1 /* ScummVM - Graphic Adventure Engine
2 *
3 * ScummVM is the legal property of its developers, whose names
4 * are too numerous to list here. Please refer to the COPYRIGHT
5 * file distributed with this source distribution.
6 *
7 * Additional copyright for this file:
8 * Copyright (C) 1994-1998 Revolution Software Ltd.
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version 2
13 * of the License, or (at your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
23 */
24
25
26
27 #include "sword2/sword2.h"
28 #include "sword2/defs.h"
29 #include "sword2/header.h"
30 #include "sword2/logic.h"
31 #include "sword2/screen.h"
32
33 namespace Sword2 {
34
35 // Max no of pixel allowed to scroll per cycle
36 #define MAX_SCROLL_DISTANCE 8
37
38 /**
39 * Sets the scroll target position for the end of the game cycle. The driver
40 * will then automatically scroll as many times as it can to reach this
41 * position in the allotted time.
42 */
43
setScrollTarget(int16 sx,int16 sy)44 void Screen::setScrollTarget(int16 sx, int16 sy) {
45 _scrollXTarget = sx;
46 _scrollYTarget = sy;
47 }
48
49 /**
50 * If the room is larger than the physical screen, this function is called
51 * every game cycle to update the scroll offsets.
52 */
53
setScrolling()54 void Screen::setScrolling() {
55 // Normally we aim to get George's feet at (320,250) from top left
56 // of screen window
57 // feet_x = 128 + 320
58 // feet_y = 128 + 250
59
60 // Set scroll offsets according to the player's coords
61
62 // If the scroll offsets are being forced in script, ensure that they
63 // are neither too far to the right nor too far down.
64 uint32 scrollX = _vm->_logic->readVar(SCROLL_X);
65 uint32 scrollY = _vm->_logic->readVar(SCROLL_Y);
66
67 if (scrollX || scrollY) {
68 _thisScreen.scroll_offset_x = MIN((uint16)scrollX, _thisScreen.max_scroll_offset_x);
69 _thisScreen.scroll_offset_y = MIN((uint16)scrollY, _thisScreen.max_scroll_offset_y);
70 return;
71 }
72
73 // George's offset from the center - the desired position for him
74
75 int16 offset_x = _thisScreen.player_feet_x - _thisScreen.feet_x;
76 int16 offset_y = _thisScreen.player_feet_y - _thisScreen.feet_y;
77
78 // Prevent scrolling too far left/right/up/down
79
80 if (offset_x < 0)
81 offset_x = 0;
82 else if (offset_x > _thisScreen.max_scroll_offset_x)
83 offset_x = _thisScreen.max_scroll_offset_x;
84
85 if (offset_y < 0)
86 offset_y = 0;
87 else if (offset_y > _thisScreen.max_scroll_offset_y)
88 offset_y = _thisScreen.max_scroll_offset_y;
89
90 // First time on this screen - need absolute scroll immediately!
91
92 if (_thisScreen.scroll_flag == 2) {
93 debug(5, "init scroll");
94 _thisScreen.scroll_offset_x = offset_x;
95 _thisScreen.scroll_offset_y = offset_y;
96 _thisScreen.scroll_flag = 1;
97 return;
98 }
99
100 // Catch up with required scroll offsets - speed depending on distance
101 // to catch up (dx and dy) and _scrollFraction used, but limit to
102 // certain number of pixels per cycle (MAX_SCROLL_DISTANCE)
103
104 int16 dx = _thisScreen.scroll_offset_x - offset_x;
105 int16 dy = _thisScreen.scroll_offset_y - offset_y;
106
107 uint16 scroll_distance_x; // how much we want to scroll
108 uint16 scroll_distance_y;
109
110 if (dx < 0) {
111 // Current scroll_offset_x is less than the required value
112
113 // NB. I'm adding 1 to the result of dx / SCROLL_FRACTION,
114 // because it would otherwise not scroll at all when
115 // dx < SCROLL_FRACTION
116
117 // => inc by (fraction of the differnce) NB. dx is -ve, so we
118 // subtract dx / SCROLL_FRACTION
119
120 scroll_distance_x = 1 - dx / _scrollFraction;
121
122 if (scroll_distance_x > MAX_SCROLL_DISTANCE)
123 scroll_distance_x = MAX_SCROLL_DISTANCE;
124
125 _thisScreen.scroll_offset_x += scroll_distance_x;
126 } else if (dx > 0) {
127 // Current scroll_offset_x is greater than
128 // the required value
129
130 // => dec by (fraction of the differnce)
131
132 scroll_distance_x = 1 + dx / _scrollFraction;
133
134 if (scroll_distance_x > MAX_SCROLL_DISTANCE)
135 scroll_distance_x = MAX_SCROLL_DISTANCE;
136
137 _thisScreen.scroll_offset_x -= scroll_distance_x;
138 }
139
140 if (dy < 0) {
141 scroll_distance_y = 1 - dy / _scrollFraction;
142
143 if (scroll_distance_y > MAX_SCROLL_DISTANCE)
144 scroll_distance_y = MAX_SCROLL_DISTANCE;
145
146 _thisScreen.scroll_offset_y += scroll_distance_y;
147 } else if (dy > 0) {
148 scroll_distance_y = 1 + dy / _scrollFraction;
149
150 if (scroll_distance_y > MAX_SCROLL_DISTANCE)
151 scroll_distance_y = MAX_SCROLL_DISTANCE;
152
153 _thisScreen.scroll_offset_y -= scroll_distance_y;
154 }
155 }
156
157 } // End of namespace Sword2
158