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8bitworkshop/presets/coleco/lines.c

74 lines
1.6 KiB
C

/*
This demo draws pixels and lines in Mode 2.
Note that when lines of two different colors overlap,
they create "clashing" effects.
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <cv.h>
#include <cvu.h>
#include "common.h"
void setup_mode2() {
cvu_vmemset(0, 0, 0x4000);
cv_set_screen_mode(CV_SCREENMODE_BITMAP); // mode 2
cv_set_image_table(IMAGE);
cv_set_character_pattern_t(PATTERN|0x1fff); // AND mask
cv_set_color_table(COLOR|0x1fff); // AND mask
cv_set_sprite_attribute_table(0x2800);
{
byte i=0;
do {
cvu_voutb(i, IMAGE+i);
cvu_voutb(i, IMAGE+0x100+i);
cvu_voutb(i, IMAGE+0x200+i);
} while (++i);
}
}
void set_pixel(byte x, byte y, byte color) {
word ofs = (x/8)*8 + (y/8)*256 + (y&7);
byte b = cvu_vinb(PATTERN + ofs);
if (y >= 192) return;
if (color>1) {
b |= 128 >> (x&7);
cvu_voutb(b, PATTERN + ofs);
cvu_voutb(color<<4, COLOR + ofs);
} else {
b &= ~(128 >> (x&7));
cvu_voutb(b, PATTERN + ofs);
}
}
void draw_line(int x0, int y0, int x1, int y1, byte color) {
int dx = abs(x1-x0);
int sx = x0<x1 ? 1 : -1;
int dy = abs(y1-y0);
int sy = y0<y1 ? 1 : -1;
int err = (dx>dy ? dx : -dy)>>1;
int e2;
for(;;) {
set_pixel(x0, y0, color);
if (x0==x1 && y0==y1) break;
e2 = err;
if (e2 > -dx) { err -= dy; x0 += sx; }
if (e2 < dy) { err += dx; y0 += sy; }
}
}
#ifdef __MAIN__
void main() {
setup_mode2();
cv_set_screen_active(true);
while(1) {
draw_line(rand()&0xff, rand()&0xbf, rand()&0xff, rand()&0xbf, rand()&15);
}
}
#endif