */
        NULL,           /* class_data */
        sizeof (GimpPreviewArea),
        0,              /* n_preallocs */
        (GInstanceInitFunc) gimp_preview_area_init,
      };

      view_type = g_type_register_static (GTK_TYPE_DRAWING_AREA,
                                          "GimpPreviewArea",
                                          &view_info, 0);
    }

  return view_type;
}

static void
gimp_preview_area_class_init (GimpPreviewAreaClass *klass)
{
  GObjectClass   *object_class = G_OBJECT_CLASS (klass);
  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  object_class->finalize      = gimp_preview_area_finalize;
  object_class->set_property  = gimp_preview_area_set_property;
  object_class->get_property  = gimp_preview_area_get_property;

  widget_class->size_allocate = gimp_preview_area_size_allocate;
  widget_class->expose_event  = gimp_preview_area_expose;

  g_object_class_install_property (object_class, PROP_CHECK_SIZE,
                                   g_param_spec_enum ("check-size",
                                                      _("Check Size"), NULL,
                                                      GIMP_TYPE_CHECK_SIZE,
                                                      DEFAULT_CHECK_SIZE,
                                                      G_PARAM_READWRITE));

  g_object_class_install_property (object_class, PROP_CHECK_TYPE,
                                   g_param_spec_enum ("check-type",
                                                      _("Check Style"), NULL,
                                                      GIMP_TYPE_CHECK_TYPE,
                                                      DEFAULT_CHECK_TYPE,
                                                      G_PARAM_READWRITE));
}

static void
gimp_preview_area_init (GimpPreviewArea *area)
{
  area->check_size = DEFAULT_CHECK_SIZE;
  area->check_type = DEFAULT_CHECK_TYPE;
  area->buf        = NULL;
  area->cmap       = NULL;
  area->offset_x   = 0;
  area->offset_y   = 0;
  area->width      = 0;
  area->height     = 0;
  area->rowstride  = 0;
}

static void
gimp_preview_area_finalize (GObject *object)
{
  GimpPreviewArea *area = GIMP_PREVIEW_AREA (object);

  if (area->buf)
    {
      g_free (area->buf);
      area->buf = NULL;
    }
  if (area->cmap)
    {
      g_free (area->cmap);
      area->cmap = NULL;
    }

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

static void
gimp_preview_area_set_property (GObject      *object,
                                guint         property_id,
                                const GValue *value,
                                GParamSpec   *pspec)
{
  GimpPreviewArea *area = GIMP_PREVIEW_AREA (object);

  switch (property_id)
    {
    case PROP_CHECK_SIZE:
      area->check_size = g_value_get_enum (value);
      break;
    case PROP_CHECK_TYPE:
      area->check_type = g_value_get_enum (value);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
      break;
    }
}

static void
gimp_preview_area_get_property (GObject    *object,
                                guint       property_id,
                                GValue     *value,
                                GParamSpec *pspec)
{
  GimpPreviewArea *area = GIMP_PREVIEW_AREA (object);

  switch (property_id)
    {
    case PROP_CHECK_SIZE:
      g_value_set_enum (value, area->check_size);
      break;
    case PROP_CHECK_TYPE:
      g_value_set_enum (value, area->check_type);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
      break;
    }
}

static void
gimp_preview_area_size_allocate (GtkWidget     *widget,
                                 GtkAllocation *allocation)
{
  GimpPreviewArea *area = GIMP_PREVIEW_AREA (widget);

  if (GTK_WIDGET_CLASS (parent_class)->size_allocate)
    GTK_WIDGET_CLASS (parent_class)->size_allocate (widget, allocation);

  if (widget->allocation.width  != area->width ||
      widget->allocation.height != area->height)
    {
      if (area->buf)
        {
          g_free (area->buf);

          area->buf       = NULL;
          area->rowstride = 0;
        }

      area->width  = widget->allocation.width;
      area->height = widget->allocation.height;
    }
}

static gboolean
gimp_preview_area_expose (GtkWidget      *widget,
                          GdkEventExpose *event)
{
  GimpPreviewArea *area;
  guchar          *buf;

  g_return_val_if_fail (GIMP_IS_PREVIEW_AREA (widget), FALSE);

  area = GIMP_PREVIEW_AREA (widget);

  if (! area->buf)
    return FALSE;

  buf = area->buf + event->area.x * 3 + event->area.y * area->rowstride;

  gdk_draw_rgb_image_dithalign (widget->window,
                                widget->style->fg_gc[widget->state],
                                event->area.x,
                                event->area.y,
                                event->area.width,
                                event->area.height,
                                GDK_RGB_DITHER_MAX,
                                buf,
                                area->rowstride,
                                area->offset_x - event->area.x,
                                area->offset_y - event->area.y);

  return FALSE;
}

static gint
gimp_preview_area_image_type_bytes (GimpImageType type)
{
  switch (type)
    {
    case GIMP_GRAY_IMAGE:
    case GIMP_INDEXED_IMAGE:
      return 1;

    case GIMP_GRAYA_IMAGE:
    case GIMP_INDEXEDA_IMAGE:
      return 2;

    case GIMP_RGB_IMAGE:
      return 3;

    case GIMP_RGBA_IMAGE:
      return 4;

    default:
      g_return_val_if_reached (0);
      break;
    }
}

/**
 * gimp_preview_area_new:
 *
 * Return value: a new #GimpPreviewArea widget.
 *
 * Since GIMP 2.2
 **/
GtkWidget *
gimp_preview_area_new (void)
{
  return g_object_new (GIMP_TYPE_PREVIEW_AREA, NULL);
}

/**
 * gimp_preview_area_draw:
 * @area:      a #GimpPreviewArea widget.
 * @x:         x offset in preview
 * @y:         y offset in preview
 * @width:     buffer width
 * @height:    buffer height
 * @type:      the #GimpImageType of @buf
 * @buf:       a #guchar buffer that contains the preview pixel data.
 * @rowstride: rowstride of @buf
 *
 * Draws @buf on @area and queues a redraw on the rectangle that
 * changed.
 *
 * Since GIMP 2.2
 **/
void
gimp_preview_area_draw (GimpPreviewArea *area,
                        gint             x,
                        gint             y,
                        gint             width,
                        gint             height,
                        GimpImageType    type,
                        const guchar    *buf,
                        gint             rowstride)
{
  const guchar    *src;
  guchar          *dest;
  guint            size;
  guchar           light;
  guchar           dark;
  gint             row;
  gint             col;

  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));
  g_return_if_fail (width > 0 && height > 0);
  g_return_if_fail (buf != NULL);
  g_return_if_fail (rowstride > 0);

  if (x + width < 0 || x >= area->width)
    return;

  if (y + height < 0 || y >= area->height)
    return;

  if (x < 0)
    {
      gint  bpp = gimp_preview_area_image_type_bytes (type);

      buf   += x * bpp;
      width -= x;

      x = 0;
    }

  if (x + width > area->width)
    width = area->width - x;

  if (y < 0)
    {
      buf    += y * rowstride;
      height -= y;

      y = 0;
    }

  if (y + height > area->height)
    height = area->height - y;

  if (! area->buf)
    {
      area->rowstride = ((area->width * 3) + 3) & ~3;
      area->buf = g_new (guchar, area->rowstride * area->height);
    }

  size = 1 << (2 + area->check_size);
  gimp_checks_get_shades (area->check_type, &light, &dark);

  src  = buf;
  dest = area->buf + x * 3 + y * area->rowstride;

  switch (type)
    {
    case GIMP_RGB_IMAGE:
      for (row = 0; row < height; row++)
        {
          memcpy (dest, src, 3 * width);

          src  += rowstride;
          dest += area->rowstride;
        }
      break;

    case GIMP_RGBA_IMAGE:
       for (row = y; row < y + height; row++)
        {
          const guchar *s = src;
          guchar       *d = dest;

          for (col = x; col < x + width; col++, s += 4, d+= 3)
            {
              switch (s[3])
                {
                case 0:
                  d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                  break;

                case 255:
                  d[0] = s[0];
                  d[1] = s[1];
                  d[2] = s[2];
                  break;

                default:
                  {
                    register guint alpha = s[3] + 1;
                    register guint check = CHECK_COLOR (area, row, col);

                    d[0] = ((check << 8) + (s[0] - check) * alpha) >> 8;
                    d[1] = ((check << 8) + (s[1] - check) * alpha) >> 8;
                    d[2] = ((check << 8) + (s[2] - check) * alpha) >> 8;
                  }
                  break;
                }
            }

          src  += rowstride;
          dest += area->rowstride;
        }
       break;

    case GIMP_GRAY_IMAGE:
      for (row = 0; row < height; row++)
        {
          const guchar *s = src;
          guchar       *d = dest;

          for (col = 0; col < width; col++, s++, d += 3)
            {
              d[0] = d[1] = d[2] = s[0];
            }

          src  += rowstride;
          dest += area->rowstride;
        }
      break;

    case GIMP_GRAYA_IMAGE:
      for (row = y; row < y + height; row++)
        {
          const guchar *s = src;
          guchar       *d = dest;

          for (col = x; col < x + width; col++, s += 2, d+= 3)
            {
              switch (s[1])
                {
                case 0:
                  d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                  break;

                case 255:
                  d[0] = d[1] = d[2] = s[0];
                  break;

                default:
                  {
                    register guint alpha = s[1] + 1;
                    register guint check = CHECK_COLOR (area, row, col);

                    d[0] = d[1] = d[2] =
                      ((check << 8) + (s[0] - check) * alpha) >> 8;
                  }
                  break;
                }
            }

          src  += rowstride;
          dest += area->rowstride;
        }
      break;

    case GIMP_INDEXED_IMAGE:
      g_return_if_fail (area->cmap != NULL);
      for (row = 0; row < height; row++)
        {
          const guchar *s = src;
          guchar       *d = dest;

          for (col = 0; col < width; col++, s++, d += 3)
            {
              const guchar *cmap = area->cmap + 3 * s[0];

              d[0] = cmap[0];
              d[1] = cmap[1];
              d[2] = cmap[2];
            }

          src  += rowstride;
          dest += area->rowstride;
        }
      break;

    case GIMP_INDEXEDA_IMAGE:
      g_return_if_fail (area->cmap != NULL);
      for (row = y; row < y + height; row++)
        {
          const guchar *s = src;
          guchar       *d = dest;

          for (col = x; col < x + width; col++, s += 2, d += 3)
            {
              const guchar *cmap  = area->cmap + 3 * s[0];

              switch (s[1])
                {
                case 0:
                  d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                  break;

                case 255:
                  d[0] = cmap[0];
                  d[1] = cmap[1];
                  d[2] = cmap[2];
                  break;

                default:
                  {
                    register guint alpha = s[3] + 1;
                    register guint check = CHECK_COLOR (area, row, col);

                    d[0] = ((check << 8) + (cmap[0] - check) * alpha) >> 8;
                    d[1] = ((check << 8) + (cmap[1] - check) * alpha) >> 8;
                    d[2] = ((check << 8) + (cmap[2] - check) * alpha) >> 8;
                  }
                  break;
                }
            }

          src  += rowstride;
          dest += area->rowstride;
        }
      break;
    }

  gtk_widget_queue_draw_area (GTK_WIDGET (area), x, y, width, height);
}

/**
 * gimp_preview_area_blend:
 * @area:       a #GimpPreviewArea widget.
 * @x:          x offset in preview
 * @y:          y offset in preview
 * @width:      buffer width
 * @height:     buffer height
 * @type:       the #GimpImageType of @buf1 and @buf2
 * @buf1:       a #guchar buffer that contains the pixel data for
 *              the first (on bottom) layer
 * @rowstride1: rowstride of @buf1
 * @buf2:       a #guchar buffer that contains the pixel data for
 *              the second (on top) layer
 * @rowstride2: rowstride of @buf2
 * @opacity:    The opacity of the first layer.
 *
 * Blend @buf1 on top of @buf2 with the given @opacity on the @area
 * and queues a redraw on the rectangle that changed.
 *
 * Since GIMP 2.2
 **/
void
gimp_preview_area_blend (GimpPreviewArea *area,
                         gint             x,
                         gint             y,
                         gint             width,
                         gint             height,
                         GimpImageType    type,
                         const guchar    *buf1,
                         gint             rowstride1,
                         const guchar    *buf2,
                         gint             rowstride2,
                         guchar           opacity)
{
  const guchar    *src1;
  const guchar    *src2;
  guchar          *dest;
  guint            size;
  guchar           light;
  guchar           dark;
  gint             row;
  gint             col;
  gint             i;

  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));
  g_return_if_fail (width > 0 && height > 0);
  g_return_if_fail (buf1 != NULL);
  g_return_if_fail (buf2 != NULL);
  g_return_if_fail (rowstride1 > 0);
  g_return_if_fail (rowstride2 > 0);

  switch (opacity)
    {
    case 0:
      gimp_preview_area_draw (area, x, y, width, height,
                              type, buf1, rowstride1);
      return;

    case 255:
      gimp_preview_area_draw (area, x, y, width, height,
                              type, buf2, rowstride2);
      return;

    default:
      break;
    }

  if (x + width < 0 || x >= area->width)
    return;

  if (y + height < 0 || y >= area->height)
    return;

  if (x < 0)
    {
      gint  bpp = gimp_preview_area_image_type_bytes (type);

      buf1  += x * bpp;
      buf2  += x * bpp;
      width -= x;

      x = 0;
    }

  if (x + width > area->width)
    width = area->width - x;

  if (y < 0)
    {
      buf1   += y * rowstride1;
      buf2   += y * rowstride2;
      height -= y;

      y = 0;
    }

  if (y + height > area->height)
    height = area->height - y;

  if (! area->buf)
    {
      area->rowstride = ((area->width * 3) + 3) & ~3;
      area->buf = g_new (guchar, area->rowstride * area->height);
    }

  size = 1 << (2 + area->check_size);
  gimp_checks_get_shades (area->check_type, &light, &dark);

  src1 = buf1;
  src2 = buf2;
  dest = area->buf + x * 3 + y * area->rowstride;

  switch (type)
    {
    case GIMP_RGB_IMAGE:
      for (row = 0; row < height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 3, s2 += 3, d+= 3)
            {
              d[0] = ((s1[0] << 8) + (s2[0] - s1[0]) * opacity) >> 8;
              d[1] = ((s1[1] << 8) + (s2[1] - s1[1]) * opacity) >> 8;
              d[2] = ((s1[2] << 8) + (s2[2] - s1[2]) * opacity) >> 8;
            }

          src1 += rowstride1;
          src2 += rowstride2;
          dest += area->rowstride;
        }
      break;

    case GIMP_RGBA_IMAGE:
      for (row = y; row < y + height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 4, s2 += 4, d+= 3)
            {
              guchar inter[4];

              inter[3] = ((s1[3] << 8) + (s2[3] - s1[3]) * opacity) >> 8;

              if (inter[3])
                {
                  for (i=0 ; i<3 ; i++)
                    {
                      gushort a = s1[i] * s1[3];
                      gushort b = s2[i] * s2[3];

                      inter[i] =
                        (((a << 8) + (b  - a) * opacity) >> 8) / inter[3];
                    }
                }
              else
                {
                  inter[0] = inter[1] = inter[2] = 0;
                }

              switch (inter[3])
                {
                case 0:
                  d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                  break;

                case 255:
                  d[0] = inter[0];
                  d[1] = inter[1];
                  d[2] = inter[2];
                  break;

                default:
                  {
                    register guint alpha = inter[3] + 1;
                    register guint check = CHECK_COLOR (area, row, col);

                    d[0] = ((check << 8) + (inter[0] - check) * alpha) >> 8;
                    d[1] = ((check << 8) + (inter[1] - check) * alpha) >> 8;
                    d[2] = ((check << 8) + (inter[2] - check) * alpha) >> 8;
                  }
                  break;
                }
            }

          src1 += rowstride1;
          src2 += rowstride2;
          dest += area->rowstride;
        }
      break;

    case GIMP_GRAY_IMAGE:
      for (row = 0; row < height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          guchar       *d  = dest;

          for (col = 0; col < width; col++, s1++, s2++, d += 3)
            {
              d[0] = d[1] = d[2] =
                ((s1[0] << 8) + (s2[0] - s1[0]) * opacity) >> 8;
            }

          src1 += rowstride1;
          src2 += rowstride2;
          dest += area->rowstride;
        }
      break;

    case GIMP_GRAYA_IMAGE:
      for (row = y; row < y + height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 2, s2 += 2, d+= 3)
            {
              guchar inter[2];

              inter[1] = ((s1[1] << 8) + (s2[1] - s1[1]) * opacity) >> 8;

              if (inter[1])
                {
                  gushort a = s1[0] * s1[1];
                  gushort b = s2[0] * s2[1];

                  inter[0] = (((a << 8) + (b  - a) * opacity) >> 8) / inter[1];
                }
              else
                {
                  inter[0] = 0;
                }

              switch (inter[1])
                {
                case 0:
                  d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                  break;

                case 255:
                  d[0] = d[1] = d[2] = inter[0];
                  break;

                default:
                  {
                    register guint alpha = inter[1] + 1;
                    register guint check = CHECK_COLOR (area, row, col);

                    d[0] = d[1] = d[2] =
                      ((check << 8) + (inter[0] - check) * alpha) >> 8;
                  }
                  break;
                }
            }

          src1 += rowstride1;
          src2 += rowstride2;
          dest += area->rowstride;
        }
      break;

    case GIMP_INDEXED_IMAGE:
      g_return_if_fail (area->cmap != NULL);
      for (row = 0; row < height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          guchar       *d  = dest;

          for (col = 0; col < width; col++, s1++, s2++, d += 3)
            {
              const guchar *cmap1 = area->cmap + 3 * s1[0];
              const guchar *cmap2 = area->cmap + 3 * s2[0];

              d[0] = ((cmap1[0] << 8) + (cmap2[0] - cmap1[0]) * opacity) >> 8;
              d[1] = ((cmap1[1] << 8) + (cmap2[1] - cmap1[1]) * opacity) >> 8;
              d[2] = ((cmap1[2] << 8) + (cmap2[2] - cmap1[2]) * opacity) >> 8;
            }

          src1 += rowstride1;
          src2 += rowstride2;
          dest += area->rowstride;
        }
      break;

    case GIMP_INDEXEDA_IMAGE:
      g_return_if_fail (area->cmap != NULL);
      for (row = y; row < y + height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 2, s2 += 2, d += 3)
            {
              const guchar *cmap1  = area->cmap + 3 * s1[0];
              const guchar *cmap2  = area->cmap + 3 * s2[0];
              guchar        inter[4];

              inter[3] = ((s1[1] << 8) + (s2[1] - s1[1]) * opacity) >> 8;

              if (inter[3])
                {
                  for (i = 0 ; i < 3 ; i++)
                    {
                      gushort a = cmap1[i] * s1[1];
                      gushort b = cmap2[i] * s2[1];

                      inter[i] =
                        (((a << 8) + (b  - a) * opacity) >> 8) / inter[3];
                    }
                }
              else
                {
                  inter[0] = inter[1] = inter[2] = 0;
                }

              switch (inter[3])
                {
                case 0:
                  d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                  break;

                case 255:
                  d[0] = inter[0];
                  d[1] = inter[1];
                  d[2] = inter[2];
                  break;

                default:
                  {
                    register guint alpha = inter[3] + 1;
                    register guint check = CHECK_COLOR (area, row, col);

                    d[0] = ((check << 8) + (inter[0] - check) * alpha) >> 8;
                    d[1] = ((check << 8) + (inter[1] - check) * alpha) >> 8;
                    d[2] = ((check << 8) + (inter[2] - check) * alpha) >> 8;
                  }
                  break;
                }
            }

          src1 += rowstride1;
          src2 += rowstride2;
          dest += area->rowstride;
        }
      break;
    }

  gtk_widget_queue_draw_area (GTK_WIDGET (area), x, y, width, height);
}

/**
 * gimp_preview_area_mask:
 * @area:           a #GimpPreviewArea widget.
 * @x:              x offset in preview
 * @y:              y offset in preview
 * @width:          buffer width
 * @height:         buffer height
 * @type:           the #GimpImageType of @buf1 and @buf2
 * @buf1:           a #guchar buffer that contains the pixel data for
 *                  the first (on bottom) layer
 * @rowstride1:     rowstride of @buf1
 * @buf2:           a #guchar buffer that contains the pixel data for
 *                  the second (on top) layer
 * @rowstride2:     rowstride of @buf2
 * @mask:           a #guchar buffer representing the mask of the second
 *                  layer.
 * @rowstride_mask: rowstride for the mask.
 *
 * Blend @buf1 on top of @buf2 with the given @mask on the @area
 * and queues a redraw on the rectangle that changed.
 *
 * Since GIMP 2.2
 **/
void
gimp_preview_area_mask (GimpPreviewArea *area,
                        gint             x,
                        gint             y,
                        gint             width,
                        gint             height,
                        GimpImageType    type,
                        const guchar    *buf1,
                        gint             rowstride1,
                        const guchar    *buf2,
                        gint             rowstride2,
                        guchar          *mask,
                        gint             rowstride_mask)
{
  const guchar    *src1;
  const guchar    *src2;
  const guchar    *src_mask;
  guchar          *dest;
  guint            size;
  guchar           light;
  guchar           dark;
  gint             row;
  gint             col;
  gint             i;

  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));
  g_return_if_fail (width > 0 && height > 0);
  g_return_if_fail (buf1 != NULL);
  g_return_if_fail (buf2 != NULL);
  g_return_if_fail (mask != NULL);
  g_return_if_fail (rowstride1 > 0);
  g_return_if_fail (rowstride2 > 0);
  g_return_if_fail (rowstride_mask > 0);

  if (x + width < 0 || x >= area->width)
    return;

  if (y + height < 0 || y >= area->height)
    return;

  if (x < 0)
    {
      gint  bpp = gimp_preview_area_image_type_bytes (type);

      buf1  += x * bpp;
      buf2  += x * bpp;
      mask  += x;
      width -= x;

      x = 0;
    }

  if (x + width > area->width)
    width = area->width - x;

  if (y < 0)
    {
      buf1   += y * rowstride1;
      buf2   += y * rowstride2;
      mask   += y * rowstride_mask;
      height -= y;

      y = 0;
    }

  if (y + height > area->height)
    height = area->height - y;

  if (! area->buf)
    {
      area->rowstride = ((area->width * 3) + 3) & ~3;
      area->buf = g_new (guchar, area->rowstride * area->height);
    }

  size = 1 << (2 + area->check_size);
  gimp_checks_get_shades (area->check_type, &light, &dark);

  src1     = buf1;
  src2     = buf2;
  src_mask = mask;
  dest     = area->buf + x * 3 + y * area->rowstride;

  switch (type)
    {
    case GIMP_RGB_IMAGE:
      for (row = 0; row < height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          const guchar *m  = src_mask;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 3, s2 += 3, m++, d+= 3)
            {
               d[0] = ((s1[0] << 8) + (s2[0] - s1[0]) * m[0]) >> 8;
               d[1] = ((s1[1] << 8) + (s2[1] - s1[1]) * m[0]) >> 8;
               d[2] = ((s1[2] << 8) + (s2[2] - s1[2]) * m[0]) >> 8;
            }
          src1     += rowstride1;
          src2     += rowstride2;
          src_mask += rowstride_mask;
          dest     += area->rowstride;
        }
      break;

    case GIMP_RGBA_IMAGE:
       for (row = y; row < y + height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          const guchar *m  = src_mask;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 4, s2 += 4, m++, d+= 3)
            {
              switch (m[0])
                {
                case 0:
                  switch (s1[3])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = s1[0];
                      d[1] = s1[1];
                      d[2] = s1[2];
                      break;

                    default:
                      {
                        register guint alpha = s1[3] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = ((check << 8) + (s1[0] - check) * alpha) >> 8;
                        d[1] = ((check << 8) + (s1[1] - check) * alpha) >> 8;
                        d[2] = ((check << 8) + (s1[2] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  break;

                case 255:
                  switch (s2[3])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = s2[0];
                      d[1] = s2[1];
                      d[2] = s2[2];
                      break;

                    default:
                      {
                        register guint alpha = s2[3] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = ((check << 8) + (s2[0] - check) * alpha) >> 8;
                        d[1] = ((check << 8) + (s2[1] - check) * alpha) >> 8;
                        d[2] = ((check << 8) + (s2[2] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  break;

                default:
                  {
                    guchar inter[4];

                    inter[3] = ((s1[3] << 8) + (s2[3] - s1[3]) * m[0]) >> 8;

                    if (inter[3])
                      {
                        for (i=0 ; i<3 ; i++)
                          {
                            gushort a = s1[i] * s1[3];
                            gushort b = s2[i] * s2[3];

                            inter[i] =
                              (((a << 8) + (b  - a) * m[0]) >> 8) / inter[3];
                          }
                      }

                  switch (inter[3])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = inter[0];
                      d[1] = inter[1];
                      d[2] = inter[2];
                      break;

                    default:
                      {
                        register guint alpha = inter[3] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = ((check << 8) + (inter[0] - check) * alpha) >> 8;
                        d[1] = ((check << 8) + (inter[1] - check) * alpha) >> 8;
                        d[2] = ((check << 8) + (inter[2] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  }
                  break;
                }
            }

          src1     += rowstride1;
          src2     += rowstride2;
          src_mask += rowstride_mask;
          dest     += area->rowstride;
        }
       break;

    case GIMP_GRAY_IMAGE:
      for (row = 0; row < height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          const guchar *m  = src_mask;
          guchar       *d  = dest;

          for (col = 0; col < width; col++, s1++, s2++, m++, d += 3)
            {
              d[0] = d[1] = d[2] = ((s1[0] << 8) + (s2[0] - s1[0]) * m[0]) >> 8;
            }

          src1     += rowstride1;
          src2     += rowstride2;
          src_mask += rowstride_mask;
          dest     += area->rowstride;
        }
      break;

    case GIMP_GRAYA_IMAGE:
      for (row = y; row < y + height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          const guchar *m  = src_mask;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 2, s2 += 2, m++, d+= 3)
            {
              switch (m[0])
                {
                case 0:
                  switch (s1[1])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = d[1] = d[2] = s1[0];
                      break;

                    default:
                      {
                        register guint alpha = s1[1] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = d[1] = d[2] =
                          ((check << 8) + (s1[0] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  break;

                case 255:
                  switch (s2[1])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = d[1] = d[2] = s2[0];
                      break;

                    default:
                      {
                        register guint alpha = s2[1] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = d[1] = d[2] =
                          ((check << 8) + (s2[0] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  break;

                default:
                  {
                    guchar inter[2];

                    inter[1] = ((s1[1] << 8) + (s2[1] - s1[1]) * m[0]) >> 8;

                    if (inter[1])
                      {
                        gushort a = s1[0] * s1[1];
                        gushort b = s2[0] * s2[1];

                        inter[0] =
                          (((a << 8) + (b  - a) * m[0]) >> 8) / inter[1];
                      }
                    else
                      {
                        inter[0] = 0;
                      }

                  switch (inter[1])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = d[1] = d[2] = inter[0];
                      break;

                    default:
                      {
                        register guint alpha = inter[1] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = d[1] = d[2] =
                          ((check << 8) + (inter[0] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  }
                  break;
                }
            }

          src1     += rowstride1;
          src2     += rowstride2;
          src_mask += rowstride_mask;
          dest     += area->rowstride;
        }
      break;

    case GIMP_INDEXED_IMAGE:
      g_return_if_fail (area->cmap != NULL);
      for (row = 0; row < height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          const guchar *m  = src_mask;
          guchar       *d  = dest;

          for (col = 0; col < width; col++, s1++, s2++, m++, d += 3)
            {
              const guchar *cmap1 = area->cmap + 3 * s1[0];
              const guchar *cmap2 = area->cmap + 3 * s2[0];

              d[0] = ((cmap1[0] << 8) + (cmap2[0] - cmap1[0]) * m[0]) >> 8;
              d[1] = ((cmap1[1] << 8) + (cmap2[1] - cmap1[1]) * m[0]) >> 8;
              d[2] = ((cmap1[2] << 8) + (cmap2[2] - cmap1[2]) * m[0]) >> 8;
            }

          src1     += rowstride1;
          src2     += rowstride2;
          src_mask += rowstride_mask;
          dest     += area->rowstride;
        }
      break;

    case GIMP_INDEXEDA_IMAGE:
      g_return_if_fail (area->cmap != NULL);
      for (row = y; row < y + height; row++)
        {
          const guchar *s1 = src1;
          const guchar *s2 = src2;
          const guchar *m  = src_mask;
          guchar       *d  = dest;

          for (col = x; col < x + width; col++, s1 += 2, s2 += 2, m++, d += 3)
            {
              const guchar *cmap1  = area->cmap + 3 * s1[0];
              const guchar *cmap2  = area->cmap + 3 * s2[0];

              switch (m[0])
                {
                case 0:
                  switch (s1[1])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = cmap1[0];
                      d[1] = cmap1[1];
                      d[2] = cmap1[2];
                      break;

                    default:
                      {
                        register guint alpha = s1[1] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = ((check << 8) + (cmap1[0] - check) * alpha) >> 8;
                        d[1] = ((check << 8) + (cmap1[1] - check) * alpha) >> 8;
                        d[2] = ((check << 8) + (cmap1[2] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  break;

                case 255:
                  switch (s2[1])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = cmap2[0];
                      d[1] = cmap2[1];
                      d[2] = cmap2[2];
                      break;

                    default:
                      {
                        register guint alpha = s2[1] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = ((check << 8) + (cmap2[0] - check) * alpha) >> 8;
                        d[1] = ((check << 8) + (cmap2[1] - check) * alpha) >> 8;
                        d[2] = ((check << 8) + (cmap2[2] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  break;

                default:
                  {
                    guchar inter[4];

                    inter[3] = ((s1[1] << 8) + (s2[1] - s1[1]) * m[0]) >> 8;

                    if (inter[3])
                      {
                        for (i = 0 ; i < 3 ; i++)
                          {
                            gushort a = cmap1[i] * s1[1];
                            gushort b = cmap2[i] * s2[1];

                            inter[i] =
                              (((a << 8) + (b  - a) * m[0]) >> 8) / inter[3];
                          }
                      }
                    else
                      {
                        inter[0] = inter[1] = inter[2] = 0;
                      }

                  switch (inter[3])
                    {
                    case 0:
                      d[0] = d[1] = d[2] = CHECK_COLOR (area, row, col);
                      break;

                    case 255:
                      d[0] = inter[0];
                      d[1] = inter[1];
                      d[2] = inter[2];
                      break;

                    default:
                      {
                        register guint alpha = inter[3] + 1;
                        register guint check = CHECK_COLOR (area, row, col);

                        d[0] = ((check << 8) + (inter[0] - check) * alpha) >> 8;
                        d[1] = ((check << 8) + (inter[1] - check) * alpha) >> 8;
                        d[2] = ((check << 8) + (inter[2] - check) * alpha) >> 8;
                      }
                      break;
                    }
                  }
                  break;
                }
            }

          src1     += rowstride1;
          src2     += rowstride2;
          src_mask += rowstride_mask;
          dest     += area->rowstride;
        }
      break;
    }

  gtk_widget_queue_draw_area (GTK_WIDGET (area), x, y, width, height);
}

/**
 * gimp_preview_area_fill:
 * @area:   a #GimpPreviewArea widget.
 * @x:      x offset in preview
 * @y:      y offset in preview
 * @width:  buffer width
 * @height: buffer height
 * @red:
 * @green:
 * @blue:
 *
 * Fills the @area in the given color.
 *
 * Since GIMP 2.2
 **/
void
gimp_preview_area_fill (GimpPreviewArea *area,
                        gint             x,
                        gint             y,
                        gint             width,
                        gint             height,
                        guchar           red,
                        guchar           green,
                        guchar           blue)
{
  guchar *dest;
  guchar *d;
  gint    row;
  gint    col;

  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));
  g_return_if_fail (width > 0 && height > 0);

  if (x + width < 0 || x >= area->width)
    return;

  if (y + height < 0 || y >= area->height)
    return;

  if (x < 0)
    {
      width -= x;
      x = 0;
    }

  if (x + width > area->width)
    width = area->width - x;

  if (y < 0)
    {
      height -= y;
      y = 0;
    }

  if (y + height > area->height)
    height = area->height - y;

  if (! area->buf)
    {
      area->rowstride = ((area->width * 3) + 3) & ~3;
      area->buf = g_new (guchar, area->rowstride * area->height);
    }

  dest = area->buf + x * 3 + y * area->rowstride;

  /*  colorize first row  */
  for (col = 0, d = dest; col < width; col++, d+= 3)
    {
      d[0] = red;
      d[1] = green;
      d[2] = blue;
    }

  /*  copy first row to remaining rows  */
  for (row = 1, d = dest; row < height; row++)
    {
      d += area->rowstride;

      memcpy (d, dest, width * 3);
    }

  gtk_widget_queue_draw_area (GTK_WIDGET (area), x, y, width, height);
}

/**
 * gimp_preview_area_set_offsets:
 * @area: a #GimpPreviewArea
 * @x:    horizontal offset
 * @y:    vertical offset
 *
 * Sets the offsets of the previewed area. This information is used
 * when drawing the checkerboard and to determine the dither offsets.
 *
 * Since: GIMP 2.2
 **/
void
gimp_preview_area_set_offsets (GimpPreviewArea *area,
                               gint             x,
                               gint             y)
{
  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));

  area->offset_x = x;
  area->offset_y = y;
}

/**
 * gimp_preview_area_set_cmap:
 * @area:       a #GimpPreviewArea
 * @cmap:       a #guchar buffer that contains the colormap
 * @num_colors: the number of colors in the colormap
 *
 * Sets the colormap for the #GimpPreviewArea widget. You need to
 * call this function before you use gimp_preview_area_draw() with
 * an image type of %GIMP_INDEXED_IMAGE or %GIMP_INDEXEDA_IMAGE.
 *
 * Since GIMP 2.2
 **/
void
gimp_preview_area_set_cmap (GimpPreviewArea *area,
                            const guchar    *cmap,
                            gint             num_colors)
{
  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));
  g_return_if_fail (cmap != NULL || num_colors == 0);
  g_return_if_fail (num_colors >= 0 && num_colors <= 256);

  if (num_colors > 0)
    {
      if (! area->cmap)
        area->cmap = g_new0 (guchar, 3 * 256);

      memcpy (area->cmap, cmap, 3 * num_colors);
    }
  else
    {
      g_free (area->cmap);
      area->cmap = NULL;
    }
}


/*  popup menu  */

static void
gimp_preview_area_menu_toggled (GtkWidget       *item,
                                GimpPreviewArea *area)
{
  gboolean active = gtk_check_menu_item_get_active (GTK_CHECK_MENU_ITEM (item));

  if (active)
    {
      const gchar *name;
      gint         value;

      name  = g_object_get_data (G_OBJECT (item),
                                 "gimp-preview-area-prop-name");
      value = GPOINTER_TO_INT (g_object_get_data (G_OBJECT (item),
                                                  "gimp-preview-area-prop-value"));

      if (name)
        g_object_set (area,
                      name, value,
                      NULL);
    }
}

static GtkWidget *
gimp_preview_area_menu_new (GimpPreviewArea *area,
                            const gchar     *property)
{
  GParamSpec *pspec;
  GEnumClass *enum_class;
  GEnumValue *enum_value;
  GtkWidget  *menu;
  GtkWidget  *item;
  GSList     *group = NULL;
  gint        value;

  pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (area), property);

  g_return_val_if_fail (G_IS_PARAM_SPEC_ENUM (pspec), NULL);

  g_object_get (area,
                property, &value,
                NULL);

  enum_class = G_PARAM_SPEC_ENUM (pspec)->enum_class;

  menu = gtk_menu_new ();

  for (enum_value = enum_class->values; enum_value->value_name; enum_value++)
    {
      const gchar *name = gimp_enum_value_get_name (enum_class, enum_value);

      item = gtk_radio_menu_item_new_with_label (group, name);

      gtk_menu_shell_append (GTK_MENU_SHELL (menu), item);
      gtk_widget_show (item);

      g_object_set_data (G_OBJECT (item),
                         "gimp-preview-area-prop-name",
                         (gpointer) property);

      g_object_set_data (G_OBJECT (item),
                         "gimp-preview-area-prop-value",
                         GINT_TO_POINTER (enum_value->value));

      gtk_check_menu_item_set_active (GTK_CHECK_MENU_ITEM (item),
                                      (enum_value->value == value));

      g_signal_connect (item, "toggled",
                        G_CALLBACK (gimp_preview_area_menu_toggled),
                        area);

      group = gtk_radio_menu_item_get_group (GTK_RADIO_MENU_ITEM (item));
    }

  item = gtk_menu_item_new_with_label (g_param_spec_get_nick (pspec));

  gtk_menu_item_set_submenu (GTK_MENU_ITEM (item), menu);

  gtk_widget_show (item);

  return item;
}

/**
 * gimp_preview_area_menu_popup:
 * @area:  a #GimpPreviewArea
 * @event: the button event that causes the menu to popup or %NULL
 *
 * Creates a popup menu that allows to configure the size and type of
 * the checkerboard pattern that the @area uses to visualize transparency.
 *
 * Since: GIMP 2.2
 **/
void
gimp_preview_area_menu_popup (GimpPreviewArea *area,
                              GdkEventButton  *event)
{
  GtkWidget *menu;

  g_return_if_fail (GIMP_IS_PREVIEW_AREA (area));

  menu = gtk_menu_new ();
  gtk_menu_set_screen (GTK_MENU (menu),
                       gtk_widget_get_screen (GTK_WIDGET (area)));

  gtk_menu_shell_append (GTK_MENU_SHELL (menu),
                         gimp_preview_area_menu_new (area, "check-type"));
  gtk_menu_shell_append (GTK_MENU_SHELL (menu),
                         gimp_preview_area_menu_new (area, "check-size"));

  if (event)
    gtk_menu_popup (GTK_MENU (menu),
                    NULL, NULL, NULL, NULL, event->button, event->time);
  else
    gtk_menu_popup (GTK_MENU (menu),
                    NULL, NULL, NULL, NULL, 0, gtk_get_current_event_time ());
}