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