aboutsummaryrefslogtreecommitdiff
path: root/sword2/scroll.cpp
blob: fd960caa2b384fb5c6597d4102ebcfb7f6e0fa27 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
/* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $Header$
 */

#include "common/stdafx.h"
#include "sword2/sword2.h"
#include "sword2/defs.h"
#include "sword2/logic.h"

namespace Sword2 {

// Max no of pixel allowed to scroll per cycle
#define MAX_SCROLL_DISTANCE 8

/**
 * Sets the scroll target position for the end of the game cycle. The driver
 * will then automatically scroll as many times as it can to reach this
 * position in the allotted time.
 */

void Screen::setScrollTarget(int16 sx, int16 sy) {
	_scrollXTarget = sx;
	_scrollYTarget = sy;
}

/**
 * If the room is larger than the physical screen, this function is called
 * every game cycle to update the scroll offsets.
 */

void Screen::setScrolling() {
	// 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.
	uint32 scrollX = _vm->_logic->readVar(SCROLL_X);
	uint32 scrollY = _vm->_logic->readVar(SCROLL_Y);

	if (scrollX || scrollY) {
		_thisScreen.scroll_offset_x = MIN((uint16)scrollX, _thisScreen.max_scroll_offset_x);
		_thisScreen.scroll_offset_y = MIN((uint16)scrollY, _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