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checks.cpp

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2006 The ScummVM project
 *
 * Copyright (C) 1999-2001 Sarien Team
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL: https://svn.sourceforge.net/svnroot/scummvm/scummvm/tags/release-0-9-1/engines/agi/checks.cpp $
 * $Id: checks.cpp 22638 2006-05-25 22:39:44Z wjpalenstijn $
 *
 */

#include "common/stdafx.h"
#include "agi/agi.h"

namespace Agi {

static int check_position(struct vt_entry *v) {
      debugC(4, kDebugLevelSprites, "check position @ %d, %d", v->x_pos, v->y_pos);

      if (v->x_pos < 0 ||
                  v->x_pos + v->x_size > _WIDTH ||
                  v->y_pos - v->y_size + 1 < 0 ||
                  v->y_pos >= _HEIGHT ||
                  ((~v->flags & IGNORE_HORIZON) && v->y_pos <= game.horizon)) {
            debugC(4, kDebugLevelSprites, "check position failed: x=%d, y=%d, h=%d, w=%d",
                        v->x_pos, v->y_pos, v->x_size, v->y_size);
            return 0;
      }

      /* MH1 needs this, but it breaks LSL1 */
      if (agi_get_release() >= 0x3000) {
            if (v->y_pos < v->y_size)
                  return 0;
      }

      return 1;
}

/**
 * Check if there's another object on the way
 */
static int check_collision(struct vt_entry *v) {
      struct vt_entry *u;

      if (v->flags & IGNORE_OBJECTS)
            return 0;

      for (u = game.view_table; u < &game.view_table[MAX_VIEWTABLE]; u++) {
            if ((u->flags & (ANIMATED | DRAWN)) != (ANIMATED | DRAWN))
                  continue;

            if (u->flags & IGNORE_OBJECTS)
                  continue;

            /* Same object, check next */
            if (v->entry == u->entry)
                  continue;

            /* No horizontal overlap, check next */
            if (v->x_pos + v->x_size < u->x_pos ||
                        v->x_pos > u->x_pos + u->x_size)
                  continue;

            /* Same y, return error! */
            if (v->y_pos == u->y_pos)
                  goto return_1;

            /* Crossed the baseline, return error! */
            if ((v->y_pos > u->y_pos && v->y_pos2 < u->y_pos2) ||
                        (v->y_pos < u->y_pos && v->y_pos2 > u->y_pos2)) {
                  goto return_1;
            }
      }

      return 0;

 return_1:
      debugC(4, kDebugLevelSprites, "check returns 1 (object %d)", v->entry);
      return 1;
}

static int check_priority(struct vt_entry *v) {
      int i, trigger, water, pass, pri;
      uint8 *p0;

      if (~v->flags & FIXED_PRIORITY) {
            /* Priority bands */
            v->priority = game.pri_table[v->y_pos];
      }

      trigger = 0;
      water = 0;
      pass = 1;

      if (v->priority == 0x0f)
            goto _check_ego;

      water = 1;

      p0 = &game.sbuf[v->x_pos + v->y_pos * _WIDTH];

      for (i = 0; i < v->x_size; i++, p0++) {
            pri = *p0 >> 4;

            if (pri == 0) {   /* unconditional black. no go at all! */
                  pass = 0;
                  break;
            }

            if (pri == 3)     /* water surface */
                  continue;

            water = 0;

            if (pri == 1) {   /* conditional blue */
                  if (v->flags & IGNORE_BLOCKS)
                        continue;

                  debugC(4, kDebugLevelSprites, "Blocks observed!");
                  pass = 0;
                  break;
            }

            if (pri == 2) {   /* trigger */
                  debugC(4, kDebugLevelSprites, "stepped on trigger");
                  if (!debug_.ignoretriggers)
                        trigger = 1;
            }
      }

      if (pass) {
            if (!water && v->flags & ON_WATER)
                  pass = 0;
            if (water && v->flags & ON_LAND)
                  pass = 0;
      }

      _check_ego:
      if (v->entry == 0) {
            setflag(F_ego_touched_p2, trigger ? true : false);
            setflag(F_ego_water, water ? true : false);
      }

      return pass;
}

/*
 * Public functions
 */

/**
 * Update position of objects
 * This function updates the position of all animated, updating view
 * table entries according to its motion type, step size, etc. The
 * new position must be valid according to the sprite positioning
 * rules, otherwise the previous position will be kept.
 */
void update_position() {
      struct vt_entry *v;
      int x, y, old_x, old_y, border;

      game.vars[V_border_code] = 0;
      game.vars[V_border_touch_ego] = 0;
      game.vars[V_border_touch_obj] = 0;

      for (v = game.view_table; v < &game.view_table[MAX_VIEWTABLE]; v++) {
            if ((v->flags & (ANIMATED | UPDATE | DRAWN)) != (ANIMATED | UPDATE | DRAWN)) {
                  continue;
            }

            if (v->step_time_count != 0) {
                  if (--v->step_time_count != 0)
                        continue;
            }

            v->step_time_count = v->step_time;

            x = old_x = v->x_pos;
            y = old_y = v->y_pos;

            /* If object has moved, update its position */
            if (~v->flags & UPDATE_POS) {
                  int dx[9] = { 0, 0, 1, 1, 1, 0, -1, -1, -1 };
                  int dy[9] = { 0, -1, -1, 0, 1, 1, 1, 0, -1 };
                  x += v->step_size * dx[v->direction];
                  y += v->step_size * dy[v->direction];
            }

            /* Now check if it touched the borders */
            border = 0;

            /* Check left/right borders */
            if (x < 0) {
                  x = 0;
                  border = 4;
            } else if (x <= 0 && agi_get_release() == 0x3086) {   /* KQ4 */
                  x = 0;      /* See bug #590462 */
                  border = 4;
            } else if (v->entry == 0 && x == 0 && v->flags & ADJ_EGO_XY) {
                  /* Extra test to walk west clicking the mouse */
                  x = 0;
                  border = 4;
            } else if (x + v->x_size > _WIDTH) {
                  x = _WIDTH - v->x_size;
                  border = 2;
            }

            /* Check top/bottom borders. */
            if (y - v->y_size + 1 < 0) {
                  y = v->y_size - 1;
                  border = 1;
            } else if (y > _HEIGHT - 1) {
                  y = _HEIGHT - 1;
                  border = 3;
            } else if ((~v->flags & IGNORE_HORIZON) && y <= game.horizon) {
                  debugC(4, kDebugLevelSprites, "y = %d, horizon = %d", y, game.horizon);
                  y = game.horizon + 1;
                  border = 1;
            }

            /* Test new position. rollback if test fails */
            v->x_pos = x;
            v->y_pos = y;
            if (check_collision(v) || !check_priority(v)) {
                  v->x_pos = old_x;
                  v->y_pos = old_y;
                  border = 0;
                  fix_position(v->entry);
            }

            if (border != 0) {
                  if (is_ego_view(v)) {
                        game.vars[V_border_touch_ego] = border;
                  } else {
                        game.vars[V_border_code] = v->entry;
                        game.vars[V_border_touch_obj] = border;
                  }
                  if (v->motion == MOTION_MOVE_OBJ) {
                        in_destination(v);
                  }
            }

            v->flags &= ~UPDATE_POS;
      }
}

/**
 * Adjust position of a sprite
 * This function adjusts the position of a sprite moving it until
 * certain criteria is matched. According to priority and control line
 * data, a sprite may not always appear at the location we specified.
 * This behaviour is also known as the "Budin-Sonneveld effect".
 *
 * @param n view table entry number
 */
void fix_position(int n) {
      struct vt_entry *v = &game.view_table[n];
      int count, dir, size;

      debugC(4, kDebugLevelSprites, "adjusting view table entry #%d (%d,%d)", n, v->x_pos, v->y_pos);

      /* test horizon */
      if ((~v->flags & IGNORE_HORIZON) && v->y_pos <= game.horizon)
            v->y_pos = game.horizon + 1;

      dir = 0;
      count = size = 1;

      while (!check_position(v) || check_collision(v) || !check_priority(v)) {
            switch (dir) {
            case 0:     /* west */
                  v->x_pos--;
                  if (--count)
                        continue;
                  dir = 1;
                  break;
            case 1:     /* south */
                  v->y_pos++;
                  if (--count)
                        continue;
                  dir = 2;
                  size++;
                  break;
            case 2:     /* east */
                  v->x_pos++;
                  if (--count)
                        continue;
                  dir = 3;
                  break;
            case 3:     /* north */
                  v->y_pos--;
                  if (--count)
                        continue;
                  dir = 0;
                  size++;
                  break;
            }

            count = size;
      }

      debugC(4, kDebugLevelSprites, "view table entry #%d position adjusted to (%d,%d)", n, v->x_pos, v->y_pos);
}

} // End of namespace Agi

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