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/* Copyright (C) 1994-1998 Revolution Software Ltd.
* Copyright (C) 2003-2005 The ScummVM project
*
* 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.
*
* $Header$
*/
#include "common/stdafx.h"
#include "sword2/sword2.h"
#include "sword2/defs.h"
#include "sword2/interpreter.h"
#include "sword2/logic.h"
namespace Sword2 {
// Max no of pixel allowed to scroll per cycle
#define MAX_SCROLL_DISTANCE 8
/**
* If the room is larger than the physical screen, this function is called
* every game cycle to update the scroll offsets.
*/
void Sword2Engine::setScrolling(void) {
// Normally we aim to get George's feet at (320,250) from top left
// of screen window
// feet_x = 128 + 320
// feet_y = 128 + 250
// Set scroll offsets according to the player's coords
// If the scroll offsets are being forced in script, ensure that they
// are neither too far to the right nor too far down.
if (Logic::_scriptVars[SCROLL_X] || Logic::_scriptVars[SCROLL_Y]) {
_thisScreen.scroll_offset_x = MIN((uint16) Logic::_scriptVars[SCROLL_X], _thisScreen.max_scroll_offset_x);
_thisScreen.scroll_offset_y = MIN((uint16) Logic::_scriptVars[SCROLL_Y], _thisScreen.max_scroll_offset_y);
return;
}
// George's offset from the centre - the desired position for him
int16 offset_x = _thisScreen.player_feet_x - _thisScreen.feet_x;
int16 offset_y = _thisScreen.player_feet_y - _thisScreen.feet_y;
// Prevent scrolling too far left/right/up/down
if (offset_x < 0)
offset_x = 0;
else if (offset_x > _thisScreen.max_scroll_offset_x)
offset_x = _thisScreen.max_scroll_offset_x;
if (offset_y < 0)
offset_y = 0;
else if (offset_y > _thisScreen.max_scroll_offset_y)
offset_y = _thisScreen.max_scroll_offset_y;
// First time on this screen - need absolute scroll immediately!
if (_thisScreen.scroll_flag == 2) {
debug(5, "init scroll");
_thisScreen.scroll_offset_x = offset_x;
_thisScreen.scroll_offset_y = offset_y;
_thisScreen.scroll_flag = 1;
return;
}
// Catch up with required scroll offsets - speed depending on distance
// to catch up (dx and dy) and _scrollFraction used, but limit to
// certain number of pixels per cycle (MAX_SCROLL_DISTANCE)
int16 dx = _thisScreen.scroll_offset_x - offset_x;
int16 dy = _thisScreen.scroll_offset_y - offset_y;
uint16 scroll_distance_x; // how much we want to scroll
uint16 scroll_distance_y;
if (dx < 0) {
// Current scroll_offset_x is less than the required value
// NB. I'm adding 1 to the result of dx / SCROLL_FRACTION,
// because it would otherwise not scroll at all when
// dx < SCROLL_FRACTION
// => inc by (fraction of the differnce) NB. dx is -ve, so we
// subtract dx / SCROLL_FRACTION
scroll_distance_x = 1 - dx / _scrollFraction;
if (scroll_distance_x > MAX_SCROLL_DISTANCE)
scroll_distance_x = MAX_SCROLL_DISTANCE;
_thisScreen.scroll_offset_x += scroll_distance_x;
} else if (dx > 0) {
// Current scroll_offset_x is greater than
// the required value
// => dec by (fraction of the differnce)
scroll_distance_x = 1 + dx / _scrollFraction;
if (scroll_distance_x > MAX_SCROLL_DISTANCE)
scroll_distance_x = MAX_SCROLL_DISTANCE;
_thisScreen.scroll_offset_x -= scroll_distance_x;
}
if (dy < 0) {
scroll_distance_y = 1 - dy / _scrollFraction;
if (scroll_distance_y > MAX_SCROLL_DISTANCE)
scroll_distance_y = MAX_SCROLL_DISTANCE;
_thisScreen.scroll_offset_y += scroll_distance_y;
} else if (dy > 0) {
scroll_distance_y = 1 + dy / _scrollFraction;
if (scroll_distance_y > MAX_SCROLL_DISTANCE)
scroll_distance_y = MAX_SCROLL_DISTANCE;
_thisScreen.scroll_offset_y -= scroll_distance_y;
}
}
} // End of namespace Sword2
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