chibicc/examples/star.c at uxn · lynn/chibicc · GitHub

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
// star demo for chibicc-uxn by hikari_no_yume (2023-06-10 ~ 2023-06-14)

#include <varvara.h>

// generated with JS: x="";for(i=0;i<64;i++)x+=((Math.sin(i*Math.PI/128)*128)|0)+",";
char SIN_TABLE[64] = {0,3,6,9,12,15,18,21,24,28,31,34,37,40,43,46,48,51,54,57,60,63,65,68,71,73,76,78,81,83,85,88,90,92,94,96,98,100,102,104,106,108,109,111,112,114,115,117,118,119,120,121,122,123,124,124,125,126,126,127,127,127,127,127,};
char sin(char a)
{
  return SIN_TABLE[(a & 0x40 ? ~a : a) & 0x3f] * (a & 0x80 ? -1 : 1);
}
char cos(char a)
{
  return sin(a + 0x40);
}

// https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm#All_cases
void line_low(int x0, int y0, int x1, int y1, char pixel)
{
  int dx = x1 - x0;
  int dy = y1 - y0;
  int yi = 1;
  if (dy < 0) {
    yi = -1;
    dy = -dy;
  }
  int d = (2 * dy) - dx;
  int y = y0;
  for (int x = x0; x <= x1; x++) {
    set_screen_xy(x, y);
    draw_pixel(pixel);
    if (d > 0) {
      y += yi;
      d += 2 * (dy - dx);
    } else {
      d += 2 * dy;
    }
  }
}
void line_high(int x0, int y0, int x1, int y1, char pixel)
{
  int dx = x1 - x0;
  int dy = y1 - y0;
  int xi = 1;
  if (dx < 0) {
    xi = -1;
    dx = -dx;
  }
  int d = (2 * dx) - dy;
  int x = x0;
  for (int y = y0; y <= y1; y++) {
    set_screen_xy(x, y);
    draw_pixel(pixel);
    if (d > 0) {
      x += xi;
      d += 2 * (dx - dy);
    } else {
      d += 2 * dx;
    }
  }
}
void line(int x0, int y0, int x1, int y1, char pixel)
{
  int y1y0 = y1 - y0;
  if (y1y0 < 0) y1y0 = -y1y0;
  int x1x0 = x1 - x0;
  if (x1x0 < 0) x1x0 = -x1x0;
  if (y1y0 < x1x0) {
    if (x0 > x1)
      line_low(x1, y1, x0, y0, pixel);
    else
      line_low(x0, y0, x1, y1, pixel);
  } else {
    if (y0 > y1)
      line_high(x1, y1, x0, y0, pixel);
    else
      line_high(x0, y0, x1, y1, pixel);
  }
}

char SPRITE[8] = {
  0b10000001,
  0b10000001,
  0b10000001,
  0b10000001,
  0b10000001,
  0b10000001,
  0b10000001,
  0b01111111,
};

char t = 0;

void on_screen(void)
{
  t++;

  // clear layer 0
  set_screen_xy(0, 0);
  draw_pixel(BgFillBR);
  // draw star
  _Bool first = 1;
  int last_x;
  int last_y;
  for (unsigned i = 0; i < 11; i++) {
    unsigned char angle = t + (256 * (i % 10)) / 10;
    int x = sin(angle) >> (i & 1);
    int y = cos(angle) >> (i & 1);
    if (first) {
      first = 0;
    } else {
      line(127 + last_x, 127 + last_y, 127 + x, 127 + y, 0x03);
      line(127 + (last_x * 3 >> 2), 127 + (last_y * 3 >> 2), 127 + (x * 3 >> 2), 127 + (y * 3 >> 2), 0x02);
      line(127 + (last_x >> 1), 127 + (last_y >> 1), 127 + (x >> 1), 127 + (y >> 1), 0x01);
    }
    last_x = x;
    last_y = y;
  }
  // draw u
  set_screen_addr(SPRITE);
  set_screen_xy(113, 123);
  draw_sprite(0x01);
  // draw x
  int x = sin(t + 0x20) >> 5;
  int y = cos(t + 0x20) >> 5;
  line(127 - x - 1, 127 - y - 1, 127 + x, 127 + y, 0x03);
  x = sin(t + 0x60) >> 5;
  y = cos(t + 0x60) >> 5;
  line(127 - x - 1, 127 - y - 1, 127 + x, 127 + y, 0x03);
  // draw n
  set_screen_addr(SPRITE);
  set_screen_xy(133, 123);
  draw_sprite(0x31);
}

void main(void)
{
  set_palette(0x0aaf, 0x0ffc, 0x0faa);
  set_screen_size(256, 256);
}