summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/video/skyraid.cpp
blob: d82515f8b31b7de8cc5af21dc7dcb1a506e13176 (plain) (blame)
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
// license:BSD-3-Clause
// copyright-holders:Stefan Jokisch
/***************************************************************************

Atari Sky Raider video emulation

***************************************************************************/

#include "emu.h"
#include "includes/skyraid.h"


void skyraid_state::video_start()
{
	m_helper.allocate(128, 240);
}


void skyraid_state::draw_text(bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	const UINT8* p = m_alpha_num_ram;

	int i;

	for (i = 0; i < 4; i++)
	{
		int x;
		int y;

		y = 136 + 16 * (i ^ 1);

		for (x = 0; x < bitmap.width(); x += 16)
			m_gfxdecode->gfx(0)->transpen(bitmap,cliprect, *p++, 0, 0, 0,   x, y, 0);
	}
}


void skyraid_state::draw_terrain(bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	const UINT8* p = memregion("user1")->base();

	int x;
	int y;

	for (y = 0; y < bitmap.height(); y++)
	{
		int offset = (16 * m_scroll + 16 * ((y + 1) / 2)) & 0x7FF;

		x = 0;

		while (x < bitmap.width())
		{
			UINT8 val = p[offset++];

			int color = val / 32;
			int count = val % 32;

			rectangle r(x, x + 31 - count, y, y+ 1);

			bitmap.fill(color, r);

			x += 32 - count;
		}
	}
}


void skyraid_state::draw_sprites(bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	int i;

	for (i = 0; i < 4; i++)
	{
		int code = m_obj_ram[8 + 2 * i + 0] & 15;
		int flag = m_obj_ram[8 + 2 * i + 1] & 15;
		int vert = m_pos_ram[8 + 2 * i + 0];
		int horz = m_pos_ram[8 + 2 * i + 1];

		vert -= 31;

		if (flag & 1)
			m_gfxdecode->gfx(1)->transpen(bitmap,cliprect,
				code ^ 15, code >> 3, 0, 0,
				horz / 2, vert, 2);
	}
}


void skyraid_state::draw_missiles(bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	int i;

	/* hardware is restricted to one sprite per scanline */

	for (i = 0; i < 4; i++)
	{
		int code = m_obj_ram[2 * i + 0] & 15;
		int vert = m_pos_ram[2 * i + 0];
		int horz = m_pos_ram[2 * i + 1];

		vert -= 15;
		horz -= 31;

		m_gfxdecode->gfx(2)->transpen(bitmap,cliprect,
			code ^ 15, 0, 0, 0,
			horz / 2, vert, 0);
	}
}


void skyraid_state::draw_trapezoid(bitmap_ind16& dst, bitmap_ind16& src)
{
	const UINT8* p = memregion("user2")->base();

	int x;
	int y;

	for (y = 0; y < dst.height(); y++)
	{
		UINT16* pSrc = &src.pix16(y);
		UINT16* pDst = &dst.pix16(y);

		int x1 = 0x000 + p[(y & ~1) + 0];
		int x2 = 0x100 + p[(y & ~1) + 1];

		for (x = x1; x < x2; x++)
			pDst[x] = pSrc[128 * (x - x1) / (x2 - x1)];
	}
}


UINT32 skyraid_state::screen_update_skyraid(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	bitmap.fill(0, cliprect);

	rectangle helper_clip = cliprect;
	helper_clip &= m_helper.cliprect();

	draw_terrain(m_helper, helper_clip);
	draw_sprites(m_helper, helper_clip);
	draw_missiles(m_helper, helper_clip);
	draw_trapezoid(bitmap, m_helper);
	draw_text(bitmap, cliprect);
	return 0;
}