mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-05-28 23:41:32 +00:00
140 lines
3.0 KiB
C
140 lines
3.0 KiB
C
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#include "common.h"
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//#link "common.c"
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void setup_bitmap_multi() {
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VIC.ctrl1 = 0x38;
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VIC.ctrl2 = 0x18;
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// set VIC bank ($4000-$7FFF)
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// https://www.c64-wiki.com/wiki/VIC_bank
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CIA2.pra = 0x02;
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// set VIC screen to $6000
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VIC.addr = 0x80;
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// clear bitmap and screen RAM
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memset((void*)0x4000, 0, 0x2000);
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memset((void*)0xd800, 0, 40*25);
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}
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const byte PIXMASK[4] = { ~0xc0, ~0x30, ~0x0c, ~0x03 };
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const byte PIXSHIFT[4] = { 6, 4, 2, 0 };
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byte is_pixel(byte x, byte y) {
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word ofs = ((x>>2)*8 + (y>>3)*320) | (y&7) | 0x4000;
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return PEEK(ofs) & ~PIXMASK[x & 3];
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}
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void set_pixel(byte x, byte y, byte color) {
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word ofs,b,cram,sram;
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byte ccol,scol;
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byte val;
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if (x >= 160 || y >= 192) return;
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color &= 0xf;
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// equal to background color? (value 0)
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if (color == VIC.bgcolor0) {
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val = 0;
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} else {
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cram = ((x>>2) + (y>>3)*40);
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sram = cram | 0x6000;
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cram |= 0xd800;
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ccol = PEEK(cram);
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scol = PEEK(sram);
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// color RAM contains unused bits (0x10 and 0x20)
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// unused in lower nibble of screen RAM? (value 2)
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if (color == (scol & 0xf) || !(ccol & 0x10)) {
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val = 2;
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scol = (scol & 0xf0) | color;
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ccol |= 0x10;
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POKE(sram, scol);
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// unused in upper nibble of screen RAM? (value 1)
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} else if (color == (scol >> 4) || !(ccol & 0x20)) {
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val = 1;
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scol = (scol & 0xf) | (color << 4);
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ccol |= 0x20;
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POKE(sram, scol);
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// all other colors in use, use color RAM
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} else {
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val = 3;
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ccol = 0x30 | color;
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}
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POKE(cram, ccol);
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}
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ofs = ((x>>2)*8 + (y>>3)*320) | (y&7) | 0x4000;
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x &= 3;
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b = PEEK(ofs) & PIXMASK[x];
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if (val) {
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b |= val << PIXSHIFT[x];
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}
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POKE(ofs, b);
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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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#pragma static-locals(push,off)
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byte flood_fill(byte x, byte y, byte color) {
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register byte x1 = x;
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register byte x2;
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register byte i;
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// find left edge
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while (!is_pixel(x1, y))
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--x1;
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// exit if (x,y) is on a boundary
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if (x1 == x)
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return 1;
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++x1;
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// find right edge
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x2 = x+1;
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while (!is_pixel(x2, y))
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++x2;
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// fill scanline
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for (i=x1; i<x2; i++) {
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set_pixel(i, y, color);
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}
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// fill above and below scanline
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for (i=x1; i<x2; ) {
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i += flood_fill(i, y-1, color);
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}
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for (i=x1; i<x2; ) {
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i += flood_fill(i, y+1, color);
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}
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return (x2-x1);
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}
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#pragma static-locals(pop)
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#ifdef __MAIN__
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word urand() {
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return rand();
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}
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void main() {
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setup_bitmap_multi();
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draw_line(80, 10, 100, 100, 1);
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draw_line(80, 10, 40, 80, 1);
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draw_line(100, 100, 40, 80, 1);
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draw_line(50, 0, 80, 60, 1);
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draw_line(100, 0, 80, 60, 1);
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flood_fill(80, 80, 2);
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while(1) {
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draw_line(urand()%160, urand()%192, urand()%160, urand()%192, rand()&15);
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}
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}
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#endif
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