/* GIMP - The GNU 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 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <gegl.h>

#include "core-types.h"

#include "gegl/gimp-gegl-utils.h"

#include "gimplayer.h"
#include "gimpprojectable.h"
#include "gimpprojection.h"
#include "gimpprojection-construct.h"


/*  local function prototypes  */

static void   gimp_projection_initialize (GimpProjection *proj,
                                          gint            x,
                                          gint            y,
                                          gint            w,
                                          gint            h);


/*  public functions  */

void
gimp_projection_construct (GimpProjection *proj,
                           gint            x,
                           gint            y,
                           gint            w,
                           gint            h)
{
  GeglRectangle  rect = { x, y, w, h };

  g_return_if_fail (GIMP_IS_PROJECTION (proj));

  /*  First, determine if the projection image needs to be
   *  initialized--this is the case when there are no visible
   *  layers that cover the entire canvas--either because layers
   *  are offset or only a floating selection is visible
   */
  gimp_projection_initialize (proj, x, y, w, h);

  if (! proj->processor)
    {
      GeglNode *sink = gimp_projection_get_sink_node (proj);

      proj->processor = gegl_node_new_processor (sink, &rect);
    }
  else
    {
      gegl_processor_set_rectangle (proj->processor, &rect);
    }

  while (gegl_processor_work (proj->processor, NULL));
}

/**
 * gimp_projection_initialize:
 * @proj: A #GimpProjection.
 * @x:
 * @y:
 * @w:
 * @h:
 *
 * This function determines whether a visible layer with combine mode
 * Normal provides complete coverage over the specified area.  If not,
 * the projection is initialized to transparent black.
 */
static void
gimp_projection_initialize (GimpProjection *proj,
                            gint            x,
                            gint            y,
                            gint            w,
                            gint            h)
{
  GList    *list;
  gint      proj_off_x;
  gint      proj_off_y;
  gboolean  coverage = FALSE;

  gimp_projectable_get_offset (proj->projectable, &proj_off_x, &proj_off_y);

  for (list = gimp_projectable_get_layers (proj->projectable);
       list;
       list = g_list_next (list))
    {
      GimpLayer    *layer    = list->data;
      GimpDrawable *drawable = GIMP_DRAWABLE (layer);
      GimpItem     *item     = GIMP_ITEM (layer);
      gint          off_x, off_y;

      gimp_item_get_offset (item, &off_x, &off_y);

      /*  subtract the projectable's offsets because the list of
       *  update areas is in tile-pyramid coordinates, but our
       *  external API is always in terms of image coordinates.
       */
      off_x -= proj_off_x;
      off_y -= proj_off_y;

      if (gimp_item_get_visible (item)                          &&
          ! gimp_drawable_has_alpha (drawable)                  &&
          ! gimp_layer_get_mask (layer)                         &&
          gimp_layer_get_mode (layer) == GIMP_NORMAL_MODE       &&
          gimp_layer_get_opacity (layer) == GIMP_OPACITY_OPAQUE &&
          off_x <= x                                            &&
          off_y <= y                                            &&
          (off_x + gimp_item_get_width  (item)) >= (x + w)      &&
          (off_y + gimp_item_get_height (item)) >= (y + h))
        {
          coverage = TRUE;
          break;
        }
    }

  if (! coverage)
    {
      GeglBuffer *buffer;

      /* GEGL should really do this for us... */
      gegl_node_get (gimp_projection_get_sink_node (proj),
                     "buffer", &buffer, NULL);

      gegl_buffer_clear (buffer, GEGL_RECTANGLE (x, y, w, h));
      g_object_unref (buffer);
    }
}