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https://github.com/libretro/scummvm.git
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155 lines
4.6 KiB
C++
155 lines
4.6 KiB
C++
/* Copyright (C) 1994-1998 Revolution Software Ltd.
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* Copyright (C) 2003-2006 The ScummVM project
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*/
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#include "common/stdafx.h"
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#include "sword2/sword2.h"
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#include "sword2/defs.h"
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#include "sword2/header.h"
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#include "sword2/logic.h"
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#include "sword2/screen.h"
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namespace Sword2 {
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// Max no of pixel allowed to scroll per cycle
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#define MAX_SCROLL_DISTANCE 8
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/**
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* Sets the scroll target position for the end of the game cycle. The driver
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* will then automatically scroll as many times as it can to reach this
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* position in the allotted time.
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*/
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void Screen::setScrollTarget(int16 sx, int16 sy) {
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_scrollXTarget = sx;
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_scrollYTarget = sy;
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}
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/**
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* If the room is larger than the physical screen, this function is called
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* every game cycle to update the scroll offsets.
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*/
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void Screen::setScrolling() {
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// Normally we aim to get George's feet at (320,250) from top left
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// of screen window
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// feet_x = 128 + 320
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// feet_y = 128 + 250
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// Set scroll offsets according to the player's coords
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// If the scroll offsets are being forced in script, ensure that they
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// are neither too far to the right nor too far down.
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uint32 scrollX = _vm->_logic->readVar(SCROLL_X);
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uint32 scrollY = _vm->_logic->readVar(SCROLL_Y);
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if (scrollX || scrollY) {
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_thisScreen.scroll_offset_x = MIN((uint16)scrollX, _thisScreen.max_scroll_offset_x);
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_thisScreen.scroll_offset_y = MIN((uint16)scrollY, _thisScreen.max_scroll_offset_y);
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return;
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}
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// George's offset from the centre - the desired position for him
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int16 offset_x = _thisScreen.player_feet_x - _thisScreen.feet_x;
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int16 offset_y = _thisScreen.player_feet_y - _thisScreen.feet_y;
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// Prevent scrolling too far left/right/up/down
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if (offset_x < 0)
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offset_x = 0;
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else if (offset_x > _thisScreen.max_scroll_offset_x)
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offset_x = _thisScreen.max_scroll_offset_x;
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if (offset_y < 0)
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offset_y = 0;
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else if (offset_y > _thisScreen.max_scroll_offset_y)
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offset_y = _thisScreen.max_scroll_offset_y;
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// First time on this screen - need absolute scroll immediately!
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if (_thisScreen.scroll_flag == 2) {
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debug(5, "init scroll");
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_thisScreen.scroll_offset_x = offset_x;
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_thisScreen.scroll_offset_y = offset_y;
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_thisScreen.scroll_flag = 1;
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return;
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}
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// Catch up with required scroll offsets - speed depending on distance
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// to catch up (dx and dy) and _scrollFraction used, but limit to
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// certain number of pixels per cycle (MAX_SCROLL_DISTANCE)
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int16 dx = _thisScreen.scroll_offset_x - offset_x;
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int16 dy = _thisScreen.scroll_offset_y - offset_y;
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uint16 scroll_distance_x; // how much we want to scroll
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uint16 scroll_distance_y;
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if (dx < 0) {
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// Current scroll_offset_x is less than the required value
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// NB. I'm adding 1 to the result of dx / SCROLL_FRACTION,
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// because it would otherwise not scroll at all when
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// dx < SCROLL_FRACTION
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// => inc by (fraction of the differnce) NB. dx is -ve, so we
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// subtract dx / SCROLL_FRACTION
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scroll_distance_x = 1 - dx / _scrollFraction;
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if (scroll_distance_x > MAX_SCROLL_DISTANCE)
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scroll_distance_x = MAX_SCROLL_DISTANCE;
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_thisScreen.scroll_offset_x += scroll_distance_x;
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} else if (dx > 0) {
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// Current scroll_offset_x is greater than
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// the required value
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// => dec by (fraction of the differnce)
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scroll_distance_x = 1 + dx / _scrollFraction;
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if (scroll_distance_x > MAX_SCROLL_DISTANCE)
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scroll_distance_x = MAX_SCROLL_DISTANCE;
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_thisScreen.scroll_offset_x -= scroll_distance_x;
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}
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if (dy < 0) {
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scroll_distance_y = 1 - dy / _scrollFraction;
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if (scroll_distance_y > MAX_SCROLL_DISTANCE)
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scroll_distance_y = MAX_SCROLL_DISTANCE;
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_thisScreen.scroll_offset_y += scroll_distance_y;
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} else if (dy > 0) {
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scroll_distance_y = 1 + dy / _scrollFraction;
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if (scroll_distance_y > MAX_SCROLL_DISTANCE)
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scroll_distance_y = MAX_SCROLL_DISTANCE;
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_thisScreen.scroll_offset_y -= scroll_distance_y;
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}
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}
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} // End of namespace Sword2
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